Vitamin D—One of the Simplest Solutions to many Health Problems

VITAMIN D3 is the one you need to be taking IF you are not out in the sun every day

By Dr. Mercola
Vitamin D deficiency is a pandemic in the United States, but many Americans, including physicians, are not aware that they may be lacking this important nutrient. 
Despite its name, vitamin D is not a regular vitamin. It's actually a steroid hormone that you get primarily from either sun exposure or supplementation, and its ability to influence genetic expression that produces many of its wide-ranging health benefits.
Researchers have pointed out that increasing levels of vitamin D3 among the general population could prevent chronic diseases that claim nearly one million lives throughout the world each year. Incidence of several types of cancer could also be slashed in half.
Vitamin D also fights infections, including colds and the flu, as it regulates the expression of genes that influence your immune system to attack and destroy bacteria and viruses.
In this interview, one of the leading vitamin D researchers, Dr. Michael Holick, expounds on these and many other health benefits of vitamin D. He's both an MD and a PhD, and wrote the book, The Vitamin D Solution.
Since the early 2000s, scientific investigations into the effects of vitamin D have ballooned. By the end of 2012, there were nearly 34,000 of them. Dr. Holick is one of those who has really helped advance our understanding of the massive importance of vitamin D—far beyond its influence on bone metabolism.
"I've been doing vitamin D research for more than 40 years," he says. "As a graduate student for my master's degree, I was responsible for identifying the major circulating form of vitamin D, 25-hydroxyvitamin D that doctors typically measure now for vitamin D status in their patients. For my Ph.D.,
I identified the active form of vitamin D [1,25-dihydroxyvitamin D] while working at Dr. DeLuca's laboratory."

Are You Vitamin D Deficient?

Before the year 2000, very few doctors ever considered the possibility that you might be vitamin D deficient. But as the technology to measure vitamin D became inexpensive and widely available, more and more studies were done, and it became increasingly clear that vitamin D deficiency was absolutely rampant. For example:
  • The Centers for Disease Control and Prevention (CDC) reported that 32 percent of children and adults throughout the US were vitamin D deficient
  • The National Health and Nutrition Examination Survey found that 50 percent of children aged one to five years old, and 70 percent of children between the ages of six to 11, are deficient or insufficient in vitamin D
  • Researchers such as Dr. Holick estimate that 50 percent of the general population is at risk of vitamin D deficiency and insufficiency
I've often said that when it comes to vitamin D, you don't want to be in the "average" or "normal" range, you want to be in the "optimal" range. The reason for this is that as the years have gone by, researchers have progressively moved that range upward.
At present, based on the evaluation of healthy populations that get plenty of natural sun exposure, the optimal range for general health appears to be somewhere between 50 and 70 ng/ml. For treatment of chronic disease such as cancer, recommendations go even a bit higher than that. As Dr. Holick explains:
"The Institute of Medicine, including the Endocrine Society, recommends at least 20 for bone health. But there's this area between about 21 and 30 that we consider to be an insufficient level. Most experts agree that if you're above 30 nanograms per milliliter, this is a healthy level.
Because of its variability in the assay, the recommendation from the Endocrine Society Clinical Practice Guidelines that looked at all the literature and made recommendations for prevention and treatment of vitamin D deficiency for doctors is 40 to 60 nanograms per milliliter...
GrassrootsHealth has also been looking at this issue and also recommends 40 to 60 nanograms per milliliter as the ideal level."
... A study was done in Maasai warriors who are outside every day. That really gives us an insight where we should all be with our blood levels of 25-hydroxy D. They were found to be around 50 nanograms per milliliter."

Sunshine—The Best Way to Optimize Your Vitamin D Levels

I firmly believe that appropriate sun exposure is the best way to optimize your vitamin D levels. In fact, I personally have not taken a vitamin D supplement for three or four years, yet my levels are in the 70 ng/ml range. If you can't get enough sunshine, then a safe tanning bed would be your next best option. What makes for a safe tanning bed? Most tanning equipment use magnetic ballasts to generate light.

These magnetic ballasts are well known sources of EMF fields that can contribute to cancer. If you hear a loud buzzing noise while in a tanning bed, it has a magnetic ballast system. I strongly recommend you avoid these types of beds and restrict your use of tanning beds to those that use electronic ballasts.
Dr. Holick recommends protecting your face when using a tanning bed, and to only go in for half the time recommended for tanning. Make sure the tanning bed you're using is putting out UVB radiation. There are some on the market that only put out UVA, as this is what creates a tan. UVA rays are also the ones responsible for skin damage, however, and they do NOT make your skin produce vitamin D.

