|Volume 6 Issue 51 Published - 14:00 UTC 08:00 EST 20-Feb-2004 Next Update - 14:00 UTC 08:00 EST 21-Feb-2004||Editor: Susan K. Boyer, RN
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Information for professionals: Why milk matters -- Questions and answers for professionals
Calcium plays a critical role in building strong and healthy bones. Low calcium consumption and inadequate weight-bearing exercise contribute to osteoporosis, the weakening of the bone that can occur late in adulthood and causes 1.5 million bone fractures a year. About 10 million Americans have osteoporosis. In addition, an estimated 41 million Americans may develop osteoporosis or low bone mass by 2015 unless steps are taken to prevent, detect, and treat the disease.
Two important factors that influence the incidence of osteoporosis are peak bone mass attained during the first two to three decades of life and the rate at which bone is lost in the later years.3 Childhood and adolescence are critical periods for bone development because most bone mass accumulates during this time. By the time adolescents finish their "growth spurt" around the age of 17, approximately 90% of their adult bone mass will have been established. Bones then continue to grow more dense until around age 30, when peak bone mass is reached. At this point, bone mass and density may remain steady, or bone loss may begin to occur at a rate of up to about 1% per year.
NICHD believes that osteoporosis is a pediatric preventable disease. A recent NICHD-supported study found that supplementing the diets of girls, age 12-16, with 500 mg of calcium citrate-malate produced a 14% increase in bone density in comparison to unsupplemented girls. The implications of this increase are striking: for every 5% increase, the risk of fracture later in life declines by 40%. However, subsequent study has shown that without continued supplementation at this level, the difference in the bone densities of the two groups becomes indistinguishable.4 Therefore, adequate growth, development, and maintenance of the skeletal system requires continuing calcium intake over a lifetime.
Unfortunately, most children and teens do not meet the dietary calcium recommendations that can help build maximum bone mass and protect against osteoporosis. Half of all children under five and about 85% of females age 12-19 do not meet the 1989 Recommended Dietary Allowance (RDA) for calcium. And even fewer of these children and adolescents could attain the government's new guidelines, the Dietary Reference Intakes (DRIs), set in 1997 (see Table 1).
These new guidelines set Adequate Intake (AI) values for calcium designed to lead to the fewest diet-related osteoporotic fractures later in life. Prior to the DRIs, optimal levels of calcium were recommended by the National Institutes of Health (NIH) Consensus Conference in 1994 and were slightly higher for most age groups. Parents should ensure that their children and teens get enough calcium and weight-bearing exercise to help them reach their maximum bone density.
QUESTIONS AND ANSWERS ABOUT CALCIUM INTAKE
Q: How does
bioavailability affect calcium absorption?
Q: What other factors can
affect bone development?
Physical Activity - Weight bearing activity determines the strength, shape, and mass of bone. Activities such as running, jumping, and dancing, as well as those that increase strength, can help bone development. Studies show that absence of exercise will result in a loss of bone mass, especially during long periods of immobilization.
Q: Why choose milk as a
source of calcium?
In fact, milk products provide about 3/4 of the calcium in the U.S. food supply. While other foods, such as green leafy vegetables, are healthy sources of calcium, it takes 11-14 servings of kale a day to get the same amount of calcium in 3-4 glasses of milk.
In addition to calcium, milk provides other essential nutrients which are important for optimal bone health and human development including: vitamins D, A, and B12; potassium, magnesium, protein, phosphorus, and riboflavin.
Q: How can drinking milk
fit in as part of a heart-healthy diet?
Q: At what age can
children begin to drink low-fat or fat-free milk?
Q: Aren't some people
lactose intolerant and unable to consume milk?
There are however, specific populations that are genetically lactose intolerant, including about 85 percent of Asian- Americans and 50 percent of African-Americans. Lactose intolerance is least common among people of northern European origin, affecting only about 10% of Caucasians.8 It also occurs infrequently in infants and young children. Studies have shown that lactase is high at birth in all infants regardless of race, and wanes in non-Caucasians and other populations without dairy traditionally in their diet by age 5-6.
There are some strategies for people who can not easily digest lactose. Drinking milk in servings of one cup or less and drinking milk with other food can diminish symptoms. Other dairy products, such as cheese or yogurt, can also be easier to digest. In addition, lactose containing foods may also be treated with commercial preparations of lactase.9 There are a variety of digestive aids, including drops that can be added to milk, and tablets taken with lactose-containing foods.
Q: Are there risks
associated with high calcium intake?
Q: Can children be given
calcium supplements to augment their calcium intake?
Q: Are there any special
recommendations for pregnant or lactating adolescents?
Increasing dietary calcium does not prevent the loss of calcium that occurs during lactation, and the calcium lost seems to be regained following weaning. Therefore, the DRIs do not recommend increasing calcium intake in lactating adolescents above normal levels for that age group. However, the 1994 NIH Consensus Conference statement recommends that lactating adolescents and young adults increase their ingestion of calcium to up to 1,500 mg per day.
1 USDA Continuing Survey of Food Intakes by Individuals, 1994, Table 3.
2 National Teen Nutrition Research - Final
Report. Teenage Research
3 NIH Consensus Conference Statement:
Optimal Calcium Intake, June 6-8,
4 Lloyd, Tom et al. Calcium supplementation
and bone mineral density in
5 Guyton, A.C. Textbook of Medical
Physiology, 8th Edition. Philadelphia:
6 NIH Consensus Conference Statement:
Optimal Calcium Intake, June 6-8,
7 Suarez, F.L., Savaiano, D., Arbisi, P.,
& Levitt, M.D. Tolerance to the
8 Dietary Reference Intakes for Calcium, Phosphorus, Magnesium,
9 Miller, G.D., Jarvis, J.K., McBean, L.D.
Handbook of Dairy Foods and
10 Kidney Stones in Adults. National
Institute of Diabetes and Digestive