Maintaining structural integrity

by Keith Nunes
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Bone health is most often associated with aging. As people age and become less active their risk of losing bone density or developing osteoporosis increases. But research presented earlier this year indicates that maintaining bone health may be a lifelong effort.

This past April, during the American Society of Nutrition’s (A.S.N.) annual meeting in Anaheim, Calif., researchers from North Carolina State University (N.C.S.U.) and the U.S. Army Research Institute of Environmental Medicine presented research that indicated very early calcium nutrition may have more impact on a person’s bone health than originally thought. The research was led by Chad Stahl, an associate professor in the Department of Animal Science at N.C.S.U. Dr. Stahl studies nutritional growth and development and uses neonatal pigs as a surrogate for human infants. His research focuses on understanding how much calcium babies need in order to optimize bone density and strength as they age.

The research has relevance to the food and beverage industry because the makers of infant foods currently fortify most baby formulas with calcium at levels substantially higher than those found in breast milk. The difference in calcium fortification levels has been based on studies that suggest the calcium in breast milk is more usable than the calcium fortified in infant formula. More recent research has challenged this assumption.

Dr. Stahl and his colleagues bottle-fed 12 piglets a calcium-rich diet and another 12 piglets a calcium deficient diet during the first 18 days of life. Throughout the study, blood samples were drawn and the piglets were weighed daily. At the end of the study the researchers collected samples of the animals’ bone marrow and organs as well as tested their hind legs for bone density and strength.

The results indicated there were no differences between the groups in terms of blood markers of calcium status and growth. But when they looked at the bone marrow tissue, which contains all the material that will become bone-forming cells, they found that many of the calcium-deficient piglets’ cells appeared to already have been programmed to become fat cells instead of bone-forming osteoblast cells. Fewer osteoblasts in early life may translate to a diminished ability for bones to grow and repair themselves throughout the remainder of life. It appeared as if calcium deficiency had predisposed the animals to having bones that contained more fat and less mineral.

“While the importance of calcium nutrition throughout childhood and adolescence is well recognized, our work suggests that calcium nutrition of the neonate may be of greater importance to lifelong bone health due to its programming effects on mesenchymal stem cells,” Dr. Stahl said. “It also points to a potential paradigm shift in which health professionals might want to begin thinking about osteoporosis not so much as a disease of the elderly, but instead as a pediatric disease with later onset.”

The basics of bone health

A number of minerals and vitamins working in conjunction are required by the human body to maintain bone health, but the two most important are calcium and vitamin D. A low intake of calcium may contribute to bone loss, the development of reduced bone density and the development of osteoporosis. It currently is recommended that consumers receive between 1,000 mg and 1,300 mg per day, depending on age.

Vitamin D is required by the body in order to aid in the absorption of calcium. It currently is recommended that people receive between 200 I.U.s and 600 I.U.s of vitamin D per day, depending on their age. But recent research indicates a higher level of intake may be required.

This past May, the International Osteoporosis Foundation released a position statement on vitamin D for older adults. The foundation recommended an average vitamin D requirement for older adults to be in the range of 800 I.U. to 1,000 I.U. per day. But the foundation also recommended that intakes may need to increase to as much as 2,000 I.U. per day in individuals who are obese, have osteoporosis, limited sun exposure or have malabsorption of vitamin D.

“Global vitamin D status shows widespread insufficiency and deficiency,” said Bess Dawson-Hughes, a professor at Tufts University, Boston, and the lead author of the statement. “This high prevalence of suboptimal levels raises the possibility that many falls and fractures can be prevented with vitamin D supplementation. This is a relatively easy public health measure that could have significant positive effects on the incidence of osteoporotic fractures.”

The Food and Nutrition Board of the Institute of Medicine in 1997 recommended daily Adequate Intake (A.I.) levels of vitamin D of 200 I.U. for people age 0-50, 400 I.U. for people age 51-70 and 600 I.U. for people over age 70. An Institute of Medicine committee has been analyzing A.I. levels for vitamin D and calcium and is expected to issue new A.I. level recommendations this year.

Delivering health through dairy

To maintain and improve bone health throughout childhood and beyond requires the consumption of nutrients such as calcium and vitamin D. The A.S.N. conference this past April also featured a pair of research abstracts that highlighted the role of dairy products in the maintenance of bone health. The dairy food group, which consists of milk, cheese and yogurt, was found to be the top source of calcium (38.6% contribution to overall intake of the mineral) and vitamin D (52.3%) as well as also a contributor of phosphorous and potassium.

In addition, dairy foods were found to be the top contributor of vitamin D in the diets of children 2 to 18 years of age (68.1% contribution to overall intake) and adults 19 years and older (46%).

“Without consuming the recommended daily servings of milk and milk products, it can be difficult for most people to meet their nutrient needs,” said Victor L. Fulgoni III, senior vice-president of the consulting firm Nutrition Impact, L.L.C., Battle Creek, Mich., and one of the abstracts’ authors. “Considering that higher dairy intake is associated with increased nutrient intake and diet quality, as well as numerous health benefits — such as bone health and healthy weight maintenance — these findings support that there’s few, if any, substitutes for dairy’s incomparable nutritional value.”

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