Beds tend to vary between three to 10 percent UVB, and the higher the percentage of UVB, the better. There are also beds that make UVB only. They're not as popular since they won't make you tan, but if you're only doing it solely for the health benefits, then a UVB tanning bed is certainly an option.
"I think that you're right," Dr. Holick says. "We had shown many years ago that during the winter time, if you live above Atlanta, Georgia, you basically cannot make any vitamin D in your skin from about November through March. Obviously, you need to either take a supplement or use a tanning bed or an ultraviolet light that will produce vitamin D...  
I typically recommend, if you're going to go out into the sun, expose your arms, legs, abdomen and back, two to three times a week for about half the time it would take to get a mild sunburn... [W]hen you make vitamin D in your skin, it lasts two to three times longer in your body.
You also make additional photoproducts in your skin. There's some evidence that suggests that maybe these photoproducts have some unique biologic properties in the skin. Because we do know that sensible sun exposure decreases risk for malignant melanoma, and it could be that some of these photoproducts are helping in that process. Beta-endorphin is certainly made in the skin during exposure to sunlight. That's probably the reason why people feel better when they're exposed to sunlight."

Want Safer Sun Exposure? There's an App for That!

Dr. Hollick  helped consult for a company that developed a smartphone app called DMinder, available on Based on your local weather conditions (reported from the weather service) and other individual parameters such as your skin tone and age, it tells you how much UV radiation you're getting, and how many units of vitamin D you're making. It will also tell you when to get out of the sun, to protect yourself from sunburn.
Beware that you CANNOT make any vitamin D when you're exposed to sunlight through glass since glass filters out most of the UVB that stimulates vitamin D production. All you're mostly getting are UVA rays, which penetrate deeply into your skin, causing wrinkling, and increasing your risk of skin damage and skin cancer. Also beware that UVA radiation is harsher in the morning, and late afternoon. So, contrary to popular advice, which was more tailored to tanning than optimizing your vitamin D stores, you'll want to avoid early morning and afternoon sun. According to Dr. Holick, you cannot make vitamin D until about 10:00 in the morning until about 3:00 in the afternoon.
Another important nugget that many people may not appreciate is to take into account daylight saving time. When you're in daylight saving time, the peak sun exposure is not noon – it's 1:00 pm. So if you want to get your maximum sun exposure, go out around 1:00.

Dosing Recommendations if You Need to Take a Vitamin D Supplement

If your circumstances don't allow you to access the sun then you really only have one option if you want to raise your vitamin D, and that is to take a vitamin D supplement. Here too recommendations vary, and there are no hard and fast rules.

While Dr. Holick disagrees with my recommendation to regularly test your levels in order to assess proper dosage due to the cost involved, I feel this really is your best bet. You want to make sure you're staying within the therapeutic range of 50-70 ng/ml year-round, so regardless of general guidelines, you may need to increase or decrease your dosage based on your personal requirements.
The Society Clinical Practice Guidelines Committee recommends the following dosages. Keep in mind that these guidelines are thought to allow most people to reach a vitamin D level of 30 ng/ml, which many still consider suboptimal for disease prevention.
  • Neonates: 400 to 1,000 IUs per day
  • Children one year of age and above: 600 to 1,000 IUs per day
  • Adults: 1,500 to 2,000 IUs per day
GrassrootsHealth offers a helpful chart showing the average adult dose required to reach healthy vitamin D levels based upon your measured starting point. Many experts agree that 35 IUs of vitamin D per pound of body weight could be used as an estimate for your ideal dose.
"I treat my patients, on average, with 3,000 units of vitamin D a day," Dr. Holick says. "It's been very effective. I've published a paper that over a six-year period of time, most of my patients on a 3,000-unit equivalent a day has between 40 and 60 nanograms per milliliter and there is no toxicity.
If you're obese, you need two to three times more vitamin D... But for my patients who are at a normal weight, usually 3,000 to 4,000 units a day is adequate to maintain a healthy blood level of 25-hydroxyvitamin D. I personally take 3,000 units a day. My blood level, on average, is about 55 nanograms per milliliter."
According to Dr. Holick, it makes no difference if you take your vitamin D daily or weekly, or even monthly. Personally, I'd recommend taking it daily. That way, if you miss a day or two, it's not quite as bad as missing an entire week. That said, it is fat-soluble, so a lot of it enters your body fat and is slowly released from there. So if you miss a day, you can take double the dose the next day.