Are you getting enough Vitamin D? Probably NOT!

Until recently, it was commonly believed that a daily dose of sunshine guarantees adequate vitamin D levels. Well, not anymore.

The latest studies are showing that most people are vitamin D deficient. Although our bodies do manufacture vitamin D when exposed to sunshine, how much depends on where you live and how much exposure you get. In fact, people who live in areas where the sun rarely shines make no vitamin D at all, and must depend entirely on dietary supplements and vitamin D-fortified foods.

Current recommended daily intakes (RDIs) of vitamin D are 200 IUs for people up to 50 years of age, 400 IUs for people between 51 and 70, and 600 IUs for over 70 years. But according to a recent study published in the Journal of Nutrition (March 9, 2009) adults need at least four times the current recommended dose.

In the study, young women (about 22.2 years of age) were given either a placebo or vitamin D3 supplement (200 IUs) between March and September of 2005, and then randomly assigned to receive either placebo or a daily vitamin D3 supplement (20 micrograms) until February 2006.

The researchers found that among the 86 women who completed the study, 80% of those receiving 20 micrograms (800 IUs) of vitamin D supplements achieved optimal concentrations of vitamin D (serum blood levels of at least 75 nmol/L) when compared to only 10.9 nanomoles per liter in the placebo group. The researchers concluded that this dose is adequate to optimize vitamin D levels in most, but not all, young women in Maine.

Why is Vitamin D important?

Vitamin D refers to two biologically inactive precursors—D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Vitamin D3 is produced in the skin upon exposure to UVB radiation (290 to 320 nm), and is more bioactive.

Vitamin D deficiency may exacerbate osteopenia, osteoporosis, muscle weakness, fractures, some cancers, autoimmune diseases, infectious diseases and cardiovascular disease. There is also some evidence that vitamin D may reduce the incidence of several types of cancer and type-1 diabetes.

Vitamin D3 Prevents Fractures

A new study conducted by researchers at the University of Zurich recently published in the Archives of Internal Medicine (March 23, 2009) found that older people can prevent fractures by taking vitamin D3 supplements, as long as they use a high enough dose and continue taking it. The researchers did a meta-analysis, examining the results of 12 randomized controlled trials of vitamin D supplementation. A total of 42,279 people were included in the studies of non-vertebral fractures, with 8 of the studies addressing hip fractures.

The researchers concluded that the vitamin D3 supplements cut the risk of any non-vertebral fracture by 14 percent, and of hip fractures by 9 percent. It’s important to note that although quantities below 400 IU a day had no effect on fracture risk, people who consumed more than 400 IU daily had a 20 percent lower risk of any type of fracture and an 18 percent lower risk of hip fracture.

Can you get enough vitamin D3 through food?

The answer is no, for most people. In an interview with Reuters, Dr. Bischoff-Ferrari, one of the lead researchers of the meta-analysis, said you’d have to eat two servings of fatty fish like salmon or mackerel every day. She also recommends that younger adults increase their vitamin D3 supplementation.

So please take these new studies seriously, and start taking a high-dose vitamin D3 supplement today. It is an easy, inexpensive way to protect your bones, your overall health, and possibly extend your life.

Nelson, M.L. Blum, J.M, Hollis, B.W., Rosen, C., Sullivan, S.S. Supplements of 20 ug/d Cholecalciferol Optimized Serum 25-Hydroxyvitamin D Concentrations in 80% of Premenopausal Women in Winter. Journal of Nutrition, March 9, 2009, Volume 139, Pages 540-546, doi:10.3945/jn.108.096180

Heike A. Bischoff-Ferrari, et al. Arch Intern Med. March 23, 2009;169(6):551-561. Prevention of Nonvertebral Fractures With Oral Vitamin D and Dose Dependency: A Meta-analysis of Randomized Controlled Trials.
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Excess Weight Increases Need for Vitamin D

Heavier, older adults are known to have lower levels of vitamin D in their blood, an observation that was thought to be largely explained by the fact that heavier people often cover up more or spend less time outdoors in the sun.

But when Tufts researchers divided 381 men and women age 65 or older (who were participating in a study of calcium and vitamin D supplementation to prevent bone loss) into four groups based on their body fat percentage, they found no differences among the groups in the time spent outdoors, percent of skin exposed to the sun, or sunscreen use.

What they did find was that those with the highest percentage of body fat had 20% lower levels of vitamin D than those with the least body fat – a very significant difference.

