Vitamin D: how much is enough?
Originally contributed by Wild Nutrition. Updated by femme to reflect current NHS vitamin D guidance.
Vitamin D helps regulate calcium and phosphate and is important for bones, teeth and muscles. In the UK, sunlight is not strong enough for the skin to make sufficient vitamin D between October and early March, which is why supplementation advice changes with the season.
How much vitamin D do adults need?
Children from age one and adults need 10 micrograms (400 IU) of vitamin D a day. During autumn and winter, the NHS says everyone, including pregnant and breastfeeding women, should consider a daily supplement containing 10 micrograms.
From late March or early April to the end of September, most people can make the vitamin D they need from sunlight and a balanced diet.
Who should consider a supplement all year?
The NHS advises people at particular risk of low vitamin D to consider a daily 10 microgram supplement throughout the year. This includes people who are not often outdoors, people in institutions such as care homes, people who usually cover most of their skin when outside, and people with dark skin, including people of African, African-Caribbean or south Asian backgrounds.
Babies and young children
Babies under 1
Babies need 8.5 to 10 micrograms of vitamin D a day. Babies having more than 500ml of infant formula a day do not need an additional vitamin D supplement because formula is already fortified.
Children aged 1 to 4
Children aged one to four should have a daily supplement containing 10 micrograms of vitamin D throughout the year.
Can food provide enough?
Vitamin D is found in a relatively small number of foods, including oily fish such as salmon, sardines, trout, herring and mackerel, as well as egg yolks, red meat and fortified foods.
It is difficult to get enough vitamin D from food alone, which is why the NHS recommends considering a supplement during autumn and winter rather than relying on diet.
Vitamin D in pregnancy and breastfeeding
Pregnant and breastfeeding women need 10 micrograms of vitamin D a day and are included in the NHS autumn and winter supplement recommendation. People in higher-risk groups should consider supplementation throughout the year.
A prenatal supplement may already contain vitamin D, so check the label before adding another product.
Can you get vitamin D through a window?
No. The UVB wavelengths needed for skin production of vitamin D do not pass effectively through ordinary glass. Sitting beside a sunny window is not the same as having direct sunlight on your skin outdoors.
More is not automatically better
Vitamin D can build up in the body, and taking too much over a long period can cause harmful calcium levels. Do not use high-dose vitamin D to treat a suspected deficiency without appropriate advice. If a blood test shows deficiency, a healthcare professional can recommend the correct treatment dose and duration.
The bottom line
For most UK adults, the practical advice is simple: consider 10 micrograms of vitamin D daily during autumn and winter, and consider it all year if you are in a higher-risk group. Babies and young children have specific guidance of their own.
