Minerals are the substances in rocks and subsoil which we need in our bodies and can get from nowhere else. Germs in the topsoil around plant roots ‘mine’these minerals to feed plants and fungi, from which we get them in turn. Of these minerals, calcium is far the largest requirement we have — up to 1.2 kilograms, or 1.7% of normal body weight.
Almost all of that calcium (99%) is in the bones, with about 5 grams circulating in the body fluids and another 5gm attached to proteins inside cells or to their membranes. Calcium is able to alter the structural arrangement of proteins, and is therefore involved in a great many enzyme reactions which go to make up normal metabolism. It is the substance responsible for causing muscle fibres to contract in a forceful movement: magnesium is needed to enable them to relax again. In the blood it is essential for normal clotting, to stop blood leaks following injury.
We humans have a problem retaining in our bodies all the calcium we need, after middle age. Children’s bodies are avid for it up to about 16, after which requirements fall off sharply. Even among children, however, most of the calcium eaten is excreted from the bowel without being absorbed. And in older people whose bones are losing a few grams of calcium daily, calcium deposits are forming where they are not required, hardening arteries and forming kidney stones and gallstones! No amount of supplementation seems to correct this — in fact it seems only to increase the unwanted deposits.
The solution of this paradox seems to lie in the form of the calcium, not the quantity. If it has been incorporated properly into a food and not then overcooked, it is readily absorbed and can take part in the full range of healthy actions open to calcium in the body. If the calcium has come direct from rocks (as chalk used to fortify bread, for example) or from hard water, without having grown into a food plant, then what little we do absorb only gets dumped somewhere, or may form crystals in the kidney or bladder on the way out.
Dairy produce would be our major source of calcium, but unfortunately the process of pasteurisation takes place at a high enough temperature to denature much of the calcium-bearing protein and make the calcium far less accessible for absorption. Fresh green vegetables , cooked minimally or not at all, and \"legumes’such as peas, beans and lentils — particularly when sprouted and eaten raw — are therefore important sources for most of us. Cheese from unpasteurised milk, and green top (unpasteurised) milk direct from the dairy, are also excellent where you can get it, but green top milk must be carefully refrigerated and drunk quite fresh. Having gone to the trouble of buying green top, do not then cook with it — the effect is worse than pasteurisation!
Hormone replacement therapy (HRT) is frequently offered to women in middle age as an aid to preventing the softening of bones which results from losing calcium every day. We now think the real solution to this is supplementary progesterone, which is not included in HRT. It is far more effective, completely safe and often improves other features of the menopause or premenstrual tension.
If you live in an area with fluoride in the drinking water, or you like tea and sea-food, you may be consuming more fluoride than is good for you. A helpful precaution against that is to consume more calcium-containing food, which combines with the fluoride and makes it less accessible for absorbtion from your intestine. Avoiding fluoride in the first place is a better approach, of course.
Food-state calcium supplements seem not to have been denatured sufficiently in their manufacture to reduce their absorption. We have had one or two people with obvious calcium-wasting problems who had no further problems once they began to use the food-state calcium supplement, so we can recommend that as an addition to the right food where you have a major deficit to make up.
A chemical in wholemeal cereals, known as phytic acid, is capable of reducing the calcium you are able to absorb from the meal initially, but once you are used to wholemeal you begin to make an enzyme called phytase which breaks up the phytic acid. This is perhaps an argument for adapting gradually from white to wholemeal, but even if you do it suddenly the problem is short-lived and largely hypothetical.
What to do
Rely chiefly on fresh leafy vegetables, peas and beans for the calcium that is best absorbed.
Buy unpasteurised dairy produce, if you can get it and like eating it.
Eating much meat and drinking much coffee increase your daily calcium losses, so be sparing with these.
Physical activity encourages your body to retain calcium, so don’t let yourself get idle.
Retain a youthful outlook and playful nature. Letting yourself act old is a mistake — not least because your bones lose their calcium faster. If you keep using your limbs as of habit, they will stay strong and supple enough to be used.