Essential Fatty Acids

Dietary fat is an important source of energy and is a necessary part of the human diet. Fatty acids are a component of fat molecules. Two families of essential fatty acids exist in nature: omega-3 and omega-6. These essential fatty acids help support the cardiovascular, reproductive, immune, and nervous systems. Two omega-3 fatty acids have been shown to be important for proper visual development and retinal function – Docosahexaenoic acid and Eicosapentaenoic acid.

Omega-3 is critical to the biological function of the human body. The human body requires omega-3 fatty acids for membrane structural integrity and fluidity, enabling cells to obtain optimum nutrition and expel waste products. These essential fatty acids are critical in the production of prostaglandins, which regulate such functions as heart rate, blood pressure, blood clotting, fertility, conception, and play a role in immune function by regulating inflammation. They also are needed for proper neural development and maturation of sensory systems.

DHA and EPA Omega-3 Fatty Acids and Eye Health

Docosahexaenoic acid (DHA) is found in the highest concentration in the retina, suggesting it has an important functional role. Eicosapentaenoic acid (EPA) is used in DHA biosynthesis. Studies in pre-term and full-term infants have suggested that a dietary supply of omega-3 fatty acids may be essential for optimal visual development. A number of studies have shown that, in animals, dietary deprivation of DHA results in visual impairment and retinal degradation. Dry eye syndrome also has been linked to omega-3 deficiency. Additionally, low levels of DHA and EPA have also been associated with eye diseases such as diabetic retinopathy, age-related macular degeneration (AMD), and retinopathy of prematurity.

DHA and EPA supplementation presently is being studied. In its follow-up Age-Related Eye Disease Study 2 (AREDS2), the National Eye Institute is assessing the effects of oral supplementation with the carotenoids lutein and zeaxanthin, alone or in combination with DHA and EPA, on the progression to advanced age-related macular degeneration in individuals at high risk for the disease. AREDS2 is supplementing the DHA and EPA amounts generally found in fish.

Daily Intake*

Typical intake of omega-3 fatty acids is 1.6 grams per day in the United States. EPA and DHA usually comprise 6 percent to 12 percent of this value (0.1-0.2 grams per day). This level is well below the American Heart Association recommended 0.5-1.0 grams per day of EPA + DHA. The U.S. Food and Drug Administration has stated that consuming up to 3 grams per day of DHA and EPA is generally considered as safe.

Food Sources

EPA and DHA are concentrated in fatty fish and marine mammals. For individuals who choose not to consume fish, vegetarian DHA is commercially manufactured from microalgae. Animals can convert very small amounts of DHA through consumption of α-linolenic acid, an omega-3 fatty acid found in plants, animals, and milk.

DHA and EPA are concentrated only in a small number of less-frequently consumed fish-based foods. It is possible that increasing the intake of these nutrients can reduce the risk of vascular and degenerative retinal diseases. This can be achieved through higher consumption of fatty fish such as those listed above or through omega-3 fatty acid supplements in the form of oil or capsules.

References
  1. Birch EE, Hoffman DR, Uauy R, Birch DG, and Prestidge C. Visual acuity and the essentiality of docosahexaenoic acid and arachidonic acid in the diet of term infants. Pediatr Res 44: 201-209, 1998.
  2. Chew, E. (2007). “Age-related eye disease study 2 protocol.” National Eye Institute Protocol 07-EI-0025.
  3. Cho E. et al. (2001). “Prospective study of dietary fat and the risk of age-related macular degeneration.” Am. J. Clin. Nutr. 73: 209-218.
  4. Connor W.E., et al. (1992). “Essential fatty acids: the importance of n-3 fatty acids in the retina and brain.” Nutr Rev 50(4): 21-29.
  5. Hodge W, Barnes D, Schachter HM, Pan Y, Lowcock EC, Zhang L, Sampson M, Morrison A, Tran K, Miguelez M, and Lewin G. Effects of omega-3 fatty acids on eye health. Evidence report/technology assessment (Summary) 1-6, 2005.
  6. SanGiovanni JP, and Chew EY. The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina. Prog Retin Eye Res 24: 87-138, 2005.
  7. U.S. Department of Agriculture, Agricultural Research Service, USDA Nutrient Data Laboratory. USDA National Nutrient Database for Standard Reference, Release 20 (2007). Nutrient Data Laboratory Home Page, http://www.nal.usda.gov/fnic/foodcomp

*At this time, the AOA is unaware of any studies that have examined interactions between specific medications and essential fatty acids. The AOA also is not aware of any adverse health reports from interactions between specific medications and essential fatty acids. However, the AOA recommends consulting with a health care professional before beginning any supplementation regiment.