What is it?
Vitamin D, often referred to as the sunshine vitamin, is needed by the body to support healthy teeth, muscles, and bones. It is a fat-soluble vitamin (along with vitamins A, E, and K) which means it can only be absorbed by the body in the presence of fat. Unlike all other vitamins, Vitamin D is unique in that it is the only vitamin that our body can make on its own and is not required from dietary sources. The process of the body creating it starts with the skins exposure to natural sunlight, followed by a cascade of events in the body which lead to the production of Vitamin D in its biologically active form, known as calcitriol. It is the calcitriol that is important for regulating calcium and phosphorous levels within the body which plays an essential role for healthy teeth, muscles, and bones (1).
How much do we need?
Despite our bodies ability to produce Vitamin D from UVB radiation from the sun, in the UK sunlight exposure becomes limited in the autumn and winter months. It is therefore recommended that we take a supplement during this time (October – March). The Scientific Advisory Committee on Nutrition (SACN) recommend a daily intake of 10 micrograms (mcg), or 400IU, throughout the year for individuals aged 4 and over in the UK (2 & 3). However, it is still possible to reach the recommended intake through sources within the diet (see below).
Sources of vitamin D (4)
Other than sunlight, there are also dietary sources which contain vitamin D, including:
- Oily fish, such as salmon, sardines, mackerel, herring, trout
- Egg yolks
- Mushrooms that have been exposed to sunlight
- Red meat and offal, such as liver and kidneys
- Fortified foods, such as milk and plant-based alternatives, and breakfast cereals
Health benefits of vitamin D
Vitamin D has numerous health benefits, which emphasises its importance. Adequate intake can help to slow down the process of and improve bone mineral density loss in peri- and post-menopausal women and ageing populations, to prevent and/or manage adverse implications, such as osteoporosis. It is recommended that post-menopausal women consume between 500-800IU a day of Vitamin D (5), whilst older adults should consume the recommended 10mcg per day (2).
Vitamin D is an important nutrient needed during pregnancy to ensure good maternal and foetal health. Some studies have found an association between inadequate Vitamin D intake and an increased risk of preeclampsia (a potentially life-threatening disease in pregnancy which can be harmful to both mother and baby), whilst others show the importance of sufficient Vitamin D intake in the development of a healthy baby (6).
Sufficient intake of Vitamin D has also been associated with a protective relationship against the risk of cancer by inhibiting the proliferation (rapid increase) of cancerous cells (7), as well as helping the immune system to reduce susceptibility to disease and infection (8).
So, in conclusion…
Although we can make Vitamin D within our bodies, it is still an essential nutrient to include within our diets, in the form of foods such as oily fish, eggs yolks, meat and offal, and sunlight-exposed mushrooms, and a 10mcg supplementation during the winter months within the UK. The positive health outcomes discussed associated with adequate Vitamin D intake also highlight its importance.
- Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Ross AC, Taylor CL, Yaktine AL, et al., editors. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US); 2011. 3, Overview of Vitamin D. Available from: https://www.ncbi.nlm.nih.gov/books/NBK56061/
- Lambert R (2021) The Science of Nutrition(1st edition). Dorling Kindersley Ltd.
- Malabanan AO, Holick MF. Vitamin D and bone health in postmenopausal women. J Womens Health (Larchmt). 2003 Mar;12(2):151-6. doi: 10.1089/154099903321576547
- Wagner, C. L., Taylor, S. N., Johnson, D. D., & Hollis, B. W. (2012). The role of vitamin D in pregnancy and lactation: emerging concepts. Women’s health (London, England), 8(3), 323–340. https://doi.org/10.2217/whe.12.17
- Garland, C. F., Garland, F. C., Gorham, E. D., Lipkin, M., Newmark, H., Mohr, S. B., & Holick, M. F. (2006). The role of vitamin D in cancer prevention. American journal of public health, 96(2), 252–261. https://doi.org/10.2105/AJPH.2004.045260
- Aranow C. (2011). Vitamin D and the immune system. Journal of investigative medicine : the official publication of the American Federation for Clinical Research, 59(6), 881–886. https://doi.org/10.2310/JIM.0b013e31821b8755
Contribution by Associate Nutritionist, Ellie Morris