Beta carotene, the nutrient that gives carrots their distinctive orange color, may protect people who are genetically prone to developing type 2 diabetes, new research shows.
Scientists at the Stanford University School of Medicine found that Americans who have a common genetic predisposition to diabetes may be able to lower their risk of developing the metabolic disorder by increasing their intake of beta carotene, which the body converts to a close cousin of vitamin A.
The study, published in the journal Human Genetics, also found that gamma tocopherol — the major form of vitamin E in the American diet — may have the opposite effect and increase risk for the disease.
The findings suggest simple changes in diet could have significant implications for public health, in light of the soaring rate of diabetes in the U.S. and worldwide, researchers said.
"Type 2 diabetes affects about 15 percent of the world's population, and the numbers are increasing," noted Atul Butte, M.D., an associate professor of systems medicine in pediatrics. "Government health authorities estimate that one-third of all children born in the United States since the year 2000 will get this disease at some point in their lives, possibly knocking decades off their life expectancies."
To reach their conclusions, the scientists tracked interactions between genetic factors known to increase risk for type 2 diabetes and blood levels of substances implicated in the disease. The results showed that both beta carotene and gamma tocopherol interact with a variant in a single common gene — called, SLC30A4 — to influence diabetes risk and that a protein the gene codes for may play a crucial role in the disease.
Up to 60 percent of the U.S. population carry two copies of the altered gene, which slightly increases the risk of contracting type 2 diabetes. For those individuals, higher beta-carotene blood levels correlated with lower blood-glucose levels.
"This vitamin was already known as being 'good' with respect to type 2 diabetes, so it was no surprise that we saw it, too," said Dr. Butte. "But it was reassuring, as it suggested we were doing things right.”
The second — that high blood levels of gamma tocopherol appeared to be associated with increased risk for the disease — was surprising and “disconcerting,” Dr. Butte said.
But co-researcher Chirag Patel added: "We can't say, based on just this study, that 'vitamin E is bad for you.’ ”