Abstract
The Institutes of Medicine (IOM) recently revised the recommended dietary allowances (RDA) for vitamin D, to maintain serum 25-hydroxyvitamin D (25(OH)D) at or above 50 nmol/L, to sustain bone density, calcium absorption, and to minimize risk of osteomalacia and rickets. However there are compelling reasons why 25(OH)D should preferably exceed 75 nmol/L: (A) Scrutiny of actual data specified by the IOM relating 25(OH)D to bone density and osteomalacia shows the desirable minimum 25(OH)D to be 75 nmol/L (30 ng/mL). (B) Humans are primates, optimized through evolution to inhabit tropical latitudes, with serum 25(OH)D over 100 nmol/L. (C) Epidemiologic relationships show health benefits if 25(OH)D levels exceed 70 nmol/L; these include fewer falls, better tooth attachment, less colorectal cancer, improved depression and wellbeing. Some studies of populations at high-latitude relate higher 25(OH)D to risk of prostate cancer, pancreatic cancer or mortality. Those relationships are attributable to the dynamic fluctuations in 25(OH)D specific to high latitudes, and which can be corrected by maintaining 25(OH)D at steady, high levels throughout the year, the way they are in the tropics. (D) There are now many clinical trials that show benefits and/or no adversity with doses of vitamin D that raise serum 25(OH)D to levels beyond 75 nmol/L. Together, the evidence makes it very unlikely that further research will change the conclusion that risk of disease with serum 25(OH)D higher than 75 nmol/L is lower than the risk of disease if the serum 25(OH)D is approximately 53 nmol/L.
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