Page 24 - Summer2010

We do not yet have this type of data. We do, however, have some strong in animal experiments. I also emphasized the
support for raising 25(OH)D levels to at least 35 ng/mL (88 nmol/L). For role of vitamins A and K in protecting against
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example, as the authors of the study we have been looking at pointed out, vitamin D toxicity. So, even if these levels are in
similar attempts to use statistical approaches to define the 25(OH)D level fact harmful, they may only be harmful or may
that maximizes calcium absorption, maximally suppresses parathyroid be primarily harmful in the absence of adequate
hormone (which leaches calcium from bone), or maximizes bone mineral vitamins A and K . The presence of the other
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density have suggested similar results. A recent randomized, placebo- fat-soluble vitamins could even turn these levels
controlled trial showed that supplementing insulin-resistant women with from harmful to beneficial.
4,000 IU of vitamin D per day for six months reduced insulin resistance
and had the most powerful effect in women whose 25(OH)D level was STILL NEEDED
raised to over 32 ng/mL (80 nmol/L). Nevertheless, what we need in order to show
that levels higher than 50 ng/mL are helpful or
POSSIBLE HARM harmful are vitamin D supplementation trials
What about higher levels? The evidence is conflicting, and some of it comparing the effect of different doses result-
indicates possible harm. For example, a study in the American Journal of ing in different blood levels on clinical health
Medicine published in 2004 found that in Americans aged over fifty, the outcomes, and similar studies examining the
maximal bone mineral density (BMD) occurs around 32-40 ng/mL (80- interactions between vitamin D and the other
100 nmol/L). Among Mexican Americans, BMD continues to rise a little fat-soluble vitamins.
after this point, but for whites it plateaus and begins dropping off around Lifeguards in the tropics can reach blood
45 ng/mL (110 nmol/L) and for blacks it begins dropping off even before levels in the 50s and 60s naturally from sun
40 ng/mL (100 nmol/L). exposure, suggesting these levels are “natural,”
If 50 ng/mL (125 nmol/L) is our minimal acceptable level, this study although lifeguards in Israel have twenty times
would seem to suggest that those of us who have “acceptable” levels of the rate of kidney stones as the general popula-
25(OH)D would have lower bone mineral density than those of us who are tion.
moderately deficient. And that premise just doesn’t make sense. Kidney stones may be the most sensitive in-
Another study published in the European Journal of Epidemiology dicator of vitamin D toxicity and are a symptom
in 2001 found that South Indians with 25(OH)D levels higher than 89 of vitamin A and K deficiency. Thus, I suspect
2
ng/mL (223 nmol/L) were three times more likely to have suffered from these levels are healthful in the context of a diet
ischemic heart disease than those with lower levels—and of course with rich in vitamins A and K , and if my levels were
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such a dramatic elevation of heart disease risk, the risk may have begun to reach this high in the summer sun while I was
increasing at levels substantially lower than 89 ng/mL. eating such a diet, I certainly would not worry.
Neither of these studies was designed to show that high levels of But if you are trying desperately to maintain
25(OH)D cause decreases in bone mineral density or increases in heart year-round 25(OH)D status between 50-80 ng/
disease risk, but it is possible. As I especially emphasized in my Wise Tradi- mL using vitamin D supplements, you have en-
tions and Medical Hypotheses articles on vitamin K , bone resorption and tered the land of speculation. Enter at your own
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blood vessel calcification are prominent symptoms of vitamin D toxicity risk.
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24 Wise Traditions SUMMER 2010