Women need more iron than men

This is generally the case. How much iron (or any nutrient) we need depends on how much we absorb from our food, how much we use, and how much we lose.

There are dietary practices which affect iron absorption. For example, tea, probably on account of its tannin, decreases the iron absorption from food. On he other hand some people eat more meat than others and this increases the absorption of iron, even from plant foods. Various nutrition surveys show that the quantities of both beverages and meat consumed by men and women differ. Alcoholic beverages, either because of the iron they contain or as an effect of alcohol itself, can increase iron absorption and thus can contribute to differences in iron needs between the sexes. Iron absorption is altered by some other foods as well.

Iron metabolism is probably much the same between the sexes, allowing for body size. Losses through skin and gut are about 14 micrograms (0.014 milligrams) per kilogram of body weight per day - this is about one milligram in a 70 kilogram man and 0.8 milligrams in a 55 kilogram woman. Menstrual loss is the biggest distinguishing factor in iron requirements between the sexes. The menstrual loss of iron in one woman is relatively constant but varies considerably between women. It averages 09 milligram per day, but in 10 per cent of women it is greater than 2.2 milligrams per day. In general women in the reproductive phase of life do need more iron than men and therefore the current RDI (see appendix 2) for iron for Australian men

is 7 milligrams and for women is 5 to 16 milligrams per day.

Bleeding through injury or disease increases the need for iron in both sexes. In such circumstances, the mechanism for iron absorption adjusts so that relatively more of the iron in food and drink is absorbed.

Iron is needed for haemoglobin in red blood cells, myoglobin in muscle and for respiratory enzymes (cytochromes) inside all body cells. Iron is also stored in liver, spleen and bone marrow. As an example, the amount of iron in different forms in a 70 kg man is distributed as shown:

IRON IN DIFFERENT FORMS

MILLIGRAMS IRON

haemoglobin (blood pigment)

myoglobin (muscle pigment)

various enzymes

iron in the process of transport around the body (as transferrin)

storage iron
(ferritin or haemosiderin) (women have stores of 0-500)

2500

150

6-8

3

500-1000

TOTAL 3160-3660


The total iron requirements during pregnancy amount to about 1000 milligrams, so that the better a woman's iron stores before pregnancy, the more certain it is that this requirement will be met. During lactation no menstrual iron loss usually occurs, but about 0.25 milligram iron per day goes into breast milk. Some breast-feeding women who eat well do not need iron supplements.