Vitamin D - Fact and Fiction

The media has been full of information lately about Vitamin D. Not all of it has been correct.

Everyone from the your local newspaper to Dr. Oz have been pushing the public to increase their intake of Vitamin D. The claimed health benefits range from increased energy to cancer prevention and reductions in heart disease. While Vitamin D is an important nutrient some of its benefits are well documented and others are not. This newsletter will attempt to clarify these issues, but first a bit of the basics...

• Where do we get Vitamin D?

Vitamin D is obtained by the body from several sources. We get some naturally from our food ( fatty fish, eggs), some from fortified foods (milk, bread, and cereals) and some from sun exposure.

• How much Vitamin D do we need?

The USDA recently increased its recommendation for vitamin D. The recommended daily allowance for individuals from 1yr - 70 yrs old is 600 IU daily. Those older than 70 may need 800 IU daily. 

• Is it possible to get too much vitamin D?

Vitamin D is a fat soluble vitamin that deposits in the liver. Too much vitamin D can be toxic since the body can not easily get rid of excess amounts like it can with water soluble vitamins. The maximal amount of vitamin D that is considered unlikely to cause adverse effects is 2000 IU daily for individuals older than 1 year. 

• What are the known benefits of vitamin D?

Vitamin D has a number of well documented benefits. For many years it has been known that a deficiency in vitamin D can lead to a disease of the bones known as rickets. In addition to its importance in bone formation, Vitamin D is used by the body’s immune system and muscles. One of Vitamin D’s most important functions is in the absorption and regulation of Calcium levels which is why it’s so important to bone development.

• If all of this is old news, why all the recent attention to vitamin D?

In the past few years there have been a number of studies suggesting that vitamin D might be associated with reduced rates of some types of cancer and heart disease.  While these studies have been intriguing they have not been strong studies and results have been inconsistent.

Most of the studies involving Vitamin D have been epidemiological studies. For example, scientists noticed that people living in lower latitudes where it is sunnier where less likely to have colon cancer. They postulated that these people had higher sun exposure and higher vitamin D levels and therefore Vitamin D might explain the difference. The problem with studies like this is that there may be many other differences between these groups of people like diet, race, ethnic background, availability of heath care etc. which may have lead to the difference in cancer rates.

The most reliable type of study is a double blind placebo controlled study. This sort of study is the best way to identify whether there is a real correlation between two factors such as Vitamin D intake and cancer. To date no well designed placebo controlled studies have been done that show a reliable link between increased vitamin D intake and cancer reduction, and NONE have looked at the benefits or risks of measuring and then supplementing low vitamin D levels

Unfortunately there has been a rush to judgment on this issue within the media and even among some in the medical community in an effort to be on the leading edge. Many have begun telling people to have their vitamin D levels checked and have even recommended taking very large doses of Vitamin D if the levels are low. At the moment there is no evidence that this approach is  beneficial or even safe.

• As a patient what should I do? 

For now the only thing that any adult should do is to make sure that they are getting no less than 600 IU/day of vitamin D and no more than 2,000 IU. Efforts to measure Vitamin D levels are not recommended and efforts to supplement low levels with high doses of vitamin D may be misguided and potentially harmful.


Please visit the link below for more information on Vitamin D from the National Institutes of Health.

NIH Vitamin D Fact Sheet