OLD GREENWICH, CT—Keep an eye out for vitamin D deficiency among obese children and teenagers. The problem is very common and it can have significant long-term negative impact, said Margarita Smotkin-Tangorra, MD, at the annual meeting of the Eastern Society for Pediatric Research.
Several studies of adults show strong correlations between obesity and vitamin D deficiency. Until recently, far less was known about the situation in the under-20 set. Dr. Smotkin-Tangorra and colleagues at Infants and Children’s Hospital of Brooklyn, NY, have found the problem is just as common in kids as in adults.
They studied a cohort of 217 obese children and adolescents in the New York City area, and found that 55% were frankly deficient in 25-(OH)–vitamin D, with blood levels of less than 20 ng per ml; 22% were severely deficient, with serum levels below 10 ng per ml.
This is not surprising, given how widespread vitamin D deficiency has become in this country, even among otherwise healthy adolescents. Nationwide, roughly 20% of all school children are deficient, according to best available data.
“In obese adults, we know that it correlates with insulin resistance, progression to diabetes mellitus, metabolic and endocrine problems, and increased risk of cancer. We wanted to see if there were similar correlations in obese kids.”
Her study cohort included 118 females and 99 males, ranging in age from 7 to 18 years, and with a mean BMI of 32.2. They measured 25-OHD, as well as blood pressure, total cholesterol, LDL, HDL, TGL, liver enzymes, thyroid hormones, fasting insulin and fasting blood glucose.
They found direct relationships between low vitamin D and elevated BMI, increased systolic blood pressure, low HDL, and low alkaline phosphatase. The kids who were deficient had a mean BMI of 36.2, compared with 30.6 among those with adequate vitamin D levels. The difference was striking. Likewise, the association with systolic hypertension was robust; vitamin D deficient kids had a mean SBP of 117, compared with 111 among the sufficient subgroup.
Vitamin D deficient kids also had significantly lower HDL levels, though there were no meaningful differences in LDL or TGL. There was no correlation between vitamin D status and fasting blood glucose or thyroid hormone levels.
The prevalence of vitamin D deficiency among the nation’s young people can be attributed to a number of general trends, chiefly lousy diet and lack of outdoor exercise. Dr. Smotkin-Tangorra noted that vitamin D deficiency might be an indicator of poor overall nutritional status. Though her team did not study other vitamins, minerals or nutrients, it is reasonable to suppose that an obese child with vitamin D deficiency also lacks other important nutrients.
If this Brooklyn cohort proves to be representative of obese children nationwide, the data suggest that vitamin deficiencies among young obese people may be a far greater problem than previously imagined.
According to recent data from the National Health and Nutrition Examination Survey, a nation-wide study involving more than 8,000 children and adults, the percentage of obese boys, ages 2–19, rose from 14% to 18% from 2000 to 2004. Among girls, the number rose from 14% to 16%. Dr. Smotkin-Tangorra’s data suggest that a large number of these kids are deficient in vitamin D.
Fortunately, this is one of the few common comorbidities of childhood obesity that is easy to treat. Dr. Smotkin-Tangorra noted that at her hospital, they are routinely supplementing all obese children and teens with Oscal, 500 mg, thrice daily, and they are starting to gather data on outcomes. Vitamins are inexpensive, safe and have great potential to prevent long-term sequelae of poor nutritional status.
Hypertension is a far more difficult problem, and it, too, is very common among obese adolescents, said Mala Puri, MD, of the Montefiore Medical Center, Bronx, NY. Speaking at the same conference, Dr. Puri reported that nearly one-third of a cohort of 167 obese, mostly Black and Hispanic teens were hypertensive, compared with only 3% in non-obese kids from the same community who shared the same ethnic and racial background.
Patients in this study had a mean age of 14 years. The investigators defined hypertension as resting systolic over diastolic blood pressure at or above the 95th percentile for age. The obese kids had a mean BMI of 38, while control subjects had a mean BMI of 20.
Thirty-one percent of the obese teens were hypertensive, compared with only 3.2% of those in the control group, a tenfold difference that underscores the strong relationship between increased body weight and elevated blood pressure. The obese kids had a mean systolic pressure of 121 mmHg, compared with 105 mmHg among the normal-weight group. The heavy teens also had reduced HDL (48 mg/dl versus 66 mg/dl), and increased triglycerides (113 mg/dl versus 78 mg/dl). In short, they’re on a fast track for diabetes and cardiovascular disease.
When they looked more closely at the obese cohort alone, Dr. Puri and her colleagues found that Hispanic and Caribbean kids were two times more likely to be hypertensive than African Americans (21% versus 10%), suggesting that there are genetic differences in the extent to which obesity predicts hypertension. Not surprisingly, 80% of the hypertensive obese kids had family histories of hypertension.
Dr. Puri also believes that lifestyle and dietary factors are the main drivers of the obesity-hypertension syndrome she’s observing among the kids she treats.
Though inner-city kids are clearly at high risk, obesity and related conditions are not by any means just a ghetto problem. Other studies show similar prevalence patterns in largely white, non-urban communities.
“We really need good strategies for treating this problem, especially among minority youth,” said Dr. Puri. But she noted that like many clinicians, she and her colleagues at Montefiore hesitate to start intensive antihypertensive drug therapies in young people. Drugs should be a last resort in this population.
The Montefiore study had a few major limitations, the most important being that it relied solely on office-based blood pressure measurements. It is difficult to assess the degree to which these measurements reflect the subjects’ day-to-day physiology. To clarify this, the Montefiore group is beginning a study using 24-hour blood pressure monitoring. This, Dr. Puri said, will give a better picture of the kids’ overall cardiovascular health.
