Now as autumn is here, and winter is around the corner, the days are getting shorter and shorter and seeing the sun will soon feel like a distant memory, I thought it would be a good time to write about what does vitamin D do in the body and why it’s important.
What is vitamin D?
Vitamin D is a fat soluble vitamin and is often called the sunshine vitamin as the body can produce its own vitamin D when the skin is exposed to the sun! It does so by transforming a cholesterol molecule to vitamin D with the help of UV light from the sun. But this form of vitamin D is inactive and needs to be converted in the liver and then again the kidneys to the active form of vitamin D called calcitriol!
The majority of calcitriol is produced in the kidneys, but it’s been shown that other cells can produce calcitriol, but mainly to be used locally and not anywhere else in the body. Cells that have been shown to produce calcitriol for its own purpose are for example brain cells and intestinal cells.
Vitamin D is also often considered being more of a hormone than a vitamin due to it’s actions in the body.
There are two forms of vitamin D
- Vitamin D2 (ergocalciferol) – found in plants and yeast
- Vitamin D3 (cholecalciferol) – found in animals sources
Being a fat soluble vitamin, vitamin D is stored in the body’s fat tissue.
What does vitamin D do in the body?
So what does vitamin D do in the body? Well, it’s important for many functions in the body, and there are a lot of research going into in the link between vitamin D and how it affects us, but the most well know functions of vitamin D are
- Bone health – Vitamin D is essential for healthy bones. It plays a key role in keeping your bones and teeth strong and healthy and it’s essential for healthy muscle function.
- Calcium Balance – It helps the body to absorb calcium and helps to regulate the calcium balance in the body.
- Muscle function – Improves function and strengths of the muscle
- Immune System – Can support innate and the adaptive immune responses and control inflammation
Vitamin D deficiency
The most established effects of vitamin D deficiency are skeletal diseases, such as rickets among children and osteomalacia with adults, which in simpler tearms means weakening of the bones. Muscle weakness and increased falls with the elderly are also linked to vitamin D deficiency.
However, more research is needed before any clear associations between vitamin D deficiency and any of the conditions mentioned above can be established, as correlation does not mean causation!
Sources of Vitamin D
The sun is arguably the best source of vitamin D.
It’s difficult to say how long you need to be in the sun to make enough vitamin D though, as factors such as location, time of the day, season, skin colour and how much skin that’s exposed need to be taken into consideration.
Spending 5-15 minutes in the sun without SPF on a sunny day a few times a week can a good boost to your vitamin D3 stores. And the more skin you expose, the more vitamin D will be produced. Just make sure you don’t burn! You only have to spend half the time it takes for your skin to turn pink for the body to produce enough vitamin D to cover your daily need!
Unlike most nutrients, it’s hard to get adequate amounts of vitamin D solely from food. But there are a few food sources that contain vitamin D (either naturally or by fortification) and below are some examples
- Oily fish -salmon, herring, mackerel
- Fish – perch
- Beef Liver
- Egg – egg yolk is where you’ll find the vitamin D
- Fortified milk products – milk, yogurt
- Fortified plant based milk substitutes – almond, oats and other milks (and usually the conventional versions)
- Mushrooms – wild mushrooms and mushrooms exposed to UV light
Supplementing with vitamin D is becoming more popular, and can be a good way to ensure you meet your body’s need for vitamin D, especially if you live in a country with long dark winters or if you don’t get enough sun exposure.
Do you need to supplement with vitamin D?
You should always try to meet your nutritional needs through a good diet. However, this is not always possible and vitamin D is a nutrient that’s especially hard to get through diet alone. It’s estimated that 1 billion people are have suboptimal or are deficient in vitamin D, so supplementing may be an important strategy to meet the daily needs for many.
There are many factors that can contribute vitamin D deficiency. For example, spending time indoors, wearing covering clothes and wearing SPF all the time, skin colour, liver and kidney diseases, age and weight can affect your body’s vitamin D status.
Best way to determine if you need to supplement with vitamin D is to have your levels checked and work from there. If you supplement, taking doses up to 100μg/day (4000 IU) is considered being safe. But remember
Always consult with your doctor, dietitian or nutritionist before supplementing with larger doses of vitamin D.
Consuming larger doses than the recommended amount may be unnecessary and even harmful. Overdosing on vitamin D can lead to calcium building up in the body (hypercalcaemia), which can weaken the bones but also damage the kidneys and the heart. There have not been that many recorded incidents of overdosing on vitamin D, and the ones that exist mainly consist of people taking humungous amounts of vitamin D for an extended time, but it’s important to remember that
Like with most nutrients, more is not always necessarily better!
If you supplement with vitamin D, go for vitamin D3 (cholecalciferol) instead of D2 if possible, as vitamin D3 is absorbed more easily and be used more effectively in the body. As vitamin D is fat soluble, always take it with a source of fat such as olive oil, avocado or something similar to aid absorption (unless your supplement is oil based).
The best thing to keep you can do to keep a good vitamin D status is to spend some time in the sun without SPF a couple of times a week (but make sure you don’t burn!) during summer, include as many vitamin D rich foods as possible and take a supplement in the winter if you live somewhere were it’s dark for the most part of the winter.
One thing to remember is that you cannot overdose on vitamin D from sun exposure!
Even though food generally contain little vitamin D, here are some of my favourite vitamin D rich recipes!
One portion of salmon can contribute to around can provide you with anything from 400 IU to 900 IU vitamin D. It’s hard to estimate as there are many factors affecting vitamin D status in salmon. However, eating some will give you vitamin D in a form that’s easy for the body to absorb. This thai salmon is one of my most popular recipes on the blog and is a delicious way to get vitamin D as well as brain healthy omega-3!
Eggs contain around 20-40 IU, which is not much but every little helps! The vitamin D is found in the yolks, so there’s another reason to not throw them away! These scrambled eggs is one of my favourite ways to enjoy eggs! These ones are seasoned with chilli, chives and a drizzle of sesame oil, served with garlic kale! Have it with a slice of bread and you got yourself a well balanced meal!
Mushrooms that have been exposed to UV light contain vitamin D. It’s hard to estimate how much they contain as it’s depends on many factors. When you can, use wild mushrooms! I love using wild mushrooms in this lentil bolognese (think chantarelles, trumpet chantarelles or boletes) for some added vitamin D!
Summary: Vitamin D is a fat soluble vitamin essential for human health. The most well known function for vitamin D is its role in bone health, where it helps the intestine to absorb calcium and plays a part in the mineralisation of the bones! Severe vitamin D deficiency is linked to skeletal diseases among humans, however if slight deficiencies of vitamin D gives any problems is not as clear. The best sources of vitamin D is sunlight, and food sources are salmon and other fatty fish. If supplementing with vitamin D, go for vitamin D3 over D2 if possible!
Hope you found this article interesting and that you’ve learnt what vitamin D does in the body! If you have any questions, just comment and I’ll get back to you as soon as possible.