What does vitamin D do?
It also facilitates a normal immune system. Vitamin D deficiency is associated with an increased susceptibility to infection and autoimmunity.
Common signs of vitamin D deficiency
When vitamin D is low, it can affect the body in a number of ways. These include;
- Aching bones
- Muscle weakness
- Tiredness and fatigue
- Low mood
- Poor immune system
You can find out more about the signs of vitamin D deficiency here.
Sources of vitamin D
Sunlight – The main and best source of vitamin D is from sunlight, which is why vitamin D is often known as the sunshine vitamin. Unlike most vitamins and minerals which are obtained through the food we eat; vitamin D is naturally created when our skin is exposed to direct sunlight.
Food – There are also a small number of foods which provide vitamin D, including oily fish, red meat and eggs.
Some foods are also fortified with vitamin D, such as cereal, bread, fat spreads and non-dairy milk alternatives, though the amount added varies and may only be in small amounts.
Supplementation – Dietary supplements are another source of vitamin D.
Public Health England now recommends everyone in the UK supplements at least 400IU (10mcg) daily of vitamin D through the winter months – October to March, with at risk groups advised to supplement all year round to maintain sufficient levels.
Who needs vitamin D?
Everyone needs vitamin D to help maintain healthy bones and a robust immune system, but there a number of groups that are more at risk of vitamin D deficiency and are recommended to supplement all year round.
At risk groups
- Pregnant and breastfeeding women
- Infants and young children (under 5 years)
- People aged 65 years and over
- People with low sun exposure
- People with darker skin
Factors that affect vitamin D levels
Location – For those living in the northern hemisphere the amount of UVB radiation required for the skin to synthesise vitamin D is not adequate enough all year round to maintain sufficient levels.
Seasons – During the autumn and winter months those living in the northern hemisphere are not able to gain vitamin D from sunlight. This is because due to the positioning of the sun throughout October to March, the sun’s rays are not strong enough. Even during the Summer months, it is predicted that up to 13% of the population will be deficient.
Sun exposure – Those who have little to no sun exposure, either because they are not often outdoors or cover up most of their skin when in direct sunlight, won’t get enough vitamin D.
Sun cream – Sun creams and moisturisers with a factor of 15 SPF and above block the UVB rays required to obtain vitamin D.
Skin pigmentation – Those with darker skin pigmentation have higher levels of melanin. Melanin helps protect the skin from sun damage by reducing the amount of UVB allowed to enter. However, this also reduces the amount of vitamin D produced from UVB exposure.
Diet – While the majority of vitamin D comes from sunlight it is not possible to obtain this source all year round, so it is important to also eat vitamin D rich foods. Those who eat little or no vitamin D rich foods, such as vegans and vegetarians, will not be obtaining enough through their diet.
Gut health - Vitamin D is a fat soluble nutrient, so if you suffer from a gastrointestinal condition that affects your ability to absorb fat, it will also affect your absorption of vitamin D from food and potentially from oral supplements as well, putting you at greater risk of a deficiency.
Age – As we age our bodies ability to synthesise the vitamin D reduces.