Vitamin D and vision protection — time for a closer look

Getting enough vitamin D may help prevent women from losing their vision in old age. That's the quick and easy conclusion from a new study, just perhaps not one that will require you to change your diet.

In a study of 1,313 women ages 50 to 79, researchers from the University of Buffalo in New York found that women with adequate levels of vitamin D were at 48% decreased odds for developing age-related macular degeneration (AMD) compared with women with insufficient levels of the vitamin. The work was published in the April Archives of Ophthalmology.

The team writes in its abstract:

“… Among women younger than 75 years, intake of vitamin D from foods and supplements was related to decreased odds of early AMD in multivariate models.”

Seems straightforward: Women under 75 who get enough vitamin D have a reduced risk of going blind, which other studies have suggested.

But hold on. The individual risk of developing AMD is relatively low if you're young. Only about 2 out of 100 middle-aged adults will develop the blindness. But that risk increases to nearly 30 in 100 for those over age 75. So in a study of women 50 to 79, most of whom are getting reasonable amounts of vitamin D, the big risk factor is age, not diet.

Other factors are related to AMD as well, such as race (whites are more likely than African Americans to lose vision through AMD) and family history, which the study didn't control for. Still, there's no predicting precisely who will develop the disease — as with most diseases.

Besides, people get vitamin D through vitamin supplements, eating foods such as fish and fortified milk and orange juice or by spending time in the sun. In fact, most people are getting an adequate supply of the vitamin, a survey last month found.

Reality check: Vitamin D is of course good for us, and there are plenty of good reasons to make sure you're getting enough. You don't need to obsess about this one study.

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