Vitamin D, also known as the sunshine vitamin, is a fat-soluble vitamin, produced by the body in response to the skin being exposed to sunlight.
Vitamin D is very important throughout the body and has powerful effects on many systems. It is essential for strong bones as it helps the body to use calcium. It regulates the amount of calcium and phosphate in the body, needed to keep bones, teeth and muscles healthy. It is also required for bone growth and, without sufficient levels, bones can become thin and brittle. Traditionally Vitamin D deficiency was associated with rickets in children and osteomalacia in adults (soft bones and skeletal deformities). Together with calcium, vitamin D also helps protect older adults from osteoporosis.
However, increasing research is revealing the importance of vitamin D in protecting against a host of health problems.
Although it is naturally present in a few foods and added to some, it is very difficult to get sufficient levels from diet alone. Sources include:
- Oily fish – salmon, sardines, trout, herring and mackerel
- Red meat
- Eggs yolks
- Fortified foods – mainly dairy and grains
In the UK from late March/early April to the end of September, most people should be able to get all the vitamin D they need from sunlight. However, between October and early March this is difficult.
Symptoms of a deficiency can include bone pain and muscle weakness. However, for many people, the symptoms are subtle and even symptomless.
Research is constantly being carried out looking into the relationship between too little vitamin D and health risks including: cardiovascular disease, cancer (breast, colon and prostate), asthma, autoimmune diseases, depression, autism, weight gain and dementia.
Many factors can affect the synthesis of vitamin D including, the season, time of day, length of day, cloud cover, smog, skin melanin content, and sunscreen. Adverse factors include:
- Having darker skin
- Being elderly
- Being overweight or obese
- Lack of fish or dairy in the diet
- Over use of sun cream
- Spending most of the day indoors
The Recommended Dietary Allowance (RDA) for adults is 600IU (international units) of vitamin D per day. Increasing to 800IU per day for those older than 70. Click here for the NHS guidelines.
If you are concerned about whether you are getting enough vitamin D, talk to your Doctor.
Harvard T.H. Chan (2018) Vitamin D and Health. https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vitamins/vitamin-d/#vitamin-d-sources-and-function
Littlejohns TJ. (2014) Neurology. Vitamin D and the risk of dementia and Alzheimer disease. http://n.neurology.org/content/early/2014/08/06/WNL.0000000000000755
NHS (2019) Vitamin D
Norman PE, Powell JT (2014). Vitamin D and Cardiovascular Disease. https://www.ahajournals.org/doi/full/10.1161/circresaha.113.301241
Vitamin D Council (2019) https://www.vitamindcouncil.org