Calcium Secondary to Vitamin D for Bone Health
November 9, 2005
A new study from Iceland supports American experts' recommendation that vitamin D should be taken in larger quantities. The study suggests that vitamin D intake is more important than calcium for improving bone-health and preventing conditions such as osteoporosis.
The study by Laufey Steingrimsdottir, PhD, et al., was published in the Journal of the American Medical Association on 9 November and reported by Healthday.com/ScoutNews LLC on 8 November 2005.
"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, according to Healthday.com. "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."
Vitamin D and calcium are interconnected in the body. Adequate calcium levels are necessary to reduce osteoporosis-linked bone-loss in older people, while vitamin D plays a vital role in helping the body absorb calcium.
The body naturally makes vitamin D when the skin is exposed to sunlight. Supplements are also available that enhance vitamin D levels.
Results of the Study
The study by Dr Steingrimsdottir et al examined levels of parathyroid hormone (PTH) in 2,310 healthy people, relative to both vitamin D and calcium intake. PTH regulates blood levels of calcium.
The results showed that PTH levels 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 than 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," Dr Steingrimsdottir et al wrote.
The results strengthen "current opinion that recommendations for vitamin D intake should be adjusted upward," reported Susan Harris, a nutritional epidemiologist at the Tufts University Jean Mayer Human Nutrition Research Center on Aging, to HealthDay.com.
How Much Vitamin D Is Enough?
Currently, health professionals recommend taking 300-600 International Units (IU) of vitamin D daily, and that amount increases 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, according to HealthDay.com.
Dr Robert P Heaney, an endocrinologist and university professor at Creighton University, in Omaha, Nebraska, also supports much higher vitamin D intake levels for older people.
"I am concerned about the elderly and infirm," Heaney said to HealthDay.com. "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 unusual in that little of it comes from food, Heaney notes. "My best estimate is that the body uses 4,000 International Units a day," he reportedly said. "We get about a tenth of that by mouth. The other 90 percent comes from the skin, created by exposure to sunlight."
Of course, how much of one's skin is exposed to sunlight varies with not only climate but also local custom. For example, despite the strong sunshine in Saudi Arabia, vitamin D deficiency is common because men and women cover most of their bodies with robes, said Heaney.
"Vitamin D is probably more important than most of us realized until recently," he said to HealthDay.com. "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."
For more information about osteoporosis, talk to your health practitioner or visit these websites:
Sources:
Relationship
Between Serum Parathyroid Hormone Levels, Vitamin D Sufficiency,
and Calcium Intake, Laufey Steingrimsdottir, PhD, et al.,
Journal of the American Medical Association, volume 294,
pages 2336-2341, 9 November 2005.
Vitamin D
Intake Vital for Bone Health: Calcium consumption is secondary, a
new study finds, Healthday.com, 8 November 2005.
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