Why do we need vitamin D?
Vitamin D is made in our skin via direct exposure to sunlight. Our liver and kidneys then convert it into a form we can use. Vitamin D is extremely important for strong bones and teeth, as it helps us absorb the calcium we eat and it also controls the amount of calcium in our blood. It’s important that our vitamin D levels aren’t low or our body won’t absorb the calcium we eat. There aren't any visual signs of vitamin D deficiency. If our levels are very low and we are severely deficient, we are at risk of developing weaker bones which is a condition known as osteomalacia. Severe deficiency in children may result in soft skull or leg bones and their legs may look curved or bow-legged, which is a condition called rickets. A recent study has shown that healthy vitamin D levels during pregnancy may impact other aspects of your child’s early development including their social skills and co-ordination. As low levels of vitamin D are common in the UK, it's worth talking to your GP if you are concerned – they may suggest a blood test. Vitamin D levels explained Vitamin D blood ranges by classification:
- Under 25nmol/L – Deficient
- 25 - 50nmol/L – Insufficient
- 50-75nmol/L – Sufficient
- Over 75nmol/L – Optimal
How much sun do we need?
It is difficult to give a one-size-fits-all recommendation for sunlight exposure during the summer months. This is because so many other factors affect the amount of vitamin D that's made in the skin, including your skin colour and age, the strength of the sun, the time of day and where you live. The 2016 SACN report suggests that everyone over the age of one requires 10mcg of vitamin D daily in order to protect bone and muscle health. In addition, public health officials say that in the winter months people should consider getting this from vitamin D supplements, if their diet is unlikely to provide it. See the NHS website for current advice.
A word of caution though – too much sun exposure can be damaging due to the risk of developing skin cancer. Only spend a small amount of time in the sun without sunscreen either early in the morning or late in the afternoon, and the rest of the time be sure to cover up and avoid any chance of sunburn.
The British Skin Foundation says that research suggests that, "for lighter skin types – daily sunlight exposure for 10-15 minutes between April and September provides sufficient year-round vitamin D while also minimising the risks of sunburn and skin cancer. For darker skin types, 25-40 minutes is recommended."
What affects our Vitamin D levels?
Several different factors can affect our vitamin D levels such as skin pigmentation, age, season, clothing and use of high factor sunscreens. As elderly people are less likely to access the outdoors they may be more at risk of deficiency. Also, the position of the UK means that 90% of it lies above the latitude that permits exposure to the sun rays necessary for vitamin D synthesis. The southern part of the country is marginally better positioned for vitamin D synthesis (the closer you are to the equator the better). All of these factors will have an effect on our levels.
Approximately 60-70% of the UK adult population have insufficient levels of vitamin D in winter and spring and 16% are considered deficient.
Some groups are considered to be at higher risk for developing deficiencies. These include:
- People who aren't often outdoors, such as those who are frail or housebound
- People who have darker skin, such as those of south Asian, African or African-Caribbean backgrounds
- People who stay out of the sun or cover up when outside
Can you take too much vitamin D?It is possible to supplement with too much vitamin D. This may cause a build up of calcium in the body (hypercalcaemia), which may weaken your bones and damage organs like the kidneys and heart. If you choose to take vitamin D supplements, 10mcg a day is enough for most people, unless your doctor has told you otherwise. You may wish to stop supplementing during the summer months. It's also worth considering the form of vitamin D you take because studies suggest that some forms are more easily absorbed by the body.If you are considering taking a vitamin D supplement or you are concerned that you may be taking too much, consult your GP for advice.
Vitamin D in our dietsFoods that naturally contain vitamin D include oily fish such as mackerel, sardines, tinned salmon, herring and kippers. Some foods are fortified with small amounts of vitamin D, including breakfast cereals, infant formula and margarine. There are smaller amounts found in eggs and some red meats, such as duck, goose, pheasant and venison however, the exact amount is unknown. Breast milk also contains vitamin D and mums should make sure they aren’t deficient as this will affect the levels in their milk.Vitamin D-rich foodsVitamin D content of different types of food:
- Kipper (grilled, 140g) – 14µg vitamin D
- Herring (grilled, 140g) – 22.5µg vitamin D
- Mackerel (grilled, 140g) – 11.9µg vitamin D
- Tinned salmon (140g) – 19µg vitamin D
- Sardines (grilled, 140g) – 7µg vitamin D
- Branflakes (fortified, 30g) – 1.4µg vitamin D
- Hen eggs (poached, 2) – 2.9µg vitamin D
Recipes containing Vitamin D-rich foods:
Herrings rolled with mushrooms & pancetta
Grilled herrings with mustard & basil dressing
Spaghetti with sardines
Sardines with Sicilian fennel salad
Sardines with chickpeas, lemon & parsley
Spiced rice with kippers & poached eggs
Also containing vitamin D:
This article was last reviewed on 6th November 2019 by Kerry Torrens.
Emer Delaney BSc (Hons), RD has an honours degree in Human Nutrition and Dietetics from the University of Ulster. She has worked as a dietitian in some of London's top teaching hospitals and is currently based in Chelsea.
Kerry Torrens BSc. (Hons) PgCert MBANT is a Registered Nutritionist with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.
All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.