In the Middle Ages, although there seems to have been a slight numerical predominance of males over females at birth, the sex ratios increased in adulthood and, as David Herlihy said, there “was a spirited competition for scarce women.” Several factors have been suggested to explain this shortage of females, including widespread female infanticide, abandonment, and simply underreporting or lack of reporting of females. Although all of these factors might have been at work for much of the Middle Ages, and probably for other periods as well, much of the discrepancy was a result of female anemia. This resulted in a high female mortality, and this in itself worked to cut down family size.
Even though the nutrition of Paleolithic times has sometimes been used as a reference standard for modern nutrition and a model for defense against certain “diseases of civilization,” it seems clear that no such use can be made of the diet of either the classical or early medieval period. In fact, from what we can reconstruct of the Roman and early medieval diet, proteins and iron, the essential components for building hemoglobin, were in short supply. Though the protein content of the diet increased gradually in the medieval period as meat became more plentiful and beans (a good source of protein) became a standard fare, the lack of iron was slow to be remedied until the use of iron pots became common.
Although iron is present in many foods, the amount that can be absorbed from grains and vegetables in general is less than that absorbed from iron salts, liver, and muscle. It is not possible to determine precisely what the amount of iron absorption from the early medieval diet was but it has been estimated to have been between 0.25 and 0.75 mg per day. This amount would have been marginal for men and less than adequate for women between the beginning of the menarche and until the menopause began. For women, before menarche and after menopause, the needs are the same as men, but the loss of iron in the menstrual flow adds substantially to this loss, resulting in a total replacement need of 1-2 mg per day. In sum, a woman during her years of menstruation requires at least twice as much iron as a man. During pregnancy, a woman’s need for replacement iron is even greater than when she is not pregnant because the demands of the pregnancy increase the need until, during the last two-thirds of the pregnancy, somewhere between 3 and 7.5 mg per day are required. This demand continues until breast-feeding is terminated.
Anemia is seldom the primary cause of death, rather it is a predisposing factor, and anemic women are more likely to get pneumonia, bronchitis, and emphysema, and in fact more women died during the medieval bubonic plague than did men. Because the average age of menarche in the medieval period was fourteen years, the net loss of iron per year for a woman over fourteen on the average diet would have been 274 mg per year, which would have reduced body stores of iron to near zero within eight years. Pregnancy would have complicated matters still further because a single pregnancy would result in losses of 1,467 mg of iron in two years (680 mg for 9 months of pregnancy, 765 mg for 14 months of lactation, and 22 mg for each month of normal menstruation). At this rate a woman’s iron stores would be reduced to zero by the time she was twenty-two. The result was a high rate of female mortality and a tendency to have spontaneous abortions when pregnant. Overall this would lead to both a shortage of women and to smaller family size. Conditions conducive to anemia began to ameliorate with diet change in the later Middle Ages and women began to live longer than men and the number of children surviving infancy also increased. Still in many parts of the world, female anemia has to be regarded as a major factor in controlling family size and in curtailing the life span of women.
