Requirements: Since absorption of calcium is so variable, it is difficult to determine the right amount of calcium for all people. Many factors regarding absorption come into play. And the body can adapt to lower levels of calcium, even as low as 200 mg. per day, and still maintain calcium balance, though this adjustment usually needs to be started in childhood. In most Western cultures, with average absorption rates ranging from 30-50 percent, even the 800 mg. RDA may not be enough to prevent osteoporosis and other calcium deficiency problems. Possibly half of the population is getting less than the RDA, and many people are consuming a diet that supplies less than two-thirds of the RDA for calcium. An additional concern is that absorption usually decreases with age and with excessive use of antacids. But, luckily, humans are adaptable. Lower intake may lead to greater absorption efficiency, and higher intake usually leads to more elimination in the urine and feces. And the body may naturally guide us to calcium foods that we can use.

The RDAs for calcium, shown in the table, are based on an absorption rate of approximately 40 percent and average daily losses of an estimated 320 mg.

A more liberal (or, really, conservative) suggestion is 1,000 mg. (1 gram) daily in adults. In pregnancy and during nursing, 1.5 grams per day of calcium are suggested, especially in the last two months of pregnancy when over half of the baby's calcium needs are supplied. The calcium intake suggested for postmenopausal women has recently been changed to 1.5 grams per day with some additional magnesium and vitamin D because of higher elimination and decreased absorption in these women.

People with high-protein, high-fat, or high-phosphorus diets need even more calcium. When we increase calcium, we should also increase our magnesium intake, keeping it at about one-half the calcium supply. Magnesium helps calcium stay more soluble, and thereby may reduce the risk of kidney stone formation and other calcifications. For phosphorus, an intake of about 800-1,000 mg. is recommended when the calcium intake is 1,000-1,200 mg.

Calcium is not absorbed well in an alkaline environment because it is less soluble. It is best taken between meals or in the absence of foods when the stomach is more acidic. Taking calcium with vitamin D and extra hydrochloric acid also increases absorption. Supplements of calcium or of calcium and magnesium are often taken at night before bed to help absorption and to prevent the extra loss of body calcium that can occur during the night. And calcium with magnesium is a good evening tranquilizer.

Other ideas for maximizing use of dietary calcium are spreading out calcium intake in balanced portions throughout the day; consuming protein, vitamin D, and vitamin C foods or supplements; adding more calcium-rich foods to the diet, especially in place of junk foods or phosphorus-rich soda pops; and taking supplemental calcium as part of a total mineral balance with magnesium, zinc, and manganese, for example. Recently, the trace mineral boron has been shown to help in calcium utilization and bone health.

The form in which calcium is supplied is also very important. Bonemeal and dolomite are good natural calcium and magnesium sources. They do not contain vitamin D but are still reasonably absorbable, though less so than other forms. There is some concern over lead and other toxic metals contaminating both dolomite and bonemeal. The form that I most highly recommend is aspartate or citrate salts of calcium, which are probably the most absorbable. Calcium aspartates are between 50-90 percent absorbable, which will likely place us in a positive calcium balance-exactly where we wish to be. Chelated calcium with amino acids are also easily absorbed. Calcium gluconate is the next choice, followed by calcium carbonate and lactate, which are also absorbable sources.