With June already upon us (can you believe it?!), and some glorious sunshine forecast for the next week or so, today I want to touch briefly on Vitamin (a.k.a hormone) D.
Have you ever heard of someone being diagnosed with ‘Vitamin D Deficiency’? Nope - probably not, and that’s because although Vitamin D plays a really crucial role in health, it’s often not diagnosed. Deficiency has been linked to many cancers, high blood pressure, heart disease, diabetes, depression, fibromyalgia, chronic muscle pain, bone loss and autoimmune diseases - all incredibly common in our society.
You may also be interested to know that Vitamin D is virtually absent from our food supply yet we need it in amounts almost 25 times the recommended government guidelines to be healthy.
So, as you probably already know, our bodies make Vitamin D from sunshine coming directly into contact with our skin - 80-100% of the Vitamin D we need comes from sunlight. The sun exposure that makes our skin a bit red (called 1 minimum erythemal dose) produces the equivalent of 10,000 to 25,000 international units (IU) of vitamin D in our bodies. But we’ve been taught to fear sun exposure and cover up with sunscreen whenever we’re outdoors. Moreover, if you live in the northern hemisphere like most of you reading this do, we simply can’t synthesise vitamin D precursors during the winter months as the sun is not strong enough. That leaves us with the stores of Vit D that our bodies have (hopefully) built up over summer, plus some dietary sources which I’ll talk about later.
Vit D has a huge impact on the health of our cells, and everything in our body is made up of cells - so take note! It reduces cellular growth (which is how Cancer forms), and improves cell differentiation (which puts cells into an anti-cancer state).
It also has a big impact on our genes which is how it has such a diverse range of action from cancer prevention, boosting mood, calming inflammation, easing muscle aches and building bone. Dark skin produces less Vit D, as does aging skin - so if you fall into either of these categories then it’s even more important you get your levels checked. Speaking of - I have started testing all my patients for Vit D, it’s simple, cheap and has such profound benefits if your levels are optimal.
NHS England recommends 600 IU (International Units) of Vit D per day. This is about the amount you need to avoid rickets, but in functional medicine terms it is really suboptimal. We need to think about how much we need to thrive, not survive. How much we need to help prevent disease, high blood pressure, depression, osteoporosis etc.
Recent research by vitamin D pioneer Dr. Michael Holick, Professor of Medicine, Physiology, and Dermatology at Boston University School of Medicine, recommends intakes of up to 2,000 IU a day — or enough to keep blood levels of 25 hydroxy vitamin D (that’s the storage form) at between 75 to 125 nmol/L (nanomoles per liter).
However, there’s a missing link here because most research papers, and indeed the blood tests you can have done quickly and easily either with your GP or using an online service like Thriva or Medichecks, all measure 25 Hydroxy vitamin D, our storage form, rather than the active form 1,25 hydroxy. The thing I want to really be clear on is that Vitamin D is actually a hormone, and this is why I personally don’t supplement with it unless I’ve tested levels beforehand - and even then, as I’m only measuring the storage form, I’d probably only supplement if it was in the middle of winter and the levels were well below 75 nmol/L - otherwise I’d give a prescription for daily sun exposure!
My reasoning for this is that the feedback system that controls our active levels of vitamin D is really complex - like everything in the body - and your body will only convert the inactive form of vitamin D to the active form when it senses a requirement for it, for example in disease or infection or during winter. So conversely, we do actually make Vitamin D in the winter (so long as you got adequate sun exposure in the summer!) Now, the interesting thing here is that the primary catalyst that helps convert stored vitamin D to the active form is magnesium, yet another reason why it’s crucial to get enough magnesium in via a healthy diet, or via supplementation or something like epsom salt baths.
The bottom line is this: Test don’t guess, and even then, be cautious. If we were able to accurately test the 1,25 hydroxy active form of vitamin D I think we would see a very different picture to the one that we currently see with regards to our storage form of the vitamin (hormone!)
If you are low, well below 75nmol/L, I still would think about supplementing for a short period of time. But first and foremost we all need to be exposing our skin to some unadulterated sunshine during the months when the sun is close enough to the Earth to make vitamin D precursors. It is simply not a viable solution to this incredibly complex feedback system to cover our skin at all times and apply factor 50, assuming that taking a vitamin D supplement will make up for the short fall. Be sensible, don’t get burnt, but do get some sun when you can!
There’s a great app you can download called D minter that tells you when you can make hormone D and how much you’re making based on your sun exposure.
There are a few food sources of Vitamin D that you can prioritise during winter too:
Fish liver oils, such as cod liver oil. One tablespoon (15 ml) = 1,360 IU of vitamin D
- Cooked wild salmon. (3.5) ounces = 360 IU of vitamin D
- Cooked mackerel. (3.5) ounces = 345 IU of vitamin D
- Sardines, canned in oil, drained. (1.75) ounces = 250 IU of vitamin D
- One whole egg = (20) IU of vitamin D