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Lutein is just one of the more than 600 phytochemicals in the carotenoid family. These compounds are pigments that give plants their orange, yellow, and red hues, but they are more than just good looking: carotenoids, including lutein, have antioxidant and other health-promoting properties. “What makes lutein unique among the carotenoids is that it is selectively taken up into the eye and the brain,” says Elizabeth Johnson, a former scientist with the Jean Mayer USDA Human Nutrition Research Center on Aging.
Eye Health: Lutein is not considered an essential nutrient; there is no evidence you will die without it. But as Americans are living longer, they are experiencing more age-related macular degeneration (AMD) and cataracts, the two major causes of visual impairment in the U.S. It is much better to prevent rather than treat these diseases, and research on lutein demonstrates that diet could help. “The eye is very vulnerable to oxidative stress because it is constantly bombarded by the sun’s rays,” says Johnson. “Lutein and its isomer zeaxanthin are concentrated in the lens of the eye and the macula of the retina, where their antioxidant effects may help to prevent damage.”
Higher intake of foods containing lutein has been associated with lower risk for both cataracts and AMD. In a randomized controlled trial, a research group from the National Institutes of Health National Eye Institute found that supplements containing lutein along with other vitamins, minerals, and carotenoids delayed the progression of macular degeneration in people with low intake of dietary lutein. “These findings make sense given lutein’s role in the eye,” says Johnson. “There is very consistent evidence that consuming lutein is good for the eye at all ages.”
Cognitive Health: The retina is actually an extension of the brain, so in order for lutein to get to the eye it has to pass through the blood-brain barrier, a highly selective membrane that protects the brain. “When we matched samples of retina tissue to samples of brain tissue, we found a strong correlation between the amount of lutein in the retina and the amount in the rest of the brain,” says Johnson. “My research and that of others has found a positive correlation between the amount of lutein in the retina and measures of cognitive function.”
In 2008, a small randomized controlled trial led by Johnson and published in Nutritional Neuroscience found that supplementation of 49 older women with 12 milligrams (mg) of lutein a day over four months was associated with significantly higher scores on cognitive function tests for verbal fluency. Memory scores and rate of learning improved significantly when the lutein was paired with the omega-3 fatty acid DHA. In 2017, Johnson and other Tufts researchers published an intervention trial (funded by the Haas Avocado Board) in which participants were given either one avocado (a lutein source) or the same number of calories from chickpeas and/or potatoes (which have no lutein) each day for six months. At the end of the trial period, the researchers found significant increases in macular pigment (a measure of lutein in the retina and a biomarker of lutein in the brain), along with improvements in problem solving and other brain functions, in the avocado group. “We don’t really know yet how lutein acts in the brain to protect or improve cognitive function,” says Johnson, “but researchers are looking at lutein’s relationship to genes related to inflammation and at its antioxidant function.”
Diet and Lutein: “The lutein levels at which we see these effects are higher than what most Americans typically consume,” says Johnson. “The average dietary intake of lutein in the U.S. is less than two mg per day. To put that into perspective, just two ounces of spinach has about 10 mg.” So, getting the amount of lutein that may help nurture eye and brain health from food is not difficult. “I had a student plan a week’s menu following the Dietary Guidelines for Americans and then calculate how much lutein a person would consume in that week,” says Johnson. “It turns out that just following a healthy dietary pattern with a variety of colorful vegetables and fruits provides all the lutein one needs!”