Parents have been urged to give their children a supplement if they are aged between one and four years old. According to the NHS, most young children should take it daily.

While parents probably understand why adults are advised to take vitamin D during the winter months, when the body can't make enough from sunlight, they might not realise it's especially important for children to get enough of the vitamin. The nutrient helps support healthy bone and muscle growth.

The NHS website explains: "Government advice is that everyone should consider taking a daily vitamin D supplement during the autumn and winter. People at high risk of not getting enough vitamin D, all children aged one to four, and all babies (unless they're having more than 500ml of infant formula a day) should take a daily supplement throughout the year."

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As the health service explains, a lack of vitamin D can lead to bone deformities, such as rickets, in children. Rickets is usually caused by low levels of vitamin D and calcium, leading to a child's bones becoming weak and soft.

As such, it's important that families help children reach their recommended daily intake. The NHS explains: "The Department of Health and Social Care recommends that babies from birth to one year of age should have a daily supplement containing 8.5 to 10 micrograms of vitamin D throughout the year if they are breastfed or formula-fed and are having less than 500ml (about a pint) of infant formula a day, as infant formula is already fortified with vitamin D."

It adds: "Children aged one to four years old should be given a daily supplement containing 10 micrograms of vitamin D throughout the year." However, it's important not to exceed the recommended amount.

The NHS said: "Children aged 1 to 10 years should not have more than 50 micrograms (2,000 IU) a day. Infants under 12 months should not have more than 25 micrograms (1,000 IU) a day."

Most pharmacies and supermarkets sell vitamin D supplements and vitamin D drops for children under five. Women and children who qualify for the Healthy Start scheme can receive free vitamin D supplements.

For example, Boots sells Ddrops One Liquid Vitamin D3 10μg - 60 dropsfor £11. According to the product description, the drops are suitable for adults and children aged one year old and above. The drop can be put on food, added to a drink, or licked from a clean surface, such as a spoon, the description adds.

Praising the drops, a reviewer commented: "I started using these drops with my one year old boy. We add them to his drink in the morning and he gets excited when he sees me add it.

"I think it’s great to teach children about leading a healthy lifestyle and this is a great start. They are so easy to administer and it’s great knowing he is getting the vitamin d dose he requires."