Fat

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This article is about the type of nutrient in food. Fat_sentence_0

For fat in humans and animals, see Adipose tissue. Fat_sentence_1

For other uses, see Fat (disambiguation). Fat_sentence_2

In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds; most commonly those that occur in living beings or in food. Fat_sentence_3

The term often refers specifically to triglycerides (triple esters of glycerol), that are the main components of vegetable oils and of fatty tissue in animals; or, even more narrowly, to triglycerides that are solid or semisolid at room temperature, thus excluding oils. Fat_sentence_4

The term may also be used more broadly as a synonym of lipid -- any substance of biological relevance, composed of carbon, hydrogen, or oxygen, that is insoluble in water but soluble in non-polar solvents. Fat_sentence_5

In this sense, besides the triglycerides, the term would include several other types of compounds like mono- and diglycerides, phospholipids (such as lecithin), sterols (such as cholesterol), waxes (such as beeswax), and free fatty acids, which are usually present in human diet in smaller amounts. Fat_sentence_6

Fats are one of the three main macronutrient groups in human diet, along with carbohydrates and proteins, and the main components of common food products like milk, butter, tallow, lard, bacon, and cooking oils. Fat_sentence_7

They are a major and dense source of food energy for many animals and play important structural and metabolic functions, in most living beings, including energy storage, waterproofing, and thermal insulation. Fat_sentence_8

The human body can produce the fat that it needs from other food ingredients, except for a few essential fatty acids that must be included in the diet. Fat_sentence_9

Dietary fats are also the carriers of some flavor and aroma ingredients and vitamins that are not water-soluble. Fat_sentence_10

Chemical structure Fat_section_0

The most important elements in the chemical makeup of fats are the fatty acids. Fat_sentence_11

The molecule of a fatty acid consists of a carboxyl group HO(O=)C− connected to an unbranched alkyl group –(CH x) nH: namely, a chain of carbon atoms, joined by single, double, or (more rarely) triple bonds, with all remaining free bonds filled by hydrogen atoms Fat_sentence_12

The most common type of fat, in human diet and most living beings, is a triglyceride, an ester of the triple alcohol glycerol H(–CHOH–) 3H and three fatty acids. Fat_sentence_13

The molecule of a triglyceride can be described as resulting from a condensation reaction (specifically, esterification) between each of glycerol's –OH groups and the HO– part of the carboxyl group HO(O=)C− of each fatty acid, forming an ester bridge −O−(O=)C− with elimination of a water molecule H 2O. Fat_sentence_14

Other less common types of fats include diglycerides and monoglycerides, where the esterification is limited to two or just one of glycerol's –OH groups. Fat_sentence_15

Other alcohols, such as cetyl alcohol (predominant in spermaceti), may replace glycerol. Fat_sentence_16

In the phospholipids, one of the fatty acids is replaced by phosphoric acid or a monoester thereof. Fat_sentence_17

Conformation Fat_section_1

The shape of fat and fatty acid molecules is usually not well-defined. Fat_sentence_18

Any two parts of a molecule that are connected by just one single bond are free to rotate about that bond. Fat_sentence_19

Thus a fatty acid molecule with n simple bonds can be deformed in n-1 independent ways (counting also rotation of the terminal methyl group). Fat_sentence_20

Such rotation cannot happen across a double bond, except by breaking and then reforming it with one of the halves of the molecule rotated by 180 degrees, which requires crossing a significant energy barrier. Fat_sentence_21

Thus a fat or fatty acid molecule with double bonds (excluding at the very end of the chain) can have multiple cis-trans isomers with significantly different chemical and biological properties. Fat_sentence_22

Each double bond reduces the number of conformational degrees of freedom by one. Fat_sentence_23

Each triple bond forces the four nearest carbons to lie in a straight line, removing two degrees of freedom. Fat_sentence_24

It follows that depictions of "saturated" fatty acids with no double bonds (like stearic) having a "straight zig-zag" shape, and those with one cis bond (like oleic) being bent in an "elbow" shape are somewhat misleading. Fat_sentence_25

While the latter are a little less flexible, both can be twisted to assume similar straight or elbow shapes. Fat_sentence_26

In fact, outside of some specific contexts like crystals or bilayer membranes, both are more likely to be found in randomly contorted configurations than in either of those two shapes. Fat_sentence_27

Examples Fat_section_2

Fat_table_general_0

Examples of 18-carbon fatty acids.Fat_table_caption_0
Stearic acid

saturatedFat_header_cell_0_0_0

Fat_cell_0_0_1
Oleic acid

unsaturated cis-8Fat_header_cell_0_1_0

Fat_cell_0_1_1
Elaidic acid

unsaturated trans-8Fat_header_cell_0_2_0

Fat_cell_0_2_1
Vaccenic acid

unsaturated trans-11Fat_header_cell_0_3_0

Fat_cell_0_3_1

Stearic acid is a saturated fatty acid (with only single bonds) found in animal fats, and is the intended product in full hydrogenation. Fat_sentence_28

Oleic acid has a double bond (thus being "unsaturated") with cis geometry about midway in the chain; it makes up 55–80% of olive oil. Fat_sentence_29

Elaidic acid is its trans isomer; it may be present in partially hydrogenated vegetable oils, and also occurs in the fat of the durian fruit (about 2%) and in milk fat (less than 0.1%). Fat_sentence_30

Vaccenic acid is another trans acid that differs from elaidic only in the position of the double bond; it also occurs in milk fat (about 1-2%). Fat_sentence_31

Nomenclature Fat_section_3

Common fat names Fat_section_4

Fats are usually named after their source (like olive oil, cod liver oil, shea butter, tail fat) or have traditional names of their own (like butter, lard, ghee, and margarine). Fat_sentence_32

Some of these names refer to products that contain substantial amounts of other components besides fats proper. Fat_sentence_33

Chemical fatty acid names Fat_section_5

In chemistry and biochemistry, dozens of saturated fatty acids and of hundreds of unsaturated ones have traditional scientific/technical names usually inspired by their source fats (butyric, caprylic, stearic, oleic, palmitic, and nervonic), but sometimes their discoverer (mead, osbond). Fat_sentence_34

A triglyceride would then be named as an ester of those acids, such as "glyceryl 1,2-dioleate 3-palmitate". Fat_sentence_35

IUPAC Fat_section_6

In the general chemical nomenclature developed by the International Union of Pure and Applied Chemistry (IUPAC), the recommended name of a fatty acid, derived from the name of the corresponding hydrocarbon, completely describes its structure, by specifying the number of carbons and the number and position of the double bonds. Fat_sentence_36

Thus, for example, oleic acid would be called "(9Z)-octadec-9-enoic acid", meaning that it has a 18 carbon chain ("octadec") with a carboxyl at one end ("oic") and a double bound at carbon 9 counting from the carboxyl ("9-en"), and that the configuration of the single bonds adjacent to that double bond is cis ("(9Z)") The IUPAC nomenclature can also handle branched chains and derivatives where hydrogen atoms are replaced by other chemical groups. Fat_sentence_37

