Kale and collard greens contain vision-protecting plant nutrients such as zeaxanthin that may significantly lower the risk of glaucoma, a leading cause of blindness.
Images thanks to Community Eye Health via Flickr. Thanks to Ellen Reid for her image-finding expertise and Jeff Thomas for his Keynote help.
Glaucoma is the second leading cause of legal blindness in white women, but the #1 cause of blindness in African-American women. That's one reason researchers chose a population of African-American women to study the effects of fruit and vegetable consumption on glaucoma risk, but the other reason is because they were specifically interested in foods with the highest concentration of those eye-protecting phytonutrients like zeaxanthin--kale and collard greens— but you'd be lucky if you could find 1 in 10 white people eating even a single serving a month, whereas that was a no-brainer for African Americans.
What'd they find? Well as I've stressed over the years, all fruits and vegetables are not the same. Whether you hardly ever ate bananas or had one or more every day didn't seem to matter much, but eating a couple oranges every week was associated with dramatically lower risk. Not orange juice, though, you can drink orange juice every day and it didn't seem to matter. A similar finding with peaches. Fresh peaches seemed to work but canned peaches didn't.
Similarly vegetables in general as a catch-all term didn't seem to matter. For example, whether you ate a green salad twice a week, once a week or zero times a week didn't seem to matter when it came to reducing glaucoma risk--you know how pitiful most people's salads are. But here's the kale and collard greens. Check it out: just two or three servings a month was associated with half the risk of glaucoma compared to once a month or less. White people, take note, as you may need it even more. The lighter your eye color, the more greens you need to eat. Blue eyes let 100 times more light through, so people with blue or gray eyes appear significantly more vulnerable to damage compared to brown or black, with green and hazel somewhere in the middle.
It's interesting - carrots appeared to be less protective in black women compared to white women. They suggest it could be a difference in food preparation methods. Perhaps the African-American subjects tended to eat carrots raw, limiting the absorption of certain nutrients, while they chopped and prepared their collard greens with oil making the nutrients more bioavailable, (because the absorption of carotenoid phytonutrients depends on the presence of fat, which is why I encourage people to eat nuts or seeds with the greens or a little tahini sauce).
Why not just take a zeaxanthin pill? Well we don't know what exactly it is in these wonderful foods that’s working their wonders so it may be better to just recommend folks eat them, rather than take supplements. And, in fact, people that take calcium or iron supplements may be doubling, quadrupling or septupling their odds of glaucoma. Better to get most of our nutrients from produce not pills
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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I demonstrated the not-all-fruits-and-veggies-are-the-same motif recently in my video How to Reach the Antioxidant RDA.
I explored the fat-enhanced absorption of carotenoid phytonutrients in Forgo Fat-Free Dressings?
Don’t eggs also have zeaxanthin? Find out how much in Egg Industry Blind Spot.
I wish there were more studies on under-represented minorities. I’ve covered a few, such as Preventing Breast Cancer By Any Greens Necessary, but am constantly on the lookout for more.
The only other video I’ve done on glaucoma is Prevent Glaucoma and See 27 Miles Farther, though I have a video coming up soon on treating the disease, Dietary Treatment of Glaucoma. Next, however, is macular degeneration: Dietary Prevention of Age-Related Macular Degeneration.
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