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Probably not. "Deficiencies have been found in people across the age spectrum, from babies with the bone-weakening disease rickets to the elderly in nursing homes," says Catherine Gordon, MD, a pediatric bone specialist at Children's Hospital Boston.When she tested 307 healthy teenagers, Dr. Gordon found that 24 percent were vitamin D deficient. When measured against the higher blood levels experts now say we need for good health, 42 percent of the young people fell short. Similar results have been found among adults of all ages. "Worldwide, one billion people are vitamin D deficient," explains Dr. Holick.
Check out the current vitamin D guidelines and find out which foods are its best sources.
Dr. Holick and others now prescribe at least 1000 IU daily from the sun, supplements or food. A diet designed to give you 1000 IU of D daily would be pretty monotonous (mostly milk, juice and cereal that have been fortified, plus oily fish and cod liver oil), so the alternatives are the sun and supplements.
Most multivitamins provide 400 IU of D, a level calculated to prevent rickets. This disease was nearly eradicated in the 1930s, when milk was fortified, but is now on the rebound thanks to widespread vitamin D deficiency. The government's recommended daily allowances for D will be re-examined starting in 2008 and may be pushed up to 1000 IU (or higher) for everyone over age one in 2010, says Dr. Holick. In the meantime, he takes 1200 IU daily ("and so does my family"). Holick and other experts see no reason why we shouldn't all aim for at least 1000 IU right away. Look for "vitamin D3" on the label, the most effective form, according to Dr. Garland.
There's little danger of overdose, say experts. In fact, some researchers are beginning to forecast an RDA of 2000 IU. That much is generally considered safe, but it's not a great idea to assume that more is better.
Toxicity symptoms include nausea, vomiting, loss of appetite and constipation. Excess vitamin D can also dangerously elevate calcium levels, causing confusion and bizarre behavior. However, you can't overdose on vitamin D from the sun. Once the skin absorbs enough UVB rays to make D, the conversion process shuts down. But the threat of sunburn, of course, continues.
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