Calcium is very important in a wide variety of bodily functions. You would find Ninety-nine percent of body calcium is in the bones and teeth, with the remaining percent playing a role in blood clotting, nerve and muscle stimulation, and thyroid gland function. It also helps to prevent bowel cancer. Calcium is a natural tranquillizer, so a milky drink at night will help you to sleep well.

With the growing concern about osteoporosis, much attention has been paid to ensuring there is enough calcium in the diet. Many nutritionists are also concerned that the average diet in developed countries does not supply enough magnesium and contains excessive phosphorus. The balance between these three minerals in the body is critical for healthy bones, but they are both work mates and rivals. Acting together, they build up the bones in early life and maintain the skeleton later on in life. They also work together to relay messages along the nerves, and to enable muscles to function normally. Unfortunately, they compete with one another for absorption into the body, and phosphorus is more easily absorbed than the other two. When the diet is unbalanced, one way for the body to restore the correct proportions is to sacrifice some of the calcium that is stored in the bones.

Calcium and magnesium work together to maintain good heart and artery function. The passage of nutrients into and out of cells is reliant on calcium.

Availability in food

Even when dietary supplies of calcium and magnesium are adequate, neither mineral is easily absorbed from the intestine. Diets that are high in protein, fat or phosphorus can lead to deficiency, as can a sedentary lifestyle.

Absorption is also reduced if the stomach secretes insufficient acid, for example in the elderly, after surgery or in pernicious anaemia.

Calcium is widely available in food, but few foods contain it in large amounts. The richest sources include milk and milk products, beans, nuts, molasses and fruits. It cannot be absorbed unless vitamin D is also available either in the diet or from the action of the sun on the skin.

What if your intake is too low?

Excessive, long-term calcium deficiency causes rickets, osteomalacia (see vitamin D, p45) and osteoporosis. It may increase the risk of tooth decay, gum disease, deafness, toxaemia of pregnancy, muscle aches and cramps, anxiety, painful and heavy periods, cataracts and, in children, impaired growth and behavioural problems.

When extra may be needed

  • If you live in a soft-water area or drink bottled water that has a low mineral content
  • If your diet consists mostly of processed foods, or contains excessive protein, fat, sugar, caffeine, salt or fizzy drinks
  • If you regularly consume moderate or large amounts of alcohol
  • If you have heavy or painful periods, or are prone to pre-menstrual symptoms
  • If you are at risk of osteoporosis (take only under medical supervision)
  • During pregnancy and when breast feeding
  • When taking the birth-control pill regularly, diuretics (water pills), antacid preparations (for indigestion) or receiving hormone replacement therapy
  • When you are lacking in vitamin D
  • If you have gum disease, such as gingivitis

Can too much be toxic?

Calcium excess is easily eliminated in the short term in the urine and faeces. If excess calcium is combined with magnesium deficiency, calcium can be deposited in the soft tissues, including the kidneys, and cause damage. In the long term, excessive calcium may cause kidney stones, weakness, constipation, abdominal pain, decreased appetite and nausea.

There is some concern that excessive calcium may contribute to atherosclerosis (hardening of the arteries), eventually causing dementia. Further research is needed, but it may be wise to avoid high doses of calcium over a long period of time, unless there is a good medical reason.

Natural sources are dairy products, almonds, soybean curd (tofu), broccoli, black-eyed peas, and leafy green vegetables.

The recommended daily dosage: 300-500 mg for men; 600-1,200 mg for women, as calcium citrate, calcium lactate, or calcium gluconate. These are the forms that are best absorbed in the digestive tract.

Using a supplement

Calcium and magnesium should normally be taken together and the amount absorbed depends on the form in which they are taken. Dolomite and bonemeal contain both minerals and appear to be fairly well absorbed, but there have been concerns about contamination from Icad and other toxic metals and it is best to choose a preparation that is specified as being contaminant-free.

Of the chemical preparations, calcium is probably absorbed best when taken as the aspartate or citrate salts, and magnesium as the gluconate salt, or when chelated with amino acids.

As the body's absorption of calcium and magnesium can be altered by food, supplements with a little vitamin C may be most efficiently taken between meals or at bedtime, when they may also enhance sleep. Preparations that include hydrochloric acid and vitamin D are well absorbed by the body.

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