'TC Bones make their greatest gains in calcium storage beginning at age 11. They get increasingly stronger and peak by age 20, although important smaller gains can be made through the 30s.
While it's all downhill from there, adequate calcium can minimize bone loss and reduce osteoporosis risk in later life.
But how much calcium do you really need to have the strongest possible bones at every age?
In June, the National Institutes of Health sponsored a consensus conference on Optimal Calcium Intake. Forty-seven experts reviewed available research to establish the best levels of calcium for bone strength, as well as prevention of colon cancer, high blood pressure and preeclampsia, a hypertensive disorder of pregnancy.
* Ideals for every age: The current Recommended Dietary Allowances of the National Academy of Sciences were used as a base, then ideals were adjusted based on new data. Their recommendations : ages 0-6 months, 400 mg/day; 6-12 months, 600 mg/day; 1-10 years, 800 mg/day; 11-24 years, 1,200-1,500 mg/day; 25-50 years, 1,000 mg/day; postmenopausal women treated with estrogen, 1,000 mg/day; postmenopausal women not being treated with estrogen, 1,500 mg/day (may limit loss of bone, but should not be considered a replacement for estrogen); women well beyond menopause, 1,500 mg/day; pregnant women and nursing mothers, 1,200 mg/day; adult men of all ages, 800 mg/day.
* Food first: The consensus statement notes that the best way to get your calcium is from food.
Dairy products contain the most calcium, at 300 mg per 8-ounce glass of milk, 200 mg per ounce of cheese, and 450 mg per 8-ounce serving of yogurt. If you get cramping or diarrhea due to lactose intolerance, try Lactaid milk, cheese or ice cream, or Lactaid or Dairy Ease drops or tablets with your meals. They work wonders.
Other good calcium sources include green vegetables offering 100 mg per serving (broccoli, kale, turnip greens and Chinese cabbage), calcium-set tofu, some legumes (baked beans, soybeans, black-eyed peas), canned fish with bones, seeds, nuts and some fortified food products (juice, fruit drinks, bread and some cereals).
* Supplements, too: If you just can't get all your calcium from food, supplements can complete the picture.
Limit each dose to 500 mg or less (two TUMS, for example) and take them at mealtime. Avoid dolomite and bone meal supplements, sometimes contaminated with lead.
Combinations of food and supplements totaling 1,500 mg have been shown to be safe in studies lasting four years.
* More is not always better: The recommended levels are meant to be the sum of all sources of calcium. Exceeding these limits can have some drawbacks. Four thousand mg/day can produce high blood calcium levels and kidney damage.
Excessive calcium intake can decrease iron absorption by as much as 50 percent, producing iron deficiency anemia, and disrupt absorption of some medicines, including tetracyclines. Some folks get constipated. Other experience rebound hyperacidity. Those with a history of kidney stones might have increased stone formation.
* Improving absorption: Vitamin D is essential for calcium absorption. Most people get enough through sunlight, or from milk and margarine. But housebound elderly people often require vitamin D supplementation. However, excessive doses can be toxic.
The effect of exercise on bone density has not been established conclusively. One study showed improvements in bone mass in young adults with increased activity. Studies in elderly and perimenopausal women failed to show that increased calcium and exercise could actually increase bone mass.
Diets high in animal protein or sodium can cause calcium loss, while high intakes of caffeine, phosphate and magnesium seem to have no effect.
A few foods, such as spinach, contain elements that prevent absorption of the calcium found naturally in that food but do not decrease calcium absorption from other foods at the same meal. High fiber intake does not interfere with calcium absorption except for very large amounts of wheat bran.
* Other diseases: At the time of the conference, panelists and presenters could not find enough agreement among studies to recommend calcium increases to prevent preeclampsia, colon cancer or hypertension.
Colleen Pierre, a registered dietitian, is the nutrition consultant to the Union Memorial Sports Medicine Center and Vanderhorst & Associates in Baltimore.