What’s the fuss about Vitamin D?

Something you’ve read in the papers or been told by a friend or seen on social media may have convinced you that you should pay attention to your vitamin D levels, but do you understand why this much talked about nutrient matters?

Until the pandemic struck many, if not most, people will have assumed that vitamin D is all about, and perhaps only about, bone health. Now we are being told that it plays an important role in immunity. And indeed it does, but much, much more besides.

Vitamin D comes, but in limited amounts only, from the diet. Most originates in the skin when exposed to UVB rays from a bright, high-in-the-sky middle-of-the-day sun. This generates what is called “pre-vitamin D2” in the upper layers of the skin. It is inactive at this stage. Then it goes first to the liver and thence the kidneys where complex chemical processes (every one of which, incidentally, involves magnesium, a mineral commonly deficient in the UK diet) convert it to vitamin D3. This is the “active” form of the vitamin which, and despite its name, is actually a hormone (a chemical messenger).   

Once activated, vitamin D3 goes to work in EVERY organ of the body where it binds to vitamin D receptors on cell membranes and once there,  switches “on” or “off” or “up” or “down” genes which control, amongst other things;  calcium balance, insulin secretion, blood pressure regulation, immune tolerance and include oncogenes (cancer-promoting genes). It is no surprise that deficiency has been linked in research to a range of conditions including, but not limited to; rheumatoid arthritis, diabetes (Types 1 and 2), multiple sclerosis, osteoporosis, low mood/depression, psoriasis, poor sleep, breast cancer and also, cognitive decline. Vitamin D receptors are located in high numbers on the membranes of brain cells leading researchers to conclude that this key anti-inflammatory vitamin plays a pivotal role in protecting the brain against Alzheimer’s and other conditions involving mental deterioration. 

Currently, the spotlight is being shone on vitamin D’s role in the immune response. Put simply, the T-cells (foot soldiers), of the immune system are on constant patrol searching out invading, unfriendly organisms then marching them off to the lymph nodes for destruction and excretion. However, each T-cell going out on patrol requires to be “armed” with a molecule of vitamin D to do its job effectively.  Low levels of vitamin D are therefore likely to compromise the effectiveness of this aspect of the immune response.

Vitamin D also plays an increasingly recognised role in cancer. Consider this:

 “Vitamin D can adjust almost anything in the cancer cell….it can switch genes on and off and reduce cell division.  It can ‘calm’ cancer cells so that they settle rather than spread. It seems that vitamin D can actually return a cancer cell to a normal state...”
J Cell Biol Nov 2008;183(4):697-710

 And this:

“If women obtained adequate levels of vitamin D there would be 25% less deaths from breast cancer.”
Prof Hollick, Boston School of Medicine

So how much is enough?  In the UK levels are regarded as “adequate” if above 50nmol/L. But reflect; “adequate” is not the same as “good” and different countries apply their own yardsticks. In the UK most GPs will be satisfied with levels of 50nmol/L or above. Research from the US, however, suggests we should aim for a baseline of closer to 100nmol/L (even higher where cancer is an issue).  In the UK the sun, even if you can see it and feel its warmth, is, typically, not high enough in the sky between October and March to allow us to make meaningful amounts of pre-vitamin D2. Add to that the complex conversion process which may be limited for want, for example, of co-factors such as vitamin K and/or magnesium and/or a diet low in the relatively few food sources of vitamin D (such as oily fish, liver and egg yolks) and you will appreciate that deficiency can easily occur over the Winter months in the UK.

You can find out your levels very easily using a simple and inexpensive home finger-prick test. There are a number available on-line. “Better You” do a good one.   So why not do a test and know for certain?  Knowledge is power. Vitamin D is generally speaking easy and safe to supplement which can be done with a pill or an oral spray. It does not become toxic until levels of circa 250nmol/L are reached. Just bear in mind that vitamin D is best absorbed in the presence of fat so make sure, if and when you decide to supplement, that you do it with some fat-containing food.