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Genes May Influence Breast Milk Nutrition

Some women naturally incorporate more nutrients in milk than others, study finds

WEDNESDAY, May 18, 2005 (HealthDay News) -- A woman's genes, not just her diet, may influence the nutritional composition of her breast milk, claims new research.

"It is well known that genes control the nutrient levels in cow's milk. But until now, no one has considered how genes might affect human breast milk. This is the first study to demonstrate a genetic effect on human lactation," researcher Dr. Richard B. Weinberg, a professor of gastroenterology and a nutrition researcher at Wake Forest University Baptist Medical Center, said in a prepared statement.

His team's study of 111 women examined just how much of an important dietary nutrient called docosahexaenoic acid (DHA) makes its way into breast milk. DHA is found mainly in cold water fish such as tuna, salmon and mackerel and is essential for healthy brain and eye development, especially in newborns.

In the study, the women consumed a meal with added DHA and then pumped their breast milk hourly for 12 hours. Researchers analyzed the amount of DHA and other fats in both the milk and in the women's blood.

They found that women with the 347S variant of the ApoA4 gene -- involved in dietary fat absorption -- had 40 percent more DHA in their breast milk than women with the more common 347T version of the gene.

The 347S variant is present in about a third of the U.S population.

"These women were more successful at getting the DHA they had just eaten into their bloodstreams and then into their breast milk," Weinberg said.

His team also found that women who carried one or two copies of the E4 variant of the ApoE gene -- which regulates fat metabolism in the bloodstream -- had 40 percent to 75 percent less total fat in their breast milk than women without this variant. About 20 percent of the population carries the E4 variant of ApoE.

"This unexpected finding suggests that the E4 variant could affect the total amount of calories that a mother can provide to her infant in her milk," Weinberg said.

More research is needed before these findings could possibly be used to develop nutritional recommendations for pregnant and nursing women, he added.

The study was presented Tuesday at the Digestive Disease Week 2005 conference in Chicago.

More information

The American College of Nurse-Midwives has more about how diet, medications and alcohol affect breast-feeding.

SOURCE: Wake Forest University Baptist Medical Center, news release, May 17, 2005
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