The nutrition naysayers among eyecare professionals frequently cite
these two studies to support their contention that nutritional
supplementation
is of no value for age related macular disease. While these
studies
were large population studies they had some fatal flaws, which we will
discuss here.
First of all, neither study isolated the most important nutrients and dosed them to the patients, but instead relied on food diaries to determine dietary levels consumed, a very unreliable method which can result in varying results (see article).
From the studies on our research page, it's clear that lutein is the most important of all the nutrients to protect from age related macular degeneration. It's curious that in the Blue Mountain Study "carotene" and vitamin A were studied, but not the most important carotenoids lutein and zeaxanthin. While carotene had an average relative risk factor for ARMD 30% lower than expected (with some having up to 2X as high a risk), vitamin A had an INCREASED risk of 20%. (This makes sense, since vitamin A actually can block the transport of lutein/zeaxanthin to the eye by competing for space on the blood cholesterol.) I would assume that some patients consumed lutein-rich carotene foods, while others consumed very little, which would account for the high variability in the relative risk ratio among this group.
These studies, in my opinion, are worse than worthless. They are actually harmful to the public's welfare, because they discourage many doctors from recommending a nutritional program to their patients which includes increased lutein consumption from diet or supplements. Other antioxidants play a smaller supporting role, but still significant, in protection of the fragile retinal tissues from oxidative damage.