Researchers checked vitamin D levels in nearly 4,700 British children between 2004 and 2007 and found that about 7 out of 10 kids weren’t getting enough of this important nutrient. The problem was especially common in children with South Asian, Black African, and Caribbean backgrounds. Girls were more likely to have low vitamin D than boys. During winter months, almost all children had low levels. The study suggests that the UK needs better ways to help children, especially those from certain ethnic backgrounds, get enough vitamin D for healthy bones and immune systems.

The Quick Take

  • What they studied: How many British schoolchildren have low vitamin D levels and which groups are most affected
  • Who participated: 4,650 children aged 9-10 years old from three UK cities (London, Birmingham, and Leicester) with different ethnic backgrounds including South Asian, Black African and Caribbean, and White European families
  • Key finding: About 68% of children had vitamin D levels that were too low, with South Asian children having the lowest levels (25 times more likely to be deficient than White European children) and Black African and Caribbean children also at high risk (10 times more likely)
  • What it means for you: If you have children, especially from South Asian or Black African and Caribbean backgrounds, they may need more vitamin D through sunlight, food, or supplements. This is particularly important during winter months when everyone’s vitamin D levels drop. Talk to your doctor about whether your child needs a vitamin D supplement.

The Research Details

This was a cross-sectional study, which means researchers took a snapshot in time (2004-2007) and measured vitamin D levels in a large group of children all at once, rather than following them over many years. The researchers measured a specific form of vitamin D in the children’s blood called 25(OH)D, which is the best way to check if someone has enough vitamin D in their body. They also measured the children’s height, weight, and body fat to see if these factors were connected to vitamin D levels.

The study included children from different ethnic backgrounds living in three major UK cities. The researchers looked at whether the season (winter versus summer), the child’s sex, their family’s income level, and their body fat percentage affected their vitamin D status. This allowed them to understand not just how many children had low vitamin D, but also which factors made it more likely.

This research approach is important because it gives us a clear picture of a real health problem in UK children at a specific point in time. By including children from different ethnic backgrounds and measuring multiple factors, the study helps identify which groups need the most help. Understanding these patterns is the first step toward creating solutions.

This study is reliable because it included a large number of children (4,650) from multiple cities, making the results more likely to represent the whole UK population. The researchers used a standard blood test to measure vitamin D, which is accurate and objective. However, because this was a snapshot study from 2004-2007, vitamin D levels might be different today. The study was also limited to children in three cities, so results might vary in other parts of the UK.

What the Results Show

The study found that vitamin D deficiency is a widespread problem among UK schoolchildren. Nearly 7 out of 10 children (68%) had vitamin D levels that were too low. Of these, about 45% had insufficient levels (meaning they were low but not critically low) and 23% had deficient levels (meaning they were dangerously low).

The problem was not equally distributed across ethnic groups. South Asian children, especially those with Bangladeshi heritage, had the lowest vitamin D levels overall. Black African and Caribbean children also had very low levels. White European children had higher vitamin D levels, though even they often had insufficient amounts.

Season made a big difference. During winter months, almost all children had low vitamin D levels. During other seasons, White European children’s levels improved, but South Asian and Black African and Caribbean children remained low year-round. This suggests that these groups may have less sun exposure or may need more vitamin D from food and supplements.

Girls were significantly more likely to have low vitamin D than boys. When researchers adjusted for all other factors (age, ethnicity, family income, and body fat), girls had about 1.5 times the risk of vitamin D deficiency compared to boys.

The study found that family income level (socio-economic status) was connected to vitamin D levels, though ethnicity was a much stronger factor. Body fat percentage also played a role, with children who had higher body fat more likely to have low vitamin D. These secondary findings suggest that vitamin D deficiency is a complex problem with multiple causes.

This study was one of the first large investigations of vitamin D levels specifically in UK children from different ethnic backgrounds. It confirmed what smaller studies had suggested: that vitamin D deficiency is common in the UK, especially in children with darker skin tones. The findings align with research from other countries showing that people with darker skin produce less vitamin D from sunlight exposure, which is a key reason for the differences between ethnic groups.

This study has several important limitations. First, it was conducted between 2004 and 2007, so vitamin D levels in today’s children might be different due to changes in sun exposure habits, diet, or supplement use. Second, the study only included children in three UK cities, so results might not apply to children in other parts of the country. Third, the study measured vitamin D at one point in time rather than following children over months or years, so we can’t say whether low vitamin D caused health problems or just that it was present. Finally, the study didn’t measure how much time children spent outdoors or their dietary intake of vitamin D, which would have helped explain why some groups had lower levels.

The Bottom Line

Based on this research, health experts should consider recommending vitamin D supplements for all UK children during winter months, and year-round for children with South Asian or Black African and Caribbean backgrounds. The evidence is strong (high confidence) that these groups are at risk. Parents should talk to their child’s doctor about whether a vitamin D supplement is appropriate. The UK government may want to consider adding vitamin D to more foods or running public health campaigns about vitamin D, especially targeting families from high-risk ethnic groups.

Parents of children aged 9-10 should pay attention to this research, especially if their child has South Asian, Black African, or Caribbean heritage. Girls may need particular attention. Children who spend little time outdoors or who wear clothing that covers most of their skin may also benefit from vitamin D supplements. However, this research is less relevant for families who already ensure their children get regular sunlight exposure and eat vitamin D-rich foods like fatty fish, eggs, and fortified milk.

Vitamin D builds up in the body over weeks and months, not days. If a child starts taking a vitamin D supplement, it typically takes 4-8 weeks to see improvements in blood levels. For bone health and immune system benefits, consistent vitamin D intake over months and years is important. Don’t expect immediate changes, but consistent supplementation can prevent serious problems like weak bones later in life.

Want to Apply This Research?

  • Track your child’s vitamin D supplement intake daily (yes/no for each day) and note outdoor time in minutes. Also track any symptoms like fatigue or muscle weakness that might improve with better vitamin D status. Aim for at least 10-15 minutes of midday sun exposure on most days during non-winter months.
  • Set a daily reminder to give your child their vitamin D supplement at the same time each day (such as with breakfast). On sunny days, encourage 15-20 minutes of outdoor play without sunscreen on exposed skin (arms and legs). During winter or for children at high risk, ensure consistent supplement use rather than relying on sun exposure.
  • Check in monthly to see if your child seems more energetic or has fewer complaints of muscle aches. Request a blood test from your doctor every 6-12 months to verify that vitamin D levels are improving. Keep a simple log of supplement adherence and outdoor time to identify patterns. Share results with your healthcare provider to adjust supplementation if needed.

This research describes vitamin D levels in UK children and identifies groups at higher risk of deficiency. It does not provide medical advice. If you’re concerned about your child’s vitamin D status, please consult with your child’s doctor or a registered dietitian before starting any supplements. This is especially important if your child has existing health conditions or takes other medications. The study was conducted in 2004-2007, so current vitamin D levels in UK children may differ. Always follow your healthcare provider’s recommendations for your individual child’s needs.