Obese teens lack vitamin D

Low levels of vitamin D are common in obese adolescents.

Obesity in children and adolescents has reached epidemic proportions and this increased prevalence may lead to increased risk of diabetes, hypertension, and cardiovascular disease, as well as to an increased risk of cancer. Some of these health consequences of obesity have also been associated with vitamin D deficiency or insufficiency. In addition, vitamin D status is significantly associated with muscle power/force, and therefore, a deficiency may interfere with the obese adolescent's ability to increase physical activity.

Vitamin D is produced by the skin in response to exposure to sunlight. It is also found in certain foods, including eggs, fish and fortified foods such as dairy products and breakfast cereals.

To explore the prevalence of low vitamin D status among obese adolescents and to examine the effect of current management of low vitamin D status in these patients, researchers from America screened 68 obese adolescents for their vitamin D levels. Vitamin D deficiency was defined as 25 (OH) D blood level of <20 ng/mL and insufficiency as level of 20–30 ng/mL. A value >30 ng/mL of 25 (OH) D implied vitamin D sufficiency. Adolescents with vitamin D deficiency were treated with 50,000 IU of vitamin D once a week for 6–8 weeks, whereas adolescents with vitamin D insufficiency were treated with 800 IU of vitamin D daily for 3 months. Repeat 25 (OH) D was obtained after treatment.

It was found that low vitamin D levels were present in all of the girls (72 percent deficient and 28 percent insufficient) and in 91 percent of the boys (69 percent deficient and 22 percent insufficient). After treatment, 43 of the youths had their vitamin D levels measured again and, although levels generally increased, normal levels were achieved in just 28 percent of the participants. In the others, repeated bouts of vitamin D treatment did not bring the teens' vitamin D levels to normal, which the researchers described as concerning.

The adolescents' lack of response to treatment could be due to the fact that vitamin D is sequestered in body fat.  The study questions whether a higher daily vitamin D intake than the one recently recommended (600 international units of vitamin D/day) may be required as part of treatment in obese adolescents, in an attempt to increase their vitamin D status. The researchers feel that it is possible that the association between obesity and low vitamin D status is indirect, arising from obese individuals having fewer outdoor activities than lean individuals, and therefore, less exposure to sun. Likewise, is it also possible that obese individuals do not consume enough foods that contain vitamin D. The study concludes by calling for increased surveillance of vitamin D levels in this population and for further studies to determine if normalizing vitamin D levels will help to lower the health risks associated with obesity.