Researchers working at Tufts Medical Center in Boston, under the direction of Professor Anastassios Pittas reported that 2,000 IU/day of vitamin D, given for 12 weeks, significantly improved pancreatic function in mildly overweight adults with pre-diabetes. Unfortunately, the lead author, Dr. Joanna Mitri, did not comment on the low dose of vitamin D they used, 2,000 IU/day, which only increased vitamin D levels from 24 to 30 ng/ml. Nor, in spite of it being a randomized controlled trial, did the authors make any new clinical recommendations for the people who paid for their study, the citizens of the United States.
They found that pancreatic function increased by 300 in the vitamin D group, but fell by 126 in the placebo group.
Joanna Mitri, Bess Dawson-Hughes, Frank B Hu, and Anastassios G Pittas. Effects of vitamin D and calcium supplementation on pancreatic b cell function, insulin sensitivity, and glycemia in adults at high risk of diabetes: the Calcium and Vitamin D for Diabetes Mellitus (CaDDM) randomized controlled trial. AJCN. First published ahead of print June 29, 2011 as doi: 10.3945/ajcn.111.011684.
In the end, they studied 22 volunteers in the vitamin D group and 22 in the placebo group. However, to give you an idea of what a feat this study was, how difficult it was to get enough subjects, they started with 911 subjects yet ended up randomizing only 44 into the vitamin D study. They did a parallel calcium study with 45 subjects, which found calcium had no benefit on pancreatic function.
The same senior author, Professor Anastassios Pittas, recently announced the results of a much larger epidemiological study that showed for every 5 ng/mL increase in vitamin D levels, the risk of developing diabetes dropped by 8%. However, he was quick to warn that such epidemiological studies should not change clinical recommendations, only randomized controlled trials can do that. Then, when he oversees just such a randomized trial, not a word of clinical advice, only the ever-present request for more research money from the citizens of this country.
Of course the Food and Nutrition Board will say they never said levels greater than 20 ng/ml had no added benefits, only that no good evidence existed for such a benefit at the time they issued their report. Actually, if you exclude the science of epidemiology, that is still a false statement. The point is that history will record that someone was wrong. Maybe it will be me and the Vitamin D Council’s recommendation, going into its fifth year, that adults should take at least 5,000 IU per day. Or maybe it will be Professor A. Catharine Ross, of Pennsylvania State University, the chairwoman of the recent FNB that concluded 600 IU/day is the Recommended Daily Allowance, all adults need. Looking at the study published today, it is clear that 600 IU/day would not have resulted in a significant improvement in pancreatic function.
I predict that after most of the randomized controlled trials are out – in another ten years – the FNB will meet again and say “whoops,” it should have been 5,000 IU/day all along. However, by then the premature death count will be in the millions.
For a list of foods highest in vitamin D click here.