Vitamin D. It’s called the ‘sunshine vitamin’ because our bodies can produce it when exposed to the sun’s UVB rays.

If that’s the case, then surely we don’t need to worry about a deficiency? While that may have been true in the past, vitamin D deficiency is a growing health concern worldwide.

Shedding light on low vitamin D levels

Factors such as broad-spectrum sunscreens that block all UV rays, lower dietary intakes and reduced sun exposure during winter means some people produce insufficient amounts of this important vitamin.

Those who shun the sun, omit dairy from their diets due to a milk allergy or lactose intolerance, or adhere to a strict vegan diet may be at the greatest risk for a deficiency, in which case fortified foods and supplements may be necessary.

More than just strong bones

Most of us already know the important role vitamin D plays in bone health – it regulates calcium absorption, so a deficiency is linked to decreased bone strength and density, and can cause rickets.

Now, a growing body of research reveals numerous other health benefits associated with adequate vitamin D levels.

These include reduced risks of heart disease and diabetes, and it could potentially lower our risk of respiratory diseases and chronic non-communicable diseases in adulthood.

Studies have also linked insufficient levels of vitamin D in females to higher body fat, depression and adverse pregnancy outcomes.

One study suggests that low vitamin D levels during pregnancy may increase the risk of ADHD in your child, while another study links higher levels of vitamin D with a decreased risk of breast cancer. Additionally, vitamin D regulates the expression of more than 200 human genes.

These insights and the fact that cells in most tissues contain a vitamin D receptor suggests that this vitamin has diverse roles in optimal health and development.

A vital immunity booster

Vitamin D’s role in the body’s immune response helps to reduce levels of inflammatory proteins called cytokines. It also increases antimicrobial proteins that destroy invading germs and viruses, which form part of our adaptive immune system.

Furthermore, there is evidence to suggest that vitamin D plays an important role in our innate immunity – the immediate, non-specific immune defence system.

More generally, vitamin D has been linked to a decrease in both a person’s susceptibility to and the duration of common infections, including the flu.

This is backed by studies, which tend to show that people who have lower vitamin D levels are more likely to get the flu, and also tended to suffer from the infection for longer (nine days versus just two in those with higher vitamin D levels, according to one study).

Vitamin D’s performance benefits

But it’s not just our general health department where vitamin D delivers benefits. It also helps to regulate fat metabolism, which can assist with weight loss and body composition.

It is also crucial for optimal muscle function, and post-workout recovery as it decreases inflammation.

You could also gain an endurance boost due to vitamin D’s role in aerobic energy production. A study showed that an increase in vitamin D was associated with a higher VO2 max, which is a physiological measure directly linked to endurance performance.

Based on its many roles and functions, adequate vitamin D levels are clearly more important than many of us realise.

The vitamin D basics

This fat-soluble vitamin is synthesised from cholesterol via the action of sunlight on a form of vitamin D contained in the skin called cholecalciferol (also known as vitamin D3) and is stored in the body.

A two-step – first in the liver, then in the kidneys – converts it into its active form known as calcitriol, which acts on vitamin D receptors on cells to deliver its numerous benefits. Once this conversion takes place, vitamin D becomes classed as a steroid hormone and is no longer a vitamin.

Boosting your vitamin D levels

Other than direct sun exposure, which we should limit to short 10-15 minutes periods a few times a day to lower the risk of skin cancer, the best dietary vitamin D sources include egg yolks, beef liver, and fatty fish such as tuna, herring, mackerel and salmon.

Vitamin D is also found in supplements and various fortified dairy and cereal products in two different forms: D2 (ergocalciferol) and D3 (cholecalciferol), which both increase vitamin D in the blood.

As vitamin D requirements are highly individualised, any recommended supplemental approaches should be determined in consultation with a qualified healthcare practitioner.

Tips to boost vitamin D levels:

  • Boost skin to the sun’s ultraviolet rays for a few minutes each day. Optimal durations vary depending on skin type.
  • Get this ultraviolet exposure as near to solar noon as possible – generally between 10h00 and 14h00.
  • Add more vitamin D-rich foods to your daily diet.
  • Supplement with vitamin D2 or D3, if additional support is required.