RESUMO
One hundred and seventy four human subjects were studied to find out the interaction of vitamin A or beta-carotene with the inhibitors of iron absorption, from a basal breakfast containing bread from either 100 g of precooked corn flour or 100 g of white wheat flour, 50 g of cheese and 10 g of margarine. Bread was labeled with either 55Fe or 59Fe. This bread was made from commercially flours fortified with iron as ferrous fumarate and vitamins. It was noticed that the percentage of iron absorption from the breakfast prepared with precooked corn flour given alone and with different concentrations of coffee was practically the same, while the iron absorption from the breakfast prepared from wheat flour decreased from 6% when the breakfast was given alone, to less than 2% when it was given with different concentrations of coffee. The only ingredient present in precooked corn flour and not in wheat flour was vitamin A. This difference encouraged the authors to perform further experiments using precooked corn and wheat flours fortified only with ferrous fumarate. These studies demonstrated that vitamin A inhibits the effect of the polyphenol and partially inhibits the effect phytate on iron absorption. HPLC and spectrophotometric studies demonstrated an interaction between vitamin A and iron. Other experiments, which included 100 volunteers, were performed to test the effect of vitamin A and beta-carotene on iron absorption from corn, wheat and rice. The presence of vitamin A increased iron absorption up to 3 times for rice, 2.4 times for wheat and 1.8 times for corn. beta-carotene increased absorption almost 3 times for the three cereals tested, showing that both compounds were capable of preventing the inhibitory effect of phytates on iron absorption. This information suggest that vitamin A and beta-carotene form a complex with iron keeping it soluble in the intestinal lumen and preventing the inhibitory effect of phytates and polyphenols on iron absorption.
Assuntos
Antioxidantes/farmacocinética , Ferro da Dieta/farmacocinética , Ácido Fítico/farmacocinética , Polímeros/farmacocinética , Vitamina A/farmacocinética , beta Caroteno/farmacocinética , Antioxidantes/administração & dosagem , Pão , Feminino , Humanos , Absorção Intestinal , Masculino , Ácido Fítico/administração & dosagem , Vitamina A/administração & dosagem , beta Caroteno/administração & dosagemRESUMO
After the rapid decrease in the prevalence of iron deficiency and iron-deficiency anemia in the Venezuelan population when a national program for fortification of flours with iron and vitamins was instituted, we studied micronutrient interactions in Venezuelan diets. One hundred human adults were fed three cereal-based diets, labelled with either 59Fe or 55Fe in six studies. Each diet contained different concentrations of vitamin A (from 0.37 to 2.78 micromol/100 g cereal) or beta-carotene (from 0.58 to 2.06 micromol/100 g cereal). The presence of vitamin A increased iron absorption up to twofold for rice, 0.8-fold for wheat and 1.4-fold for corn. beta-carotene increased absorption more than threefold for rice and 1.8-fold for wheat and corn, suggesting that both compounds prevented the inhibitory effect of phytates on iron absorption. Increasing the doses of vitamin A or beta-carotene did not further significantly increase iron absorption. We measured the iron remaining in solution performing in vitro studies in which the pH of solutions was adjusted from 2 to 6 in the presence of vitamin A or beta-carotene. All of the iron from ferrous fumarate was soluble after changing the pH of the solution containing 3.4 micromol of beta-carotene to 6.0. Vitamin A was less effective. However, 78 +/- 18% of iron was soluble in the presence of 3.3 micromol of vitamin A, whereas with no vitamin addition, only 26 +/- 13% of iron was soluble (<0.05). Vitamin A and beta-carotene may form a complex with iron, keeping it soluble in the intestinal lumen and preventing the inhibitory effect of phytates and polyphenols on iron absorption.
