Growth in girth of kids with low vitamin D

Almost 3,000 children between 5 and 12 years old attending public schools in Bogota, Colombia, participated in the study. Blood samples were taken at the beginning of the study to assess vitamin D status, and the children were weighed and measured for height, skinfold thickness, and waist circumference several times over the course of an average of 30 months.

More than half of the children had sub-optimal vitamin D levels: 10% were deficient and another 46% were insufficient. Compared to the vitamin D-sufficient children, those with insufficiency and deficiency had greater increases in the following measurements over the course of the study:

• body-mass index, or BMI, a calculated number based on weight and height that is often used to diagnose overweight and obesity;
• skinfold thickness, a marker of body fat percentage;
• and, waist circumference, an indicator of fat accumulation in the abdomen, or belly fat.

In addition, growth in height was slower in girls with low vitamin D levels compared to girls with sufficient vitamin D.

Metabolism and vitamin D

Based on their results, the authors of the study speculated that a metabolic shift stimulated by low vitamin D status could encourage more fat to be stored in the abdomen, which may threaten long-term health.

“Our results suggest that inadequate vitamin D status may lead to increased fat accumulation during childhood,” said study co-author Dr. Eduardo Villamor of the University of Michigan School of Public Health. "The findings are particularly worrisome because they might imply that low vitamin D status could be related to accumulation of fat in the abdomen, where, if carried into adulthood, it could eventually be associated with increased risks of heart disease and diabetes."

Kids need vitamin D

Like children and adults in other studies, most of the children in this study had insufficient vitamin D levels. In addition to the possibility that this could alter their metabolism and put them at risk for overweight, obesity, heart disease, and diabetes, low vitamin D status could also leave them less protected against osteoporosis, infections, depression, and some cancers.

Parents can improve the chances that their kids will have enough vitamin D by taking the following steps:

• Choose fortified dairy products and milk substitutes.
• Try giving kids a daily teaspoonful of cod liver oil, a rich source of vitamin D, especially in the winter. This will also give them some extra vitamin A and healthy omega-3 fats.
• Consider a vitamin D supplement. For kids over one year old, 700 to 1,300 IU per day is now recommended by the US Institute of Medicine.

(Am J Clin Nutr 2010;92:144651)