Black Currant Seed Oil and EFAs in Dry Eye and Immunity

Studies have shown that dry eye patients experience a chronic inflammatory cycle, causing symptoms and impacting tear production. A Phase III FDA study of cyclosporine, an immunomodulatory drug, demonstrated that in moderate and severe cases of Sjögren's syndrome and keratoconjunctivitis sicca (KCS), markers of inflammation were significantly reduced from baseline following treatment with this drug. However, this potent immunomodulatory drug is not a first-line defense.

A more effective and preventive approach may be to address the biochemical basis of a healthy and intact tear film. Studies have shown that nutritional supplementation with omega-3 and omega-6 fatty acids and nutrient cofactors involved in the biosynthesis of the prostaglandin PGE1 result in reduced symptoms in dry-eye and KCS patients (1,2). PGE1 is necessary for tear secretion and also regulates inflammation. Essentially, in the event of reduction of PGE1 synthesis (due to a deficiency of omega-3 and omega-6 fatty acids), there is overproduction of series 2 prostaglandins (PGE2). Increased PGE1 production is anti-inflammatory because it down-regulates PGE2 production, and thus reduces over-reactive B-cell activity and may be a regulator of the arachidonic acid cascade. Wu and colleagues carried out a placebo-controlled study of the effect of dietary supplementation with black current seed oil (BCSO) on immune response in healthy subjects 65 years or older (3).

Methods:

This was a randomized double-blind study. Forty patients were randomized to receive either 750 mg BCSO or 750 mg soybean oil. BCSO contains linoleic acid and 15% gamma-linolenic acid (GLA) - both omega-6 fatty acids, as well as the omega-3 fatty acids alpha-linolenic acid and stearidonic acid. The ratio of omega-3 to omega-6 fatty acids in BCSO is about 1 to 4. The level of vitamin E intake in both groups was controlled equally. Supplementation continued for 2 months.

Results:

BSCO supplementation, significantly increased plasma concentrations of gamma-linolenic acid (omega-6), alpha-linolenic acid (omega-3), and dihomo-gamma-linolenic acid compared with baseline. These increases were not evident in the control group. The BCSO group exhibited enhanced response to tetanus toxoid. In the BCSO group, stimulated PGE2 production was significantly reduced from baseline (488 ng/L to 258 ng/L). This was significantly (p<0.05) different from the control (soybean oil) group, which did not exhibit this reduction (Figure). The authors concluded that BCSO has a moderate immune enhancing effect attributable to reduction of PGE2 production.

Comment:

This study and previous research suggests that the combination of omega-3 and omega-6 fatty acids in black current seed oil both results in increased PGE1, which both stimulates aqueous tear secretion and reduces the production of PGE2.

1. References
   
   1. Horrobin DF, Campbell A, McEwen CG: Treatment of the Sicca Syndrome and the Sjögren's Syndrome with E.F.A., Pyridoxine and Vitamin C. Prog Lipid Res 8(4): 253-4, 1981
   2. Oxholm P, Manthorpe R, Prause JU, Horrobin D: Patients with Primary Sjögren's Syndrome Treated for 2 Months With Evening Primrose Oil. Scand J Rheumatology 1986; 15:103-108.
   3. Wu D, Meydani M, Leka L, et. al.: Effect of dietary supplementation with black current seed oil on the immune response of healthy elderly subjects. Am J Clin Nutr 1999;70:536-543.