Adolescents with high intakes of vitamin D may have lower overall body fat and lower amounts of abdominal fat, says a new study from the Medical College of Georgia, US.
A study with 650 adolescents aged between 14 and 19 found that only white boys were consuming the recommended minimum intake of vitamin D, while African-American girls had the lowest vitamin D intake, while also having the higher percentages of both body fat and abdominal fat.
MCG’s Yanbin Dong and Inger Stallman-Jorgensen presented their findings at the American Heart Association's Joint 49th Conference on Cardiovascular Disease Epidemiology and Prevention and Nutrition, Physical Activity and Metabolism.
The study adds to an ever-growing body of science supporting the benefits of adequate vitamin D levels throughout life, with deficiency of the vitamin linked to osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases.
"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," said Ms. Stallman-Jorgensen. "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 results have particular importance since abdominal fat, also known as visceral fat, has been linked to a range of health risks such as heart disease, stroke, diabetes and hypertension.
Dong and Stallman-Jorgensen said that the next stage in the research is to establish the feasibility of daily vitamin D pills for the teenagers. Results from this will then be used to facilitate the design of a larger study to explore the relationship between vitamin D intake and body fat levels in teens.
Previously, researchers from The Children's Hospital of Philadelphia reported that about 55 per cent of seemingly healthy adolescents may be vitamin D deficient, and are at increased risk of osteoporosis and other health problems later in life. Low vitamin D levels were even high amongst African-American adolescents at over 90 per cent.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
Current recommendations for vitamin D are 400 IU for adolescents.
“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," said Stallman-Jorgensen.
"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 added.
Source: American Heart Association's Joint 49th Conference on Cardiovascular Disease Epidemiology and Prevention and Nutrition, Physical Activity and Metabolism
Authors: Y. Dong, I. Stallman-Jorgensen