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Biomedical subjects

L Hallberg

Publications and source records attributed to L Hallberg.

At least 91 records · Page 5Linked to original sources
PubMed1984

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.

Adult↗
PubMed1984

Iron metabolism and "sports anemia". I. A study of several iron parameters in elite runners with differences in iron status.

Several reports have suggested that iron deficiency might explain "sports anemia" especially in long distance runners. The present study was made to further study the iron metabolism in runners as the proposed cause of "sports anemia" is abstruse considering the good iron nutrition in these athletes. Based on a screening of 43 elite male runners, using bone marrow hemosiderin, serum ferritin and transferrin saturation, two groups of subjects were selected for a very extensive study on iron metabolism. In group 1 (n = 5) iron depletion was suggested in at least one of the screening studies. In group 2 (n = 7) at least one test strongly indicated good iron repletion. This experimental design was chosen to obtain two groups with similar body composition and exercise load but different iron metabolism. The studies comprised determinations of red cell and plasma volumes, plasma iron turnover and red cell incorporation of radioiron, red cell indices, plasma iron and transferrin, red cell protoporphyrin, serum ferritin, serum haptoglobin, urinary iron losses, iron absorption, bone marrow hemosiderin, dietary intake of energy and nutrients and a Desferal test. Pooling the results together it was obvious that none of the subjects were truly iron-deficient. A few occasional findings suggesting low iron stores cannot be satisfactorily explained and indicate that further studies are needed.

Adult↗
PubMed1984

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.

Adult↗
PubMed1983

Iron requirements and bioavailability of dietary iron.

Over the past few decades so much knowledge has been gained about iron needs, dietary iron availability and adequacy that it is now one of the best defined nutrients in these respects. Development of new, accurate methods for the measurement of both the losses of iron from the body and the absorption of iron from the diet has significantly contributed to this situation. Present knowledge of iron needs is summarized. Specific to iron are the much higher needs in women than in men and the great variation in needs between different women due to a marked physiological variation in menstrual iron losses and to the effects of pregnancies. Iron availability is discussed separately for heme and non-heme iron (the major type of food iron). Heme iron in small amounts is, on average, better absorbed than non-heme iron. The absorption of heme iron is influenced very little by the iron status of the subject and by the other food components in the diet with the exception of meat which stimulates absorption. On the other hand, the absorption of non-heme iron is markedly influenced both by the iron status of the subject and a great number of dietary factors. The absorption of iron from the diet is thus determined more by meal composition than by the amount of iron present in the diet. The great variation in absorption between different meals is illustrated and the importance of various factors influencing non-heme iron absorption is also demonstrated. Whilst the mode of food preparation itself influences iron absorption, meat or fish and ascorbic acid are some principal food constituents that enhance absorption of iron. On the other hand, several factors like tannins, phytates, phosphates, soya protein products and various "dietary" fibres have been reported to inhibit non-heme iron absorption. A consideration of the nutritional adequacy of iron high-lights the importance of methods of evaluation, particularly the usefulness of the "bioavailable nutrient density" (BND) approach for different meals; BND for iron represents the amount of iron absorbed per 1'000 kcal (4'180 kJ). The main problem in iron nutrition in Western countries today is that arising from the combination of a low-energy intake, especially in women having the highest iron needs, with a conservation in the choice of meals/meal composition. Provision of bioavailable dietary iron to meet needs has hence not been adjusted to "modern life".

Ascorbic Acid↗
PubMed1983

Iron absorption from some Asian meals containing contamination iron.

Iron absorption was measured from 12 Asian meals using the extrinsic tag method. Up to 50% of the nonheme iron in the meals did not exchange with the added inorganic radioiron tracer. The extent of isotopic exchange, the native iron and the "contamination" iron was measured using a recently developed in vitro method. The results imply that in measurements of iron absorption from meals, especially in developing countries, it is essential to consider the presence of contamination iron and its limited bioavailability.

Absorption↗
PubMed1982

Absorption of iron from Western-type lunch and dinner meals.

