Vitamin D that is!
Vitamin D plays a vital role in many processes in the body, supports the immune system, and aids the absorption of nutrients such as calcium.
Ideally, we should get enough from around 30 minutes exposure to the sun on a daily basis (depending on factors such as skin type, location, time of year). Hard to achieve in the UK.
Although vitamin D is stored by the body, we can become deficient in winter months, as well as through wearing sunscreen and some moisturisers and cosmetics that contain sun protection factors.
Data gathered by Public Health England says one in five people have low levels of vitamin D (1), and the Scientific Advisory Committee on Nutrition (SACN) recommends we need 10mcg (400 IU) per day (2).
Deficiency can lead to tooth decay, muscular weakness and a softening of the bones (osteoporosis, rickets), and vitamin D is increasingly being studied as a contributing factor in conditions such as heart disease, multiple sclerosis, diabetes and some cancers. A recent study suggested there is a direct relationship between increasing body mass index (BMI) and falling vitamin D levels (3).
So, how do you know if you are getting enough?
Get a blood test to determine your current vitamin D levels. Ask your GP, or alternatively there are simple home finger prick tests available from reputable labs such as City Assays at www.vitamindtest.org.uk
If test results show you to be deficient, you can consider:
(safely) increasing your sun exposure – this needs to be outdoors as it is the UVB rays which are needed to produce vitamin D
ensure you eat foods which naturally contain vitamin D, mainly oily fish and egg yolks, although these contain relatively small amounts which makes it difficult to achieve adequate levels through diet alone
supplements - choose one with a GMP (Good Manufacturing Practice) mark, and ensure it is D3 ( cholecalciferol), which is 87% more effective in raising and maintaining vitamin D levels than D2 (ergocalciferol) (4)
If you'd like to know more, you can find details of the full reports in the references below...
(1).Vimaleswaran KS, Berry DJ, Lu C, Tikkanen E, Pilz S, et al. (2013) Causal Relationship between Obesity and Vitamin D Status: Bi-Directional Mendelian Randomization Analysis of Multiple Cohorts. PLoS Med 10(2): e1001383. doi: 10.1371/journal.pmed.1001383
(2). Public Health England and the Food Standards
Agency. National diet and nutrition survey: results from years 1, 2, 3 and 4 (combined) of the rolling programme (2008/2009–2011/2012). London: PHE, 2014. Available at: www.gov. uk/government/uploads/system/uploads/ attachment_data/file/310995/NDNS_Y1_to_4_UK_report.pdf
(3). Scientific Advisory Committee on Nutrition. Draft vitamin D and Health report (2015) Available at: www.gov.uk/government/uploads/system/uploads/attachment_data/file/447402/Draft_SACN_Vitamin_D_and_Health_Report.pdf
(4). Houghton, LA and Vieth R (2006)The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr, October 2006
vol. 84 no. 4 694-697
vol. 84 no. 4 694-697