Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Recent Studies Suggest Leafy Greens Tied to Cognitive Health

Dear Doctor: My girlfriend is all-in on one of those low-carb diets and has pretty much stopped eating vegetables. (When she does eat any carbs, it's the bread and sweets that she craves). I'm hoping one of the new studies about leafy greens and brain health might change her habits. Can you talk a bit about them?

Dear Reader: Any time you follow a restrictive diet -- and the low-carb variety certainly qualifies -- you run the risk of shorting the body of a range of nutrients essential to health and well-being. As we discussed in a recent column about the super-popular (for the moment, anyway) ketogenic diet, which takes the low-carb philosophy to extremes, using the allotted carbohydrates wisely becomes all the more crucial.

Fortunately, for your proposed plan to get your girlfriend to dig her salad bowl out of storage, the leafy greens in the studies you've referenced are low in carbohydrates and high in a range of health benefits. And according to several recent studies, they may quite literally be brain food.

Let's start with a study published last December in the journal Neurology. Researchers found that older individuals who ate at least one serving per day of leafy greens, like kale, lettuce, spinach, collard or mustard greens, fared better on tests that measure memory and thinking skills than did those who rarely or never included those vegetables in their diets.

The study looked at 960 people between the ages of 58 and 99 who were part of the Memory and Aging Project, which has been ongoing at Washington University in St. Louis since 1979. The purpose of the project, known as MAP, is to study changes in the intellectual functioning in individuals over time as they age. Over the course of five years, each person evaluated in the study had completed at least two cognitive assessments and had tracked their diets.

Those who ate a serving of leafy greens every day experienced half of the cognitive decline as did those who avoided those vegetables. According to the researchers, at the end of the five years, after adjusting for variables like age, sex, education, participation in cognitive and physical activities, smoking and alcohol consumption, the leafy green eaters were an equivalent of 11 years younger mentally than the other group. This bolsters the outcomes of previous studies, which found that the nutrients in these vegetables can put the brakes on cognitive decline.

The specific nutrients in those leafy greens that are most likely to be beneficial turn out to be vitamin K, lutein, folate (also known as folic acid) and beta-carotene. Researchers at the University of Illinois zeroed in on lutein, a carotenoid vitamin that accumulates in neural tissues. The results of their study suggest that, because lutein appears to support both structure and function in the neural membranes, it may be neuroprotective.

The results of these studies are fascinating and, thanks in part to ever-advancing imaging techniques, are opening up new avenues of study. When it comes to your girlfriend, though, we hope the findings are enough to get a salad on her plate.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)