The absorption of nonheme iron was measured from 20 lunch and dinner meals, in 187 subjects with varying iron status. The meals comprised both vegetarian meals and meals containing meat and fish. The extrinsic tag method was used to label the nonheme iron. All absorption figures were related to the absorption of a 3-mg reference dose of inorganic iron and all absorption figures were normalized to a 40% absorption from the reference dose, corresponding to subjects who are borderline iron deficient. Despite only a 3-fold variation in content of nonheme iron in the meals there was a 7-fold difference in absorption of nonheme iron (0.13 to 0.98 mg) and a 20-fold variation in percentage absorption (2.2 to 45%). The highest absorption (0.98 mg) was seen from a vegetarian meal with a high content of ascorbic acid. The relative role of meat/fish and ascorbic acid in stimulating the absorption of nonheme iron was studied by adding or subtracting single food components.

Adult↗
PubMed1982

Effect of soy protein on nonheme iron absorption in man.

The absorption of iron was measured from a hamburger in which half of the meat protein was substituted with various soy protein products (textured soy flour or defatted soy flour). Thge reduction of the meat content per se in the hamburgers reduced the percentage nonheme iron absorption by 25% from 11.2 to 8.4% The addition of defatted soy flour reduced the percentage absorption further from 8.4% to 5.2%. The amount of nonheme iron absorbed, however, was unchanged due to the high iron content of soy flour. A removal of phytates from soy flour did not increase the nonheme iron absorption. The total amount of iron absorbed, including the heme iron, is much lower when the content of meat was reduced by half in the soy-meat hamburgers. The addition of heme iron as blood to these hamburgers fully restored the total amount of iron absorbed to the level measured in hamburger meals prepared of meat only.

Absorption↗
PubMed1982

Bioavailability of iron from Western-type whole meals.

The absorption of non-heme iron was measured in 10 meals designed to correspond to a whole main meal with an energy content of about 1000 kcal. The extrinsic tag method was used to label the non-heme iron, and two meals were compared in each subject by means of two radioiron isotopes. All absorption figures were related to the absorption of a 3-mg reference dose of inorganic iron, and all absorption figures were normalized to a 40% absorption from the reference dose, a level corresponding to absorption in subjects who are borderline iron-deficient. In spite of the similar energy content of the meals and only a twofold variation in content of non-heme iron (3.9-7.8 mg), there was a fivefold difference in absorption of non-heme iron (0.33-1.80 mg). Considering also the content of heme iron in the meals, the calculated variation in absorption was sixfold (0.33-1.95 mg). The main part of this variation can be explained by a varying content of ascorbic acid and meat. The absorption of iron from meals can be expressed in different ways. The percentage absorption is a measure of the bioavailability, which can be markedly modified by several components of a meal. The amount absorbed is, moreover, related to the amounts of heme and non-heme iron present. The amount absorbed per unit energy in the meal, the bioavailable nutrient density, is an expression of great importance in the practical assessment of the nutritive value of a meal with respect to iron.

Absorption↗
PubMed1982

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.

Absorption↗
PubMed1981

Bioavailable nutrient density: a new concept applied in the interpretation of food iron absorption data.

The nutritive value of a diet for a certain nutrient must be based on its ability to meet certain requirements for certain target groups. The current low energy intake makes it sometimes difficult to cover the requirements of certain nutrients from the diet. Thus, an important measure of the nutritive value of a food or a meal will be obtained if the amount of a nutrient absorbed is related to the energy content of the meal studied (bioavailable nutrient density). The amount of iron absorbed from a meal depends not only on its contents of heme and nonheme iron and on various dietary factors affecting the bioavailability but also on the iron status of the subjects studied. The bioavailability of iron in a meal must therefore be given for a certain iron status. Thus the following definition of bioavailable nutrient density for iron is suggested: The amount of iron (milligrams) absorbed from a meal per unit energy (1000 kcal) by subjects who are borderline iron deficient, i.e., nonanemic subjects with depleted iron stores.

Diet↗
PubMed1981

Measurement of iron absorption from meals contaminated with iron.

A method is described to measure in vitro the extent of isotopic exchange between the native nonheme food iron and added inorganic reduction to radioiron tracer. The food is digested with pepsin and trypsin in the presence of radioiron. The exchangeability of food iron is calculated from the specific activity in the food and in an extract of bathophenantroline in isoamyl alcohol obtained after digesting this food. The precision and accuracy of the method is illustrated by two kinds of studies, those in which different amounts of contamination iron are added to a meal and those evaluating contamination iron in natural meals. The present method will make it possible to measure validly iron absorption from meals contaminated with unknown amounts of iron of unknown exchangeability with the extrinsic radioiron tracer.

Absorption↗