The Power of A… in Context

It was the closest thing to a research slam-dunk.

In 1999, after several years of painstakingly distributing vitamin A, beta carotene (a form of vitamin A) or placebos to thousands of pregnant women in Nepal, it seemed clear to Keith P. West, Jr., DrPH ’87, MPH ’79, that vitamin A was a public health powerhouse. West, the George G. Graham Professor of Infant and Child Nutrition, and his colleagues published a paper that year showing that women who had received the supplements had about a 40 percent lower risk of death up to three months after delivery than those who took capsules containing plain vegetable oil.

But in May 2011, West’s team published new results from a similar study in Bangladesh that, on the surface, seemed contradictory. There, the supplements seemed to have no effect on helping mothers and their babies survive, leading some public health researchers to question whether women anywhere might benefit from vitamin A at all. Why would these two populations—so close to each other—show such different results?

“It’s a reminder of how important context is for research, especially for nutrition,” explains West, director of the Center for Human Nutrition in the Department of International Health.

When he and his colleagues started planning the seven-year study in 1999, Nepal and Bangladesh were roughly equivalent in terms of poverty, with the resulting fallout on education, resources and nutrition. However, Bangladesh has gradually managed to pull itself up a few critical rungs on the economic ladder. Within a few decades, it has transitioned into a country where the population as a whole, including women and children, is becoming more educated. Roads were built at a dizzying pace, transporting Bangladesh’s more plentiful resources from place to place. As the country’s economic conditions improved, women had more access to vitamin A-rich foods, including fish, liver, dairy products, and fruits and vegetables.

“Even though Bangladesh is very poor, it’s still better off than Nepal,” says West. “In Bangladesh, vitamin A had already made its impact through a better diet, so the women there didn’t need supplements.”

Nancy L. Sloan, DrPH, an assistant professor in Population and Family Health at Columbia University, points out that another recent study by British researchers examining the effects of vitamin A supplementation in Ghana also showed no difference in deaths between those who received the nutrient and those who didn’t.

“Some people will say that now you have two out of three studies indicating vitamin A supplementation does not reduce maternal mortality, but I don’t think that’s necessarily conclusive,” she says. Sloan explains that as in Bangladesh, women in the study area of Ghana had no clinical vitamin A deficiency because they already eat a diet rich in vitamin A in the form of red palm oil, a favorite local condiment.

Until researchers can conduct more vitamin A research in different environments where clinical vitamin A deficiency continues to exist—an unlikely prospect, since each of the preceding studies held multimillion dollar price tags—the true value of supplementation could remain unknown, says Sloan.