A triglyceride would then be named according to general ester rules as, for example, "propane-1,2,3-tryl 1,2-bis((9Z)-octadec-9-enoate) 3-(hexadecanoate)". Fat_sentence_38

Fatty acid code Fat_section_7

A notation specific for fatty acids with unbranched chain, that is as precise as the IUPAC one but easier to parse, is a code of the form "{N}:{D} cis-{CCC} trans-{TTT}", where {N} is the number of carbons (including the carboxyl one), {D} is the number of double bonds, {CCC} is a list of the positions of the cis double bonds, and {TTT} is a list of the postions of the trans bounds. Fat_sentence_39

Either list and the label is omitted if there are no bounds of that type. Fat_sentence_40

Thus, for example, the codes for stearic, oleic, elaidic, and vaccenic acids would be "18:0", "18:1 cis-9", "18:1 trans-9", and "18:1 trans-11", respectively. Fat_sentence_41

The code for α-oleostearic acid, which is "(9E,11E,13Z)-octadeca-9,11,13-trienoic acid" in the IUPAC nomenclature, has the code "18:3 trans-9,11 cis-13" Fat_sentence_42

Classification Fat_section_8

Main article: fatty acid Fat_sentence_43

By chain length Fat_section_9

Fats can be classified according to the lengths of the carbon chains of their constituent fatty acids. Fat_sentence_44

Most chemical properties, such as melting point and acidity, vary gradually with this parameter, so there is no sharp division. Fat_sentence_45

Chemically, formic acid (1 carbon) and acetic acid (2 carbons) could be viewed as the shortest fatty acids; then triformin would be the simplest triglyceride. Fat_sentence_46

However, the terms "fatty acid" and "fat" are usually reserved for compounds with substantially longer chains. Fat_sentence_47

A division commonly made in biochemistry and nutrition is: Fat_sentence_48

Fat_unordered_list_0

  • Short-chain fatty acid (SCFA) with less than six carbons (e. g. butyric acid).Fat_item_0_0
  • Medium-chain fatty acid (MCFA) with 6 to 12 carbons (e.g. capric acid).Fat_item_0_1
  • Long-chain fatty acids (LCFA) with 13 to 21 carbons (e.g. petroselinic acid).Fat_item_0_2
  • Very long chain fatty acids (VLCFA) with 22 or more carbons (e. g. cerotic acid with 26)Fat_item_0_3

A triglyceride molecule may have fatty acid elements of different lengths, and a fat product will often be a mix of various triglycerides. Fat_sentence_49

Most fats found in food, whether vegetable or animal, are made up of medium to long-chain fatty acids, usually of equal or nearly equal length. Fat_sentence_50

Saturated and unsaturated fats Fat_section_10

For human nutrition, an important classification of fats is based on the number and position of double bonds in the constituent fatty acids. Fat_sentence_51

Saturated fat has a predominance of saturated fatty acids, without any double bonds, while unsaturated fat has predominantly unsaturated acids with double bonds. Fat_sentence_52

(The names refer to the fact that each double bond means two fewer hydrogen atoms in the chemical formula. Fat_sentence_53

Thus, a saturated fatty acid, having no double bonds, has the maximum number of hydrogen atoms for a given number of carbon atoms — that is, it is "saturated" with hydrogen atoms.) Fat_sentence_54

Unsaturated fatty acids are further classified into monounsaturated (MUFAs), with a single double bond, and polyunsaturated (PUFAs), with two or more. Fat_sentence_55

Natural fats usually contain several different saturated and unsaturated acids, even on the same molecule. Fat_sentence_56

For example, in most vegetable oils, the saturated palmitic (C16:0) and stearic (C18:0) acid residues are usually attached to positions 1 and 3 (sn1 and sn3) of the glycerol hub, whereas the middle position (sn2) is usually occupied by an unsaturated one, such as oleic (C18:1, ω–9) or linoleic (C18:2, ω–6).) Fat_sentence_57

While it is the nutritional aspects of polyunsaturated fatty acids that are generally of greatest interest, these materials also have non-food applications. Fat_sentence_58

They include the drying oils, such as linseed (flax seed), tung, poppy seed, perilla, and walnut oil, which polymerize on exposure to oxygen to form solid films, and are used to make paints and varnishes. Fat_sentence_59

Saturated fats generally have a higher melting point than unsaturated ones with the same molecular weight, and thus are more likely to be solid at room temperature. Fat_sentence_60

For example, the animal fats tallow and lard are high in saturated fatty acid content and are solids. Fat_sentence_61

Olive and linseed oils on the other hand are unsaturated and liquid. Fat_sentence_62

Unsaturated fats are prone to oxidation by air, which causes them to become rancid and inedible. Fat_sentence_63

The double bonds in unsaturated fats can be converted into single bonds by reaction with hydrogen effected by a catalyst. Fat_sentence_64

This process, called hydrogenation, is used to turn vegetable oils into solid or semisolid vegetable fats like margarine, which can substitute for tallow and butter and (unlike unsaturated fats) can be stored indefinitely without becoming rancid. Fat_sentence_65

However, partial hydrogenation also creates some unwanted trans acids from cis acids. Fat_sentence_66

In cellular metabolism, unsaturated fat molecules yield slightly less less energy (i.e., fewer calories) than an equivalent amount of saturated fat. Fat_sentence_67

The heats of combustion of saturated, mono-, di-, and tri-unsaturated 18-carbon fatty acid esters have been measured as 2859, 2828, 2794, and 2750 kcal/mol, respectively; or, on a weight basis, 10.75, 10.71, 10.66, and 10.58 kcal/g — a decrease of about 0.6% for each additional double bond. Fat_sentence_68

The greater the degree of unsaturation in a fatty acid (i.e., the more double bonds in the fatty acid) the more vulnerable it is to lipid peroxidation (rancidity). Fat_sentence_69

Antioxidants can protect unsaturated fat from lipid peroxidation. Fat_sentence_70

Cis and trans fats Fat_section_11

Another important classification of unsaturated fatty acids considers the cis-trans isomerism, the spatial arrangement of the C–C single bonds adjacent to the double bonds. Fat_sentence_71

Most unsaturated fatty acids that occur in nature have those bonds in the cis ("same side") configuration. Fat_sentence_72

Partial hydrogenation of cis fats can turn some of their fatty acids into trans ("opposite sides") variety. Fat_sentence_73

Elaidic acid is the trans isomer of oleic acid, one of the most common fatty acids in human diet. Fat_sentence_74

The single change of configuration in one double bond causes them to have different chemical and physical properties. Fat_sentence_75

Elaidic acid has a much higher melting point than oleic acid, 45 °C instead of 13.4 °C. Fat_sentence_76

This difference is commonly attributed to the supposed ability of the trans molecules to pack more tightly, forming a solid that is more difficult to break apart. Fat_sentence_77

