Requirements

The current Recommended Dietary Allowance (RDA) is 800mg.


Signs of Deficiency
A deficiency in calcium is associated with aching joints, eczema, brittle nails, elevated blood cholesterol, hypertension, heart palpitations, insomnia, muscle cramps, nervousness, rickets, tooth decay, rheumatoid arthritis, cognitive impairment, depression and, in severe cases convulsions and delusions.1,2


Safety
Individuals who suffer from recurrent kidney stones, have kidney disease, cancer, hyperparathyroidism or who take calcium channel blocking medication should consult a physician or health care professional before taking a calcium product. 2


Signs of Toxicity
Calcium intakes of several grams per day combined with vitamin D may result in calcium deposition in soft tissue. High doses of calcium can impair absorption of other minerals including iron, magnesium and zinc.

Current Research

Arthritis
According to the Nutrition Almanac, "arthritis, structural rigidity often caused by depletion of bone calcium, can be helped with regular supplements of calcium. Early consumption of calcium may help prevent arthritis. Rheumatism can also be helped with calcium therapy."3

Blood Pressure
Calcium supplementation can lower hypertension. Researchers at Cornell University Medical School studied 26 hypertensive adults and administered 2,000 mg of calcium. After six months, researchers found a "modest but consistent" drop in blood pressure from an average of 164/91 at the beginning of the study to 154/89 at the study's conclusion.4

Cancer
Researchers at Memorial Sloan-Kettering Cancer Center and Cornell University Medical College in New York found that when they gave 1,250 mg to individuals with a high family history of colon cancer, calcium reduced excessive cell duplication. Excessive cell duplication is often found in people that are susceptible to developing colon cancer. Before calcium supplementation, researchers found that cell proliferation was what they would expect in people prone to colon cancer. However, after two to three months on the calcium regimen, cell duplication, or proliferation, was lower, nearly comparable to that of people with a lower risk of colon cancer. The researchers theorised that calcium binds the bile and fatty acids, thereby reducing the irritation it can cause to the lining of the colon, which would decrease cell proliferation and, thus, colon cancer.4

Osteoporosis
Research shows that increasing calcium for children, adolescents, young adults, middle-aged women can increase bone density. However, according to Alexander Schauss, if one is desiring to develop or maintain bone mineral density, "an optimal intake of all nutrients essential to bone formation and homeostasis is required."5 In fact, two studies show that other micronutrients such as trace elements are needed for proper bone metabolism and re-absorption. In one study, a group of post-menopausal women were given a combined trace element and calcium supplement, a calcium supplement or placebo. In the group receiving the combined trace element and calcium supplement, bone density increased 1.48 %. In the group receiving only the calcium supplement, bone density decreased with an average of 1.25 %. For the placebo group, bone density decreased 3.53 %.6,7

In the second study, post-menopausal women on HRT were given a multi-vitamin, multi-mineral supplement containing 500 mg. of calcium, 600 mg. of magnesium, 2 mg. of copper and 10 mg. of manganese. Control subjects receiving the supplement experienced an increase in bone density from 0.303 g/cm2 to 0.337g/cm2.7,8