On Wednesday, November 30, 2010, the Institute of Medicine's Food and Nutrition Board (FNB) issued a report saying, in essence, that supplemental vitamin D over 800 IUs is unnecessary and could even be harmful (more on this in a minute). Should you ignore this report? Yes. And I'll tell you why.
The committee only looked at the amount of vitamin D known to be needed for strong bones. That's like evaluating an iPhone based solely on the ability of its built-in calculator to add and subtract. The calculator is one tiny feature of the iPhone, but it's hardly a complete picture of what a good smartphone can do.
Similarly, vitamin D is important for strengthening bones, but that's only one of the many important things this miraculous "smart" nutrient does. Vitamin D expert William Grant, PhD, puts it this way: "The health benefits of vitamin D extend to at least 100 types of disease, with the strongest evidence for many types of cancer (breast, colon, ovarian, pancreatic, prostate, and rectal), cardiovascular disease, type 1 and 2 diabetes, respiratory infections such as the flu and pneumonia, other infections such as sepsis, and autoimmune diseases such as multiple sclerosis."
A massive amount of research shows that low levels of vitamin D increase the risk for every disease mentioned by Grant. What's more, when people are low in vitamin D levels, it affects mood, ability to lose weight, physical performance, immune system function, and even chances of dying. (A 2008 study found that low levels of vitamin D increased the risk for death from any cause-called the mortality risk-by a whopping 26 percent compared with those who had "optimal" levels in their blood.) Which brings us to the question of "optimal" levels, and the related question of toxicity.
Dietitians and doctors are mired in a culture that looks at vitamin needs solely in terms of what's required to prevent deficiency diseases. The "recommended daily allowance" for vitamin C is the amount you need to prevent scurvy; the recommended daily allowance for vitamin B1 (thiamine) is the amount you need to prevent beriberi. I call this "minimum wage nutrition," and consider it utterly irrelevant to those interested in optimal health and well-being.
If you've got enough vitamin D in your system, taking more won't necessarily make you faster or stronger or give you the energy to run a marathon. Problem is, many people are very far from having "enough" of it. And when you don't have enough, it can cost you dearly in terms of energy, health, and physical performance.
We first began to notice the connection between vitamin D and physical performance when a pair of studies-one published in The Journal of Clinical Endocrinology and Metabolism and another by the Gerontological Society of America-reported on the relationship between vitamin D, physical performance, and disability in older people. In a third study, Netherlands researchers at The American Society for Mineral and Bone Research's annual meeting in 2005 also found that low levels of vitamin D are associated with low physical performance. In that study, older men and women with low serum levels of vitamin D performed significantly worse than a control group on standard tests of balance and strength. Scores for all tests showed significant improvement with increased vitamin D.
Subsequent research has confirmed, once again, that those with lower levels of vitamin D performed much worse than those who weren't deficient.
Memory, Weight Loss, and More
The literature on vitamin D is enormous, and the above studies are only the tip of the iceberg. Here's a quick overview of other research on the health benefits of vitamin D:
- According to Oregon State University researchers, vitamin D induces the expression of a gene that's antimicrobial.
- A study in the Archives of Internal Medicine found that adults with the lowest vitamin D levels were most likely to experience cognitive decline with age.
- Researchers measured circulating blood levels of vitamin D in overweight women and men, before and after they followed an 11-week diet plan (750 calories a day). You would expect everyone to lose on such a diet, and most did. But researchers found that "pre-diet" levels of vitamin D predicted weight loss success. For every increase of 1 ng/mL in blood levels of vitamin D, folks ended up losing almost a half-pound more on their calorie-restricted diet. In addition, higher baseline values of vitamin D in the blood predicted greater abdominal fat loss.
Your Ideal Dosage of D
So what is the optimal level of vitamin D anyway? Well-not surprisingly-there's some dispute about this. Grant says it should be "at least 40-60 ng/mL." According to Grant's research, raising serum vitamin D levels to 40 ng/mL could reduce mortality rates by 15 percent in the United States, corresponding to a two-year increase in life expectancy.
The Vitamin D Council thinks 50 ng/mL is the minimum acceptable level, and that optimal levels are between 50 ng/mL and 80 ng/mL. It's impossible to get anywhere near that number without supplements. And there's virtually no chance of achieving it with the paltry 600 IUs a day recommended by the FNB.
The FNB admits that 97 percent of Americans have a vitamin D level that falls within the range of 20 ng/mL to 30 ng/mL. Someone with an "average" level of 25 ng/mL would need to take at least 2,000 IUs a day to get to 45 ng/mL. And according to The Vitamin D Council-which is far more on top of this than the FNB-45 ng/mL doesn't even begin to cut it. According to vitamin D expert Zoltan Roma, MD, author of Vitamin D: The Sunshine Vitamin, research now indicates the correct figure for minimum daily requirement is 4,000 IUs.
Toxicity: A Real Danger?
The FNB also reported that vitamin D toxicity might occur at an intake of 10,000 IUs per day. Strangely, the board could not show reproducible evidence that 10,000 IUs per day has ever caused toxicity in humans, and only one poorly conducted study indicating 20,000 IUs per day may cause mild elevations in serum calcium-but not clinical toxicity.
In an excellent review of all the literature on vitamin D, Reinhold Vieth, PhD, a professor at the University of Toronto, had this to say: "I was amazed at the lack of evidence supporting statements about the toxicity of moderate doses of vitamin D." Vieth believes human toxicity probably begins to occur after chronic daily intake of about 40,000 IUs a day. Let's remember that the body itself will easily make 10,000 IUs a day in a few hours in the sun.
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