Omega number Fat_section_12

Another classification considers the position of the double bonds relative to the end of the chain (opposite to the carboxyl group). Fat_sentence_78

The position is denoted by "ω−k" or "n−k", meaning that there is a double bond between carbons k and k+1 counted from 1 at that end. Fat_sentence_79

For example, alpha-Linolenic acid is a "ω−3" or "n−3" acid, meaning that there is a double bond between the third and fourth carbons, counted from that end; that is, its structural formula ends with –CH=CH–CH 2–CH 3. Fat_sentence_80

Examples of saturated fatty acids Fat_section_13

Main article: List of saturated fatty acids Fat_sentence_81

Some common examples of fatty acids: Fat_sentence_82

Fat_unordered_list_1

Examples of unsaturated fatty acids Fat_section_14

Main article: List of unsaturated fatty acids Fat_sentence_83

Fat_unordered_list_2

Biological importance Fat_section_15

In humans and many animals, fats serve both as energy sources and as stores for energy in excess of what the body needs immediately. Fat_sentence_84

Each gram of fat when burned or metabolized releases about 9 food calories (37 kJ = 8.8 kcal). Fat_sentence_85

Fats are also sources of essential fatty acids, an important dietary requirement. Fat_sentence_86

Vitamins A, D, E, and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats. Fat_sentence_87

Fats play a vital role in maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. Fat_sentence_88

Fat also serves as a useful buffer against a host of diseases. Fat_sentence_89

When a particular substance, whether chemical or biotic, reaches unsafe levels in the bloodstream, the body can effectively dilute—or at least maintain equilibrium of—the offending substances by storing it in new fat tissue. Fat_sentence_90

This helps to protect vital organs, until such time as the offending substances can be metabolized or removed from the body by such means as excretion, urination, accidental or intentional bloodletting, sebum excretion, and hair growth. Fat_sentence_91

Adipose tissue Fat_section_16

In animals, adipose tissue, or fatty tissue is the body's means of storing metabolic energy over extended periods of time. Fat_sentence_92

Adipocytes (fat cells) store fat derived from the diet and from liver metabolism. Fat_sentence_93

Under energy stress these cells may degrade their stored fat to supply fatty acids and also glycerol to the circulation. Fat_sentence_94

These metabolic activities are regulated by several hormones (e.g., insulin, glucagon and epinephrine). Fat_sentence_95

Adipose tissue also secretes the hormone leptin. Fat_sentence_96

The location of the tissue determines its metabolic profile: visceral fat is located within the abdominal wall (i.e., beneath the wall of abdominal muscle) whereas subcutaneous fat is located beneath the skin (and includes fat that is located in the abdominal area beneath the skin but above the abdominal muscle wall). Fat_sentence_97

Visceral fat was recently discovered to be a significant producer of signaling chemicals (i.e., hormones), among which several are involved in inflammatory tissue responses. Fat_sentence_98

One of these is resistin which has been linked to obesity, insulin resistance, and Type 2 diabetes. Fat_sentence_99

This latter result is currently controversial, and there have been reputable studies supporting all sides on the issue. Fat_sentence_100

Production and processing Fat_section_17

A variety of chemical and physical techniques are used for the production and processing of fats, both industrially and in cottage or home settings. Fat_sentence_101

They include: Fat_sentence_102

Fat_unordered_list_3

Nutritional and health aspects Fat_section_18

The benefits and risks of various amounts and types of dietary fats have been the object of much study, and are still highly controversial topics. Fat_sentence_103

Essential fatty acids Fat_section_19

There are two essential fatty acids (EFAs) in human nutrition: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid). Fat_sentence_104

Other lipids needed by the body can be synthesized from these and other fats. Fat_sentence_105

Saturated vs. unsaturated fats Fat_section_20

Different foods contain different amounts of fat with different proportions of saturated and unsaturated fatty acids. Fat_sentence_106

Some animal products, like beef and dairy products made with whole or reduced fat milk like yogurt, ice cream, cheese and butter have mostly saturated fatty acids (and some have significant contents of dietary cholesterol). Fat_sentence_107

Other animal products, like pork, poultry, eggs, and seafood have mostly unsaturated fats. Fat_sentence_108

Industrialized baked goods may use fats with high unsaturated fat contents as well, especially those containing partially partially hydrogenated oils, and processed foods that are deep-fried in hydrogenated oil are high in saturated fat content.. Fat_sentence_109

Plants and fish oil generally contain a higher proportion of unsaturated acids, although there are exceptions such as coconut oil and palm kernel oil. Fat_sentence_110

Foods containing unsaturated fats include avocado, nuts, olive oils, and vegetable oils such as canola. Fat_sentence_111

Fat_table_general_1

Saturated esterified fatty acids as percentage of total fatFat_table_caption_1
FoodFat_header_cell_1_0_0 Lauric acidFat_header_cell_1_0_1 Myristic acidFat_header_cell_1_0_2 Palmitic acidFat_header_cell_1_0_3 Stearic acidFat_header_cell_1_0_4
Coconut oilFat_cell_1_1_0 47%Fat_cell_1_1_1 18%Fat_cell_1_1_2 9%Fat_cell_1_1_3 3%Fat_cell_1_1_4
Palm kernel oilFat_cell_1_2_0 48%Fat_cell_1_2_1 1%Fat_cell_1_2_2 44%Fat_cell_1_2_3 5%Fat_cell_1_2_4
ButterFat_cell_1_3_0 3%Fat_cell_1_3_1 11%Fat_cell_1_3_2 29%Fat_cell_1_3_3 13%Fat_cell_1_3_4
Ground beefFat_cell_1_4_0 0%Fat_cell_1_4_1 4%Fat_cell_1_4_2 26%Fat_cell_1_4_3 15%Fat_cell_1_4_4
SalmonFat_cell_1_5_0 0%Fat_cell_1_5_1 1%Fat_cell_1_5_2 29%Fat_cell_1_5_3 3%Fat_cell_1_5_4
Egg yolksFat_cell_1_6_0 0%Fat_cell_1_6_1 0.3%Fat_cell_1_6_2 27%Fat_cell_1_6_3 10%Fat_cell_1_6_4
CashewsFat_cell_1_7_0 2%Fat_cell_1_7_1 1%Fat_cell_1_7_2 10%Fat_cell_1_7_3 7%Fat_cell_1_7_4
Soybean oilFat_cell_1_8_0 0%Fat_cell_1_8_1 0%Fat_cell_1_8_2 11%Fat_cell_1_8_3 4%Fat_cell_1_8_4

Many careful studies have found that replacing saturated fats with cis unsaturated fats in the diet reduces risk of risks of cardiovascular diseases, diabetes, or death. Fat_sentence_112

These studies prompted many medical organizations and public health departments, including the World Health Organization, to officially issue that advice. Fat_sentence_113

