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Think Tank: See food
Omega-3s in fish may mitigate effects of age-related macular degeneration
By Lauren Kramer
August 01, 2010
As kids we are taught that eating carrots leads to better vision. But in future years we could be telling our children the same thing about seafood. Among the many health benefits of seafood consumption, one presently being researched is age-related macular degeneration (AMD). A leading cause of blindness in the elderly - particularly among women - AMD is associated with a decrease in the optical density of the macular pigment of the eye.
That optical density has been shown to be influenced by a number of factors, one of which is docosahexaenoic acid (DHA), an omega-3 fatty acid found in coldwater marine fish such as tuna, salmon and herring.
Carol Lammi-Keefe, professor in human nutrition and food at Louisiana State University in Baton Rouge, La., has long been interested in the notion that fish is brain food and has written extensively about functional food in pregnancy and its benefits to infant development.
"Today we know that our grandmothers and their old wives' tales about fish's healthy attributes were right on target," she says. "Fish,
especially fatty fish from cold marine waters, contains fats important to the development of the brain. Recent research has demonstrated that women who consume the fats of these fish during pregnancy have babies who see better and are better able to problem solve."
While there are several studies that examine the relationship between omega-3 fatty acid consumption and the optical density of the macular pigment, what distinguishes Lammi-Keefe's work is her focus on pregnant women. "We know that DHA is important for everyone, but what we're particularly interested in is why women are at higher risk than men," she says.
"We're looking at pregnancy as a lifestyle choice that may explain that higher risk of AMD in women. Maternal stores of DHA are depleted as it is transferred across the placenta, and pregnant women tend to consume dietary amounts of DHA that are less than the 200-mg-per-day recommended amount. Depletion, coupled with low consumption, potentially puts the woman at risk for insufficient DHA for her own health," she says. "We posed the question: Is macular pigment optical density (MPOD) decreased during pregnancy?"
Starting a year ago, Lammi-Keefe and her team began measuring MPOD using a macular metrics densitometer for 22 women at various stages of pregnancy, collecting dietary information by using repeated food frequency questionnaires. They found that women who consumed a prenatal supplement containing DHA during the third trimester tended to have a higher MPOD than those not using a supplement.
"We concluded that seafood as a source of DHA, and dietary carotenoids lutein and zeaxanthin were associated with increased MPOD during pregnancy, and that prenatal supplements with DHA/fish oil may be important to maintaining MPOD during pregnancy," she says.
One of her graduate students is doing an intervention study where pregnant participants are provided with canned salmon and canned tuna, and asked to consume a certain quantity of fish meals each week.
"We're trying to see how those meals in particular relate to the macular pigment," Lammi-Keefe says. "What we have to date is good pilot or preliminary data with which to seek funding and propose an intervention study on pregnant women, but a larger sample size is necessary."
That study would take several years to complete, but should the results be comparable to the ones she has obtained to date, there are almost certainly long-term implications for DHA consumption and AMD prevention.
"Already, pregnant women are being advised to consume omega-3s for the health of the infant," she says. "It's possible they should be consuming even more omega-3s, or continuing to consume it after pregnancy so they will have a protection against age-related macular degeneration."
Contributing Editor Lauren Kramer lives in British Columbia