A study published in the Oct 2012 issue of the Journal of Sports Sciences by the Research Institute for Sport and Exercise Sciences , Liverpool John Moores University , Liverpool , UK. (read abstract here) showed that 62% of a group of 61 professional UK athletes in winter months who were not taking vitamin D supplements were vitamin D deficient (average blood level of 25-hydroxy vitamin D was 12 ng/ml), which is quite low indeed. The control group was a group of 30 age matched healthy non athletes, who were also not taking vitamin D supplements, and 73% of them were deficient. The athletes were supplemented with 5,000 units of vitamin D per day (despite regulatory councils in both the US and the EU stating that 4,000 IU is the “upper safe limit”), which brought their average blood levels up to 41 ng/ml. (the units were expressed in nmol/L, which must be divided by 2.5 to get the units in ng/ml). The control group received a look alike placebo, and their blood levels of 25-hydroxy vitamin D levels did not change. The researchers then tested muscular performance with the following results: “There was a significant increase in 10 m sprint times (P = 0.008) and vertical-jump (P = 0.008) in the vitamin D group whereas the placebo showed no change (P = 0.587 and P = 0.204 respectively). The current data supports previous findings that athletes living at Northerly latitudes (UK = 53° N) exhibit inadequate vitamin D concentrations (<50 nmol · l(-1)). Additionally the data suggests that inadequate vitamin D concentration is detrimental to musculoskeletal performance in athletes. Future studies using larger athletic groups are now warranted.”
P values of .008 in a group this small (91 people) means that this effect is HUGE. Many clinical trials require thousands of participants to obtain statistically significant results, with p values of only .05 — .008 is HIGHLY significant. Of course, skeletal muscle in professional athletes and elderly people, who are prone to falls and hip fractures, is made of the same stuff. Studies from years ago have shown that vitamin D supplementation reduces falls in the elderly. Muscle is muscle. Muscle, indeed EVERY tissue in the human body functions better with blood levels of 25 hydroxy vitamin D above 40 ng/ml (I prefer 50 ng/ml, for optimum health, and in my cancer patients, I aim for 70-80 ng/ml). Any athlete, trainer, or owner of professional sports team who is not measuring blood vitamin D levels and supplementing vitamin D to be sure their blood levels are >40 ng/ml is missing a very significant competitive edge. And if you have elderly parents who are looking frail, ask their doctor to measure their blood levels as well, and see that they are corrected if low. This will not only reduce the risk of falls, but of many many negative health consequences. Vitamin D is not only a ‘vitamin’— it is the most potent steroid hormone in the human body. Before the industrial revolution when people started working inside, humans got it from the sun in the summer, and stored enough in body fat to make it through the winter. These days, most people require 4000 to 5000 IU per day for optimum function, during the winter months in temperate regions, and all the time for people who don’t get regular sun exposure without sunscreen in the summer months. An hour of sun exposure in mid summer produces 10 to 20 thousand IUs of vitamin D, which was discovered for the first time by Dr. Michael Holick and his team in the late 1980s. Up till then everyone assumed that 400 IU of vitamin D (the amount in a teaspoon of cod liver oil, which has been known for 100 years to prevent rickets in a baby), was all that healthy adults needed. We were only off by a power of 10…….