Fatty Acids essential, omega-6, saturated and unsaturated, research and influence on health by Ray Sahelian, M.D.

A fatty acid is a carboxylic acid often with a long unbranched aliphatic tail (chain), which is either saturated or unsaturated. Carboxylic acids as short as butyric acid (4 carbon atoms) are considered to be fatty acids, while fatty acids derived from natural fats and oils may be assumed to have at least 8 carbon atoms, e.g. caprylic acid (octanoic acid). Most of the natural fatty acids have an even number of carbon atoms, because their biosynthesis involves acetyl-CoA, a coenzyme carrying a two-carbon-atom group.

Fatty Acids in Fish
Fatty acids found in fish can help in weight loss when combined with moderate exercise. The University of South Australia study found that daily doses of fish oil containing omega-3 fatty acids helped obese people burn off excess weight. The omega-3 found in fish oil increases fat-burning ability by improving the flow of blood to muscles during exercise/ The university's study monitored 68 overweight and obese people, divided into four groups, over three months. One group took small daily doses of fish oil and another was given sunflower oil with no other alteration to their normal diet. Both groups undertook moderate exercise programs of a 45-minute walk or run three times a week. Another two groups received either fish oil or sunflower oil but did no exercise. Those who took the fish oil doses and exercised lost an average of 2 kg (4.5 lb) over the three months. The groups that took sunflower oil, which does not contain omega-3 fatty acids, and exercised did not lose any weight. The two groups that did not exercise also lost no weight. Fish oil fatty acids include docosahexaenoic acid and EPA.
   Omega-3 fatty acids help boost brain functioning as well as cut the risk of stroke.

Fatty acid and depression
The imbalance of fatty acids in the typical American diet may be partly associated with the increase in heart disease and depression seen over the past century. Specifically, the more omega-6 fatty acids people have in their blood compared with omega-3 fatty acid levels, the more likely they are to suffer from symptoms of depression and have higher blood levels of inflammation-promoting compounds. These compounds include tumor necrosis factor alpha and interleukin-6. Dr. Janice K. Kiecolt-Glaser and her colleagues from Ohio State University College of Medicine in Columbus investigated the relationship among fatty acid consumption, depression and inflammation in 43 older men and women. The 6 individuals diagnosed with major depression had nearly 18 times as much omega-6 as omega-3 in their blood, compared with about 13 times as much for subjects who didn't meet the criteria for major depression. Depressed patients also had higher levels of tumor necrosis factor alpha, interleukin-6, and other inflammatory compounds. And as levels of depressive symptoms rose, so did the omega 6 and omega 3 ratio. Psychosomatic Medicine, online March 30, 2007.

Fatty acids and cancer
Role of fatty acids in malignancy and visual impairment: epidemiological evidence and experimental studies.
Histol Histopathol. 2009 February. Tsubura A, Yuri T, Yoshizawa K, Uehara N, Takada H. Tsubura A, Yuri T, Yoshizawa K, Uehara N, Takada H. Department of Pathology II, Kansai Medical University, Takii Hospital, Moriguchi, Osaka, Japan.
Total fat consists of different fatty acid families, e.g., saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and n-3 and n-6 polyunsaturated fatty acids (PUFAs). Epidemiological evidence and experimental studies suggest that these fatty acid families have different effects on breast and colon carcinogenesis. Therefore the action of each fatty acid on carcinogenesis should be evaluated separately. Although it is difficult to establish firm conclusions on the effect of each fatty acid in human epidemiological studies, experimental studies on animals and cultured cells suggest that n-6 polyunsaturated fatty acids (linoleic acid and arachidonic acid) may have a tumor promoting effect, while n-3 polyunsaturated fatty acids (eicosapentaenoic acid, docosahexaenoic acid and alpha-linolenic acid) and conjugated fatty acids (CFAs; a mixture of positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds) exert an inhibitory effect on tumor growth. Saturated fatty acids such as palmitic acid and stearic acid show little or no tumor promoting effect, and the action of oleic acid, a monounsaturated fatty acid, is inconclusive. In addition to regulation of abnormal cell growth seen in cancers, fatty acids also control cell loss seen in degenerative eye diseases, such as degeneration of lens material in cataract and degeneration of photoreceptor cells in retinitis pigmentosa. Experiments suggest that n-6 polyunsaturated fatty acids cause deleterious effects, while n-3 polyunsaturated fatty acids result in beneficial effects on the lens and retina. In particular, docosahexaenoic acid is known to be effective in rescuing photoreceptor cells from damage. Thus, understanding the function of each fatty acid is likely to be important for making progress in treating these and other diseases.

Types of fatty acid
Caprylic acid is a short or medium chain saturated fatty acid, see also , and corosolic acid.

I had read that fatty acids like evening primrose oil and borage oil are anti-thyroid. Is this true?
    I am not sure what you mean by anti thyroid. Do you mean they decrease thyroid hormone levels? I have not seen such evidence.