By Lynn A. Kuntz, Editor-in-Chief
Modern lifestyles have set the stage for another health crisis: vitamin D deficiency. Lack of outdoor activities, copious use of sunscreens and a decline in consumption of vitamin D–fortified products, especially dairy milk, is creating widespread deficits in vitamin D across the United States, from infants to the elderly and everyone in between. Lack of vitamin D impairs the body’s ability to absorb calcium from the diet, resulting in poor bone development and, according to recent research, a whole host of other serious health problems.
A growing deficit
This year, researchers at Albert Einstein College of Medicine of Yeshiva University, Bronx, NY, found 70% of U.S. children have low levels of vitamin D (Pediatrics, doi:10.1542/peds.2009-0051). Based on the results, 9% of children have vitamin D deficiency (less than 15 ng per mL of blood), and 61% have vitamin D insufficiency (15 to 29 ng per mL). Children who were older, female, African-American, Mexican-American, obese, drank milk less than once a week, or spent more than four hours a day in front of TV, videogames, or computers were at higher risk.
Lead author Dr. Juhi Kumar, M.P.H., recommends children consume more vitamin D–rich foods, such as milk and fish. “But it’s very hard to get enough vitamin D from dietary sources alone,” she says.
Insufficient vitamin D is not just a problem for bones; it might also play a role in the development of heart disease, some immune disorders and diabetes, and reduce inflammation. It’s also important to “maintain muscle strength and reduce the risk of falls and fractures, maintain immune function, and for the regulation of cell cycles potentially involved in cancer,” says Michael I. McBurney, Ph.D., F.A.C.N., head of scientific affairs, DSM Nutritional Products, Parsippany, NJ.
McBurney notes that, according to the USDA Agriculture Research Service, 30% to 97% of Americans consume less vitamin D in their diet than is believed adequate, as outlined by the 1997 Dietary Reference Intakes (DRIs) for vitamin D. “With the average blood concentration of vitamin D declining over the past decade due to less exposure to the sun, increased use of sunscreen and declining milk sales, coupled with emerging science suggesting higher vitamin D intake levels (1,000 IU to 2,000 IU) over the current RDI (400 IU), it is more important now than ever to increase levels of vitamin D in current foods and beverages from a ‘good’ to ‘excellent’ source, but also look for new product applications to add vitamin D,” he says.
The D-tails
Vitamin D, a fat-soluble vitamin, occurs naturally in two forms: D2, or ergocalciferol, found in plants, yeasts and fungi, and D3, found in animals and fish, or cholecalciferol. It’s found in very few foods, but is synthesized by the body as vitamin D3 when ultraviolet rays from sunlight strike the skin. Most of the vitamin D in the U.S. diet comes from fortified foods, particularly milk, which is fortified with 100 IU per 8 oz. In addition to dairy products, other FDA-allowed fortified foods include calcium-fortified, plant-based milks, such as soy; breakfast cereals; grain products and pastas; infant formulas; and margarine. It is also added to meal replacements, nutritional supplements and formulated liquid diets. Fortification is limited because too high a level could be toxic: the Institute of Medicine has set a tolerable upper intake level (UL) of 1,000 IU per day for infants, and 2,000 IU for children and adults, although some experts believe that number is too low.