Some countries with such recommendations include: Fat_sentence_114

Fat_unordered_list_4

  • United KingdomFat_item_4_34
  • United StatesFat_item_4_35
  • IndiaFat_item_4_36
  • CanadaFat_item_4_37
  • AustraliaFat_item_4_38
  • SingaporeFat_item_4_39
  • New ZealandFat_item_4_40
  • Hong KongFat_item_4_41

A 2004 review concluded that "no lower safe limit of specific saturated fatty acid intakes has been identified" and recommended that the influence of varying saturated fatty acid intakes against a background of different individual lifestyles and genetic backgrounds should be the focus in future studies. Fat_sentence_115

This advice is often oversimplified by labeling the two kinds of fats as bad fats and good fats, respectively. Fat_sentence_116

However, since the fats and oils in most natural and traditionally processed foods contain both unsaturated and saturated fatty acids, the complete exclusion of saturated fat is unrealistic and possibly unwise. Fat_sentence_117

For instance, some foods rich in saturated fat, such as coconut and palm oil, are an important source of cheap dietary calories for a large fraction of the population in developing countries. Fat_sentence_118

Concerns were also expressed at a 2010 conference of the American Dietetic Association that a blanket recommendation to avoid saturated fats could drive people to also reduce the amount of polyunsaturated fats, which may have health benefits, and/or replace fats by refined carbohydrates — which carry a high risk of obesity and heart disease. Fat_sentence_119

For these reasons, the United States Food and Drug Administration (FDA), for example, does not advise the complete elimination of saturated fat, but only recommends that it does not exceed 30% of one's daily caloric intake. Fat_sentence_120

A 2003 report by the World Health Organization and the Food and Agriculture Organization (FAO) recommends limiting the saturated fatty acids to less than 10% of daily energy intake and less than 7% for high-risk groups. Fat_sentence_121

A general 7% limit was recommended also by the American Heart Association in 2006. Fat_sentence_122

The WHO/FAO report also recommended replacing fats so as to reduce the content of myristic and palmitic acids, specifically. Fat_sentence_123

The so-called Mediterranean diet, prevalent in many countries in the Mediterranean Sea area, includes more total fat than the diet of Northern European countries, but most of it is in the form of unsaturated fatty acids (specifically, monounsaturated and omega-3) from olive oil and fish, vegetables, and certain meats like lamb, while consumption of saturated fat is minimal in comparison. Fat_sentence_124

A 2017 review found evidence that a Mediterranean-style diet could reduce the risk of cardiovascular diseases, overall cancer incidence, neurodegenerative diseases, diabetes, and mortality rate. Fat_sentence_125

A 2018 review showed that a Mediterranean-like diet may improve overall health status, such as reduced risk of non-communicable diseases. Fat_sentence_126

It also may reduce the social and economic costs of diet-related illnesses. Fat_sentence_127

A small number of contemporary reviews have challenged this negative view of saturated fats. Fat_sentence_128

For example, an evaluation of evidence from 1966-1973 of the observed health impact of replacing dietary saturated fat with linoleic acid found that it increased rates of death from all causes, coronary heart disease, and cardiovascular disease. Fat_sentence_129

These studies have been disputed by many scientists, and the consensus in the medical community is that saturated fat and cardiovascular disease are closely related. Fat_sentence_130

Still, these discordant studies fueled debate over the merits of substituting polyunsaturated fats for saturated fats. Fat_sentence_131

Cardiovascular disease Fat_section_21

Main article: Saturated fat and cardiovascular disease Fat_sentence_132

The effect of saturated fat on cardiovascular disease has been extensively studied. Fat_sentence_133

The general consensus is that there is evidence of moderate-quality of a strong, consistent, and graded relationship between saturated fat intake, blood cholesterol levels, and the incidence of cardiovascular disease. Fat_sentence_134

The relationships are accepted as causal, including by many government and medical organizations. Fat_sentence_135

A 2017 review by the American Heart Association estimated that replacement of saturated fat with polyunsaturated fat in the American diet could reduce the risk of cardiovascular diseases by 30%. Fat_sentence_136

The consumption of saturated fat is generally considered a risk factor for dyslipidemia — abnormal blood lipid levels, including high total cholesterol, high levels of triglycerides, high levels of low-density lipoprotein (LDL, "bad" cholesterol) or low levels of high-density lipoprotein (HDL, "good" cholesterol). Fat_sentence_137

These parameters in turn are believed to be risk indicators for some types of cardiovascular disease. Fat_sentence_138

These effects were observed in children too. Fat_sentence_139

Several meta-analyses (reviews and consolidations of multiple previously published experimental studies) have confirmed a significant relationship between saturated fat and high serum cholesterol levels, which in turn have been claimed to have a causal relation with increased risk of cardiovascular disease (the so-called lipid hypothesis). Fat_sentence_140

However, high cholesterol may be caused by many factors. Fat_sentence_141

Other indicators, such as high LDL/HDL ratio, have proved to be more predictive. Fat_sentence_142

In a study of myocardial infarction in 52 countries, the ApoB/ApoA1 (related to LDL and HDL, respectively) ratio was the strongest predictor of CVD among all risk factors. Fat_sentence_143

There are other pathways involving obesity, triglyceride levels, insulin sensitivity, endothelial function, and thrombogenicity, among others, that play a role in CVD, although it seems, in the absence of an adverse blood lipid profile, the other known risk factors have only a weak atherogenic effect. Fat_sentence_144

Different saturated fatty acids have differing effects on various lipid levels. Fat_sentence_145

Cancer Fat_section_22

The evidence for a relation between saturated fat intake and cancer is significantly weaker, and there does not seem to be a clear medical consensus about it. Fat_sentence_146

Fat_unordered_list_5

Bones Fat_section_23

Various animal studies have indicated that the intake of saturated fat has a negative effect on effects on the mineral density of bones. Fat_sentence_147

One study suggested that men may be particularly vulnerable. Fat_sentence_148

Disposition and overall health Fat_section_24

Studies have shown that substituting monounsaturated fatty acids for saturated ones is associated with increased daily physical activity and resting energy expenditure. Fat_sentence_149

More physical activity, less anger, and less irritability were associated with a higher-oleic acid diet than one of a palmitic acid diet. Fat_sentence_150

Monounsaturated vs. polyunsaturated fat Fat_section_25

Assuming given that unsaturated fatty acids (UFAs) are generally healthier than saturated ones (SFAs), another question that has gained attention in recent decades is the risks and benefits of monounsaturated fatty acids (MUFAs, with a single double bond) versus polyunsaturated fatty acids (PUFAs, with two or more double bonds). Fat_sentence_151

The most common fatty acids in human diet are unsaturated or mono-unsaturated. Fat_sentence_152

Monounsaturated fats are found in animal flesh such as red meat, whole milk products, nuts, and high fat fruits such as olives and avocados. Fat_sentence_153

Algal oil is about 92% monounsaturated fat. Fat_sentence_154

Olive oil is about 75% monounsaturated fat. Fat_sentence_155

The high oleic variety sunflower oil contains at least 70% monounsaturated fat. Fat_sentence_156

