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Recently, a nutritional newsletter I subscribe to had the following headline: Vitamin D improves physical performance.

That got my attention.

I’ve long felt vitamin D is one of the most underrated vitamins on the planet, for reasons I’ll discuss in a bit. I’ve also long felt most of us are far too sun phobic for our own good. And the sun is our best source of vitamin D.

But as great as I think both sunlight and vitamin D are for health and for the prevention of disease, they also have an important connection to overall energy and well-being. Three recent studies shed some light on the connection.

One 2005 study by Netherlands researchers, reported at the American Society of Mineral and Bone Research’s 27th annual meeting in Nashville, showed that low levels of vitamin D were associated with low physical performance.

“This study shows that neuromuscular performance in (people) with lower levels of vitamin D was significantly lower than those with adequate levels,” said Ilse Wicherts, a doctoral candidate at the Vu University Medical Center in Amsterdam, and one of the researchers on the study. “The change in performance scores with increasing serum (vitamin D) was significant,” she said.

Granted, this study was done on older people, where physical performance is a matter of some urgency; the folks whose physical performance is impaired literally can’t get up out of a chair without help. But there’s no reason to think the effect of vitamin D that they demonstrated in this older population doesn’t happen with “young 'uns” as well. Why would it not?

Even more recently, researchers writing in the Journals of Gerontology Series A: Biological and Medical Sciences analyzed data from a study known as the InChianti study (Invecchiare in Chianti, Italy). The InChianti study is a large population-based study of older people aimed at identifying risk factors for late life disability, something every one of us wants to avoid like the plague. The study looked at more than 1,000 participants aged 65 and older in the Chianti area of Italy. It found that vitamin D status was inversely associated with poor physical performance. Those with the lowest levels of vitamin D performed the worst on a battery of physical performance tests, including handgrip strength, balance, and the like. Those with the highest levels performed the best. Interestingly, nearly 30 percent of the sample had vitamin D levels that would be considered deficient. We can only guess at how many had vitamin D levels that were less than optimal.

Although the effect of vitamin D on physical performance is documented, you might think we’d have to play connect-the-dots to make any assumptions or reach any conclusions about energy and well-being. But we don’t. Researchers in the prestigious Nutrition Journal specifically investigated the effect of vitamin D supplements on well-being.

First they gathered outpatients in an endocrinological clinic who, by any measure, had levels of vitamin D in their blood lower than what is considered desirable by even the most conservative estimates. Current opinion is that desirable vitamin D concentrations should exceed 70 nmol/L, and these folks had levels of less than 61 in spring and summer, and were expected to develop concentrations of less than 40 by the winter. They gave the participants one of two doses of vitamin D supplements—either 600 IUs per day or 4,000 IUs per day.

The subjects were asked to fill out the Seasonal Health Questionnaire, a standard instrument to screen for seasonal affective disorder, as well as an additional 10 questions that functioned as a well-being questionnaire, which could easily have been labeled an “energy” questionnaire, since well-being is pretty much a synonym for energy and vitality. They answered the questionnaires both before the start of the supplementation program and after the completion of the three-month research.

  1. Has your general health been less than average lately?
  2. Have you felt less rested upon waking from sleep lately?
  3. Have you experienced a down feeling or inappropriate guilt?
  4. Have you felt less socially active lately?
  5. Have you been indecisive lately?
  6. Have you felt less productive or less creative lately?
  7. Has your appetite increased or decreased?
  8. Have you experienced any cravings for carbohydrates (bread, pasta, rice, sugary foods), more than normal?
  9. Has it been more difficult to deal with daily stress?
  10. Have you felt irritable or anxious lately?

The well-being score for this part of the study was simply the total number of “yes” responses. The lower the score, the better the well-being. Simple.

Both vitamin D groups exhibited highly statistically significant (meaning dramatic and almost definitely not coincidental) improvements in well-being. The response was greater with the higher dose of vitamin D than with the lower dose, but there was improvement with both doses. The only group that did not improve was a subgroup of participants who had been consuming the higher dosage (4,000 IUs) since the previous year, and that’s because they were already so high on the well-being scale to begin with.

And in case you’re wondering, the authors clearly state, based on a ton of research, that “vitamin D consumption in the amount of 4,000 IUs per day is safe and physiologic for adults.” Did I mention the current Recommended Daily Allowance is 400 IUs? (Actually I didn’t. I just wanted to make sure you were paying attention.)

So the connection between vitamin D, energy, and well-being is pretty clear. Patients in the northern United States who show up at doctors’ offices with diffuse musculoskeletal symptoms have low levels of the vitamin in their blood. Women in Saudi Arabia who have low back pain do too (and respond well to supplementation of what we would consider a very high level of vitamin D—5,000-10,000 IU per day). Depression scores in the northern latitudes are worst between December and February when vitamin D levels are at their lowest. And one study of healthy students concluded that as little as 400 or 800 IUs of vitamin D supplementation per day for only five days during the winter improved mood.

Given that many of us don’t actually go in the sun at all or don’t have a lot of access to it, I think it makes sense to take a vitamin D supplement. In fact, I think it’s a no-brainer. Not only can it improve your energy and performance, it has anti-cancer activity as well, not to mention it’s critical for bone health. And most of us are massively deficient.

Here’s something else to think about, particularly if you’re overweight. Vitamin D is stored in your body fat, so if you’ve got enough of it in your cellular bank account, you can always release it when you need it—like in the winter time. But in obese people vitamin D gets sucked into the fat cells and it can’t get out. And Dr. Michael F. Holick’s (Boston University Medical Center) research has found because of this, overweight people are much more prone to vitamin D deficiency; their vitamin D bank account system just doesn’t work as well. So if you are overweight, that’s all the more reason why you should supplement with an even higher dose of vitamin D if you want to get all the great, anti-cancer fighting benefits of this vitamin.

So give your energy and your health a boost with a daily shot of vitamin D. A conservative recommendation is at least 1,000 IUs a day, preferably 2,000 IUs Best of all, they’re tiny little supplements, easy to swallow, and even the best brands are inexpensive.

Jonny Bowden, PhD, CNS

Jonny Bowden, PhD, CNS, (aka "The Rogue Nutritionist") is a nationally known expert on weight loss, nutrition and health. He is a board-certified nutritionist with a master’s degree in psychology and the author of nine books on health, healing, food and longevity including two best-sellers, “The 150 Healthiest Foods on Earth” and “Living Low Carb”. A frequent guest on television and radio, he has appeared on Fox News, CNN, MSNBC, ABC, NBC, and CBS as an expert on nutrition, weight loss, and longevity. He is a past member of the Editorial Advisory Board for Men’s Health magazine, is the Nutrition Editor for Pilates Style, and is a regular contributor to AOL, Vanity Fair Online, Clean Eating Magazine, Better Nutrition, and Total Health Magazine Online.