UMaine Researchers Highlight Anti-Cancer Benefits of Vitamin D
Contact: Betty Ingraham (207) 581-2281
Susan Sullivan (207) 581-3130
Anja Nohe (207) 581-2270
Tom Weber (207) 581-3777
ORONO — Vitamin D has long been recognized for its role in making healthy bones, but a growing body of evidence now suggests that it can also significantly reduce the risk of developing several types of cancers.
That’s the promising message that a group of University of Maine researchers found when they reviewed medical research, from 1970 to 2007, that examined the protective effects of the “sunshine vitamin” against cancers of the breast, colon, prostate, lung and ovary.
There are receptors for the most active form of vitamin D, a steroid hormone called calcitriol, in many tissues in the body that are not related to bone development, says Betty Ingraham, a UMaine doctoral student in nutrition and a co-author of the paper. In the body, the genes that respond to active vitamin D are critical to maintaining the health of cells and in regulating cell growth and differentiation.
The UMaine team, which includes doctoral student Beth Bragdon and Anja Nohe, assistant professor of chemical and biological engineering, cited one especially encouraging randomized clinical trial in Nebraska as an example of the mounting evidence that has emerged in recent years regarding the health benefits of vitamin D.
The Creighton University study involved 1,179 postmenopausal women divided into three groups. One group took 1,400-1,500 milligrams of supplementary calcium a day, another took the same amount of calcium plus 1,100 international units (IU) of vitamin D — nearly triple the currently recommended intake for that age group. The third group took placebo pills each day. After four years, those women in the combined calcium-vitamin D group showed a 60-percent lower risk of developing cancer when compared to the placebo group. The calcium-only group had a reduced cancer risk of 47 percent.
When the researchers threw out the data from the study’s first year, on the chance that some women might have begun the study with cancers that had yet to be diagnosed, the results were even more remarkable. For the last three years of the study, women in the calcium-vitamin D group showed a 77-percent reduced risk of cancer compared to the placebo group. Risk for the calcium-only group was essentially unchanged.
As encouraging as that study and others may be, however, maintaining desirable levels of vitamin D in the body remains a challenge, especially for people living in northern latitudes. The most important source of vitamin D is the skin, which makes the nutrient quickly and in large amounts when exposed to bright sunlight. Yet in states such as Maine, ultraviolet-B radiation from the sun is not intense enough in winter to promote synthesis of vitamin D in the skin. Consequently, blood levels of vitamin D drop from November on, reaching their lowest levels by March.
Susan Sullivan, a researcher in UMaine’s Department of Food Science and Human Nutrition, and doctoral student Monica Nelson recently studied 86 college-age women from the Bangor area and found that 38 percent had deficient levels of vitamin D in winter. The young women were then put on vitamin D supplements of 800 IU a day, which, when added to the 140 IU they got from fortified foods such as milk, boosted their intake to nearly 1000 IU, or five times the currently recommended amount for that age group. By the end of the one-year study, only nine percent of the women remained deficient in vitamin D, and 80 percent had achieved optimal levels.
“But 80 percent is not good enough,” says Sullivan, who was not part of the review paper. “We want to optimize vitamin D levels in 97 percent of that population of women, which means they need supplements of more than 800 IU. Older people, who get less sun exposure, need even more.”
Sullivan’s earlier three-year study of 23 Bangor-area adolescent girls revealed that nearly half of them had insufficient levels of vitamin D in their blood by late winter. In September, when the nutrient is usually at its highest level after an abundance of summer sun, 17 percent remained deficient. Because puberty is a critical period in the development of bone mass, Sullivan says, a serious lack of vitamin D, the nutrient known to promote calcium absorption, could lead to health problems such as osteoporosis later in life.
In their review paper on vitamin D and cancer, the UMaine team says researchers are now studying physiological evidence and data from clinical trials in order to revise the recommendations on vitamin D intake for optimal health. Many nutrition experts, Sullivan among them, believe that the current dietary recommendations for vitamin D are too low.
Foods fortified with vitamin D are helpful, she says, but don’t provide nearly enough of the nutrient in a normal diet. In the spring, summer and early fall in Maine, getting five to 10 minutes of midday sun each day on bare arms and legs, followed by an application of sunscreen to avoid sunburn, can make a big difference in boosting vitamin D levels.
Sullivan also joins many other nutrition experts in suggesting that people should consider taking a daily vitamin D supplement of 1,000 IU in the winter, but only after consulting a physician.