Canola oil and cashews are both about 58% monounsaturated fat. Fat_sentence_157

Tallow (beef fat) is about 50% monounsaturated fat. Fat_sentence_158

and lard is about 40% monounsaturated fat. Fat_sentence_159

Other sources include hazelnut, avocado oil, macadamia nut oil, grapeseed oil, groundnut oil (peanut oil), sesame oil, corn oil, popcorn, whole grain wheat, cereal, oatmeal, almond oil, sunflower oil, hemp oil, and tea-oil Camellia. Fat_sentence_160

Polyunsaturated fatty acids can be found mostly in nuts, seeds, fish, seed oils, and oysters. Fat_sentence_161

Food sources of polyunsaturated fats include: Fat_sentence_162

Fat_table_general_2

Food source (100g)Fat_header_cell_2_0_0 Polyunsaturated fat (g)Fat_header_cell_2_0_1
WalnutsFat_cell_2_1_0 47Fat_cell_2_1_1
Canola OilFat_cell_2_2_0 34Fat_cell_2_2_1
Sunflower seedsFat_cell_2_3_0 33Fat_cell_2_3_1
Sesame SeedsFat_cell_2_4_0 26Fat_cell_2_4_1
Chia SeedsFat_cell_2_5_0 23.7Fat_cell_2_5_1
Unsalted PeanutsFat_cell_2_6_0 16Fat_cell_2_6_1
Peanut ButterFat_cell_2_7_0 14.2Fat_cell_2_7_1
Avocado OilFat_cell_2_8_0 13.5Fat_cell_2_8_1
Olive OilFat_cell_2_9_0 11Fat_cell_2_9_1
Safflower OilFat_cell_2_10_0 12.82Fat_cell_2_10_1
SeaweedFat_cell_2_11_0 11Fat_cell_2_11_1
SardinesFat_cell_2_12_0 5Fat_cell_2_12_1
SoybeansFat_cell_2_13_0 7Fat_cell_2_13_1
TunaFat_cell_2_14_0 14Fat_cell_2_14_1
Wild SalmonFat_cell_2_15_0 17.3Fat_cell_2_15_1
Whole Grain WheatFat_cell_2_16_0 9.7Fat_cell_2_16_1

Cardiovascular disease Fat_section_26

Studies have given conflicting indications about the effect of MUFA/PUFA intake and cardiovascular disease. Fat_sentence_163

Although PUFAs seem to protect against cardiac arrhythmias, a study concluded that PUFA intake is positively associated with coronary atherosclerosis progression in a group of post-menopauseal women, whereas MUFA intake is not. Fat_sentence_164

This probably is an indication of the greater vulnerability of polyunsaturated fats to lipid peroxidation, against which vitamin E has been shown to be protective. Fat_sentence_165

Insulin resistance and sensitivity Fat_section_27

MUFAs (especially oleic acid) have been found to lower the incidence of insulin resistance PUFAs (especially large amounts of arachidonic acid) and SFAs (such as arachidic acid) increased it. Fat_sentence_166

These ratios can be indexed in the phospholipids of human skeletal muscle and in other tissues as well. Fat_sentence_167

This relationship between dietary fats and insulin resistance is presumed secondary to the relationship between insulin resistance and inflammation, which is partially modulated by dietary fat ratios (Omega-3/6/9) with both omega 3 and 9 thought to be anti-inflammatory, and omega 6 pro-inflammatory (as well as by numerous other dietary components, particularly polyphenols and exercise, with both of these anti-inflammatory). Fat_sentence_168

Although both pro- and anti-inflammatory types of fat are biologically necessary, fat dietary ratios in most US diets are skewed towards Omega 6, with subsequent disinhibition of inflammation and potentiation of insulin resistance. Fat_sentence_169

But this is contrary to the suggestion of more recent studies, in which polyunsaturated fats are shown as protective against insulin resistance. Fat_sentence_170

The large scale KANWU study found that increasing MUFA and decreasing SFA intake could improve insulin sensitivity, but only when the overall fat intake of the diet was low. Fat_sentence_171

However, some MUFAs may promote insulin resistance (like the SFAs), whereas PUFAs may protect against it. Fat_sentence_172

Cancer Fat_section_28

Levels of oleic acid along with other MUFAs in red blood cell membranes were positively associated with breast cancer risk. Fat_sentence_173

The saturation index (SI) of the same membranes was inversely associated with breast cancer risk. Fat_sentence_174

MUFAs and low SI in erythrocyte membranes are predictors of postmenopausal breast cancer. Fat_sentence_175

Both of these variables depend on the activity of the enzyme delta-9 desaturase (Δ9-d). Fat_sentence_176

Results from observational clinical trials on PUFA intake and cancer have been inconsistent and vary by numerous factors of cancer incidence, including gender and genetic risk. Fat_sentence_177

Some studies have shown associations between higher intakes and/or blood levels of omega-3 PUFAs and a decreased risk of certain cancers, including breast and colorectal cancer, while other studies found no associations with cancer risk. Fat_sentence_178

Pregnancy disorders Fat_section_29

Polyunsaturated fat supplementation was found to have no effect on the incidence of pregnancy-related disorders, such as hypertension or preeclampsia, but may increase the length of gestation slightly and decreased the incidence of early premature births. Fat_sentence_179

Expert panels in the United States and Europe recommend that pregnant and lactating women consume higher amounts of polyunsaturated fats than the general population to enhance the DHA status of the fetus and newborn. Fat_sentence_180

"Cis fat" vs. "trans fat" Fat_section_30

In nature, unsaturated fatty acids generally have double bonds in cis configuration (with the adjacent C–C bonds on the same side) as opposed to trans. Fat_sentence_181

Nevertheless, trans fatty acids (TFAs) occur in small amounts in meat and milk of ruminants (such as cattle and sheep), typically 2–5% of total fat. Fat_sentence_182

Natural TFAs, which include conjugated linoleic acid (CLA) and vaccenic acid, originate in the rumen of these animals. Fat_sentence_183

CLA has two double bonds, one in the cis configuration and one in trans, which makes it simultaneously a cis- and a trans-fatty acid. Fat_sentence_184

Fat_table_general_3

Trans fat contents in various natural and traditionally processed foods, in g per 100 gFat_table_caption_3
Food typeFat_header_cell_3_0_0 Trans fat contentFat_header_cell_3_0_1
butterFat_cell_3_1_0 2g to 7 gFat_cell_3_1_1
whole milkFat_cell_3_2_0 0.07g to 0.1 gFat_cell_3_2_1
animal fatFat_cell_3_3_0 0g to 5 gFat_cell_3_3_1
ground beefFat_cell_3_4_0 1 gFat_cell_3_4_1

Concerns about trans fatty acids in human diet were raised when they were found to be an unintentional byproduct of the partial hydrogenation of vegetable and fish oils. Fat_sentence_185

While these trans fatty acids (popularly called "trans fats") are edible, they have been implicated in many health problems. Fat_sentence_186

