Vitamin D is certainly one of the nutritional darlings of the moment. One that everyone is talking about and one that seems to dominate the popular pres. Bearing in mind the discoveries of recent years, this isnt surprising. Lets take a look at what it is and then we will get on to ways to get more in.
Vitamin D is a fat soluble vitamin that is found in very few foods, just a key few. The primary source of vitamin D for Humans is the conversion of cholesterol into vitamin D precursors, that then go through a few further steps of biochemical change, according to body need, to become vitamin D, when our skin is exposed to ultraviolet radiation.
What we get from food and what we get from the sun is incomplete and needs to go through these processes known as hydroxylation, in order to become metabolically active. The first of these steps, which happens in the liver, produces something called calcidiol 0r 25-hydroxyvitamin D. The next step is the formation of the metabolically active calcitriol or 1,25 hydroxyvitamin D. Dont necessarily worry about this detail, I just wanted to make sure that you had the background.
The primary and most widely understood effect of vitamin D is in relation to clacium. Vitamin D promotes the absorption of calcium from the gut, and to also maintain serum concentrations of calcium. It is also needed for normal bone growth and remodelling by osteoblasts and osteoclasts, the cells that breakdown and rebuild our bone throughout the lifecycle - osteoclasts break it down, osteoblasts rebuild it. This is why low levels of vitamin D can be associated with brittle thin bones, or in developing children, bones that are soft and can become bowed - ie rickets. That double whammy of calcium absorption and utilisation, coupled with regulation of osteoblast and osteoclast activity. Low levels can be a serious problem for skeletal health.
However, in recent years we have found that the role of vitamin D can go way above and beyond this. Almost ever cell type in our body contain a vitamin D receptor. That in itself should be an indicator that it has roles to play far beyond just bone density regulation.
It plays a role in modulating cell growth, regulating immunity, and also managing inflammation. There have been links with vitamin D and colon, prostate, and breast cancer risk reduction.
The problem is, it is a nutrient that has become commonly deficient, especially here in the Uk. It is estimated that anywhere between 30% - 80% of the population have lower than adequate levels. This is of course a sliding scale and different segments of the population will be affected in different ways. Darker skinned individuals and people who wear a lot of sunscreens are typically at greater risk of deficiency, although the second of those two examples is a bit of a joke for us Brits. In the UK, the sun is like a rumour most of the time. That in itself is what poses the greatest risk to those of us in the UK across the board - insufficient exposure to ultraviolet radiation.
Restricted diets can also pose a potential issue. The food sources of Vitamin D tend to be animal foods such as full fat dairy and oily fish, so vegans particularly have an issue. However, there are now types of mushroom freely available in the supermarket that are vitamin D enriched. More on that later.
Age is another factor in this. Reduced 25 and 1,25 hydroxyvitamin D synthesis, plus reduced breadth of diet, and less time outdoors can all be factors that affect an ageing population.
So, getting to the big point of all of this, what can we do to top up our levels?
Shock horror, me recommending oily fish. You’ve never heard that before! This time though it has nothing to do with Omega 3 fatty acids. This time it is because oily fish such as salmon, mackerel, herrings etc are very rich sources of Vitamin D. One single wild salmon fillet can deliver up to 2 thirds of our daily requirements. Vitamin D is a fat soluble nutrient remember, so it will be found in these fattier cuts of fish.
For decades we have been sold the idea that the low fat diet was the key to immunity from heart disease and was the quick road to longevity - oh how that one backfired. The low fat model meant that we were encouraged to abandon full fat dairy products for skimmed and fat free versions. These are some of the richest dietary sources of vitamin D. The fat soluble nutrient is found in the fatty portion of the product. Takeaway the fat, takeaway the vitamin D, alongside the other big fat soluble vitamin - Vitamin A.
Eggs are another rich vitamin D source. Strangely, in the midst of all this low fat fuss, people were told to avoid the yolks of eggs. We were led to believe that it was a bathing pool of cholesterol that would stop our heart flat if we dipped in so much as one soldier!! Thankfully we have moved way way past that but some people still habitually avoid the yolks. If you’ve ever had an egg white omelette you will know how utterly dull it can be! The yolks are where the highest concentration of fat is, and along with it, where all the vitamin D is found.
Now, all of the foods that have been listed so far have been animal foods, which presents a big problem to the vegans in the house! But now there is an ingenious product on the market. Fortified mushrooms! Yes, mushrooms. There are varieties of mushroom, most commonly chestnut, that have been exposed to artificial ultraviolet radiation. Like Humans, mushrooms can synthesise vitamin D upon exposure to UV. By bathing the growing fungus in this radiation, they produce significant levels of vitamin D naturally. Genius!!
I truly believe that everyone in the UK should consider a vitamin D supplement. That sounds like a big claim know, but with the massive diversity of actions that vitamin D has and the vital roles it plays in the body, coupled with the levels of inadequate intake to outright deficiency, taking a single supplement may have a profound intake on a lot of peoples health. But how much and what kind!
There are literally thousands on the market, with some going up to some insanely high dosages. NHS UK state around 10mcg per day. Some supplements will deliver the dosage in micrograms (mcg), others will deliver it in international units (IU). 10 mcg is equal to 400 iu. This simple one a day strategy may be all you need.