Omega-3 fatty acids and macular degeneration
A recent study examined the effect of dietary long-chain omega-3 fatty acids (e.g. those from fish and fish oil) on the progression of age-related macular degeneration (AMD) in individuals already at high risk with symptoms in one or both eyes. The results were presented in terms of quintiles of intake expressed as a percentage of total energy intakes. Since there was a wide range of energy intake this makes it hard to apply the results in a simple fashion as regards recommended intakes based on the data. It was found that in comparison between those in the highest intake quintile and those in the lower four quintiles, there was a 30% decrease in the risk of progressing to advanced AMD. For someone with an energy intake of 1800 cal, the highest quintile for docosahexaenoic acid (DHA) was 120 mg/day and for eicosapentaenoic acid (EPA) it was 88 mg/day, based on 9 cal/g of fatty acid.

These results make one wonder about the benefits if much larger amounts had been consumed by supplementation with fish oil capsules. Individuals taking fish oil for cardiovascular protection typically take 1-2 g of fish oil giving them 400 mg of EPA and 200 mg of DHA per gram of oil. However, the authors point to an ongoing trial that will include supplementation with 350 mg of DHA and 650 mg EPA per day, amounts which clearly represents a big advance over typical amounts obtained just from the diet. This study will also look at supplementation with lutein/zeaxanthin (10mg/2mg day) alone or in combination with the above dose of EPA/DHA. This is a 4000 person, 5-year randomized clinical trial and also involves individuals at high risk of AMD. The study was started in late 2006. Readers are referred to the December 2009-January 2010 issue of International Health News for a discussion of a study that used eggs to enhance the intake of retinal pigments in the context of preventing AMD. Eggs are rich in lutein and zeaxanthin. Incidentally, so- called omega-3 eggs typically contain about 400 mg of omega-3 fatty acids per egg but this includes the short chain omega-3 fatty acids which are inefficiently converted to the long-chain acid in human biochemistry.
Sangiovanni JP, Agron E, Meleth AD et al. {omega}-3 Long-chain polyunsaturated fatty acid intake and 12-y incidence of neovascular age-related macular degeneration and central geographic atrophy: AREDS report 30, a prospective cohort study from the Age-Related Eye Disease Study. Am J Clin Nutr 2009 December;90(6):1601-7

Oily fish prevents macular degeneration
LONDON, ENGLAND. Age-related macular degeneration (AMD) is the major cause of adult blindness in developed countries. A large study involving researchers and patients from eight European countries now report that regular consumption of oily fish may reduce the risk of developing AMD by 53%. The study involved 105 patients with neovascular AMD and 2170 controls without any features of early or late AMD. All participants were 65 years of age or older. They were interviewed by field workers, underwent an eye examination, including fundus photography, and gave a blood sample. During the interview, dietary intake during the previous 12 months was assessed using a semi-quantitative food-frequency questionnaire.

Analysis of the collected data revealed that study participants who ate only oily fish (mackerel, tuna, salmon, sardines and herring) once a week (one serving equaling 4 oz or 113 g) had half the risk of AMD when compared to those who ate oily fish less frequently. No beneficial effect was observed from consuming non-oily (white) fish such as cod. Not surprisingly, the researchers observed a strong correlation between oily fish intake and the dietary intake of the two main components of fish oil – EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Study participants whose energy-adjusted EPA + DHA intake was greater than 302 mg/day had one-third the risk of AMD than did those whose daily intake was 105 mg or less.

The researchers found no independent association between vitamin D intake and AMD risk and adjusting for lifestyle factors such as smoking, alcohol consumption, and education did not affect the observed correlations. They point out that current recommendations for the combined intake of EPA and DHA range between 400 and 1000 mg/day, an amount that could be obtained by eating 2 servings of salmon or 26 servings of cod a week.
Augood, C, et al. Oily fish consumption, dietary docosahexaenoic acid and eicosapentaenoic acid intakes, and associations with neovascular age-related macular degeneration. American Journal of Clinical Nutrition, Vol. 88, 2008, pp. 398-406

Editor's comment: A large clinical trial (AREDS2) involving 4000 patients with early AMD is currently underway to determine if supplementation with EPA + DHA and/or lutein/zeaxanthin can stop the progression to advanced AMD. However, based on the results of the large European study reported above, there would certainly seem to be good reason to believe that EPA + DHA can materially reduce the risk of developing AMD in the first place. Please remember that fish oil supplements should always be accompanied by adequate amounts of vitamin E (gamma E) and vitamin C to avoid lipid peroxidation.

Fish oils may help prevent vision loss
SYDNEY, AUSTRALIA. Could eating more fish protect against age-related blindness? Researchers from the University of Sydney, Australia investigated this link by analyzing n-3 fatty acid intakes and incidence of age-related maculopathy (ARM) among 2,895 men and women aged 49 years or over. ARM is the most common cause of severe vision loss in the elderly. The participants in the top fifth for n-3 FA intake had a 59 per cent lower risk than those in the bottom fifth of developing early-stage ARM over the five years of follow-up. Also significant was the 55 per cent lower risk of early-stage ARM among those in the top fifth for alpha-linolenic acid intake. The results also showed a 40 per cent reduction in risk of early-stage ARM for those eating fish at least once a week, compared with little or no fish intake. The authors conclude that a diet high in n-3 FA, especially from fish, may offer protection against both early and late ARM.
Chua, B. et al. Dietary Fatty Acids and the 5-Year Incidence of Age-Related Maculopathy. Archives of Ophthalmology, Vol. 124, July 2006, pp.981-86

Fish oils help prevent macular degeneration
BOSTON, MASSACHUSETTS. Age-related macular degeneration (AMD) is a leading cause of blindness for which treatment options are limited. Note: The macula is responsible for detailed, fine central vision and is located at the center of the retina. Researchers at the Harvard Medical School have just released a major study that points to a close association between the development of AMD and the consumption of certain fats. The study involved 42,743 female nurses enrolled in 1984 and 29,746 male health professionals enrolled in 1986. The nurses completed 130-item food frequency questionnaires in 1984, 1986 and 1990 and the men completed them in 1986 and 1990.

By 1996 a total of 567 study participants (351 women and 216 men) had developed AMD with visual loss of 20/30 or worse. The researchers found that women with a high fat intake (fifth quintile) had a 63 per cent greater risk of AMD than women with a low intake (first quintile). For men, the increased risk was 36 per cent. The major contributors to the increased risk were high intake of linolenic acid and trans-fatty acids. In contrast, a high intake of docosahexaenoic acid (DHA), a main component of fish oils, was found to lower the risk of AMD by about 30 per cent. More than one serving per week of beef, pork or lamb as a main dish was associated with a 35 per cent increased risk of AMD when compared to an intake of less than three servings per month. Fish, especially canned tuna, was found to have a protective effect, with the participants who ate fish more than four times per week having a 35 per cent lower risk of AMD than people eating fish three times per month or less.

The researchers conclude that a high intake of linolenic acid may increase the risk of AMD. They caution though that their finding contradicts other studies that have shown that linolenic acid is protective against coronary heart disease.
Cho, Eunyoung, et al. Prospective study of dietary fat and the risk of age-related macular degeneration. American Journal of Clinical Nutrition, Vol. 73, February 2001, pp. 209-18

Fish consumption protects against macular degeneration
SYDNEY, AUSTRALIA. Age-related macular degeneration (maculopathy) is a leading cause of blindness in both Australia and the United States. There is some evidence that atherosclerosis and macular degeneration may both be related to a high intake of saturated fat and cholesterol. A large Australian study (Blue Mountain Eye Study) now confirms this connection. The study involved 3654 men aged 49 years or older who completed a 145-item, semi-quantitative food frequency questionnaire and also underwent a detailed eye examination including stereoscopic macular photography. Among the participants there were 240 cases (6.5%) of early-stage degeneration and 72 cases (2%) of late-stage disease. The study results confirmed that the incidence of late-stage macular degeneration was almost 3 times higher among the men with a daily cholesterol intake of 400 mg or more than among the men with an intake of 231 mg/day or less. Somewhat surprisingly there was also a strong correlation between the intake of monounsaturated fat (olive oil) and the incidence of early-stage macular degeneration. The men with an intake of 34 grams/day or more had a 48% greater incidence than the men with an intake of 25 grams/day or less. Regular fish consumption was found to be highly protective. The men who ate fish more than once a week had a 50% lower incidence of late-stage macular degeneration than did the men who ate fish less than once per month.
Smith, Wayne, et al. Dietary fat and fish intake and age-related maculopathy. Archives of Ophthalmology, Vol. 118, March 2000, pp. 401-04