Vitamin D (a.k.a the ‘sunshine vitamin’) plays an important role in supporting our health, including our bones and immune system. Unfortunately, vitamin D deficiency is highly prevalent worldwide. So let’s go back to basics to understand what vitamin D is, what it does and how we can get it.

What is vitamin D?

Vitamin D (calciferol) is a fat-soluble vitamin made by our skin when it is directly exposed to sunlight, or absorbed through certain foods or supplements. It is the only nutrient where the main source is not from the diet, but rather sunlight exposure.

There are 2 main types of vitamin D: vitamin D2 and D3. Essentially, vitamin D2 is found in some plants and fungi, while D3 is the type we make through sunlight and is found in some animal products (e.g. fish or eggs).

What does vitamin D do?

Vitamin D regulates many processes in our bodies to keep us healthy. Its most common function is to help balance the amount of calcium and phosphate in the body. 

Calcium and phosphate are needed to form and maintain strong bones and teeth, help our muscles contract (such as our heart), aid nerve function (such as carrying messages from the brain to the rest of the body), support our immune system, and reduce inflammation.

What foods contain vitamin D?

As previously mentioned, our main source of vitamin D is sunlight exposure. However, food sources of vitamin D are particularly important when our sunlight exposure is lower, such as during autumn and winter months. 

Vitamin D rich foods include:

• Oily fish (e.g. herring, salmon & mackerel)

• Egg yolks

• Meat (e.g. red meat & liver)

• Fortified foods and drinks (e.g. margarine, plant-based milks, yoghurts or cereals)

• Mushrooms (when grown in sunlight or UV light)

How much vitamin D?

For children and healthy adults, including during pregnancy and lactation, an adequate intake of vitamin D is 15 micrograms (μg) or 600 international units (iu) per day. 

We can get our recommended amount of vitamin D by eating a balanced diet and through regular sun exposure - exposing your arms and face to sunlight without sunscreen for 15-20 minutes (while avoiding sunburn) can provide all the daily vitamin D our body needs. 

When to pay attention to Vitamin D?

In some situations, we do not make/get enough vitamin D from sunlight and our diets, and may need to supplement* to help meet our needs.

Here are some factors that may influence our vitamin D levels:

• Low sun exposure, location and season - our vitamin D stores do not typically last throughout the winter season, and depending on our location, the sunlight during wintertime may not be strong enough for us to produce adequate amounts of vitamin D.

• Skin pigmentation - higher levels of melanin protect the skin from UV lights which also make it more difficult to make vitamin D through sunlight. 

• Clothing - wearing clothes exposing minimal skin for medical, social, cultural, or religious reasons can leave insufficient skin exposed to sunlight to produce vitamin D.

• Sunscreen use - frequent use of sunscreen, although protecting the skin from damage by the sun, blocks vitamin D production.

• Ageing - with age our skin tends to get thinner which reduces its ability to produce vitamin D. Additionally, older adults are more likely to stay indoors.

*For more information on vitamin D supplementation check your country’s dietary guideline, speak to your doctor, or consult a registered nutritionist or dietitian to discuss how you can meet your nutritional needs.

An easy way to tell if your body is making vitamin D from the sun is by looking at your shadow.

If your shadow is longer than your height, you aren’t making vitamin D.

What happens if we don’t get enough vitamin D?

Low levels of vitamin D can reduce our ability to absorb enough calcium and phosphate, which in turn can impact our bone density and make them weaker. 

• In children - it can lead to rickets (softening and weakening of the bones), which affects bone growth and causes a bowing of the leg bones. 

• In adults - it leads to osteomalacia (softening of the bones) or osteoporosis (“brittle bones” - weakening of the bone), both of which increase the risk of bone fracture.

Here are the top signs and symptoms of lower vitamin D levels - sometimes overlooked as they have become a part of our daily lives - to be aware of: 

• Fatigue and tiredness

• Muscle cramps, pains, and weakness

• Joint and/or bone pains

• Hair loss

• Weakened immune system with a higher risk of infection

• Mood changes, irritability, depression or anxiety

• Pale skin with dark circles

What’s the take-home?

1. ​​Vitamin D is essential for a lot of our bodies processes, to keep us both physically and mentally healthy.

2. The main source of vitamin D is exposure to sunlight, but we can also find it in foods, such as oily fish, egg yolk, meat and mushrooms. 

3. Vitamin D supplementation is important in certain situations, like during the winter months in certain regions, to ensure our levels remain stable and we don’t run the risk of becoming deficient.

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References

1. Amrein, K., Scherkl, M., Hoffmann, M. et al. 2020. Vitamin D deficiency 2.0: an update on the current status worldwide. Eur J Clin Nutr 74, 1498–1513. https://doi.org/10.1038/s41430-020-0558-y 

2. European Food Safety Authority. 2016. Scientific opinion on dietary reference values for vitamin D. EFSA Journal 2016;14(10):4547

3. World Health Organization. ‎2005‎. Vitamin and mineral requirements in human nutrition, 2nd ed. World Health Organization. https://apps.who.int/iris/handle/10665/42716