High Omega-3 Intake Protective Against Age-Related Macular Degeneration

A higher intake of omega-3 fatty acids (median of .35 g/day) could have prevented an estimated 22% of the cases of age-related macular degeneration (AMD) in a recent study, according to the study's authors.

Published in the July Archives of Ophthalmology, the study finds that dietary omega-3 intake is inversely associated with incidence of AMD, Johanna Seddon, MD, Massachusetts Eye & Ear Infirmary, Harvard Medical School, et al., conclude.

Furthermore, "the protective effect of long-chain polyunsaturated omega-3 fatty acid intake was seen only when linoleic acid intake (an omega-6 fatty acid) was below the median [11.8 g]," the authors state.

"Our results suggest that when our diet is rich in these omega-6 fatty acids (as measured here by linoleic acid), the protective effect of omega-3 fatty acids is dampened," Seddon et al. maintain.

The findings are supportive of other research regarding the need to maintain a healthy balance of the fatty acids, the authors note. The "ideal" omega-6/omega-3 ratio is 3:1 to 4:1; however, the diet of the average American has a ratio that ranges from 10:1 to 50:1, according to Seddon et al.

The case-control study of risk factors followed 681 elderly male twins from the National Academy of Sciences-National Research Council World War II Veteran Twin Registry.

The participants were examined by an ophthalmologist, interviewed by telephone to assess risk factors, and filled out a food frequency questionnaire that included questions about dietary supplement use. AMD was diagnosed using photographs of the inner eye.

A "significant trend" for reduced risk of AMD was also found with increasing intake of fish, "particularly for two or more servings per week," Seddon et al. find.

Consumption of dietary omega-3s and fish also is found beneficial in a separate article published in the July Archives of Ophthalmology.

Brian Chua, Centre for Vision Research, Department of Ophthalmology, University of Sydney, Australia, et al., conducted a five-year follow-up on 2,335 participants from the 2000 Blue Mountains Eye Study who had completed food frequency questionnaires at baseline (¹ (Also see "Macro-, Micro-Nutrients May Help Prevent Cataract - Studies" - Pink Sheet, 27 Mar, 2000.), p. 6).

The researchers "found that participants within the lowest intake of dietary [mono-unsaturated fatty acids] and [omega-3 fatty acids], particularly the omega-3 fatty acid alphalinolenic acid, may be at increased risk of incident early AMD after simultaneously adjusting for the intakes of other fatty acid subtypes."

Additionally, eating fish at least once a week reduced the risk of early AMD by 40%, and the incidence of late AMD was reduced when fish was consumed at least three times per week, Chua et al. find.

"It may be reasonable for physicians to make dietary recommendations for eye health, including intake of fish along with fruits and vegetables," Seddon et al. write, adding that "a good source of omega-3 fatty acids is the diet, and there is an increasing trend for the addition of this nutrient to many common foods in the American diet."

Martek Biosciences entered into a license and supply agreement with General Mills June 16 and an agreement with Kellogg last year (² 'The Tan Sheet' June 19, 2006, In Brief and ³ (Also see "Martek Reaches Beyond Infant Formula To Grab Perinatal, Food Markets" - Pink Sheet, 16 Jan, 2006.), p. 12). In late June, Ocean Nutrition Canada announced the addition of its MEG-3 EPA/DHA to a line of pizza (⁴ 'The Tan Sheet' July 3, 2006, In Brief).

Seddon et al. also find current smokers had an almost double (1.9-fold) increased risk of AMD and former smokers had a 1.7-fold increased risk of the eye disease. Almost one-third of the cases in the studies were attributable to smoking, the authors estimate.

"These and other modifiable behaviors and preventative measures deserve increased attention and evaluation to reduce the increasing burden of AMD," Seddon et al. conclude, noting that AMD is the leading cause of blindness among the "expanding elderly population."

The effect of omega-3 fatty acids on the progression of AMD is slated for study in the NIH National Eye Institute's second Age-Related Eye Disease Study [AREDS II] (⁵ 'The Tan Sheet' Jan. 9, 2006, In Brief).

According to an NEI spokesperson, more than 80 centers will be involved in the study and more than 4,000 participants will be recruited. NEI hopes to officially launch the study with an informational website this fall.

- Katia Fowler