Bottomline: Eating a diet high in omega-6 fats, from salad dressing, mayonnaise, and margarine, was associated with increased prevalence of age-related macular degeneration, a leading cause of blindness worldwide. Arch Ophthalmol.2009 Nov;127(11):1483-9

Background: Age-related macular degeneration (AMD) is the leading cause of blindness in the USA, and is expected to increase in prevalence by 50% in ten years.

Previous studies suggest a direct association between vegetable oils and AMD. Omega-6 fats is thought to contribute to retinal damage, via the inflammation cascade, which in turn may promote AMD.

In women of all ages, omega-6 fats was directly associated with AMD, which is consistent with data in five previous studies on Americans.

Notably, omega-3 fats were associated with higher risk in women who ate more than 6% of their calories from omega-6 fats.

Previous studies have shown a protective effect of omega-3 fats (or fish) to be stronger among people who ate lower omega-6 diets. Therefore, a protective influence of omega-3 fats may depend on the intake of omega-6 polyunsaturated fatty acids.

Interestingly, the scientists note in this paper that some studies have found atherosclerosis to be associated with AMD.

Quote: "In this particular sample, adverse associations were particularly attributed to diets high in omega-6 fats..."

Source:

Parekh N, Voland RP, Moeller SM, Blodi BA, Ritenbaugh C, Chappell RJ, Wallace RB, Mares JA; CAREDS Research Study Group. Association between dietary fat intake and age-related macular degeneration in the Carotenoids in Age-Related Eye Disease Study (CAREDS): an ancillary study of the Women's Health Initiative. Arch Ophthalmol.2009 Nov;127(11):1483-93.