Vitamin D in Autumn and Winter: What UK Guidance Says

As the days shorten, UK public health guidance changes for one nutrient in particular: vitamin D. This article sets out what the NHS and the government’s Scientific Advisory Committee on Nutrition (SACN) say about vitamin D in autumn and winter, who may need to think about it all year round, and where it is found in food. It is general information, not individual advice.

What vitamin D does

Vitamin D helps regulate the amount of calcium and phosphate in the body, and these nutrients are needed to keep bones, teeth and muscles healthy (NHS). “Vitamin D contributes to the maintenance of normal bones” is one of the authorised health claims on the Great Britain nutrition and health claims register.

Why autumn and winter are different

Most of our vitamin D is made in the skin when it is exposed to sunlight. The NHS explains that from about late March or early April to the end of September, most people can make all the vitamin D they need this way. During autumn and winter the sun is not strong enough in the UK for the body to make vitamin D, so it needs to come from food or supplements.

What the guidance recommends

In 2016, SACN reviewed the evidence and recommended a reference nutrient intake of 10 micrograms of vitamin D a day for everyone in the UK aged 4 years and over. Because it is difficult to get enough vitamin D from food alone, the NHS advises that everyone, including pregnant and breastfeeding women, should consider taking a daily supplement containing 10 micrograms of vitamin D during autumn and winter.

Supplement labels sometimes show vitamin D in international units (IU). 10 micrograms is the same as 400 IU.

Who may need vitamin D all year round

The NHS advises some people to consider a daily 10 microgram supplement throughout the year, not only in winter. This includes people who:

• are not often outdoors, for example because they are frail or housebound;
• live in a care home;
• usually wear clothes that cover most of their skin when outdoors.

The NHS also notes that people with dark skin, for example from African, African-Caribbean or south Asian backgrounds, may not make enough vitamin D from sunlight and should consider taking a supplement all year. Separate guidance applies to babies and young children; the NHS page linked below sets this out.

Food sources of vitamin D

Only a small number of foods provide vitamin D, which is why food alone rarely meets the 10 microgram recommendation. The NHS lists these sources:

• oily fish, such as salmon, sardines, herring and mackerel;
• red meat;
• egg yolks;
• fortified foods, such as some fat spreads and breakfast cereals.

Fortification varies between brands, so the nutrition label is the best guide. Including oily fish once a week, choosing fortified products where they suit you and eating eggs are practical ways to add some vitamin D through the winter months, alongside the supplement advice above.

More is not better

Taking too much vitamin D over a long period can cause too much calcium to build up in the body, which can weaken bones and damage the kidneys and heart (NHS). The NHS advises that 10 micrograms a day will be enough for most people, and that adults should not take more than 100 micrograms (4,000 IU) a day, as this could be harmful. Some medical conditions mean people may not be able to safely take as much.

When to speak to your GP or pharmacist

If you have a medical condition, take regular medication, or have been advised by a doctor to take a different amount of vitamin D, follow their advice and check with your GP or pharmacist before starting a supplement. If you are concerned about your vitamin D levels or your bone health, speak to your GP.

The bottom line

From October to March, UK guidance suggests most adults consider a daily 10 microgram vitamin D supplement, and some people may need one all year. Food sources help but rarely provide enough on their own.

If you would like help building an eating pattern that works for you, get in touch or read more about what we do.

Emily Dixon ANutr — Registered Associate Nutritionist. This article is general information and is not a substitute for individual medical advice.

Sources

• NHS. Vitamin D. nhs.uk/conditions/vitamins-and-minerals/vitamin-d
• Scientific Advisory Committee on Nutrition (2016). Vitamin D and Health. gov.uk
• Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. gov.uk
• British Dietetic Association. Vitamin D: Food Fact Sheet. bda.uk.com