Why Calcium Is Vital For Far More Than Just Strong Bones
It's well known that adequate calcium is essential for the maintenance of strong, healthy, bones and teeth, and indeed this is where around 99% of the approximately 1.2 kg stored in the average adult human body is to be found. But this is not in fact this vital mineral's most important function within the body, because calcium is also needed in the blood in very precise quantities to ensure that certain vital physiological processes can carry on unimpaired.
These include the constriction and dilation of blood vessels essential for the body's internal temperature regulation, the transmission of nerve impulses, the release of energy for muscle contraction, the secretion of certain vital hormones such as insulin, and the clotting of the blood. As evidence for the importance of these functions it is only necessary to observe that the body will strip the bones of calcium in order to maintain the necessary blood levels of the mineral should these be in danger of falling too low because of inadequate dietary intake. Since the bones, like all the body's structures, are in a constant state of regeneration and repair, the potential consequences if this deficiency is allowed to persist over time can be catastrophic.
In extreme cases, deficiency in children and adolescents may lead to the weakness and malformation characteristic of the disease, rickets. In adults, especially older adults, the most obvious consequence may be the loss of bone density known as osteoporosis - a major cause of the greatly increased incidence of the serious fractures which are such a significant risk factor for the health of the elderly.
But there are other problems which may be associated with low intakes of calcium.
There is good evidence to implicate low calcium intake as a risk factor for the development of high blood pressure during pregnancy (pre-eclampsia) in those women who are susceptible to this potentially dangerous condition; and, interestingly, research has shown that supplementation with calcium to a daily intake of 1,000-1,200 mg a day may also be effective in reducing blood pressure in the general population. A number of studies have linked low levels of calcium with pre-menstrual syndrome (PMS) and indicate that supplementation may help reduce the severity of these symptoms.
There is even now some evidence that low calcium intakes may tend to encourage the body to deposit more fat within existing fat cells. Although the relationship is not fully understood, it appears safe to say that a plentiful supply of dietary or supplemental calcium is essential for success in the pursuit of any weight loss program.
Given the importance of calcium in all these ways, it's alarming to note that average intakes for most people in the developed world are known to fall well short of the suggested level, and the figures are particularly serious for adolescents whose growing bones who have the greatest need. Perhaps as many as 75% of boys and 90% of girls in this age group may be calcium deficient.
Dairy products are by far the best sources of dietary calcium and an 8 oz serving of milk or yogurt, or 1 ½ oz of cheese, will provide around 300 mg of calcium. Leafy green vegetables, with the exception of spinach, are also a useful source, although you would need 3 - 4 servings of, for example, broccoli or kale, to match the calcium obtained from a single standard glass of milk. It should also be realized that the consumption of diets high in protein and salt, ie those characteristic of the affluent Western world, is known to increase the excretion of calcium and consequently the risk of deficiency and associated problems with bone strength and health.
Owing to this, and a number of other possible variables affecting the individual's need for dietary calcium, the Food and Nutrition Board has set out figures for Adequate Intake (AI) of the mineral rather than the Recommended Dietary Allowance (RDA) which it commonly prescribes for vitamins and other vital nutrients. Babies and infants should begin with an intake of around 200 mg per day, rising to 800 mg by the age of eight. Children of nine and over, young people whose bones are still growing, the over 50s, and pregnant or breast-feeding women, will have higher needs and should aim to consume 1,200 - 1,300 mg of calcium a day.
To maintain the health and density of fully formed bones, adults between about 20 and 50 should aim to consume 1,000 mg of calcium daily, through a combination of diet and supplements. In all cases, combining this supplementation with at least 400 IU of vitamin D will greatly assist with the absorption of the necessary calcium.
Calcium supplements should also always be taken with food; the recommended upper safe limit for total calcium intake being 2,500 mg, below which there should be no problems. However, since high calcium intakes can adversely effect the absorption of other essential minerals, notably magnesium, zinc and iron, it is recommended that supplementary calcium should always be taken as part of a comprehensive multi-mineral supplement.