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Vitamin D Intake Vital for Bone Health
By Ed Edelson
TUESDAY, Nov. 8 (HealthDay News) -- A new Icelandic study bolsters recommendations that vitamin D supplementation should be increased to help promote bone health and ward off diseases like osteoporosis, American experts say.
"Our data suggest that vitamin D sufficiency is more important that high calcium intake," said Dr. Gunnar Sigurdsson, professor of endocrinology and metabolism at Landspitali-University Hospital in Reykjavik. "You need less calcium for normal homeostatis (balance) if your vitamin D (or sunshine) is good. But still you need some calcium in your diet."
Calcium is important for reducing osteoporosis-linked bone loss in older people, and vitamin D -- which the body makes naturally through exposure to sunlight -- plays a vital role in helping the body absorb that calcium. Supplements can also be used to raise vitamin D levels.
The Icelandic study analyzed levels of parathyroid hormone (PTH), which regulates blood levels of calcium, in 2,310 healthy people on the basis of both vitamin D and calcium intake.
The researchers found that levels of that hormone depended more on vitamin D than on calcium.
"Our results suggest that vitamin D sufficiency can ensure ideal serum PTH values even when the calcium intake level is less that 800 milligrams a day, while high calcium intake (greater than 1,200 milligrams a day) is not sufficient to maintain ideal serum PTH, as long as vitamin D status is insufficient," the researchers wrote.
The study results appear in the Nov. 9 issue of the Journal of the American Medical Association.
The findings add "to the current opinion that recommendations for vitamin D intake should be adjusted upward," said Susan Harris, a nutritional epidemiologist at the Tufts University Jean Mayer Human Nutrition Research Center on Aging.
Current recommendations call for 300 to 600 International Units of vitamin D a day, with the amount increasing with age. "Quite a few people advocate as much as 1,000 International Units a day, with 1,000 to 1,200 milligrams of calcium," Harris said.
One of those advocating much higher levels of vitamin D intake is Dr. Robert P. Heaney, an endocrinologist who holds the title of university professor at Creighton University, in Omaha, Neb.
"I am concerned about the elderly and infirm," Heaney said. "They don't make as much vitamin D as other people and they have a higher requirement for it. We need to consider giving everyone enough so that the vulnerable get as much as they need. I think we could do that without endangering people who get above-the-normal blood level range, but that is not a universal consensus."
Vitamin D is an unusual nutrient, Heaney noted, because people get very little of it from food. "My best estimate is that the body uses 4,000 International Units a day," he said. "We get about a tenth of that by mouth. The other 90 percent comes from the skin, created by exposure to sunlight."
And exposure to sunlight can vary widely, affected by not only the weather but also social influences, Heaney said. For example, vitamin D deficiency is common in Saudi Arabia, he said, because men and women cover most of their bodies with flowing robes.
And there is still a lot to be learned about vitamin D, Heaney said. "Vitamin D is probably more important than most of us realized until recently," he said. "But we have studied it in the context of vitamin deficiency. We have to do a better job of nailing down the optimum daily requirements."
Osteoporosis, which increases the risk of fractures in the elderly, is explained by the National Institutes of Health.
http://www.forbes.com/lifestyle/health/ ... 29005.html