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|CORRECTION: In the Winter 2004 “Know Your Fats” column we stated that Siberian pinenut oil was a good source of gamma-linolenic acid (GLA). This was indicated from fatty acid analyses performed in Siberia. We have since performed further tests on the oil and found that it does not contain significant amounts of GLA but rather a fatty acid called pinoleic acid, an 18-carbon fatty acid with three double bonds but with the first double bond on the fifth carbon, not the sixth, as in GLA. We are sorry for any inconvenience this may have caused.|
The human body uses fatty acids from food for building tissues and for specialized functions such as the production of prostaglandins, localized tissue hormones. One major group of fatty acids is called essential fatty acids, which are polyunsaturated, and include two major groups, omega-3 and omega-6 fatty acids. They are called “essential” because the body cannot make them but must get them from food.
The terms omega-3 and omega-6 actually designate two families of fatty acids; the former has the first double bond on the third carbon from the end of the fatty acid chain and the latter has the first double bond on the sixth carbon from the end of the fatty acid chain. The first fatty acid in the omega-6 family is called linoleic acid. It contains 18 carbons and has 2 double bonds.
Gamma-linolenic acid (GLA) is the second fatty acid in the omega-6 family. It has 18 carbons and three double bonds (with the first double bond positioned six carbons from the end). The third fatty acid in the omega-6 family is dihomo-gamma-linolenic acid (DGLA) with 20 carbons and three double bonds. Next comes arachidonic acid (AA) with 20 carbons and 4 double bonds. The Series 1 prostaglandins are made out of DGLA and the Series 2 prostaglandins are made out of AA. Thus, GLA is an important transition product for the production of these prostaglandins.
GLA is found in small amounts in organ meats and in certain seed oils such as evening primrose oil, borage oil, and black currant oil. Hemp oil also contains GLA but this oil has no history of consumption by humans. The percentages of GLA in these specialty oils are as follows:
- Evening Primrose Oil 10%
- Black Currant Oil 17%
- Borage Oil 23%
These three oils are available in capsule form. The body needs an enzyme called delta-6 desaturase (D6D) to transform linoleic acid into GLA. Under normal conditions, most people make adequate amounts of D6D and hence the by-product GLA; however, a number of disease and deficiency conditions as well as components of the modern diet can interfere with the conversion of linoleic acid to GLA. Diabetics, for example, do not normally make adequate amounts of D6D and hence of GLA, nor do people with poor pituitary or thyroid function. Both malnutrition and overeating can interfere with D6D and inhibit the production of GLA. Trans fatty acids definitely inhibit the production of GLA as does overconsumption of sugar and alcohol. Deficiencies of protein, zinc, biotin and vitamins B6, B12 and E can all inhibit D6D function and hence the production of GLA. In addition, some individuals are not genetically programed to produce D6D at all, mainly those whose ancestors had lots of preformed D6D metabolites from organ meats and fish in their diets. Researchers have called such individuals “obligate carnivores.” They are especially prone to diseases like diabetes and alcoholism if they do not eat enough fish and organ meat.
Some of the disease conditions that result from defective D6D function include premature aging, irritable bowel syndrome, cirrhosis of the liver, skin conditions like eczema, menstrual problem such as PMS, noncancerous breast disease, Sjogren’s syndrome, alcoholism, diabetes and cancer. Thus, investigators have hypothesized that GLA can be an important component of treatment for these conditions.
An excellent review of the beneficial effects of GLA was published in the Journal of Nutrition, 1998 (Vol 128 No 9, 1411-1414). Several studies have demonstrated the beneficial effects of GLA on rheumatoid arthritis. Said the authors: “The use of GLA as a benign, adjunctive therapy is relevant because rheumatoid arthritis patients are at high risk for developing complications from traditional nonsteroidal anti-inflammatory drug and corticosteroid medications.”
Other studies have shown that GLA has a favorable effect on cardiovascular risk factors, notably a reduction in the size of plaque in vessel walls.
The review article also notes that GLA is unique among the omega-6 family in its “potential to suppress tumor growth and metastasis.” Other studies report very favorable results in the treatment of diabetic neuropathy with GLA.
Several studies involving rats have indicated that GLA can have a favorable effect on blood pressure and one human study, carried out in France ,found the GLA not only lowered blood pressure but had a favorable effect on other cardiovascular risk factors (Bratisl Led Listy 2002;103(3):101-7).
Studies that looked at the effect of GLA on skin conditions have been mixed, some showing no effect but others resulting in the alleviation of symptoms of dermatitis, especially in young children.
Finally, GLA has been shown to encourage weight loss in individuals who are considerably overweight, making it a good aid for dieting (Horrobin DF, ed. Clinical Uses of Essential Fatty Acids. Montreal: Eden Press, pp 53-61, 1982).
This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Winter 2004.