Are you one of the many people taking vitamin D supplements just to be on the safe side? Wouldn’t surprise me since evidence points to an exponential growth in the use of vitamin D supplements with sales increasing more than tenfold in the USA during the period 2002—2011, from US$42 million to US$605 million. Or maybe you have even gone to your medical practitioner to test your vitamin D levels? Also increasingly popular with a six per cent increase in testing volume year on year expected. Australia alone spent about A$150 million a year on vitamin D testing, despite limited knowledge about optimal levels and the unreliability of the test.
It might be worthwhile to first ask yourself if you spend less than ten minutes out in the sun each day or are always meticulous in covering up your entire body. Because most of us are self-sufficient in the production of vitamin D with ten minutes in the sun sufficient to produce our daily need. This is a bit of an anomaly since the definition of a vitamin is that they are vital nutrients that cannot be synthesized by the body, are required in limited amounts to sustain life, and must be obtained through the diet. But vitamin D is an exception.
Vitamin D is important
Don’t get me wrong. Vitamin D is important for several bodily functions. First and foremost it is needed to maintain strong bones. It does that by regulating the absorption of calcium and phosphorus. Deficiency can lead to rickets in infants or osteoporotic fractures in the elderly. There are also non-skeletal actions of vitamin D with suggestions that deficiency might result in a higher incidence of cancer, cardiovascular diseases, diabetes, infections, neuropsychiatric disorders, and a higher risk of death.
Thus it seems to be a clear case for keeping vitamin D at adequate levels. The range of potential benefits have led to calls for widespread vitamin D supplementation. But now to some puzzling findings.
Review of existing findings
A recently published report reviewed the outcomes of a number of trials testing vitamin D supplements for the prevention of myocardial infarction, stroke, cancer, or hip fracture in seniors in general. It found that taking vitamin D did not lower the incidence of these diseases. Of skeletal endpoints, only a clear reduction in the risk of hip fracture was seen for the combination of calcium and vitamin D in elderly nursing home residents. Vitamin D supplementation without the addition of calcium did not reduce hip fracture or total fracture risk.
In terms of harm, there is uncertainty as to whether vitamin D without calcium might actually increase the risk of hip fracture.
It has also been stated that without stringent indications there is a legitimate fear that vitamin D supplementation might actually cause net harm.
So what is a common person to believe?
The take-away message seems to be that there is little justification currently for prescribing vitamin D to prevent heart attack, stroke, cancer, or fractures in otherwise healthy people living in the community. Possible exceptions could be people who truly have very low levels of vitamin D, frail elderly people living in residential care, people who actively avoid the sun, and people with deeply pigmented skin.
In an even more surprising comment, the research team claimed that the body of evidence is already sufficiently large to conclusively state that vitamin D supplementation is of no use to most people and that future trials will not change that conclusion. This is a bold statement from scientists who are often keen to emphasise remaining uncertainties and the need for more research.
Despite such clear advice, research funding bodies continue to support new studies of the effects of vitamin D supplementation. The same month that the review was published, a new five-year study was launched in Australia, the sun-drenched nation, funded by the National Health and Medical Research Council. A bit of an irony, don’t you think?
- Controversy in vitamin D supplement (Deccan Chronicle)
- Study of Vitamin D supplements for older people (SBS World News Australia)
- Vitamin D and its role in maintaining bone health (Nursing Times.net)
- Vitamin D for bone health and little else, says Lancet (The Age)
- Testing whether vitamin D delays onset of diabetes (MedicalXpress)
- Vitamin D: Do You REALLY Need to Supplement? (She Runs Strong)