Bone Up On Calcium
by Gretchen K. Vannice, M.S., R.D.
Mom was right when she told you to drink your milk
Calcium is good for more than just fortifying bones. In fact, this important nutrient can also help prevent a number of diseases and conditions. Making sure you and your family are getting enough is vital to optimal health.
Essential for resilient bones and healthy teeth, 99 percent of calcium is stored in the skeleton. The remaining 1 percent — a relatively small but crucial amount — is absorbed into the bloodstream, monitored second by second to effectively regulate muscle contractions, including the heart, and hormone secretions, such as insulin. Calcium is also involved in blood clotting, wound healing, nerve transmission and more.
That's why it's critical to get enough calcium on a daily basis. Otherwise the blood will leach this nutrient from bones, causing the skeleton to become porous and lose strength over time. Osteoporosis, often called the "silent disease," may result.
Beyond preventing disease, adequate calcium can optimize health. According to Bonnie Bruce, D.P.H., clinical researcher at Stanford University School of Medicine in California and co-author of Calcium, Nature's Bone Builder (Penguin-Putnam), "If we get enough calcium for our bones, the rest of our body will benefit." For example:
- Calcium may reduce blood pressure and prevent hypertension (New England Journal of Medicine, 1997, vol. 336).
- 1,200 mg of calcium daily from foods may protect against colon cancer (Journal of the American Medical Association, 1998, vol. 280).
- Calcium deficiency is often found in women with premenstrual syndrome (PMS); 1,200 mg/day has been shown to reduce PMS symptoms (American Journal of Obstetrics and Gynecology, 1998, vol. 179).
- Regular calcium consumption may help reduce cholesterol levels (Archives of Family Medicine, 2000, vol. 9).
- High calcium intake from food is not a risk factor for kidney stones and, in fact, may reduce the risk of kidney stone formation (American Journal of Obstetrics and Gynecology, 1999, vol. 181).
How Much is Enough?
New recommendations for daily calcium intakes were made in 1997 when the National Academy of Sciences began establishing Dietary Reference Intakes (DRIs), rendering the Recommended Dietary Allowances (RDAs) outdated (Institute of Medicine, National Academy Press, 1997). "RDAs were designed to prevent nutrient deficiency diseases, which are no longer a major concern in this country," according to May-Choo Wang, D.P.H., R.D., nutrition professor and researcher at San Jose State University in California. "The DRIs are designed to address chronic diseases and to optimize health." DRIs also include additional information beyond RDAs, such as tolerable upper limits and average requirements, for use by health care professionals.
The human skeleton is similar to the structure of a home: Built correctly, it will support a lifetime of wear and tear. The skeleton, however, is a living structure that requires daily support throughout a lifetime. And as we grow, our needs change.
Infants, until 6 months of age, need about 210 mg calcium/day to strengthen their rapidly growing bones. This amount is easily met with breast milk or infant formula, as cow's milk should be avoided in children under one year of age. Since infants absorb calcium better from breast milk than from formula, calcium is often added to infant formula to compensate. From 6 months to 1 year, babies need a total of 270 mg/day. The introduction of soft foods usually meets this requirement. Toddlers between the ages of 1 and 3 need about 500 mg calcium/day. This requirement increases to 800 mg/day among children 48 years old.
Puberty through adolescence is a critical time for adequate calcium intake. Between the ages of 9 and 18, a hefty 1,300 mg calcium/day is recommended. During puberty, bones become stronger as they become larger. Some researchers now believe that osteoporosis may begin during childhood when bone growth is occurring so rapidly (Pediatric Annals, 1995, vol. 24). This is a time to be vigilant about calcium intake.
Bones peak in strength and size during the 20-something years. Adults need about 1,000 mg calcium/day. This can be achieved by eating 23 servings of dairy products (yogurt, kefir, cheese), calcium-fortified soy milk or juice and 23 servings of select vegetables, almonds, tofu or beans. During pregnancy and lactation — whether you're a teen or an adult — calcium requirements increase by 300 mg/day. For people over the age of 50, an extra 200 mg calcium/day is recommended for a total of 1,200 mg/day.
"Most children and adults in the United States do not get enough calcium," says Wang. When choosing calcium-fortified foods or supplements, be aware of how much calcium these products actually contain. While too much calcium can cause soft tissue calcification, even large doses rarely show such effects. "It may be possible to get too much calcium, but to my knowledge, there are no published reports of calcium toxicity arising from consuming calcium-fortified foods and/or supplements," says Wang. "Focus on getting enough calcium by making educated and informed decisions."
Supplemental Health Insurance
The best way to get your calcium is from calcium-rich food so you derive maximum benefit from other nutrients at the same time. If you can't get what you need from your diet, consider a supplement. Select one free of sugar, salt, additives and artificial coloring.
Calcium carbonate, gluconate and lactate supplements are absorbed at approximately the same rate (New England Journal of Medicine, 1987, vol. 317), but they may differ in price. Calcium carbonate is usually the least expensive, and recent research shows that, when taken with food, it's absorbed equally as well as calcium citrate (Osteoporosis International, 1999, vol. 9). This supplement is better for those who take supplements on an empty stomach, have low amounts of stomach acid or take antacids. To ensure you're choosing a quality brand, ask your health care professional or pharmacist for a recommendation.
Calcium may compete for absorption with magnesium, iron and zinc. When supplementing with these minerals, consider upping your calcium intake. In general, calcium supplements are better absorbed with vitamin D and when taken with food. For optimal use, take calcium supplements with your last meal or snack of the day.
Gretchen K. Vannice, M.S., R.D., is a science-based writer and educator specializing in nutrition, dietary supplements and integrative health care.
Photography by: Rita Maas