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NEW YORK (Reuters Health) - A glass of orange juice may not only help the vitamin pill go down. A new study suggests that fortified varieties can also help the body's vitamin D levels go up - just as effectively as the supplement itself.
The finding could bring a welcome addition to a very short list of sources for vitamin D, which is thought to help fend off an array of health problems including brittle bones, diabetes, and cancer.
"A lot of people don't drink milk," which has been fortified with vitamin D since the 1930s, "but they do drink OJ in the morning," the study's study author, Dr. Michael Holick, of the Boston University School of Medicine, told Reuters Health.
Simply adding a vitamin to a food does not guarantee its absorption in the body. In fact, since vitamin D dissolves in fat but not water, there was concern that only fatty foods such as milk could be used.
But preliminary research several years ago by Holick and his team suggested that orange juice - not known for its fat content -- might be an effective way to deliver the vitamin. This prompted Minute Maid and Tropicana to begin adding it, along with calcium, to some of their products. (A division of Coca-Cola, which owns Minute Maid, funded Holick's study.)
Still, the question remained of whether the body could make use of as much vitamin D from orange juice as it could from a supplement. So the team recruited about 100 adults and had them drink a glass of orange juice every morning and to swallow a capsule every night for 11 weeks.
Some of the juices were fortified with 1,000 international units (IU) of vitamin D; others were vitamin-free placebos that looked and tasted the same. The capsules also came with or without vitamin D. Participants were randomly assigned one of each.
About 85 percent of the participants began the study with blood levels of vitamin D below the recommended healthy minimums, report the researchers in the American Journal of Clinical Nutrition. Over the course of the 11 weeks, levels among those receiving vitamin D rose significantly. And the rise appeared to be the same regardless of whether the vitamin was consumed in juice or capsule form.
As expected, participants who had received both placebos showed no improvement in their vitamin D levels.
"The consumer now has one more option for obtaining vitamin D in the diet," Dennis Wagner, a PhD candidate at the University of Toronto, told Reuters Health by email. His research group recently added to the list themselves: cheese.
Unfortunately, he said, government regulations currently allow only 100 IU of vitamin D to be added to a serving of food or drink.
While that number could go up when the U.S. government revises its dietary guidelines this summer, Holick is concerned that it will still be too low to ensure healthy levels of vitamin D through diet alone. He recommends 2,000 IU a day for adults, and 1,000 IU for children.
Natural food sources are rare - mostly just oily fish and mushrooms - and Holick thinks it would be unrealistic to expect everyone to start taking supplements.
His solution is a controversial one: short spurts of unprotected time in the sun, the major natural source of vitamin D. He does, however, advise always protecting the face.
"Mother Nature designed the system very early to guarantee that we got enough vitamin D," said Holick. "Everyone was outside all the time, making it for free.'"
Wagner agrees, saying that humans are able to make a healthy dose of vitamin D in a relatively short amount of time before the skin starts to turn red and the risk of skin cancer begins to rise.
"However, the reliance on sunlight exposure as the primary source of vitamin D is often impractical, especially in northern latitudes during the winter," added Wagner. "An increase in the number and variety of foods fortified with vitamin D will increase the availability of this important vitamin ... and prevent the detrimental health consequences associated with vitamin D deficiency."
SOURCE: here American Journal of Clinical Nutrition, April 28, 2010.