When the conversation around me turns to health problems linked to nutrition, I have to resist the urge to chime in with advice. Instead, I write a blog post. A recent conversation was about Age Related Macular Degeneration, or AMD. This is a common problem of aging and the primary cause of vision loss in older adults.
The medical community is focused on drug treatments. I usually look for the nutrition connection, and AMD has some significant links to nutrition. But there is no evidence that better diet will prevent AMD, and no evidence that improving nutrition will stop or reverse the vision loss once it starts. Mainly there’s no evidence because there isn’t research. Who would do such research? It would be ethically impossible to put a large group of study subjects on a bad diet for years and compare their eye health to a group that ate a healthy diet.
What is the Macula?
The macula is a small area in the center of the retina, in the back of the eye. It’s key for seeing things up close, such as for reading or recognizing faces. If the macula is damaged or diseased, up-close vision is impaired. Macular Degeneration is a specific type of macular problem, associated with aging.
Lutein and zeaxanthin are two carotenoids found in foods like green leafy vegetables, avocado, egg yolk and corn. These carotenoids are concentrated in the macula, where they function as antioxidants and filter blue light, protecting the retina from damage. Lutein and zeaxanthin are used up in these important functions, so they need to be replenished from food.
Age-Related Macular Degeneration
The American Academy of Opthalmology has some helpful short videos that explain macular degeneration. The brief explanation for AMD is that macular integrity deteriorates over time, and central vision worsens. There are two main forms of AMD: wet and dry. The dry form is more common; the wet form is less common but more serious.
What can be done? There are medical treatments for the wet form, but not for the dry form. The current recommendation for Dry AMD is a specialized vitamin/mineral preparation, developed for the Age-Related Eye Disease Study, which was a two part study. The AREDS forumula used in Part 2 seemed to provide more benefit, which was attributed to the luetin and zeaxanthin content.
- 500 mg vitamin C
- 400 IU vitamin E
- 10 mg lutein
- 2 mg zeaxanthin
- 80 mg zinc
- 2 mg copper
The medical community takes pains to clarify that this formula is not a cure for AMD. At best, it may slow deterioration. The medical community also takes the position that eye-healthy foods are a good idea, but probably won’t prevent AMD. Like I said, there aren’t any studies investigating this possibility.
There are some diet studies that compare incidence of AMD with previous diet, and/or with blood levels of lutein/zeaxanthin. These studies do find a link between higher intake of lutein/zeaxanthin and much lower risk for AMD. Note that smoking is a major risk factor for AMD, and an eye-healthy diet is unlikely to cancel out that risk.
Eye Health Diet
The retina and the macula are built from nutrients. Lutein and zeaxanthin are concentrated in the macula and are key for macular function. Zinc, omega-3 fats, vitamin A (carotenes), vitamin E and vitamin C are also all important. As your eyes react to light and the environment, the nutrients must be replaced. It stands to reason a diet with plenty of these nutrients is better for eye health.
It turns out an eye health diet is essentially a plant-based/sometimes vegetarian/Mediterranean style diet. Lutein, zeaxanthin, vitamin A (carotenes), vitamin C and vitamin E are concentrated in vegetables and fruit. Some of the best foods for lutein/zeaxanthin are:
- turnip greens
- dark green lettuces
- egg yolk*
*Let’s think about egg yolk for a minute. What have we been told for decades to avoid? Egg yolks, based on a now-obsolete belief that egg yolks cause heart attacks. All that lutein tossed out with the egg yolks.
Lutein and zeaxanthin are fat-soluble, so you need to consume these foods in a meal that contains some fat. Greens in a salad, with oil-based dressing, solves that problem. Egg yolk already contains fat. This isn’t terribly complicated, but if you limit yourself to fat-free meals, your absorption of these important nutrients can be impaired.
Both lutein and zeaxanthin are included in the AREDS2 formula. You can also purchase them separately. But why? If you’re eating a healthful plant-based diet, you should be consuming plenty of greens, which are the most concentrated sources of these carotenoids.
An intake of 10 mg lutein and 2 of zeaxanthin (as in the AREDS2 formula) seems to provide reasonable benefit. Taking more isn’t known to be helpful, although there are supplements with higher doses. If you do take a supplement, take it with a meal that contains fat, to help with absorption.
As I noted at the beginning, there’s no evidence that high intake of lutein/zeaxanthin and other eye nutrients will prevent AMD, because there’s no research. Some diet/disease surveys have linked a plant-based Mediterranean/semi-vegetarian diet to lower incidence of AMD. You should be following this sort of diet anyway. If you’re particularly worried about AMD, eat lots of greens, and include fat in the meal to enhance lutein absorption.