The hydrogenation process, invented and patented by Wilhelm Normann in 1902, made it possible to turn relatively cheap liquid fats such as whale or fish oil into more solid fats and to extend their shelf-life by preventing rancidification. Fat_sentence_187

(The source fat and the process were initially kept secret to avoid consumer distaste.) Fat_sentence_188

This process was widely adopted by the food industry already in the early 1900s; first for the production of margarine, a replacement for butter and shortening, and eventually for various other fats used in snack food, packaged baked goods, and deep fried products. Fat_sentence_189

Full hydrogenation of a fat or oil produces a fully saturated fat. Fat_sentence_190

However, hydrogenation generally was interrupted before completion, to yield a fat product with specific melting point, hardness, and other properties. Fat_sentence_191

Unfortunately, partial hydrogenation turns some of the cis double bonds into trans bonds by an isomerization reaction. Fat_sentence_192

The trans configuration is favored because it is the lower energy form. Fat_sentence_193

This side reaction accounts for most of the trans fatty acids consumed today, by far. Fat_sentence_194

An analysis of some industrialized foods in 2006 found up to 30% "trans fats" in artificial shortening, 10% in breads and cake products, 8% in cookies and crackers, 4% in salty snacks, 7% in cake frostings and sweets, and 26% in margarine and other processed spreads. Fat_sentence_195

Another 2010 analysis however found only 0.2% of trans fats in margarine and other processed spreads. Fat_sentence_196

Up to 45% of the total fat in those foods containing man-made trans fats formed by partially hydrogenating plant fats may be trans fat. Fat_sentence_197

Baking shortenings, unless reformulated, contain around 30% trans fats compared to their total fats. Fat_sentence_198

High-fat dairy products such as butter contain about 4%. Fat_sentence_199

Margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight, but some reformulated ones are less than 1% trans fat. Fat_sentence_200

High levels of TFAs have been recorded in popular "fast food" meals. Fat_sentence_201

An analysis of samples of McDonald's French fries collected in 2004 and 2005 found that fries served in New York City contained twice as much trans fat as in Hungary, and 28 times as much as in Denmark, where trans fats are restricted. Fat_sentence_202

For Kentucky Fried Chicken products, the pattern was reversed: the Hungarian product containing twice the trans fat of the New York product. Fat_sentence_203

Even within the United States there was variation, with fries in New York containing 30% more trans fat than those from Atlanta. Fat_sentence_204

Cardiovascular disease Fat_section_31

Numerous studies have found that consumption of TFAs increases risk of cardiovascular disease. Fat_sentence_205

The Harvard School of Public Health advises that replacing TFAs and saturated fats with cis monounsaturated and polyunsaturated fats is beneficial for health. Fat_sentence_206

Consuming trans fats has been shown to increase the risk of coronary artery disease in part by raising levels of low-density lipoprotein (LDL, often termed "bad cholesterol"), lowering levels of high-density lipoprotein (HDL, often termed "good cholesterol"), increasing triglycerides in the bloodstream and promoting systemic inflammation. Fat_sentence_207

The primary health risk identified for trans fat consumption is an elevated risk of coronary artery disease (CAD). Fat_sentence_208

A 1994 study estimated that over 30,000 cardiac deaths per year in the United States are attributable to the consumption of trans fats. Fat_sentence_209

By 2006 upper estimates of 100,000 deaths were suggested. Fat_sentence_210

A comprehensive review of studies of trans fats published in 2006 in the New England Journal of Medicine reports a strong and reliable connection between trans fat consumption and CAD, concluding that "On a per-calorie basis, trans fats appear to increase the risk of CAD more than any other macronutrient, conferring a substantially increased risk at low levels of consumption (1 to 3% of total energy intake)". Fat_sentence_211

The major evidence for the effect of trans fat on CAD comes from the Nurses' Health Study – a cohort study that has been following 120,000 female nurses since its inception in 1976. Fat_sentence_212

In this study, Hu and colleagues analyzed data from 900 coronary events from the study's population during 14 years of followup. Fat_sentence_213

He determined that a nurse's CAD risk roughly doubled (relative risk of 1.93, CI: 1.43 to 2.61) for each 2% increase in trans fat calories consumed (instead of carbohydrate calories). Fat_sentence_214

By contrast, for each 5% increase in saturated fat calories (instead of carbohydrate calories) there was a 17% increase in risk (relative risk of 1.17, CI: 0.97 to 1.41). Fat_sentence_215

"The replacement of saturated fat or trans unsaturated fat by cis (unhydrogenated) unsaturated fats was associated with larger reductions in risk than an isocaloric replacement by carbohydrates." Fat_sentence_216

Hu also reports on the benefits of reducing trans fat consumption. Fat_sentence_217

Replacing 2% of food energy from trans fat with non-trans unsaturated fats more than halves the risk of CAD (53%). Fat_sentence_218

By comparison, replacing a larger 5% of food energy from saturated fat with non-trans unsaturated fats reduces the risk of CAD by 43%. Fat_sentence_219

Another study considered deaths due to CAD, with consumption of trans fats being linked to an increase in mortality, and consumption of polyunsaturated fats being linked to a decrease in mortality. Fat_sentence_220

Trans fat has been found to act like saturated in raising the blood level of LDL ("bad cholesterol"); but, unlike saturated fat, it also decreases levels of HDL ("good cholesterol"). Fat_sentence_221

The net increase in LDL/HDL ratio with trans fat, a widely accepted indicator of risk for coronary artery, is approximately double that due to saturated fat. Fat_sentence_222

One randomized crossover study published in 2003 comparing the effect of eating a meal on blood lipids of (relatively) cis and trans fat rich meals showed that cholesteryl ester transfer (CET) was 28% higher after the trans meal than after the cis meal and that lipoprotein concentrations were enriched in apolipoprotein(a) after the trans meals. Fat_sentence_223

The citokyne test is a potentially more reliable indicator of CAD risk, although is still being studied. Fat_sentence_224

A study of over 700 nurses showed that those in the highest quartile of trans fat consumption had blood levels of C-reactive protein (CRP) that were 73% higher than those in the lowest quartile. Fat_sentence_225

Breast feeding Fat_section_32

It has been established that trans fats in human breast milk fluctuate with maternal consumption of trans fat, and that the amount of trans fats in the bloodstream of breastfed infants fluctuates with the amounts found in their milk. Fat_sentence_226

In 1999, reported percentages of trans fats (compared to total fats) in human milk ranged from 1% in Spain, 2% in France, 4% in Germany, and 7% in Canada and the United States. Fat_sentence_227

Other health risks Fat_section_33

There are suggestions that the negative consequences of trans fat consumption go beyond the cardiovascular risk. Fat_sentence_228

In general, there is much less scientific consensus asserting that eating trans fat specifically increases the risk of other chronic health problems: Fat_sentence_229

