D for Don’t really know yet
It has been a long wet and dreary winter with little sun. There is no doubt this affects our mood and our vitamin D levels however whether these two are connected or just have the same causal link is currently a matter of scientific debate.
Our skin makes Vitamin D when exposed to the sun. We do not need much sun exposure to produce the amount of Vitamin D required to fulfil its main metabolic function of ensuring our bones have enough calcium. In the summer this is easy but in the winter our Vitamin D levels will fall. As we get older our skin is less efficient at making Vitamin D and this means that probably half of the older adult population has a low Vitamin D level in the winter. As a result Public Health England advise older adults to take a Vitamin D supplement during the winter months. These are 10mcg / 400 international unit tablets that can be bought cheaply over the counter in a pharmacy, they are not prescribed by GPs. Oily fish and eggs are the alternative main dietary source of Vitamin D. Optimising our bone strength is dependent on both having enough vitamin D and also doing sufficient daily exercise; walking in the sun ensures both needs are covered. Patients who have osteoporosis (weak bones), normally discovered following a low impact fracture, are treated with Vitamin D and calcium supplements plus a once weekly medication that ensures the calcium is deposited in the bones.
Whilst we have a good understanding of Vitamin D’s role in bone health the search continues for other roles that it might play within our bodies. There are Vitamin D receptors in some parts of our brain and there are also some trials that show it has a role in optimising our immune system. Taking a Vitamin D supplement in the winter is linked with fewer days of illness from viral infections. There is currently a trial being run by Exeter University testing whether taking very high daily doses of Vitamin D will decrease risks of dementia and other studies are trying to establish links to depression. No data is available yet. It is perhaps because so little is known, apart from the fact that levels are variable, that Vitamin D has been linked to so many pathological pathways. It was hailed as a panacea for Covid and as a protector against cardiovascular disease however neither of these claims stood up to scientific analysis.
One thing that is very clear from the research is that there is no benefit in measuring Vitamin D levels unless there is a clear medical indication for doing so. This is because the levels are predictable; if you have reduced sun exposure your levels will be lower than they could be. Nothing is gained from analysing the actual level as we are a long way from establishing what the most beneficial level is. So, this summer get out, get exercising, use suncream (it does not affect Vitamin D production) and next winter consider taking a tablet during the darker months.
Anthony O’Brien, Wyndham House Surgery