This makes sense because vitamin D is a fat-soluble nutrient. "The idea is that somehow vitamin D is getting trapped in fat tissue, so it's not available to the blood for circulation," explained one of the study's authors, Dr. Susan Harris.

"In general, it seems that heavier people may need more vitamin D…because a given intake is not going to lead to the same blood level," Harris noted.

At what body fat percentage do vitamin D needs increase?

The American Council on Exercise guidelines state that men's body fat should be in the range of 6-25%, and women's body fat percentage should fall somewhere between 14-31%.

American Dietetic Association guidelines are more stringent. The ADA recommends that men's body fat be in the range of 15-18%, and women's in the range of 20-25%. Healthy male athletes might be as low as 5-12% body fat and healthy female athletes as low as 10-20%.

If your body fat percentage is higher than 25% (for men) or 31% (for women), you may need more vitamin D to prevent vitamin D deficiency than someone with a lower body fat.

How to determine your body fat percentage

A variety of affordable scales are now available for home use that measure body fat percentage along with weight. A good review of the options can be found at www.epinions.com. Your physician or fitness consultant at your gym may either use fat calipers or have a bioelectronic impedance machine to measure body fat.

Do you need more vitamin D3?

While higher body fat levels can predict vitamin D deficiency, checking your blood levels of D3 is the only way to determine your actual vitamin D status. Optimal blood levels of D3 range are thought to be 32 ng/mL (80 nmol/L). Anything lower than 30 ng/mL (75 nmol/L) indicates deficiency; levels greater than 150 ng/mL (375 nmol/L) indicate toxicity.

If your blood levels of D3 are below 30 ng/mL (75 nmol/L), ask your physician about taking 2,000 IU of vitamin D3 daily. Although recent recommendations suggest that in the absence of sun exposure, adults should ingest 1,000 IU of vitamin D3 per day, vitamin D3 supplements providing 2,000 IU/day may be more appropriate for heavier individuals.

Is taking 2,000 IU/day of vitamin D safe?

Currently, the tolerable upper limit for vitamin D set by the Institute of Medicine is 2,000 IU per day. However, many of the experts responsible for setting this limit now believe it needs to be substantially increased. Research published in the January 2007 American Journal of Clinical Nutrition reviewed dozens of vitamin D toxicity studies, including some in which volunteers took 100,000 IU a day without any adverse effects!

The authors of the vitamin D toxicity review concluded that the upper limit for daily intake of vitamin D could safely be set at 10,000 IU. This is not surprising when one realizes that just 10-15 minutes whole-body exposure to peak summer sun will generate and release up to 20,000 IU vitamin D3 into the circulation.

In the March 2007 issue of the American Journal of Clinical Nutrition, a group of 15 nutrition experts cited the vitamin D toxicity review in an editorial calling for an overhaul of vitamin D guidelines. The experts — including Dr. Walter C. Willett, chair of the Harvard School of Public Health’s nutrition department — noted that 400 IU only produces a very small increase in the amount of vitamin D circulating in the blood. Daily intake of about 2,000 IU is necessary before blood levels increase to 80 nmol/L (32 ng/mL), the level at which vitamin D is thought to have its full disease-fighting effects.

Hollis BW. Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: implications for establishing a new effective dietary intake recommendation for vitamin D. J Nutr. 2005 Feb;135(2):317-22.
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Holick MF. The role of vitamin D for bone health and fracture prevention. Curr Osteoporos Rep. 2006 Sep;4(3):96-102.
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Kimball SM, Ursell MR, O'connor P, Vieth R. Safety of vitamin D3 in adults with multiple sclerosis. Am J Clin Nutr. 2007 Sep;86(3):645-51.
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Vieth R, Bischoff-Ferrari H, Boucher BJ, et al. The urgent need to recommend an intake of vitamin D that is effective. Am J Clin Nutr. 2007 Mar;85(3):649-50.
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Vitamin D Supplements Reduce Risk of Death from All Causes

A meta-analysis published in the September 2007 issue of the AMA journal Archives of Internal Medicine reveals vitamin D supplementation is linked with reduced risk of death from any cause.

Researchers analyzed 18 randomized, controlled clinical trials involving a total of 57,311 participants. Subjects given supplemental vitamin D received doses ranging from 300 to 2000 IU (averaging 528 IU) daily over a 5.7 year average follow-up period.

Subjects who received vitamin D were found to have a 7% lower risk of dying of any cause compared to those who did not supplement with the vitamin. In half of the studies, blood levels of vitamin D were measured and were found to be 1.4 to 5.2 times greater among participants who received vitamin D supplements than in those who did not.

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