We may have gotten ahead of ourselves with vitamin D; gotten too excited about all the possibilities and all the promises. It may be time to slow down and even back track a bit.
For the last decade vitamin D has been the biggest, most exciting new thing in nutritional medicine. It seems like almost every patient is taking vitamin D and doing so in doses once thought massive.
Since the mid 1990s, thousands of studies have linked low serum vitamin D to a list of maladies including heart disease, cancer, infection, autoimmune, obesity, osteoporosis, depression and so on. While early studies focused on UV radiation exposure and its inverse association with disease, along the way we made the jump and started talking about vitamin D as if it were the only active agent in sunlight.
Avenell’s 2014 Cochrane review combined data from 54 clinical trials in which vitamin D was given in the hope of reducing bone fractures. Vitamin D taken alone is unlikely to prevent hip or other fractures (n=91,791). Actually, people given vitamin D in clinical trials trend toward greater risk of hip and other fractures. Combined with calcium, Vitamin D did slightly reduce risk of hip fracture, but only by about 5% (n=49,976). Risk of dying was not affected by taking vitamin D or vitamin D plus calcium (n=71,032). Vitamin D supplementation was however associated with double the risk for mild hypercalcemia (n=17,124) and gastrointestinal symptoms (n=47,761).1
A meta-analysis by Bolland published in April 2014 examined vitamin D supplementation on skeletal, vascular and cancer outcomes. Using vitamin D to change any of these conditions was termed ‘futile’.2 “Futile” is not what we expected.
A second meta-analysis by Bolland et al was published in July 2014 and looked only at vitamin D given to prevent falls. Data from 20 randomized controlled trials (n=29,535) again reported that supplementation proved futile.3 Recent reports actually suggest high doses of D increase risk of falls in the elderly. In fact a warning was published in November 2016 that vitamin D “bolus dosing or daily doses should not exceed 3,000 IU and serum levels of 25-hydroxyvitamin D should not exceed 40-45 ng/ml in elderly individuals.”4
A Cochrane review by Bjelakovic et al published in June 2014 analyzed data from clinical trials on cancer prevention in adults: data from 18 randomized clinical trials (n=50,623), done in high-income countries, mostly older women (47-97 years old) supplemented with vitamin D for a mean of 6 years. In the end, 7.6% of the women receiving vitamin D developed cancer versus 7.7% of the women in the control group not receiving D. Again using vitamin D proved futile.3
It’s time to rethink what we know and move on from this vitamin D as a panacea paradigm. What happened to nature cure? That whole Vis medicatrix naturae, the healing power of nature thing? How did we convert our appreciation of the healing action of sunlight into a hormone deficiency?
Sunlight has a range of actions on the human body, only some of which we understand. Besides triggering vitamin D production it also triggers production of p53,4 the enzyme that regulates apoptosis (cell suicide) and destroys cancer cells, or at least is supposed to. Increasing p53 activity is the primary goal of both conventional and naturopathic oncologists. This may be why sun exposure is associated with decreased cancer risk.
Sunlight also triggers nitric oxide (NO) production, which in turn causes vasodilation, lowering blood pressure. NO may be why sunlight lowers risk of heart disease and strokes.
Perhaps it’s not the D but the sun that is protective. As high blood pressure is the leading cause of death in the world, even small improvements in blood pressure might have widespread consequences. This NO discovery explains a long-time mystery, why blood pressures are higher during the winter. It also explains why blood pressures increase with latitude.
A December 2016 article in the journal Medical Hypotheses, suggests several other possible explanations for the benefits of sunlight including immunomodulation, melatonin, serotonin, and the effect on circadian clocks, which are also involved in triggering the health benefits of sunlight.5 A paper published in late January 2017 reported that sun exposure stimulates lymphocyte motility and gets those white blood cells to chase down invading microbes in the body.6 Perhaps this is why sun exposure reduces rates of infection?
Thus the benefits we expect to see from taking vitamin D may be the result of some other more complex and dynamic actions caused by sun exposure. We should go back to thinking of vitamin D as a measure of sun exposure, but not the direct effecter. It may be a combination of reactions that sunlight triggers which certainly might include vitamin D. While our patients may love the ease of swallowing vitamin D, we need to remember that randomized clinical trials have not confirmed the promises. Rather meta-analyses of multiple trials suggest our efforts are proving futile. If you want a patient to get the benefits of sunlight, they may have to do it the old-fashioned way.
Recall how we once thought vitamin D was totally safe. As naturopathic physicians we pride ourselves for being on the cutting edge of nutritional medicine, of being early adopters of new discoveries, the explorer scouts who range ahead of mainstream medicine. That’s well and good, but sometimes it is our responsibility to turn back and warn our followers, “Sorry, we made a mistake, we need to back up and rethink where we are headed.”