Should you take a Vitamin D supplement?

Feb 10, 2021

The importance of vitamin D

Although classed as a vitamin, vitamin D is actually a hormone, and unlike other vitamins, the main source is not the food we eat, but the sun, specifically the sun’s UVB rays. It plays several important roles in the body. It aids calcium absorption, thereby protecting the bones; supports the immune system, thereby helping to protect against infection; and enabling our muscles to move efficiently. It also plays a role in reducing inflammation, and is involved in glucose metabolism.

When is it best to start your supplement?

During the summer months (April to September), the sun’s rays are strong enough to enable our bodies to make vitamin D. During the winter months (October to March) we have to rely on our body’s stores and food sources. However, even combined these are not sufficient and it is recommended that everyone, regardless of their diet, should take a vitamin D supplement throughout the autumn and winter months.

How much should you take?

For the majority of adults, a 400 IU (10 micrograms) of Vitamin D is recommended daily during Autumn and Winter. However, anyone who has been diagnosed as vitamin D deficient will need to take a higher dose for a set period of time. Taking higher doses for a prolonged period needs supervision by a medical professional, as vitamin D is a fat-soluble vitamin. This means that unlike water-soluble vitamins, any excess is not excreted via the kidneys into the urine, and is instead stored in the liver. Very high doses can cause nausea, vomiting, confusion, impaired appetite and, can ultimately result in calcium building up in the body, which can weaken bones and damage the kidneys and the heart.

It is worth noting that UK dose guidelines are much lower than many other countries and there is ongoing discussion over optimal dosage. Some experts advocate taking up to 2000IU (50mcg) daily. The NHS advice is not to exceed 4000 IU (100mcg) per day due to the risk of harm.

There are certain groups who may need to take a supplement all year around. Adults over the age of 65 are included in this category, as when we age, our bodies become less efficient at making vitamin D. People with darker skin tones are not able to make vitamin D efficiently, and groups with limited sun exposure are unlikely to produce enough vitamin D without supplements. These include those who cover the majority of their skin and those who spend a lot of time indoors.  People who live in areas with higher levels of pollution may also need to take a supplement during the summer months, as air pollution affects the amount of UVB rays reaching the earth’s surface. Pregnant and breast-feeding mothers also fit into this category as their needs are higher.

The Covid-19 pandemic has escalated the debate around the issue of vitamin D supplementation, and the link between severity of Covid-19 and Vitamin D status is being explored. We wrote about it in one of our previous blogs.

Vegans and vegetarians get Vitamin D the same way that omnivores – from a supplement, fortified foods and sun exposure. Regardless of whether one eats animal products or is plant-based, we are unlikely to consume enough dietary vitamin D and a supplement should always be taken between October and March. Suitable vegan sources of vitamin D include colecalciferol (vitamin D3) or those derived from lichen or ergocalciferol (vitamin D2) which is derived from yeast. Colecalciferol (D3) may be slightly more effective than ergocalciferol (D2). The main dietary sources of vitamin D in a plant-based diet are fortified milks and yoghurts, providing an average of 1.1mcg per 100ml/g, fortified breakfast cereal, and mushrooms which have been ‘sunbathed.’ This means exposing them to sunlight, either outside during the summer months, or on a windowsill with the window open to enable to UVB rays to reach them. They can also be bought ‘pre-sunbathed.’

Further information can be found on our vitamin D factsheet at Plant Based Health Professionals


BDA food fact sheet Vitamin D

Vitamins and minerals – Vitamin D – NHS (

Vitamin D – Health Professional Fact Sheet (

Vitamin D and COVID-19: why the controversy? (

Image source: Canva

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