The Importance of Vitamin D

Vitamin D used to be something of a ‘hidden secret’, at least in terms of interest from the media and general public. For many years, vitamin D deficiency has been a concern for many populations across the world, but has only recently become increasingly recognized in places like the United States. This surge of interest in vitamin D arose when a new wave of rickets emerged in the southern states – if even people living in a sunny place like Alabama can have vitamin D deficiency, then what about people in the infamously rainy Pacific Northwest? Whatever the logic, it brought attention to vitamin D as an important public health issue and this attention is still very much ongoing.

How does one become deficient in vitamin D?

In places like the Middle East, vitamin D deficiency is a big problem in women, not so much because of skin pigmentation but because of the clothing. Although avoidance of sunlight is certainly part of the problem in this and other populations, it is increasingly recognized that, for most people, food and sunlight alone does not satisfy the body’s need for vitamin D. We are simply not ingesting enough of it, and this can be especially important in infants, teenagers, and those in late life.

Many of the effects of vitamin D deficiency are still being investigated, but the evidence for lifelong effects in bone health is already compelling. In some ways, you could say that osteoporosis is a disease that starts in infancy but only shows up later in life. In some surveys, up to 50–60% of the elderly population have bone disease with increased risk of fracture – an endemic that is largely preventable with physical activity and good supplementation with vitamin D.

Based on the weight of evidence in bone health, more and more agencies worldwide are recommending that vitamin D supplements be given from birth, if not before. Trials of vitamin D supplementation during pregnancy are underway, but how much is needed and how often has not yet been determined.

Dosing and overdosing

Vitamin D by itself is not that expensive and is generally recommended as part of a multivitamin strategy. Good vitamin D3 preparations are available and it is often recommended that they are taken three times a week at a dose of 1000 to 5000 units.

Overdosing is a risk, and may be more likely with some preparations than others, especially in babies and children. For example, the dose of vitamin D prepared in droppers is somewhat at the mercy of drop size. Your idea of a drop might be bigger than my idea of a drop, so rather than giving a baby the intended 400 units you might accidentally give a dose of 10,000 units. Safer options, such as capsules, may be preferred.

It is also worth noting that not all vitamin D preparations on the market are regulated. Fortunately, unless you give 10 times the recommended dose or higher, the most severe side effect of vitamin D overdose tends to be headaches caused by an increase in blood pressure within the skull.

Going beyond bone health

Emerging evidence suggests that vitamin D may play a role in boosting the body’s first-line defenses, as well as treating asthma and respiratory infections. These associations have so far not been conclusively proven, but it seems to me that a universal recommendation for appropriate vitamin D supplementation is not a bad idea from a public health perspective. Indeed, most adults in the US are already taking vitamin D supplements. We just need more evidence to be able to confidently recommend this intervention to people of all ages and from all walks of life.