From about late March to the end of September, most people should be able to get all the vitamin D they need from sunlight. But with shorter days and less sunlight in the winter months, getting your 10 micrograms of vitamin D may be more difficult.

Why do we need vitamin D?

Vitamin D is essential for regulating calcium and phosphorus metabolism, both considered important for bone health.

Severe deficiency can result in rickets in children, and osteomalacia in adults. Low levels are also associated with chronic diseases such as rheumatoid arthritis, multiple sclerosis, cardiovascular disease and diabetes — although it is unknown whether deficiency actually contributes to causing such conditions.

It is also thought that vitamin D deficiency might be associated with sub-optimal immune function and increased risk of infection.

Researchers at the University of Edinburgh reported insights into how vitamin D regulates the immune system and may influence susceptibility to autoimmunity disease.

The study investigated how vitamin D affects the ability of dendritic cells (a type of guard to the immune system) to activate T cells, which are important for fighting infection. In people with autoimmune disease, T cells mistakenly start to attack the body’s own tissues.

The study revealed that vitamin D caused dendritic cells to produce more of a molecule called CD31 on their surface and that this hindered the activation of T cells. CD31 also prevented dendritic and T cells from making a stable contact, which is essential for T cell activation, resulting in a “far reduced” immune reaction.

How can you get enough vitamin D?

You can supplement with vitamin D, but it’s best to consult a GP or nutritional therapist before doing so. You may also find that the shops are currently empty, which is why it’s good to look to nutrition first.

Dietary sources of vitamin D include oily fish (e.g tuna, mackerel, salmon and sardines), red meat, egg yolks, liver and some fortified foods (e.g nut milks, spreads and breakfast cereals).

Exposure to sunshine is another source. Studies have shown that in the UK, nine to 13 minutes of midday sunlight exposure during summer three times per week is enough to maintain healthy levels among Caucasian adults.

Note: the sun's UVB rays cannot penetrate through glass, so simply sitting by a sunny window won't be enough to reap the benefits.

If possible, following government advice, try to use your one form of exercise a day to go on a run, walk, or cycle, maintaining a safe distance from others.

Magnesium and vitamin D

A randomised trial involving 250 people has found that magnesium appears to optimise and regulate vitamin D levels.

Researchers were interested in the role of magnesium after it was observed that people synthesise vitamin D differently, with levels not rising in some people even after being given a high dose. Lead author Qi Dai, MD, PhD, Ingram Professor of Cancer Research, said that magnesium deficiency “shuts down” the pathway for vitamin D to be synthesised and metabolised.

A separate review also concluded that vitamin D needs magnesium to be metabolised; otherwise it remains stored and inactive.

Magnesium can be supplemented by adding Epsom salts to a hot bath. Dietary sources include green leafy vegetables, nuts, brown rice, bread, fish, meat and dairy foods.

Enjoyed this article? Subscribe to our free digital version of Optimum Nutrition magazine for more research updates, features and recipes!