ScienceDaily (Mar. 16, 2009) — Too little vitamin D could be bad for more than your bones; it may also lead to fatter adolescents, researchers say.
A Medical College of Georgia study of more than 650 teens age 14-19
has found that those who reported higher vitamin D intakes had lower
overall body fat and lower amounts of the fat in the abdomen, a type of
fat known as visceral fat, which has been associated with health risks
such as heart disease, stroke, diabetes and hypertension.
The group with the lowest vitamin D intake, black females, had
higher percentages of both body fat and visceral fat, while black males
had the lowest percentages of body and visceral fat, even though their
vitamin D intake was below the recommended levels. Only one group –
white males – was getting the recommended minimum intake of vitamin D.
“This study was a cross-section so, while it cannot prove that
higher intake of vitamin D caused the lower body fat, we know there is
a relationship that needs to be explored further,” says Dr. Yanbin
Dong, a molecular geneticist and cardiologist at the MCG Gerogia
Dr. Dong, who also co-directs the MCG Diabetes & Obesity
Discovery Institute, and Inger Stallman-Jorgensen, a research dietician
at the GPI, present their findings this week at the American Heart
Association’s Joint 49th Conference on Cardiovascular Disease
Epidemiology and Prevention and Nutrition, Physical Activity and
Metabolism in Palm Harbor, Fla.
The pair will next study whether it is feasible for teens to take a
daily vitamin D supplement in pill form. Those results will help them
design a larger study to explore the relationship between vitamin D
intake and body fat levels in teens.
“We already know that encouraging teens to get an adequate amount of
vitamin D in their diets will help promote a healthy body as they grow
and develop,” Ms. Stallman-Jorgensen says. “Now we need to do
intervention studies where we give teens vitamin D supplements to
determine if there is a cause and effect relationship between vitamin D
intake and fat.”
The American Academy of Pediatrics recommends adolescents get at
least 400 units of vitamin D per day – either from milk or sun
exposure. There are typically 100 units in one unce glass of whole
milk. The recommended daily dose from the sun would require at least 30
minutes of adequate exposure to direct sunlight two or three times a
week at peak hours, between noon and 3 p.m.
Ms. Stallman-Jorgensen said there are many reasons teens don’t get
enough vitamin D, which has been linked to the prevention of diabetes,
cancer and cardiovascular disease.
“As humans, our largest source of vitamin D should be the sun. But
we don’t spend enough time outdoors to get enough sun exposure and when
we do, we’re often covered up and wearing sunscreen,” she said. “We can
get vitamin D from certain foods, like fatty fish and liver, but it’s
not in a lot of foods that we commonly consume. In this country, our
milk is fortified with vitamin D. Unfortunately, teens just don’t drink
enough milk to get their daily requirements.”
She points out that low sunlight during the winter months reduces
the amount of vitamin D the skin produces, and that darker-skinned
people obtain less vitamin D from the sun because the extra melanin in
their skin filters out more sunlight.
Some people can’t tolerate milk because they lack the enzyme that
processes lactose, the natural sugar in milk, though “most people can
handle it in small amounts,” Ms. Stallman says.
Cultural issues may also be at play, Ms. Stallman-Jorgensen says.
“Most teens want to drink sodas and sugary drinks. It’s not cool to
drink milk – they think of it as more of a food for babies,” she said.
Potential study participants had their weekday and weekend diets
tracked by researchers seven times during a three-month period. Those
who provided at least four diet reports were included in the final
group of 659.
Body fat percentages were measured by dual energy X-ray
absorptiometry scans, which can measure total body composition.
Visceral fat was measured in a subset of 432 teens.