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How much vitamin D do we really need?

A few days ago, the prestigious Institute of Medicine declared that Americans need more vitamin D — although not as much as some experts believe.

What's a health-conscious consumer to do with this new information?

First, some background: Vitamin D is probably the hottest nutrient of the moment. And that's not just because our bodies make it when we're exposed to the sun's rays.

It is well known that vitamin D is needed to metabolize calcium for strong bones. That's why seniors with adequate vitamin D are less likely to suffer hip fractures.

Vitamin D has also been linked with a lower risk of some cancers (particularly colon cancer), autoimmune illnesses, infectious diseases and cardiovascular disease.

Additionally, there is a simple blood test for vitamin D levels that has become very popular; some doctors are including it in routine physicals.

The government's recommended daily allowance (RDA) for vitamin D in healthy children and most adults is 400 international units a day, a level that many experts have long considered too low.

On Tuesday, the Institute of Medicine recommended that this be increased to 600 IU for children and most adults; after age 70, the recommendation is 800 IU.

"Have they gone far enough? In my opinion probably not, but it's a step in the right direction," the prominent vitamin D researcher Dr. Michael Holick of Boston University Medical Center said Tuesday.

I agree with Dr. Holick that the IOM could have gone further, to around 2,000 IU a day for most people. I also disagree with the group's position that most people don't need vitamin D supplements.

Few foods naturally contain vitamin D; probably the best source is fatty fish such as salmon. Others are fortified with it, including milk — but a cup of fortified milk has just 100 IU, which illustrates the challenge of getting enough vitamin D through diet. Sun exposure is another way to get vitamin D, although even in Florida you might not get enough this way if you follow recommendations to protect your skin from the sun.

As a physician specializing in diet and weight loss, I believe many, if not most, people need to take vitamin supplements to reach the recommended levels.

But the IOM is correct when it cautions that it's possible to get too much of a good thing. Extremely high doses of vitamin D — above 10,000 IUs a day — cause kidney damage. The IOM report sets 4,000 IUs as an upper daily limit.

So taking a daily 1,000 to 2,000 IU supplement won't put you at risk of getting dangerous levels of vitamin D.

The bottom line in my opinion is that Americans don't get enough vitamin D. Fortified foods have helped, but they aren't the entire answer.

So what I do recommend? It is critical to ensure you get enough vitamin D from supplements, as it is next to impossible to get it from the food you eat, or from sunshine unless you are a devoted sun worshiper. Some people, including those who have dark skin or certain medical conditions, need even more than average.

Here are the supplementation guidelines I follow and recommend:

• Without sun exposure most children need 800-1,000 IU per day.

• Lactating women need at least 1,000-2,000 IU per day.

• Most adults need at least 1,000 IU daily, and I think 2,000 IU daily is better; if you have the vitamin D blood test and it comes back low, your doctor might recommend higher doses until the deficiency is corrected. People over 70 need at least 1,200 IU.

Your health care professional should be able to guide you in the proper dose for your needs.

Larry Vickman, M.D., is medical director of Inches and Pounds of Tampa Bay. He is board certified in family practice and emergency medicine and has completed two of three parts for board certification in medical bariatrics (weight management). You may contact him at (813) 868-1511 or at [email protected]

How much vitamin D do we really need? 12/03/10 [Last modified: Friday, December 3, 2010 3:30am]
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