A new study of children in Qatar has found that vitamin D deficiency was common across groups regardless of asthma or weight status, while higher body mass index (BMI) was associated with lower vitamin D concentrations among children who were overweight or obese.
The findings add to a growing body of research examining the complicated relationship between childhood weight, vitamin D status and respiratory health. But the study does not establish that asthma or excess weight causes vitamin D deficiency, and the researchers say several important factors were not measured.
Vitamin D deficiency affected most children studied
Researchers examined vitamin D levels in 364 children aged 6 to 17 living in Qatar. The participants were divided into four groups according to asthma and weight status: children with normal weight and asthma, children with overweight or obesity and asthma, children with overweight or obesity without asthma, and normal-weight children without asthma.
Vitamin D status was assessed using blood levels of 25-hydroxyvitamin D, the standard marker used to evaluate vitamin D stores.
Using a threshold of below 50 nmol/L to define deficiency, the researchers found high rates across all four groups.
The highest prevalence was recorded among children who were overweight or obese but did not have asthma, at 81.1%. Deficiency was found in 73.9% of children with overweight or obesity and asthma, 68.3% of normal-weight children without asthma and 66.3% of normal-weight children with asthma.
Vitamin D sufficiency was uncommon, ranging from only 1.1% to 6.5% across the groups.
Despite these differences in percentages, the researchers did not find a statistically significant difference in vitamin D deficiency between the four groups.
That distinction matters. The results point to a broad vitamin D problem in the study population rather than demonstrating that asthma itself was responsible for lower vitamin D levels.
Weight appeared to matter more within the overweight groups
A different pattern emerged when researchers looked specifically at the relationship between BMI and vitamin D concentration.
Among children who were overweight or obese, a higher BMI was significantly associated with lower serum vitamin D levels. The association was observed both among children with asthma and those without it.
The same relationship was not statistically significant among children with normal weight.
The finding is consistent with previous research suggesting an association between childhood obesity and vitamin D deficiency. A systematic review and meta-analysis of studies involving young children found that obesity was associated with increased odds of vitamin D deficiency, although the researchers also emphasized that much of the underlying evidence was observational and could not prove causation.
Why excess weight and vitamin D status may be connected remains an active area of research. Vitamin D is fat-soluble, and researchers have proposed that greater amounts of adipose tissue may affect how vitamin D is distributed or made available in the circulation. Lifestyle factors can also overlap: diet, physical activity and time spent outdoors may influence both body weight and vitamin D levels.
The Qatar study, however, was not designed to determine which mechanism was responsible.
Asthma was not independently linked to vitamin D status
One of the study’s important findings was the absence of a significant independent association between asthma and vitamin D status after adjusting for factors including age, sex, BMI and atopy.
Researchers also found no evidence that asthma and overweight or obesity interacted to create an additional effect on vitamin D levels.
That result is relevant because previous research has produced mixed evidence about the relationship between vitamin D and childhood asthma.
A systematic review of observational studies published previously found that children with asthma tended to have lower vitamin D levels, but results varied when researchers examined asthma incidence, disease control and lung function. The authors concluded that better-designed trials were needed to determine whether vitamin D supplementation could actually improve asthma outcomes.
More recent evidence remains cautious. A 2026 umbrella review of systematic reviews and randomized controlled trials found that vitamin D supplementation reliably increased blood vitamin D levels but did not provide convincing evidence that supplementation improves asthma control, reduces overall exacerbations or improves lung function in children.
That means low vitamin D and asthma can occur together without establishing that correcting vitamin D deficiency will necessarily treat asthma.
Qatar provides a useful setting, but also limits how far the findings can be applied
The study’s findings are particularly relevant to pediatric health in Qatar, where asthma and childhood overweight or obesity are already important areas of research.
Other recent research from Qatar has examined the biological differences between normal-weight and overweight or obese children with asthma. Work from the same broader research environment has used the Sphingolipids in Obesity and Asthma in Pediatrics (SOAP) project to investigate metabolic, inflammatory and molecular differences associated with asthma and obesity.
The new vitamin D findings therefore fit into a wider effort to understand how metabolic health and respiratory disease overlap in children.
But the study population was recruited through pediatric clinical settings rather than selected as a representative sample of all children in Qatar. That makes it difficult to assume that the exact prevalence figures apply to the country’s entire child population.
The researchers also lacked information on several factors that could influence vitamin D levels.
What the study could not determine
The cross-sectional design provides a snapshot rather than a long-term view. Researchers can identify relationships between variables, but they cannot determine which came first.
Several potentially important factors were also unavailable, including:
- Vitamin D supplement use
- Sunlight exposure
- Seasonal variation
- Dietary vitamin D intake
- Physical activity levels
These omissions are significant because vitamin D status can be influenced by lifestyle and environmental exposure.
The study therefore cannot answer whether children became vitamin D deficient because of their weight, whether low vitamin D contributed to changes in weight, or whether both were influenced by other factors.
Sources Used :
Ahmed LHM et al., Vitamin D Deficiency in Children with Asthma and Overweight/Obesity in Qatar, J Asthma Allergy (2026), as provided in the source material.
What parents should take from the findings
The results should not be interpreted as a recommendation for every child to begin taking vitamin D supplements.
Instead, they highlight the need to recognize vitamin D status as one part of pediatric nutritional and metabolic health, particularly when children have risk factors for deficiency.
The findings also reinforce a broader point about childhood obesity: excess weight can be associated with several nutritional and metabolic concerns at the same time. Previous research has linked childhood obesity with increased odds of vitamin D deficiency, while studies of asthma and obesity have also identified complex relationships between the two conditions.
For children with symptoms or medical conditions that may warrant assessment, decisions about vitamin D testing or supplementation should be made with a healthcare professional rather than based on the study alone.
The researchers’ results are best viewed as a starting point for further investigation. Longitudinal studies could help establish how vitamin D levels change as children grow and whether changes in weight, diet, physical activity or supplementation alter those levels.
Randomized trials would be needed to determine whether treating vitamin D deficiency produces meaningful health benefits beyond simply raising the blood concentration of the vitamin.
For now, the clearest message from the Qatar study is not that asthma causes vitamin D deficiency. It is that low vitamin D levels were widespread across the children studied, while higher BMI was associated with lower vitamin D concentrations among those who were already overweight or obese.
Coffee Consumption Linked to Leaner Body Composition and Distinct Hormone Patterns in Men and Women
Circadian Oncology: Could the Time of Day Change How Cancer Treatment Works?
