What’s the deal with Vitamin D

With winter approaching in the UK, shorter days, less sunlight, and covering our skin to wrap up warm; it’s time to start thinking about if you’re getting enough Vitamin D. Dr Jennifer Robinson is talking us through the ins and outs and how to get your daily boost!

Recent reports have shown that 1 in 5 adults in England may be deficient in the ‘sunshine vitamin’,in reality it’s likely that even more people than this are actually deficient.

You can get vitamin D via two different routes, your skin can produce it, you can also absorb it in your gut from foods that either naturally contain vitamin D, or are fortified with it. From April to September exposing your skin for 20-30 minutes a day is enough for most peoples bodies to produce the recommended 10micrograms of vitamin D a day for our bodies to function optimally.

How does our body make it’s own vitamin D?

UVB light from the suns rays breaks the chemical bonds in a special type of cholesterol found in the upper layers of the skin (the epidermis) to produce vitamin D3 (also called cholecalciferol), this is an ‘inactive’ form of vitamin D. It then enters the blood stream via the tiny capillaries in your skin. D3 is also found in a number of foods, (we will talk about this more later) it is absorbed in your gut, into the blood stream too.

When the blood reaches your liver, the next step is that enzymes convert vitamin D3 into calcifediol (it’s fancy chemical name is 25 hydroxycholecalciferol)…which is another ‘inactive’ form of vitamin D. This step in the liver isn’t very tightly regulated, meaning the liver will covert pretty much all of the D3 it is given into calcifediol.

Finally, the calcifediol makes it’s way to the kidneys, where the real magic happens. This is where it’s finally converted into active vitamin D! It is now called calcitroil, or 1a25-Dihydroxyvitamin-D3 if you’re feeling fancy. This last step in the kidney is super tightly regulated by parathyroid hormone (which is produced by a tiny pair of glands in your neck) and the levels of phosphate (a mineral) circulating in your blood. This tight regulation means that your body only produces as much active vitamin D as it actually needs. So… we have made some active vitamin D, what does it actually do? Vitamin D affects many different parts of your body, it has recently been reported that it regulates around 3% of the human genome!

These are four of the main ways that vitamin D affects our bodies:

Bones

It increases the amount of minerals in your bones, which protects from a condition called osteomalacia in which your bones get soft and bendy. When osteomalacia happens in children it’s called Ricketts and can lead to visible limb deformities.

Gut

In the gut, Vitamin D helps to increase the absorption of calcium and phosphate, both of which are essential for heathy bones, calcium is also important for healthy muscle function, including the muscle that makes up your heart. Immune system Vitamin D encourages your white blood cells to mature and to develop into the sub specialised types of cells that fight various infections. There is also an ongoing discussion about the role of vitamin D in preventing and treating autoimmune conditions (where your immune cells attack your own cells instead of fighting bugs that pose a threat to your health).

Tumour microenvironment

Vitamin D has been shown to inhibit proliferation (growth) of tumour cells, it has also been demonstrated to induce differentiation, which means that tumour cells will look and behave more like normal cells, reducing uncontrollable growth. Studies in the lab have also shown that vitamin D can stop the development of blood vessels (a process called angiogenesis) supplying tumour cells, this can help reduce cancer growth by stopping the flow of nutrients and oxygen vital for cell growth, it can also help prevent the cancer from spreading to other parts of the body. So far, these studies are what we call “pre-clinical”, they haven’t been carried out on actual humans. Further clinical studies are needed to show if/how this could be used for cancer prevention and mortality rates.

How to get your daily vitamin D boost

1. Spend 20-30 minutes in sunlight of the right frequency… this is simple if you happen to live on a sun drenched island year round… a bit more tricky when you live in Northern Europe. In November 2015 London had a grand total of 27 hours of actual, non cloud covered sunshine ALL MONTH! (For comparison, we had 197 hours in June.)
2. From your diet. I am a big believer that we should focus on getting the nutrients we need from actual food, but to get enough vitamin D this can be tricky unless you track your intake religiously (which I neither do myself or recommend to others). Lots of the foods that are rich in vitamin D are from animal products including oily fish, eggs, liver and red meat; there is a good list over on the NHS website. You can also get vitamin D from fortified products, such as plant based milks, however when you look at the total amount of vitamin D per 100ml, it tends to be less than 10% of the recommended daily amount so it is best not to rely solely on plant based milks for your vitamin D. Mushrooms that have been exposed to sunlight are an amazing source of vitamin D, but I don’t eat them every single day and not every box of mushrooms will necessarily have the same nutritional profile. In the UK many cereals are fortified with vitamin D but lots of them, especially those aimed at children are not only packed with added vitamins and minerals, but also an absolute ton of sugar, this is something to watch out for.
3. Take a supplement. If you can’t be certain that you are getting enough vitamin D daily from your diet and you’re living somewhere less than tropical it is now highly recommended that you take a daily supplement, particularly through the winter months.

Bread: The Food Medic Book // Vitamin D: eggs and mushrooms

My top tips:

1. Always protect you skin with SPF to reduce your risk of skin cancer when you are out enjoying the sunshine.
2. Take supplements throughout winter and consider taking them year round if you have darker skin, cover your skin whilst outdoors, spend lots of time indoors or are planning a pregnancy.
3. Branded and non-branded supplements contain the same active ingredients, there is no need to opt for more expensive supplements.