By Dietitian Hazel Clark
Are you getting enough D*?
*(vitamin D) hehe
With it not being the sunniest of summers in the UK, have we been getting enough of the “sunshine vitamin”?
What is Vitamin D?
A vitamin is something that we cannot produce within our bodies but is essential to help our bodies function. We, therefore, need to get vitamins in small quantities from our diet and in some cases from supplementation.
Vitamin D is slightly different – although we call it a vitamin, it is actually a hormone that we can produce under the skin (1). This happens when we are exposed to sunlight, which is the reason it is sometimes called the ‘sunshine vitamin’. It can also be absorbed in our gut from foods which either naturally contain vitamin D or are fortified with it (2).
Why do we need Vitamin D?
Vitamin D is important to help protect our muscle strength, bones, and teeth. It has been found to help prevent rickets in children, which can cause permanent deformities to the bone, weaken muscles and reduced growth; as well as osteomalacia in adults, which makes the bones softer and can cause bone pain and muscle weakness (4).
It does this by working with calcium and phosphorous to help maintain healthy bones, muscles, and teeth (3). Therefore, even if your diet is rich in calcium, without enough vitamin D you cannot absorb the calcium into your bones and cells where it is needed.
A number of studies have been carried out to investigate if vitamin D plays a role in other health conditions, including: cancer, cardiovascular disease, diabetes, autoimmune diseases, and even depression, which could suggest one reason why so many of us experience the ‘winter blues’. But the results of these studies are conflicting and there is currently not enough evidence to support a relationship between vitamin D deficiency and these conditions, so more research is needed (4).
Where to get Vitamin D from
Our bodies can make vitamin D under the skin when we are directly exposed to sunlight containing ultraviolet B (UVB) radiation (5) (although this does not happen through glass, unfortunately!).
The amount of vitamin D you make depends on how strong the sunlight is. You will make more in the middle of the day, when the sun is strongest or when you are in direct sunlight. There isn’t a recommended amount of time to spend in the sun to meet your bodies vitamin D requirements, as the amount of vitamin D each person makes depends on a number of factors including skin colour and how much skin is exposed to the sunlight (6).
When out in the sun it is important to remember to protect or cover up the skin before it burns, as excessive sun exposure can cause skin and eye damage and increase the risk of skin cancer. Similarly, tanning beds also cause the skin to make vitamin D, but they pose similar risks for skin cancer (7).
Vitamin D can be found naturally in foods including: oily fish (e.g. sardines, mackerel, salmon, herring, kippers, pilchards, trout and eel, cod liver oil also tends to contain a lot of vitamin D), red meat, liver, mushrooms and egg yolks. It can also be found in fortified foods like margarine, some breakfast cereals, and some yoghurts.
In the UK in the autumn and winter months, sunlight doesn’t contain enough UVB radiation for our skin to be able to make vitamin D. During these months we rely solely on getting vitamin D from our diet, but this can be tricky as there are a limited number of foods that contain vitamin D.
People at higher risk of low Vitamin D
Anyone can be at risk of vitamin D deficiency, but there are groups of people who are more likely to be at risk – these include:
- People who live in the UK or northern climates, or who cover most of their skin when outside.
- People who spend very little time outside during the summer (e.g. the housebound, shop or office workers, night shift workers).
- People with darker skin tones (e.g. people of Asian, African, Afro-Caribbean and Middle Eastern descent), living in the UK or other northern climates.
- Those living in areas with polluted air.
- Babies and young children, as well as pregnant women and breastfeeding mothers.
- People over 65 years old, because their skin is not as good at making vitamin D.
- People with certain medical conditions (e.g. coeliac disease and IBD), or taking certain medicines (e.g. anti-seizure medications).
How much Vitamin D do we need?
In the UK it is recommended that anyone over the age of 1-year-old needs 10 micrograms of vitamin D daily throughout the year4. Between late March/early April and September, most people will be able to meet these vitamin D recommendations from sunlight on the skin and a healthy balanced diet (unless you are in the ‘higher risk’ group listed above). However, between October and March, we can only rely on our body stores of vitamin D and dietary sources.
I’m a big believer in aiming to get the nutrients we need from food, but this isn’t always possible. Since vitamin D is only found in a small number of foods, it can be difficult to get enough from our diets. A survey found that the average person only gets 3 micrograms per day of vitamin D from their diet (8). Therefore Public Health England suggests that you should consider taking a daily Vitamin D supplement containing 10 micrograms during the winter months (and all year round if you are in the ‘as risk’ group) (9).
When it comes to supplements, cheaper does not always mean inferior! Do not be fooled by the packaging and advertising of some, just because a supplement is more expensive does not necessarily mean it is better. As long as you are choosing a supplement that contains the recommended amount of vitamin D, and it is brought from a reputable source, then feel free to choose the cheaper one! Just remember that too much of anything can be bad for us, supplements are no different. Vitamin D can be harmful in large doses (10), so if you choose to take a supplement make sure you only take 1 and do not exceed the recommended daily dose of 10 micrograms (unless advised by your doctor!).
1. Pike, W., & Christakos, S. (2017). Biology and Mechanisms of Action of the Vitamin D Hormone. Endocrinology & Metabolism Clinics of North America, 46(4), 815–843. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5762112/
2. Black, L., Seamans, K., Cashman, K., & Kiely, M. (2012). An Updated Systematic Review and Meta-Analysis of the Efficacy of Vitamin D Food Fortification. The Journal of Nutrition, 142(6), 1102–1108. https://doi.org/10.3945/jn.112.158014 3. DeLuca, H. (2004). Overview of general physiologic features and functions of vitamin D. The American Journal of Clinical Nutrition, 80(6), 1689S-1696S. https://doi.org/10.1093/ajcn/80.6.1689S
4. SACN (Scientific Advisory Committee on Nutrition), 2016. Vitamin D and Health Report. England, UK: Public Health England. Retrieved from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/537616/SACN_Vitamin_D_and_Health_report.pdf 5. Nair, R., & Maseeh, A. (2012). Vitamin D: The “sunshine” vitamin. Journal of Pharmacology & Pharmacotherapeutics, 3(2), 118-126. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356951/
6. NHS. (2018). How to get vitamin D from sunlight. Retrieved from https://www.nhs.uk/live-well/healthy-body/how-to-get-vitamin-d-from-sunlight/ 7. Thieden, E., Jørgensen, H., Jørgensen, N., Philipsen, P., & Wulf, H. (2008). Sunbed radiation provokes cutaneous vitamin D synthesis in humans-a randomized controlled trial. Photochemistry and Photobiology, 84(6),1487-92. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/18513233
8. Public Health England and Food Standards Agency. (2014) National Diet and Nutrition Survey: results from Years 1 to 4 (combined) of the rolling programme for 2008 and 2009 to 2011 and 2012. Retrieved from https://www.gov.uk/government/statistics/national-diet-and-nutrition-survey-results-from-years-1-to-4-combined-of-the-rolling-programme-for-2008-and-2009-to-2011-and-2012
9. Public Health England (PHE) Press Office. (2016). PHE publishes new advice on vitamin D. Retrieved from gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d
10. Marcinowska-Suchowierska, E., Kupisz-Urbańska, M., Łukaszkiewicz, J., Płudowski, P., & Jones, G. (2018). Vitamin D Toxicity–A Clinical Perspective. Frontiers in Endocrinology, 9(550). doi: 10.3389/fendo.2018.00550