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Do you need more vitamin D?

Research suggests that higher doses of the sunshine vitamin may be good for your health, but it’s too soon to be sure.

Vitamin D is needed to maintain strong bones. A flood of recent studies have also hinted that vitamin D may help to prevent a wide variety of health problems—including some of great interest to men, like heart disease and cancer. You clearly need some vitamin D to be healthy but should
you take more?

Right now, it would be premature to double down on vitamin D supplements. “There is a history of individual nutrients, taken at higher doses than obtained from diet alone, looking like the new cure-all, but then the confirming studies don’t demonstrate that,” says nutrition researcher Howard Sesso, an associate professor of epidemiology at the Harvard School of Public Health. “Experience tells us that we don’t really know that it’s safe and it works until we do a definitive clinical trial.”

How much Vitamin D do adult men need?

At least 600 international units (IU) of vitamin D per day, and 800 IU if you are over 70, according to the Institute of Medicine.

The National Osteoporosis Foundation recommends a higher
dose to maintain optimal bone health: 800 to 1,000 IU per day for everyone 50 and older.

Vitamin D and health

In clinical trials, participants are randomly assigned to take a supplement or a placebo. These randomized clinical trials are the gold standard for
determining if a drug or treatment is safe and effective.

However, most health research on vitamin D consists of observational studies, which just follow large groups of people for long periods of time. Some of these studies have shown that people who have adequate levels of the nutrient in their bodies are healthier than people who are deficient.

But observational studies have an important limitation. Finding that high blood levels of vitamin D coexist with good health does not necessarily mean that one causes the other. Perhaps vitamin D declines because of illness itself, or because of the unhealthy lifestyles that make people ill. For example, a person who eats a poor diet, is overweight, and never exercises would tend to have lower levels of vitamin D. That would make low vitamin D a red flag for an unhealthy lifestyle, not the cause of it, but taking more vitamin D would not necessarily fix it.

Randomized clinical trials can help to resolve the issue of cause and effect. In such studies, people in one group take a vitamin D supplement, and those in a matched comparison group take a
placebo pill. The researchers wait to
see if the people who took the real pill are less likely to develop health conditions or live longer than those in the placebo group.

Unfortunately, none of the completed clinical trials to date support a general recommendation to take extra vitamin D to prevent specific health conditions. Nor have they revealed how much vitamin D we would need to take, at what age we’d need to start taking it, and if it is safe to take over the long-term.

Food sources of vitamin D


Vitamin D

3 oz cooked sockeye salmon

450 IU

3 oz canned tuna (in water)

150 IU

1 cup whole milk

120 IU

1 cup breakfast cereal (no milk)*

100 IU

3 oz beef liver (cooked)

80 IU

1 egg (large)

40 IU

* Artificially vitamin fortified. IU = internatinal units

Images: Thinkstock

Studies of studies

Recently, two teams of researchers combined findings from hundreds of smaller studies, involving hundreds of thousands of people. The intention of these “studies of studies” was to get a general sense of the evidence that vitamin D prevents disease or leads to a longer life. The results were mixed.

The studies appeared in the medical journal BMJ in April 2014. One of them, touting itself as an “umbrella review,” pooled the findings of hundreds of smaller observational and clinical trials that looked at the effects of vitamin D on a total of 137 different health conditions and diseases. The review concluded only that the evidence is “suggestive” that vitamin D improves health, but “highly convincing evidence of a clear role of vitamin D does not exist for
any outcome.”

The other review covered 95 studies involving a total of 880,000 people. Compared with participants who were deficient, based on their blood levels of vitamin D, those with the highest levels in their blood had a lower risk of heart attacks, strokes, and cancer, and were less likely to die from
any cause.

The researchers also took a closer look at the clinical trials to see if the type of vitamin D supplement mattered. People who took vitamin D3 supplements were less likely to die of any cause, compared with people who took vitamin D2. Vitamin D3 is the type our bodies make when exposed to sunlight, and you also get it from eating animal foods like fish. Vitamin D2 comes from plants.

But this after-the-fact analysis of the trials cannot be used to recommend that people take D3. That would require—you guessed it—a clinical trial.

How to get vitamin D

  • SUNSHINE: Vitamin D3 is made by your skin when exposed to sunlight, hence the nickname “the sunshine vitamin.” Depending on your latitude and the time of year, exposure to full sun for 10 to 15 minutes a day could produce the vitamin D you need, but remember that unprotected sun exposure raises the risk of skin cancer.

  • FOOD: Vitamin D is found in moderate quantities in some foods, especially fish, eggs, and organ meats. Few commonly eaten plants contain significant amounts of vitamin D, except for mushrooms.

  • SUPPLEMENTS: Vitamin D supplements can be obtained in 400 IU, 600 IU, and 1,000 IU and higher doses. The Institute of Medicine found that daily supplemental vitamin D up to 4,000 IU is generally safe.

No final answer

As promising as all this sounds, none of it is final. “These observational vitamin D studies have become almost a dime a dozen,” Sesso says. “It’s going to be hard to move the science forward until we really have a large-scale, well-designed clinical trial to provide definitive data on the long-term health effects of vitamin D supplementation.”

Safety is one concern. Years ago, observational studies suggested that taking extra beta-carotene and vitamin E were probably good for your health. But confirmatory clinical trials found that taking large daily supplemental doses of these nutrients did not improve health and might actually be harmful.

An important new vitamin D trial, based at Harvard-affiliated Brigham and Women’s Hospital, is underway. The VITamin D and OmegA-3 TriaL (VITAL) involves over 25,000 people. The goal is to find out if taking 2,000 international units (IU) of vitamin D or fish oil tablets reduces the risk of cancer, heart disease, and stroke in people who do not have a history
of these illnesses.

For the time being, it’s fine to keep taking your 600 IU to 800 IU of daily vitamin D along with calcium for bone health if your doctor advises it. But until VITAL and other studies say otherwise, no additional dose of D
is warranted.

Even then, you should look at your lifestyle. “I usually try to steer people away from taking individual high-dose vitamin and mineral supplements and to think more broadly about their diet and how to improve it,” Sesso says.

And it couldn’t hurt to get outdoors a bit more in the sun to make your own supply of the sunshine nutrient. These steps would make for a healthier lifestyle then popping supplements.

Posted by: Dr.Health

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