Fat_unordered_list_6

  • Alzheimer's Disease: A study published in Archives of Neurology in February 2003 suggested that the intake of both trans fats and saturated fats promote the development of Alzheimer disease, although not confirmed in an animal model. It has been found that trans fats impaired memory and learning in middle-age rats. The trans-fat eating rats' brains had fewer proteins critical to healthy neurological function. Inflammation in and around the hippocampus, the part of the brain responsible for learning and memory. These are the exact types of changes normally seen at the onset of Alzheimer's, but seen after six weeks, even though the rats were still young.Fat_item_6_46
  • Cancer: There is no scientific consensus that consuming trans fats significantly increases cancer risks across the board. The American Cancer Society states that a relationship between trans fats and cancer "has not been determined." One study has found a positive connection between trans fat and prostate cancer. However, a larger study found a correlation between trans fats and a significant decrease in high-grade prostate cancer. An increased intake of trans fatty acids may raise the risk of breast cancer by 75%, suggest the results from the French part of the European Prospective Investigation into Cancer and Nutrition.Fat_item_6_47
  • Diabetes: There is a growing concern that the risk of type 2 diabetes increases with trans fat consumption. However, consensus has not been reached. For example, one study found that risk is higher for those in the highest quartile of trans fat consumption. Another study has found no diabetes risk once other factors such as total fat intake and BMI were accounted for.Fat_item_6_48
  • Obesity: Research indicates that trans fat may increase weight gain and abdominal fat, despite a similar caloric intake. A 6-year experiment revealed that monkeys fed a trans fat diet gained 7.2% of their body weight, as compared to 1.8% for monkeys on a mono-unsaturated fat diet. Although obesity is frequently linked to trans fat in the popular media, this is generally in the context of eating too many calories; there is not a strong scientific consensus connecting trans fat and obesity, although the 6-year experiment did find such a link, concluding that "under controlled feeding conditions, long-term TFA consumption was an independent factor in weight gain. TFAs enhanced intra-abdominal deposition of fat, even in the absence of caloric excess, and were associated with insulin resistance, with evidence that there is impaired post-insulin receptor binding signal transduction."Fat_item_6_49
  • Infertility in women: One 2007 study found, "Each 2% increase in the intake of energy from trans unsaturated fats, as opposed to that from carbohydrates, was associated with a 73% greater risk of ovulatory infertility...".Fat_item_6_50
  • Major depressive disorder: Spanish researchers analysed the diets of 12,059 people over six years and found that those who ate the most trans fats had a 48 per cent higher risk of depression than those who did not eat trans fats. One mechanism may be trans-fats' substitution for docosahexaenoic acid (DHA) levels in the orbitofrontal cortex (OFC). Very high intake of trans-fatty acids (43% of total fat) in mice from 2 to 16 months of age was associated with lowered DHA levels in the brain (p=0.001). When the brains of 15 major depressive subjects who had committed suicide were examined post-mortem and compared against 27 age-matched controls, the suicidal brains were found to have 16% less (male average) to 32% less (female average) DHA in the OFC. The OFC controls reward, reward expectation, and empathy (all of which are reduced in depressive mood disorders) and regulates the limbic system.Fat_item_6_51
  • Behavioral irritability and aggression: a 2012 observational analysis of subjects of an earlier study found a strong relation between dietary trans fat acids and self-reported behavioral aggression and irritability, suggesting but not establishing causality.Fat_item_6_52
  • Diminished memory: In a 2015 article, researchers re-analyzing results from the 1999-2005 UCSD Statin Study argue that "greater dietary trans fatty acid consumption is linked to worse word memory in adults during years of high productivity, adults age <45".Fat_item_6_53
  • Acne: According to a 2015 study, trans fats are one of several components of Western pattern diets which promote acne, along with carbohydrates with high glycemic load such as refined sugars or refined starches, milk and dairy products, and saturated fats, while omega-3 fatty acids, which reduce acne, are deficient in Western pattern diets.Fat_item_6_54

Biochemical mechanisms Fat_section_34

The exact biochemical process by which trans fats produce specific health problems are a topic of continuing research. Fat_sentence_230

Intake of dietary trans fat perturbs the body's ability to metabolize essential fatty acids (EFAs, including Omega-3) leading to changes in the phospholipid fatty acid composition of the arterial walls, thereby raising risk of coronary artery disease. Fat_sentence_231

Trans double bonds are claimed to induce a linear conformation to the molecule, favoring its rigid packing as in plaque formation. Fat_sentence_232

The geometry of the cis double bond, in contrast, is claimed to create a bend in the molecule, thereby precluding rigid formations.. Fat_sentence_233

While the mechanisms through which trans fatty acids contribute to coronary artery disease are fairly well understood, the mechanism for their effects on diabetes is still under investigation. Fat_sentence_234

They may impair the metabolism of long-chain polyunsaturated fatty acids (LCPUFAs). Fat_sentence_235

However, maternal pregnancy trans fatty acid intake has been inversely associated with LCPUFAs levels in infants at birth thought to underlie the positive association between breastfeeding and intelligence. Fat_sentence_236

Trans fats are processed by the liver differently than other fats. Fat_sentence_237

They may cause liver dysfunction by interfering with delta 6 desaturase, an enzyme involved in converting essential fatty acids to arachidonic acid and prostaglandins, both of which are important to the functioning of cells. Fat_sentence_238

Natural "trans fats" in dairy products Fat_section_35

Some trans fatty acids occur in natural fats and traditionally processed foods. Fat_sentence_239

Vaccenic acid occurs in breast milk, and some isomers of conjugated linoleic acid (CLA) are found in meat and dairy products from ruminants. Fat_sentence_240

Butter, for example, contains about 3% trans fat. Fat_sentence_241

The US National Dairy Council has asserted that the trans fats present in animal foods are of a different type than those in partially hydrogenated oils, and do not appear to exhibit the same negative effects. Fat_sentence_242

While a recent scientific review agrees with the conclusion (stating that "the sum of the current evidence suggests that the Public health implications of consuming trans fats from ruminant products are relatively limited"), it cautions that this may be due to the low consumption of trans fats from animal sources compared to artificial ones. Fat_sentence_243

More recent inquiry (independent of the dairy industry) has found in a 2008 Dutch meta-analysis that all trans fats, regardless of natural or artificial origin equally raise LDL and lower HDL levels. Fat_sentence_244

Other studies though have shown different results when it comes to animal based trans fats like conjugated linoleic acid (CLA). Fat_sentence_245

Although CLA is known for its anticancer properties, researchers have also found that the cis-9, trans-11 form of CLA can reduce the risk for cardiovascular disease and help fight inflammation. Fat_sentence_246

Two Canadian studies have shown that vaccenic acid, a TFA that naturally occurs in dairy products, could be beneficial compared to hydrogenated vegetable shortening, or a mixture of pork lard and soy fat, by lowering total LDL and triglyceride levels. Fat_sentence_247

A study by the US Department of Agriculture showed that vaccenic acid raises both HDL and LDL cholesterol, whereas industrial trans fats only raise LDL with no beneficial effect on HDL. Fat_sentence_248

