The skeletal system suffers most from calcium deficiency. Teeth minerals are more stable, though there is a possibility of poor dentition with insufficient calcium. Tooth loss, periodontal disease, and gingivitis can be problems, especially with a high phosphorus intake, particularly from soft drinks. All kinds of bone problems can occur with prolonged calcium deficiency, which causes a decrease in bone mass. Rickets in children, osteomalacia (decreased bone calcium) in adults, and osteoporosis (porous and fragile bones) can occur when calcium is withdrawn from bones faster than it is deposited. Fractures are more common with osteoporosis-almost eight million yearly in the United States are related to this prevalent nutritional deficiency disease. Although there must be loss in bone mass of almost 40 percent before it is visible by X-ray, the problem may be detected earlier through diet history or blood and nutritional tests. A program of regular exercise and calcium intake through diet and supplements, while limiting phosphorus intake, is a good way to prevent bone loss in the first place.

Calcium deficiency in the blood can cause a wide range of other symptoms, such as toxemia of pregnancy, anxiety, hyperkinesis, otosclerosis, and alcoholism. One theory about multiple sclerosis correlates it with calcium and vitamin D deficiency in puberty. Mild calcium deficiency can cause nerve sensitivity, paresthesias, muscle twitching, brittle nails, irritability, palpitations, insomnia, confusion, or a feeling of chronic depression. As it progresses, leg and foot or other muscle cramps, heart palpitations, numbness, tingling, and, finally, tetany, the sustained contraction of some muscles causing severe pain, may all occur. Evidence shows that drinking soft water, which is high in sodium and low in calcium can lead to increases in cardiovascular disease. Hard water supplies extra calcium and magnesium, which may protect the heart.