Gamma-linolenic acid is an essential fatty acid, which means that we need to get it from our food instead of making it in our bodies. Essential fatty acids come in two main forms: omega-3 and omega-6. Gamma-linolenic acid is an omega-6 fatty acid, while fish oil is an omega-3 fatty acid (discussed previously).
The best sources of gamma-linolenic acid are evening primrose oil, black currant seed oil, and borage oil. The main source is evening primrose oil, which is extracted from a North American native plant evening primrose. This wildflower is a yellow annual or biennial that grows from 3 to 10 feet tall. The dry pod, or fruit, has many small seeds, which contain gamma-linolenic acid.
Gamma-linolenic acid is used as a nutritional supplement or as an ingredient in food products in many countries. It has been used to treat elevated lipids, infections, premenstrual syndrome, eczema, rheumatoid arthritis, and other illnesses.
USES
People with diabetes use dietary supplements containing gamma-linolenic acid to treat peripheral neuropathy, a form of nerve damage. It is thought to improve problematic membrane structure, impulse conduction, and nerve blood flow.
Gamma-linolenic acid is not used to treat blood glucose. However, in one study of gamma-linolenic acid, some patients saw improvements in A1C, a measure of average blood glucose over 3 months. Some sources have stated that it may take several months to see results with gamma-linolenic acid.
Gamma-linolenic acid is relatively benign, and research on its use for neuropathy looks promising. Nevertheless, a definitive role for gamma-linolenic acid in treating neuropathy is unknown.
DOSE
A typical dose to treat neuropathy is 360–480 milligrams (mg) daily.
STUDIES
Clinical trials of gamma-linolenic acid for neuropathy have shown mixed results.
• A well-designed study (randomized, double-blind, placebo-controlled) of 22 patients with type 1 or type 2 diabetes evaluated the effects of gamma-linolenic acid on peripheral neuropathy over 6 months. Twelve patients received 360 mg daily of gamma-linolenic acid, and 10 patients received a placebo (dummy pill). At the end of 6 months, there were improvements in neuropathy symptom scores, as well as in other parameters. A1C declined from 9.1 to 8.7%, but the change was not significant.
• In another well-designed study, 111 patients with type 1 or type 2 diabetes received either 480 mg gamma-linolenic acid or a placebo for 1 year. Patients who took gamma- linolenic acid had significant improvements in 13 of 16 parameters of nerve function. A1C did not improve, but an interesting finding was that patients who had a lower A1C responded better to gamma-linolenic acid.
• Another study evaluated the impact of gamma-linolenic acid on vibration sensation and different parameters of neuropathy. The well-designed study (randomized, double-blind, placebo-controlled) evaluated 51 patients with type 1 or type 2 diabetes and neuropathy. For 1 year, they received 480 mg gamma-linolenic acid daily or a placebo. In this study, gamma-linolenic acid did not improve the symptoms of neuropathy.
SIDE EFFECTS AND DRUG INTERACTIONS
Most side effects of gamma-linolenic acid are mild and Most side effects of gamma-linolenic acid are mild and include headache and gastrointestinal discomfort such as bloating and loose stools. There are also reports of prolonged bleeding time and seizures.
In theory, gamma-linolenic acid, when combined with blood-thinning medications or dietary supplements, could increase bleeding. Gamma-linolenic acid should also not be combined with medications called phenothiazines (used in psychiatry), because together these medications may lower the threshold for seizures.