Official recommendations Fat_section_36

In light of recognized evidence and scientific agreement, nutritional authorities consider all trans fats equally harmful for health and recommend that their consumption be reduced to trace amounts. Fat_sentence_249

The World Health Organization recommended that trans fats make up no more than 0.9% of a person's diet in 2003 and, in 2018, introduced a 6-step guide to eliminate industrially-produced trans-fatty acids from the global food supply. Fat_sentence_250

The National Academy of Sciences (NAS) advises the United States and Canadian governments on nutritional science for use in public policy and product labeling programs. Fat_sentence_251

Their 2002 Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids contains their findings and recommendations regarding consumption of trans fat (). Fat_sentence_252

Their recommendations are based on two key facts. Fat_sentence_253

First, "trans fatty acids are not essential and provide no known benefit to human health", whether of animal or plant origin. Fat_sentence_254

Second, given their documented effects on the LDL/HDL ratio, the NAS concluded "that dietary trans fatty acids are more deleterious with respect to coronary artery disease than saturated fatty acids". Fat_sentence_255

A 2006 review published in the New England Journal of Medicine (NEJM) that states "from a nutritional standpoint, the consumption of trans fatty acids results in considerable potential harm but no apparent benefit." Fat_sentence_256

Because of these facts and concerns, the NAS has concluded there is no safe level of trans fat consumption. Fat_sentence_257

There is no adequate level, recommended daily amount or tolerable upper limit for trans fats. Fat_sentence_258

This is because any incremental increase in trans fat intake increases the risk of coronary artery disease. Fat_sentence_259

Despite this concern, the NAS dietary recommendations have not included eliminating trans fat from the diet. Fat_sentence_260

This is because trans fat is naturally present in many animal foods in trace quantities, and thus its removal from ordinary diets might introduce undesirable side effects and nutritional imbalances. Fat_sentence_261

The NAS has, thus, "recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet". Fat_sentence_262

Like the NAS, the World Health Organization has tried to balance public health goals with a practical level of trans fat consumption, recommending in 2003 that trans fats be limited to less than 1% of overall energy intake. Fat_sentence_263

Regulatory action Fat_section_37

Main article: Trans fat regulation Fat_sentence_264

In the last few decades, there has been substantial amount of regulation in many countries, limiting trans fat contents of industrialized and commercial food products. Fat_sentence_265

Alternatives to hydrogenation Fat_section_38

In recent years, the negative public image and strict regulations have driven many fat processing industries to replace partial hydrogenation by fat interesterification, a process that chemically scrambles the fatty acids among a mix of triglycerides. Fat_sentence_266

When applied to a suitable bend of oils and saturated fats, possibly followed by separation of unwanted solid or liquid triglycerides, this process can achieve results similar to those of partial hydrogenation without affecting the fatty acids themselves; in particular, without creating any new "trans fat". Fat_sentence_267

Researchers at the United States Department of Agriculture have investigated whether hydrogenation can be achieved without the side effect of trans fat production. Fat_sentence_268

They varied the pressure under which the chemical reaction was conducted – applying 1400  kPa (200  psi) of pressure to soybean oil in a 2-liter vessel while heating it to between 140 °C and 170 °C. Fat_sentence_269

The standard 140 kPa (20 psi) process of hydrogenation produces a product of about 40% trans fatty acid by weight, compared to about 17% using the high-pressure method. Fat_sentence_270

Blended with unhydrogenated liquid soybean oil, the high-pressure-processed oil produced margarine containing 5 to 6% trans fat. Fat_sentence_271

Based on current U.S. labeling requirements (see below), the manufacturer could claim the product was free of trans fat. Fat_sentence_272

The level of trans fat may also be altered by modification of the temperature and the length of time during hydrogenation. Fat_sentence_273

A University of Guelph research group has found a way to mix oils (such as olive, soybean, and canola), water, monoglycerides, and fatty acids to form a "cooking fat" that acts the same way as trans and saturated fats. Fat_sentence_274

Omega-three and omega-six fatty acids Fat_section_39

Main article: Omega-3 fatty acid Fat_sentence_275

Main article: Omega-6 fatty acid Fat_sentence_276

The ω−3 fatty acids have received substantial atterntion in recent years. Fat_sentence_277

In preliminary research, omega-3 fatty acids in algal oil, fish oil, fish and seafood have been shown to lower the risk of heart attacks. Fat_sentence_278

Other preliminary research indicates that omega-6 fatty acids in sunflower oil and safflower oil may also reduce the risk of cardiovascular disease. Fat_sentence_279

Among omega-3 fatty acids, neither long-chain nor short-chain forms were consistently associated with breast cancer risk. Fat_sentence_280

High levels of docosahexaenoic acid (DHA), however, the most abundant omega-3 polyunsaturated fatty acid in erythrocyte (red blood cell) membranes, were associated with a reduced risk of breast cancer. Fat_sentence_281

The DHA obtained through the consumption of polyunsaturated fatty acids is positively associated with cognitive and behavioral performance. Fat_sentence_282

In addition DHA is vital for the grey matter structure of the human brain, as well as retinal stimulation and neurotransmission. Fat_sentence_283

Interesterification Fat_section_40

Some studies have investigated the health effects of insteresterified (IE) fats, by comparing diets with IE and non-IE fats with the same overall fatty acid composition. Fat_sentence_284

Several experimental studies in humans found no statistical difference on fasting blood lipids between a with large amounts of IE fat, having 25-40% C16:0 or C18:0 on the 2-position, and a similar diet with non-IE fat, having only 3-9% C16:0 or C18:0 on the 2-position. Fat_sentence_285

A negative result was obtained also in a study that compared the effects on blood cholesterol levels of an IE fat product mimicking cocoa butter and the real non-IE product. Fat_sentence_286

A 2007 study funded by the Malaysian Palm Oil Board claimed that replacing natural palm oil by other interesterified or partial hydrogenated fats caused adverse health effects, such as higher LDL/ HDL ratio and plasma glucose levels. Fat_sentence_287

However, these effects could be attributed to the higher percentage of saturated acids in the IE and partially hydrogenated fats, rather than to the IE process itself. Fat_sentence_288

Fat digestion and metabolism Fat_section_41

Main article: Lipid metabolism Fat_sentence_289

Fats are broken down in the healthy body to release their constituents, glycerol and fatty acids. Fat_sentence_290

Glycerol itself can be converted to glucose by the liver and so become a source of energy. Fat_sentence_291

Fats and other lipids are broken down in the body by enzymes called lipases produced in the pancreas. Fat_sentence_292

Many cell types can use either glucose or fatty acids as a source of energy for metabolism. Fat_sentence_293

In particular, heart and skeletal muscle prefer fatty acids. Fat_sentence_294

Despite long-standing assertions to the contrary, fatty acids can also be used as a source of fuel for brain cells through mitochondrial oxidation. Fat_sentence_295

See also Fat_section_42

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Fat.