Effect of dietary fiber on iron absorption in man.

The binding of iron to different fibers suggest in vitro that dietary fibers might interfere with the bioavailability of iron in the diet. As it is difficult or impossible to translate in vitro studies to in vivo bioavailability and even to translate results from animal studies to man, it is necessary to study the effect of fiber in man. With the extrinsic tag method and two different radioiron tracers it is possible in the same subject to compare the iron absorption from a meal with and without a certain component of dietary fiber. With a standard reference dose of 3 mg iron it is possible to "calibrate" each subject which makes it possible to compare the absorption in different groups given different components of dietary fiber.

Low bioavailability of carbonyl iron in man: studies on iron fortification of wheat flour.

The bioavailability in man of commercially available elemental iron powders is unknown despite their extensive use for fortification of flour. Carbonyl iron, which is widely used in Europe, is considered as one of the best reduced iron powders based on studies both in vitro and in animals. In this study, a 55Fe labeled carbonyl iron was prepared by neutron irradiation and used to fortify wheat flour. The native iron of the wheat was extrinsically labeled by 59FeCl3. Doubly labeled wheat rolls were served with different meals. The ratio of absorbed 55Fe/59Fe is a direct measure of the fraction of carbonyl iron that joins the nonheme iron pool and is made potentially available for absorption. This relative bioavailability of carbonyl iron was unexpectedly low and varied from 20 to 5% when the iron fortified wheat rolls were served with different meals. The baking process did not change the relative bioavailability nor the addition of ascorbic acid. The low and variable bioavailability of carbonyl iron in man, makes it necessary to reconsider the rationale of using elemental iron powders for the fortification of foods for human consumption.

Improvement of iron nutrition in developing countries: comparison of adding meat, soy protein, ascorbic acid, citric acid, and ferrous sulphate on iron absorption from a simple Latin American-type of meal.

A study in 49 subjects compared different methods for increasing the absorption of iron from a simple Latin American-type meal composed of maize, rice, and black beans. The addition of meat (75 g) increased the nonheme iron absorption from 0.17 to 0.45 mg; soy protein in an amount corresponding to the protein content of the meat increased the absorption to 0.51 mg (due to the high iron content of soy flour); cauliflower as a source of ascorbic acid (65 mg) increased the absorption to 0.58 mg, pure ascorbic acid (50 mg) to 0.41 mg, and ferrous sulphate mixed into the meal in an amount (6 mg) corresponding to the iron content of the soy flour increased the absorption to 0.64 mg. The addition of citric acid (1 g) reduced the absorption to 0.06 mg (to about one-third). We conclude that several methods are available for increasing iron absorption from a Latin American meal and that the choice of method depends on several factors, particularly cost.

Iron metabolism and "sports anemia". II. A hematological comparison of elite runners and control subjects.

A hematological comparison was performed between 43 middle and long distance male runners and 119 male controls. The hematocrit, serum iron, transferrin saturation and serum ferritin values were significantly lower in the athletes. The amount of bone marrow hemosiderin was also lower in the athletes than in a group of non-athletic men of the same age. Even if these values were clearly lower than in the controls, they were not low enough to indicate iron deficiency. The observations that sideroblast counts in bone marrow smears were normal and that both red cell indices and red cell protoporphyrin were normal strongly support the conclusion that lack of iron had not limitated erythropoiesis or the formation of an optimal red cell mass. Low serum haptoglobin values in most athletes indicated an increased intravascular hemolysis. As the hemoglobin-haptoglobin complex formed is taken up by hepatocytes, this implies that there is a shift in the red cell catabolism in these athletes from the reticuloendothelial system to the hepatocytes. This shift may explain the paradoxical findings of low serum ferritin concentrations and reduced contents of bone marrow hemosiderin. This is consistent with the observed normal erythropoiesis. It was concluded that runners "anemia" is no true anemia and not caused by iron deficiency. "Sports anemia" is thus no indication for routine iron supplementation.

Effect of different drinks on the absorption of non-heme iron from composite meals.

A study was made on the effect of various drinks on the absorption on non-heme iron. The drinks were taken with standard meals composed of a hamburger, string beans and mashed potatoes. In each series identical meals were served to the same subject either with water or with the drink under study, labelling the meals with two different radio-iron isotopes. A reduction in iron absorption was seen when serving tea (62 per cent) or coffee (35 per cent) with the meals. Orange juice increased the iron absorption (85 per cent). Pure alcohol and wine increased only slightly the percentage absorbed. Wine often has a high iron content, which increased significantly the amount of iron absorbed (three times). Milk and beer have no significant effect. Coca-Cola increased only slightly the absorption. The present studies clearly shows that the choice of drink drunk with a meal can markedly affect the absorption of non-heme iron.

An analysis of factors leading to a reduction in iron deficiency in Swedish women.

The prevalence of iron deficiency anaemia among Swedish women of child-bearing age has fallen markedly since the mid-1960s. At that time, population studies in Göteborg and Uppsala showed that iron deficiency anaemia was present in about 25-30% of women. Later, in population studies in Göteborg in 1968-69 and 1974-75, the prevalence in the same age group was found to have fallen to 6-7%. Several factors may explain the improved iron status. The level of iron fortification of flour was increased from 30 mg/kg of flour in 1943 to 65 mg in 1970, this increase adjusting the iron intake to compensate for the lower energy requirement and expenditure of present-day living habits. There has also been a marked increase in the intake of iron tablets and of tablets containing ascorbic acid.An analysis of various factors indicates that the 20-25% improvement in iron status can be accounted for by increased use of oral contraceptives (3-4%), the impact of increased iron fortification (7-8%), the widespread use of ascorbic acid supplements (3%), and greater prescribing of iron tablets (10%).This analysis of the factors leading to the marked reduction in the prevalence of iron deficiency anaemia among Swedish women may be useful to public health planners in other countries with similar problems. Our results indicate that several factors need to be considered when planning controlled field trials and evaluating the results obtained. The methods used to analyse the impact of different factors on the reduction in iron deficiency can also be used to predict the effects of various public health measures on the iron status of a population.

Studies of dietary habits in pregnancy - with special reference to the intake of iron.

The dietary habits of 94 pregnant women (median age 26 years) were studied by means of four-day dietary records. Twenty-seven women were followed longitudinally and were observed in the 10-15th, the 24-27th and the 34-37th week of gestation (L-series). The remaining 67 women comprised the A-series, of which 20, 32, and 15 made their records during the 10-15th, 24-27th, and 34-37th week of gestation, respectively. There were no significant differences between the results from these two series. The mean daily energy intake was 2360 kcal and remained unchanged during pregnancy, exceeding by 250 kcal the average intake in non-pregnant women in Gothenburg, studied earlier. The iron intake comprised 1-2 mg of haeme iron, about 10 mg of native non-haeme iron and 5-6 mg of fortificiation iron. The mean iron intake was 7.2 mg/1000 kcal, which is below the recommendation, but it was distributed over the food groups in a manner more favourable for iron absorption than in the average Swedish population. Further effects to improve the diet so as to increase the content of iron and factors known to favour iron absorption are desirable. The results justify the normal practice of prescribing supplement iron in late pregnancy.