Here in London, the winter weather has truly set in over the past few days. The mornings are chilly, the wind is sharp, and it’s already dark by the time I go to fetch my kids from school. The increased darkness has particularly prompted me to think about vitamin D, often referred to as the sunshine vitamin.
During a checkup a few years back, a physician informed me that I was low in vitamin D. However, he declined to provide a prescription for supplements, stating plainly that everyone in the UK has a deficiency. He mentioned that providing vitamin D supplements to the entire population would be too costly for the national health service.
Nevertheless, supplementation—whether it be covered by health care or not—can play a significant role. As those of us in the Northern Hemisphere enjoy fewer sunlit hours, it’s worth thinking about the significance of vitamin D.
While it’s crucial for bone health, fresh studies are also revealing unexpected new perspectives on how this vitamin could affect other areas of our bodies, such as our immune systems and cardiovascular well-being.
Vitamin D was identified just over a century ago, when medical professionals sought methods to treat what was formerly known as “the English disease.” Nowadays, we recognize that rickets, a condition that leads to weak bones in children, is the result of vitamin D deficiency. Vitamin D is most commonly associated with its role in maintaining bone health.
This is due to its assistance in calcium absorption. Our bones are in a constant state of remodeling—they break down and rebuild—and require calcium for this process. Inadequate calcium can lead to weak and fragile bones. (Sadly, rickets remains a global health concern, which is why there is a global agreement that infants should receive vitamin D supplementation until at least their first birthday.)
In subsequent years, research has revealed that vitamin D impacts more than just our skeletal system. Some evidence indicates, for example, that a deficiency in vitamin D may increase the risk of hypertension. Those lacking vitamin D could benefit from daily or weekly supplements to help lower their blood pressure according to some findings.
A deficiency in vitamin D has also been associated with an elevated risk of cardiovascular incidents such as heart attacks, though it remains unclear if supplements can mitigate this risk, as the evidence is rather inconclusive.
Vitamin D seems to also affect our immune function. Research has identified a connection between insufficient vitamin D levels and occurrences of the common cold in various studies conducted. Furthermore, other investigations have indicated that vitamin D supplementation can impact how our genes produce proteins essential for our immune system’s functioning.
However, we are still unclear on the precise nature of these relationships. Unfortunately, a recent study covering 37 clinical trials concluded that, overall, vitamin D supplements are unlikely to prevent you from acquiring an “acute respiratory infection.”
Further studies have connected vitamin D levels with mental health, pregnancy outcomes, and even longevity following a cancer diagnosis. It’s intriguing to consider that such an inexpensive supplement could positively influence so many elements of our health.
However, as you might have inferred by this point, we haven’t quite reached that stage yet. The data surrounding the various effects of vitamin D supplementation is, at best, mixed.
To be fair to the researchers, conducting a randomized clinical trial for vitamin D supplements can pose challenges. This is because the majority of us obtain our vitamin D primarily from sunlight. Our skin converts UVB rays into a usable form of the vitamin. We also obtain small amounts from our diet. (Key sources include fatty fish, egg yolks, mushrooms, and certain fortified cereals and milk alternatives.)
The usual method for assessing a person’s vitamin D level involves measuring the blood concentration of 25-hydroxycholecalciferol (25(OH)D), which is produced when the liver metabolizes vitamin D. However, consensus on what constitutes the “ideal” level remains elusive.
Even if a common figure were established, determining how much vitamin D a person needs to consume to achieve that goal, or how much sunlight exposure is required, is not straightforward. One complicating element is that individuals react differently to UV rays—significantly influenced by the melanin content of their skin. Similarly, if you’re enjoying a meal of oily fish and mushrooms paired with fortified milk, it’s tough to ascertain how much more you may require.
Nevertheless, there is greater agreement on the definition of vitamin D deficiency itself. (It’s considered a blood level below 30 nanomoles per liter, for those curious.) Until we gain further understanding of vitamin D’s role in the body, our priority should be to prevent deficiency.
For me, that translates to supplementing my intake. The UK government recommends that everyone in the country take a 10-microgram vitamin D supplement throughout autumn and winter. This guidance doesn’t take my age, blood levels, or melanin levels into consideration. But, for now, it’s all I have to go on.
