It seems that every day we read about the next "wonder" nutrient or dietary supplement that we all need for better health. Generally, I treat these reports with a healthy dose of skepticism. It's not that I don't believe in the potential benefits of dietary supplements. Many supplements have proven benefits and can be a useful addition to a healthy eating plan. But it's not often that the next "wonder" nutrient really is necessary as a dietary supplement for everyone. Vitamin D just may be the exception to this rule.

Why D?

Vitamin D insufficiency and deficiency are much more common than health experts previously believed. A large study published in 2005 indicated that at least a third of American adults have low vitamin D levels in the body, which may increase risk of several types of cancer, heart disease, osteoporosis (excessive bone loss), auto-immune disease, and many other serious health problems.

Is It Too Late?

Vitamin D may be even more important for people who already have cancer. This means that even if there's a cancer diagnosis in your past, it's not too late to get the potential benefits of vitamin D. Several studies show that having more vitamin D in the body and/or taking a vitamin D supplement improves survival after diagnosis. This connection between more vitamin D and better cancer survival has been studied for melanoma, Hodgkin's lymphoma, and cancers of the lung, breast, prostate and colon.

The Current Recommendations

Another tip off that we all need more vitamin D is the mounting agreement among health experts that the Recommended Dietary Allowance (RDA), also called the Dietary Reference Intake (DRI), is set too low. A number of health experts who advise the government and nutrition panels that set the RDA and DRI feel that it is necessary to raise these numbers for vitamin D because so many people do not get enough of this nutrient.

At a minimum, it is suggested that these numbers should be doubled to 800 International Units (IU) from the current recommendation of 400 IU for most adults. Recent studies suggest that these numbers need to be as much as three to four times higher than the current level. This would raise the RDA/DRI for vitamin D to 1200 to 1600 IU per day for adults.

Where Do You Live?

As many people know, vitamin D is referred to as the sunshine vitamin. This is because exposure to sunlight can cause the body to manufacture vitamin D. But don't think of this as a free pass to get a suntan. You should never, ever "lay out" in the sun, increase your sun exposure on purpose, or use tanning beds for several reasons. Most importantly, exposure to the sun and tanning beds is the leading cause of skin cancer in this country, including melanoma, the deadliest type of skin cancer.

Furthermore, sun exposure is not a practical way to increase vitamin D for a significant number of people living in the United States. Many people live in locations where for nearly half of the year, the sun is not strong enough to allow the body to make vitamin D. If you live north of the 40th parallel (40 degrees north latitude) you are in this category. And if you don't live this far north, you should be using sunscreen anyway! Since it is not practical or safe to get vitamin D from the sun, it is important to get plenty of the nutrient from food and/or a dietary supplement.

Why Supplement?

In most cases, getting nutrients from food is healthier than getting them from supplements. Unfortunately, for vitamin D, food often does not provide enough vitamin D, making a supplement necessary. Some foods, such as milk and cereal are fortified with vitamin D, but many people do not eat enough of these foods to meet vitamin D needs. Other than this, vitamin D is not found naturally in many foods. Only oily fish, such as salmon, mackerel and sardines naturally contain plenty of vitamin D.

It's also reassuring to know that vitamin D is not as toxic as once believed. This doesn't mean you should load up on dozens of vitamin D pills each day. Vitamin D can be harmful in large doses. But it does mean that taken at moderate levels, vitamin D is very unlikely to cause health problems for most adults.

How Much Is Enough?

Current vitamin D recommendations tell us that most healthy adults safely can take up to 2000 IU per day. We know that the RDA/DRI is set too low, but there is no reason to take extremely high doses of vitamin D. Much of the research on vitamin D indicates that taking 1000 to 2000 IU per day is appropriate for reducing risk of cancer and its recurrence. Remember, after a certain point, more is not better!

Keep in mind that your multivitamin probably contains some vitamin D and you may be getting some of this nutrient from fortified foods. Taking all of this into account, it is reasonable for most adults to take an extra vitamin D supplement that provides around 1000 IU of additional vitamin D per day.

There are some people who should NOT take extra vitamin D. This includes people who have elevated levels of calcium in their blood as a side effect of cancer or its treatment. Also, some experimental cancer treatments are comprised of powerful forms of vitamin D. If you are taking one of these vitamin D experimental medications, do not take a vitamin D supplement.

Rare Recommendation

It is rare indeed for me to recommend a dietary supplement, across the board, for all healthy people, nearly all cancer patients, and for those with a history of cancer. In general, I really push people to get their nutrition from food. But for vitamin D, I'll make an exception! Take your vitamin D, because chances are, you need it.