It is tempting for people to suppose that if a little of something is good for them, then a lot of it must be better. Unfortunately this is not always or even usually the case; and I first realized that people are inclined to make this mistake when, as a student many years ago, I was shown a baby who was bright orange; it was suffering from a condition known as carotenemia. The parents, having heard that carrots were healthy, concluded that only carrots were healthy, and fed their baby accordingly.
A study from Sweden, recently published in the British Medical Journal, examines the important question of whether calcium supplements are good for middle-aged and old women. The question is important because millions of women around the world take such supplements – 60 percent of American middle-aged and old women, for example. There is no one quite like the Swedes for carrying out such epidemiological studies because the medical records of their population are by far the most comprehensive in the world: creepily so, one is sometimes inclined to think.
What the Swedish researchers found was that the graph of the relationship between calcium intake and death rates was a U-shaped curve. People with a low consumption of calcium had a higher mortality than those with a moderate consumption, but so did people with a high consumption.
The sample of women was not small, and in the period of study 11,944 of the 70,259 women studied had died. Those with a high dietary consumption of calcium alone had an increased death rate of 1.4 times for all causes of mortality, 1.49 times for cardiovascular mortality, and 2.14 times for ischaemic heart disease (heart attacks) compared with those whose who consumption of calcium was associated with the lowest mortality, that is to say a moderate consumption.