New research from the United Kingdom suggests few children’s multivitamins actually offer the recommended daily dose of vitamin D.

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According to the Mayo Clinic, the recommended daily amount of the vitamin is 400 international units for children up to 12 months, 600 IU for ages 1 to 70 years and 800 IU for folks older than 70. Too much vitamin D, on the other hand, can lead to significant kidney problems.

In the UK, at least 400 IU of vitamin D is recommended daily for children up to age 4, babies younger than 12 months not getting enough vitamin D through formula milk, black and Asian people, people who receive little exposure to sunlight, and everyone during the autumn or winter months, according to BBC.com.

But in this new study of 67 commercially available children’s multivitamins packaged for children under age 12, researchers found that only 25 percent to 36 percent of the lot actually contained the recommended 400 IU dose of vitamin D. Those labeled for “healthy bones,” according to the findings published in the journal Archives of Disease in Childhood, typically contained more than the recommended daily amount, though even some products labeled “for bones” had low levels of vitamin D.

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Of the 67 products, the daily vitamin D dose ranged between zero IU to 800 IU. And only five of six products suitable for infants and young children contained the recommended 340-400 IU per day.

To get the correct daily dose, BBC reported, children “would either have to take over the recommended dose, which may increase the risk of toxicity from the other components, or they would have to take a combination of vitamin D and multivitamins, which is more expensive.”

Vitamin D, according to the Mayo Clinic, is necessary for strong and healthy bones. Research shows vitamin D supplements, especially when taken with calcium, can prevent some cancers, improve cognitive function, reduce risk of multiple sclerosis, help treat some inherited disorders and prevent rickets, a rare condition in children due to vitamin D deficiency that leads to the softening and weakening of bones.

In the UK, doctors have reported an increase of rickets cases.

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"That is related to nutrition at the very least. We are seeing more advanced cases. It should be a Victorian illness. It shouldn't be around to this degree any more," London doctor Ronny Cheung, who sees kids with rickets on a fairly regular basis at his Evelina children's clinic, told the Guardian in 2017. Cheung believes the numbers aren't just exacerbated by poverty, but a result of poverty.

“What we see on a weekly basis is that poorer families who come in often take their children into hospital a bit later than they otherwise would. Maybe that’s partly down to health literacy, but – and I’ve spoke to parents about this – it is a struggle for them to bring children in. If your ability to make a living is on the line, your threshold for taking time off work to check a child’s health is going to be higher,” he said.

According to BBC, vitamin D supplements are given to low income families for free through the UK government’s Healthy Start scheme. But the supplements included in the program contain a dosage of only 300 IU per day.

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“To learn that so many products fail to provide children with the recommended level of Vitamin D is highly concerning, especially when latest evidence shows our children's average intake are still below the recommended amount,” Benjamin Jacobs of the Royal College of Paediatrics and Child Health told BBC. “These products are misleading parents who think they are protecting their children from serious conditions such as rickets, poor growth and muscle weakness.”

But industry members argue that smaller doses allow parents to vary the amounts for younger and older children.

Still, Jacobs urges parents to check their children’s vitamins and ensure they contain the recommended 400 IU and hopes the government plays a role in ensuring foods have appropriate doses of the vitamin.

Explore the full study at adc.bmj.com.