Vitamin D is unique among the nutrients, as it is the only one that we can produce by sun exposure. It is made from cholesterol molecules, so naturally-occurring food sources of the vitamin are always from animals, but there are many products fortified with vitamin D such as milk. This is why so many people do not consider the possibility of vitamin D deficiency being found in a wealthy country. However, the best way to "consume" vitamin D is still by sun exposure without burning. But the sun is dangerous, the government says. So, is there a problem?
Unfortunately, yes there is. After the Industrial Revolution and before foods were fortified with vitamin D, rickets (severe deficiency) affected 85% of children in European and American cities. But despite these public health measures, recent research has uncovered more subtle deficiencies at unbelievably high rates. For example, over half of certain elderly populations and 30% of healthy young adults in Boston have been found to be vitamin D deficient. In one Boston study, half of the women admitted to hospital for hip fractures were deficient. Older people do not produce vitamin D at the same efficiency as younger people, while our society seems to encourage them to stay inside. However, low vitamin D has been linked to weaker quadriceps, reduced postural stability, slower reaction times and overall poorer physical function in people admitted to fall clinics. On the other hand, a large placebo-controlled study found that giving adults aged 65-85 100,000 units of vitamin D every three months reduced the risk of any fracture by 22%, and osteoporosis by 33%. This was without an additional calcium supplement. Society tells us that when someone is infirm, we must "look after" them by keeping them shut inside and away from "doing too much". It looks like it's time to re-evaluate our ideas, and the way our lives are structured. Our previous struggles for survival may have led us to associate nature with danger, and so favour the indoors, but the way we work, play and even build our houses possibly should be restructured to enable the right amount of exposure to sun and air.
Many of us now seem to fear the sun because of its association with skin cancers. However, this may be an all-or-nothing approach, taken to extremes. Dr David Hoel writes:
"The body of science concerning the benefits of moderate sun exposure is growing rapidly, and is causing a different perception of sun/UV as it relates to human health. Melanoma and its relationship to sun exposure and sunburn is not adequately addressed in most of the scientific literature."
Research has also shown that outdoor workers may actually have a 14% lower risk of melanoma than people who work inside. It is not as one-sided as the PSAs tell you: non-burning sun exposure has been linked to a reduced risk of melanoma, while sunburn doubles the risk of developing the cancer. Many others have shown that vitamin D reduces the risk of different types of cancer such as breast, colon and prostate cancers. Some of these benefits are only seen with sun exposure, not vitamin D status in general which includes supplementation.
High blood levels of vitamin D are also linked with lower all-cause mortality. When 32 studies were analysed in a meta-analysis (research on research), vitamin D levels under 9ng/mL were associated with a 90% higher all-cause death rate compared to people with levels over 50ng/mL. In a study involving women in Sweden, avoiding sun exposure was linked with double the risk of death over the research period, compared to those who embraced the outdoors. Looking at all of this, it's no surprise that researchers have now said:
"Insufficient sun exposure has become a major public health problem, demanding an immediate change in the current sun-avoidance public health advice. The degree of change needed is small but critically important."
Let's change things sooner rather than later.