FATTY ACIDS

IV. FATTY ACIDS

Fatty acids are any of several organic acids produced by the hydrolysis of neutral fat (134). Essential fatty acids, like essential amino acids, cannot be produced by the body and must be provided by diet. Essential fatty acids include linoleic acid (omega-6 family) and alpha-linolenic (omega-3 family). These two fatty acids are parent compounds for other biologically active long-chain polyunsaturated fatty acids (LCPUFAs). Linoleic acid can be converted to gamma-linolenic acid (GLA) and arachidonic acid (AA). Alpha- linolenic acid can be converted to docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) (135). These fatty acids are necessary for proper growth, maintenance, and functioning of the body. The LCPUFAs are major essential components of membrane phospholipids.

Of all nutrients, fat is most often linked with chronic diseases. Too much fat or the wrong kind of fat may raise the risks of heart disease, some types of cancer, and obesity. Research is ongoing as to the pros and cons of fatty acids and various diseases. Arachi- donic acid and DHA are present in human milk and support exists for adding these acids to formula milk for premature infants. Unexplained failure-to-thrive in infants has been found to be caused by a defect in the mitochondrial metabolism of fat. When low fat diets were given to these infants, improvements were shown and the infants caught up on growth factors. Researchers suspect that either because of genetics or diet, the fatty acid content in regular diets may be causing infants to lose their ability to metabolize fatty acids. Docosahexaenoic acid is depleted in pregnant and lactating women and supplementation may be desired to regain adequate DHA status (136). Women with high-risk pregnancies Of all nutrients, fat is most often linked with chronic diseases. Too much fat or the wrong kind of fat may raise the risks of heart disease, some types of cancer, and obesity. Research is ongoing as to the pros and cons of fatty acids and various diseases. Arachi- donic acid and DHA are present in human milk and support exists for adding these acids to formula milk for premature infants. Unexplained failure-to-thrive in infants has been found to be caused by a defect in the mitochondrial metabolism of fat. When low fat diets were given to these infants, improvements were shown and the infants caught up on growth factors. Researchers suspect that either because of genetics or diet, the fatty acid content in regular diets may be causing infants to lose their ability to metabolize fatty acids. Docosahexaenoic acid is depleted in pregnant and lactating women and supplementation may be desired to regain adequate DHA status (136). Women with high-risk pregnancies

Debates continue among professionals as to the role fat plays in breast and prostate cancer. Positive associations have been suggested but have not been supported by large prospective studies where confounding factors are minimized. There is strong evidence that some aspects of foods high in fat increase risk of prostate cancer. Further studies are required of specific dietary fatty acids and their relationship to various malignancies (139).

Over the last five years, there has been growing concern regarding trans fatty acids. Trans fatty acids are formed during the process of hydrogenation. This process of con- verting liquid oils into solid or semisolid fats dramatically changed the composition of the food supply. Growing numbers of metabolic studies and epidemiological studies are finding that trans fatty acids increase plasma concentrations of low-density-lipoprotein cholesterol and reduce concentrations of high-density-lipoprotein cholesterol relative to the parent natural fat (140). Debate continues regarding the extent of a public health con- cern related to trans fatty acids consumption. The American Society for Clinical Nutrition and the American Institute of Nutrition in their joint position paper on trans fatty acid were unable to conclude that intake of trans fatty acids were a risk factor for coronary heart disease. However, they did recommend that in order to achieve greatest cholesterol- lowering effects, fats that are sources of unsaturated fatty acids are preferred to fats rich in trans fatty acids. One’s primary objective for a healthier diet should be to reduce total fat to less than 30% and to reduce saturated fat to less than 10% of energy (141).

According to the Federal Commercial Codex, linoleic acid is the only fatty acid with monograph specifications. Linoleic acid (CAS: 60-33-3) is the major component in various vegetable oils including cottonseed, soybean, peanut, corn, sunflower seed, saf- flower, poppy seed, and linseed. This colorless to pale yellow oily liquid is easily oxidized by air. Although insoluble in water, it is freely soluble in ether, soluble in absolute alcohol and in chloroform. Linoleic acid can be mixed with dimethylformamide, fat solvents, and oils. Packaging and storage should be in tight containers (142).

Gas–liquid chromatography (GLC) is used for the analysis of fatty acids. This pre- ferred method of analysis provides very high resolution, high sensitivity, and very good reproducibility in quantitative analyses. The acid hydrolysis–packed column gas–chroma- tography method satisfies national labeling requirements for the determination of total fat and saturated fat for a large number of foods (143). High-performance liquid chromatogra- phy is currently being used for the isolation of specific fatty acid fractions and on a small scale. This type of analysis will pass GLC as technology advances and more highly resolu- tive capillary columns are developed. Sempore and Bezard provide a detailed history and discussion on the analysis of fatty acids (144).