Fat
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.
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.
[1] 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),[1] and free fatty acids, which are usually present in human diet in smaller amounts.
[4] The human body can produce the fat it requires from other food ingredients, except for a few essential fatty acids that must be included in the diet.
Under energy stress these cells may degrade their stored fat to supply fatty acids and also glycerol to the circulation.
In the intestine, following the secretion of lipases and bile, triglycerides are split into monoacylglycerol and free fatty acids in a process called lipolysis.
These are excreted from the cells and collected by the lymph system and transported to the large vessels near the heart before being mixed into the blood.
Special enzymes on the walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol.
Triglycerides, as major components of very-low-density lipoprotein (VLDL) and chylomicrons, play an important role in metabolism as energy sources and transporters of dietary fat.
[9] 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.
Some countries with such recommendations include: 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.
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.
[74] 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.
[81] These studies have been disputed by many scientists,[82] and the consensus in the medical community is that saturated fat and cardiovascular disease are closely related.
[87] 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.
[104] 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,[53][105] which in turn have been claimed to have a causal relation with increased risk of cardiovascular disease (the so-called lipid hypothesis).
[107] 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.
[108] 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.
[110] 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.
[119] Studies have shown that substituting monounsaturated fatty acids for saturated ones is associated with increased daily physical activity and resting energy expenditure.
[132][133][clarification needed] Levels of oleic acid along with other MUFAs in red blood cell membranes were positively associated with breast cancer risk.
[127] 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.
[137] Nevertheless, trans fatty acids (TFAs) occur in small amounts in meat and milk of ruminants (such as cattle and sheep),[138][139] typically 2–5% of total fat.
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.
[134] The DHA obtained through the consumption of polyunsaturated fatty acids is positively associated with cognitive and behavioral performance.
[143] In addition, DHA is vital for the grey matter structure of the human brain, as well as retinal stimulation and neurotransmission.
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.
[163][164][165][166] This may include dietary changes such as restriction of fat and carbohydrates (specifically fructose[165][167] and sugar-sweetened beverages[164]) and increased consumption of omega-3 fatty acids from algae, nuts, and seeds.
