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Elizabeth J. Johnson |
BOSTON — "In nature there are hundreds of carotenoids. We eat only 50 of those; only 20 to 30 end up in your body and only two get to your eye: lutein and zeaxanthin," according to a speaker here at the Ocular Nutrition Society meeting preceding Academy
2011 Boston.
Lutein makes up about one-sixth of all carotenoids in the US diet, about three-eighths of carotenoids found in serum and about three-fourths of the carotenoids found in the brain. "There's preferential uptake of lutein to the brain," according to Elizabeth J. Johnson, PhD, of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston. "Maybe it's going there for a reason."
Two separate studies have shown that older adults consuming the highest amounts of green leafy vegetables and cruciferous vegetables, both rich sources of lutein, had slower cognitive decline than those consuming the lowest amounts, Dr. Johnson said.
Another study found that "a higher mini mental state examination (MMSE) score was significantly associated with higher lutein and higher DHA," she said.
Studies have shown that about 6 mg of lutein and zeaxanthin in the diet is related to a significant decrease in age-related macular degeneration, Dr. Johnson reported. "This is about 2 oz. to 4 oz. of spinach a day," she said. "One block of frozen spinach in a week would give you a lot of lutein, but most people in the US don't get that."
Macular pigment density and cognitive function were studied in 108 subjects with a mean age of 78 years. Heterochromatic flicker photometry was used to measure the macular pigment. "This is a quick and easy way to measure macular pigment," Dr. Johnson noted. "I measured 300 people in 3 days at a dietitian's meeting.
"We found that those with higher macular pigment had significantly higher MMSE score," she said. "This has a significant relationship to cognitive function."
Dr. Johnson and colleagues conducted a study to analyze the effects of docosahexaenoic acid and lutein supplementation on cognitive findings in older women. In four arms of the study, subjects took placebo, lutein, DHA, or lutein and DHA.
"The combination treatment improved cognition in older adults," Dr. Johnson said. "We were surprised. It didn't just keep it from going down; it improved it.
"Lutein is important to visual function and health and in brain function and health," she added.
Four effective, common sources of lutein and zeaxanthin are eggs, broccoli, corn and dark, green leafy vegetables, according to Dr. Johnson. "An egg yolk is yellow because it is lutein and it's very bioavailable," she said. "The lutein in an egg is three times more bioavailable than lutein in dark, green leafy vegetables There is about 0.5 mg of lutein in one egg. The best diet is a diverse diet."
She noted that cooked vegetables are more effective than raw vegetables. "You get past the cell wall and there's more bioavailability that way," she said.