Vitamin D in a UK Winter: What the NHS Advises From October

Every October the clocks go back, the evenings draw in and most of us spend far more time indoors. There is one change you cannot see: from around October to early March, the sun in the UK is not strong enough for our skin to make the vitamin D we need. This guide explains why, what the NHS advises and how to read a vitamin D label.

Why the UK is affected

Our skin makes vitamin D when it is exposed to UVB light from the sun. The UK sits between roughly 50 and 58 degrees north, and between October and early March the sun is too low in the sky for enough UVB to reach us, however long we spend outdoors. In spring and summer, most people make what they need from sunlight on their skin, although many still choose to supplement.

What the NHS advises

The NHS advises that everyone, including pregnant and breastfeeding women, should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D during autumn and winter. Some people are advised to consider it all year round, for example people who are rarely outdoors, people who usually cover most of their skin when outside, and people with dark skin. Babies and young children have their own advice, so check the NHS website or ask your health visitor.

What vitamin D does

Vitamin D is one of the few nutrients with several authorised health claims:

• Vitamin D contributes to the maintenance of normal bones.
• Vitamin D contributes to the maintenance of normal teeth.
• Vitamin D contributes to the maintenance of normal muscle function.
• Vitamin D contributes to the normal function of the immune system.

Food sources

Vitamin D is found in a small number of foods: oily fish such as salmon, sardines, herring and mackerel, red meat, liver and egg yolks, plus fortified foods such as some breakfast cereals and fat spreads. It is hard to get enough from food alone, which is why the NHS advice focuses on a supplement in the darker months.

D2 or D3, and what to look for on a label

• The form. Vitamin D3 (cholecalciferol) is the form most supplements use. Vitamin D2 (ergocalciferol) is plant or fungal in origin.
• The source. D3 is usually made from lanolin, the natural wax in sheep's wool, so it is not suitable for vegans. Vegan D3 is made from lichen.
• The amount. Labels show micrograms (µg) and often IU as well. 10 µg is 400 IU, and 100 µg is 4,000 IU.
• %NRV. The Nutrient Reference Value for vitamin D is 5 µg, so 10 µg is 200% NRV.
• Other ingredients. Vitamin D is often paired with vitamin K2. Vitamin K contributes to the maintenance of normal bones.

How much, and when to talk to your GP

The NHS says 10 micrograms a day is enough for most people, and that you should not take more than 100 micrograms (4,000 IU) a day, as it could be harmful. Higher-strength products exist, but a higher dose is not automatically better. If you are thinking about a high-strength vitamin D product, talk to your GP or pharmacist first, particularly if you have a medical condition. Your GP can also arrange a blood test if you want to know your vitamin D status. Always add up the vitamin D from every product you take, including multivitamins.

Who should check with a doctor or pharmacist first

• you are pregnant or breastfeeding and considering anything above the NHS 10 microgram advice
• you take any prescription medication, especially anticoagulants such as warfarin if the product contains vitamin K
• you have a kidney condition or another long-term health condition
• you are under 18 (our products are not intended for anyone under 18)

Frequently asked questions

Can I get vitamin D through a window?

No. Most glass blocks the UVB light your skin needs to make vitamin D.

Is D3 better than D2?

Both are recognised forms of vitamin D. Most supplements use D3. If you are vegan, look for D3 from lichen or for D2.

Do I still need a supplement if I go outside every day in winter?

Between October and early March the sun in the UK is too weak for your skin to make enough vitamin D, which is why the NHS advice applies to everyone in those months.

Mother Nature products

Our Vitamin D3 4000IU K2 MK7 200mcg Capsules provide 100 µg (4,000 IU) of vitamin D3 from lanolin (2,000% NRV) and 200 µg of vitamin K2 as MK-7 (267% NRV) per capsule, with 20 mg of magnesium from magnesium glycinate. One capsule daily. This is a high-strength product at the NHS maximum of 100 micrograms a day, so speak to your GP or pharmacist before taking it, do not combine it with other vitamin D supplements without medical advice, and check with your doctor first if you take warfarin. It is not suitable for vegans or vegetarians.

You can see our other everyday vitamins and minerals in the Daily Foundations collection.

Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle.