Iron deficiency through inadequate dietary intake is more common in women than in men. And yet women have the highest requirements. Although iron deficiency anaemia is often attributed to bleeding or malabsorption, it appears, however, that in many cases the required level of iron intake is not achieved because of dietary restrictions or poor eating patterns.

For the physician, the causes of iron deficiency anaemia are, essentially, genital-related (menorrhagia, metrorrhagia) or gastro-intestinal-related (bleeding, indigestion, malabsorption). In fact, in nearly 40% of cases of moderate iron deficiency anaemia, inadequate iron intake, in combination or not with folate deficiency, is the only responsible cause. Furthermore, in approximately one third of the cases of anaemia associated with gastro-intestinal bleeding or malabsorption, patients have insufficient dietary intake of iron and folic acid. Often, there is a tendency to attribute iron deficiency anaemia to bleeding or malabsorption a little too quickly!

More generally, the French, in particular French women, restrict their diet with the aim of avoiding gaining weight. In France, the ingestion of meat and giblets is decreasing. Under these conditions, the required level of iron and folic acid (vitamin B9) intake is not easy to achieve.

Gastro-intestinal absorption of iron is beginning to be better understood. It is low: only 5% to 10% of ingested iron is absorbed. Thus dietary intake should be 10 to 20 times higher than requirements! Fortunately, the yield of gastro-intestinal absorption doubles in case of a chronic iron deficiency and during pregnancy.

The coefficient of gastro-intestinal absorption of heminic iron from meat and fish is about 15 to 20%, versus 3 to 5% for non-heminic iron in vegetables. This is the case for three reasons: heme "provides" iron in ferrous form (the only form absorbed) to the apex of the enterocyte; there are substances present in meat which promote iron absorption while in vegetables there are substances which limit iron absorption: insoluble dietary fibres, phytates, certain tannins (tea). Conversely, vitamin C increases this absorption.

MEAN IRON INTAKE

A few French studies are available concerning dietary iron intake. On the other hand, the percentage of persons receiving iron supplementation is unknown.
Mean iron intake in the population of French women is often relatively lower than the recommended nutritional allowance (RDA). Figure 1 shows that many women have an iron intake which is less than two thirds of the RDA (16 mg/day). Why is this figure so high, while documented iron "deficiency" is much rarer? It is likely that the RDA have over estimated the necessary requirements. In the absence of proven "anaemia" (Hb<10 g %), it is not certain that such "insufficient" intake represents an extra risk for women's health. On the other hand, an increase in losses makes this insufficient intake harmful.
Mean iron intake among the population of French men is rarely less than the recommended intake in men (11 mg/day): only 1% of men have iron intake less than two-thirds of RDA. Consequently, in men, there is little chance that iron deficiency anaemia is exclusively due to insufficient iron intake.

In practice, faced with an iron deficiency anaemia that is inadequately explained by minimal bleeding, it is thus necessary to search for an insufficient dietary intake in both men and women.

IRON CONTENT OF FOODS

Table 1 shows mean iron content of certain foods. Animal meat and liver are rich in iron, and in addition, these organs store iron in heminic form. Thus not only does meat contain more iron than spinach, but some of their components promote the absorption of iron from other foods. The reverse occurs for foods rich in dietary fibres (in particular, vegetables) which limit iron absorption.

Table 1 : The iron, folate and vitamin B12 content in foods.

	Iron (mg)	Folates (µg)	B 12 (µg)
Need	15 à 18 mg / j	300 µg / j	3 µg / j
for 100 g cooked
Red meat	2,2 à 4,0	4 à 16	2 à 3
White meet	1,1 à 2,0	4 à 10	0,8 à 1,2
Ham	1,0 à 1,1	20 à 30	0,2 à 0,4
Sausage	1,2 à 1,3	2 à 6	2 à 3
Fish	0,5 à 2,3 (bar)	5 à 20	1 à 10
Eggs	1,8 à 1,9	40 à 60	1,2 à 1,4
Liver and Kidney	6 à 14	250 à 650	40 à 70
Mussels	7 à 8	27	10
Poultry, rabbit	1,3 à 2,7	7 à 10	0,3 à 10
Vegetables	0,3 à 1,6	30 à 70	0
Spinach	2,4	140	0
Fruits	0,2 à 0,4	10 à 60	0
Dried vegetables	1,8 à 3,3	50 à 100	0
Potatoes	0,2 à 0,4	10 à 14	0
Avocado	1,0	50	0

Source : CIQUAL

Women: they are the ones most exposed to iron deficiency since they have the lowest intake and the highest losses (see insert 1). Currently, women tend to restrict their diet in order to control their weight. And yet long term calorie restriction is often accompanied by decreased iron intake. Furthermore, meat sometimes has a bad reputation with women. Lastly, heavy or frequent menstrual bleeding and the use of an intra-uterine device are additional risk factors. Conversely, regular intake of estrogen-progestin pills decrease menstrual losses of iron, and thus requirements.

It is recognised that iron losses are about 0.5 to 2 mg/day for women with normal menstrual bleeding. This figure doubles in case of heavy and frequent menstrual bleeding; iron losses would then exceed 1.7 mg/day in about 30% of women. Keeping in mind the low rate of gastro-intestinal absorption of iron (20% at best, in case of an iron deficiency), it is easy to understand the prevalence of iron deficiency anaemia in women: 5 to 10% of women have haemoglobin levels less than 10 g %.

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