Assuntos
Ferro/farmacocinética , Oryza/metabolismo , Triticum/metabolismo , Vitamina A/farmacologia , Zea mays/metabolismo , beta Caroteno/farmacologia , Absorção/efeitos dos fármacos , Adulto , Feminino , Humanos , Concentração de Íons de Hidrogênio , Ferro/química , Masculino , Oryza/química , Solubilidade , Triticum/química , Zea mays/químicaRESUMO
In Venezuela a severe economic crisis beginning in 1983 provoked a progressive reduction of the quality and quantity of food consumed by the low socioeconomic strata of the population. In these strata, which represent > or = 80% of the Venezuelan population, we had seen a continuous increase in the prevalence of iron deficiency during that recent decade. As a result, in 1993 the Venezuela Government created the Special Commission for Enrichment of Foods. That same year a fortification program began in which precooked yellow and white maize and wheat flours were enriched with 20 and 50 mg Fe (as ferrous fumarate)/kg flour, respectively. The corn flour was also enriched with vitamin A, thiamine, riboflavin, and niacin, whereas the wheat flour was enriched with these same vitamins, except vitamin A. These two cereals represent 45% of the total energy consumed daily by the low socioeconomic strata of the population. A preliminary survey carried out in Caracas in 1994 in a population of 307 children aged 7, 11, and 15 y showed that the prevalence of iron deficiency determined by measuring the serum ferritin concentration and the prevalence of anemia were reduced from 37% and 19%, respectively, in 1992 to 15% and 10%, respectively in 1994.
Assuntos
Anemia Ferropriva/epidemiologia , Ferro da Dieta/farmacologia , Adolescente , Adulto , Anemia Ferropriva/tratamento farmacológico , Anemia Ferropriva/prevenção & controle , Criança , Pré-Escolar , Coleta de Dados , Dieta/normas , Feminino , Ferritinas/sangue , Farinha/análise , Análise de Alimentos , Indústria de Processamento de Alimentos/métodos , Indústria de Processamento de Alimentos/normas , Humanos , Incidência , Lactente , Ferro da Dieta/análise , Ferro da Dieta/uso terapêutico , Masculino , Pessoa de Meia-Idade , Niacina/análise , Niacina/farmacologia , Controle de Qualidade , Riboflavina/análise , Riboflavina/farmacologia , Classe Social , Tiamina/análise , Tiamina/farmacologia , Triticum/química , Venezuela/epidemiologia , Vitamina A/análise , Vitamina A/farmacologia , Zea mays/químicaRESUMO
The iron bioavailability from three typical diets consumed by socioeconomic stratum IV (SES IV--working class) of the Venezuelan population was determined by the extrinsic label method. Although the iron content of the SES IV diets was about the same (250 mumol/d) as that of upper (SES I-III) and lower (SES V) socioeconomic strata diets, iron-replete subjects absorbed 43 and 61% more iron from the SES I-III diets than from the SES IV and V diets, respectively, and absorption from the main meal of the SES I-III diets was 100% greater. However, iron deficient subjects absorbed about the same amount of iron (45 mumol/d) from the SES IV diets as from the SES I-III diets. The SES I-III diets contained more iron absorption enhancers (ascorbic acid and meat protein) and less of the inhibitor phytate, than the SES IV and V diets. Iron absorption from the meals of four diets consumed at different times during the day was also measured. There was no significant difference in the percentage iron absorption from the same meals eaten in the morning after an overnight fast, and when eaten at the customary time of day.
Assuntos
Dieta , Ferro/farmacocinética , Fenômenos Fisiológicos da Nutrição , Classe Social , Absorção , Adulto , Ácido Ascórbico/administração & dosagem , Disponibilidade Biológica , Criança , Dieta/normas , Proteínas Alimentares/administração & dosagem , Feminino , Humanos , Ferro/administração & dosagem , Deficiências de Ferro , Masculino , Valor Nutritivo , Ácido Fítico/administração & dosagem , VenezuelaRESUMO
The possibility of improving the dietary value of precooked maize flour through fortification with 11% coarse defatted maize germ was investigated. The results of tests in humans presented here show that the total iron absorption from the fortified preparation is similar to that from the precooked maize alone, but with the advantage of being richer in several nutrients: protein (25%), zinc (61%), potassium (47%) and magnesium (112%), as well as fiber (34%). Fortification lowers (by 20%) rather than raises the cost of the flour, and may be an important contribution to the diet of those populations where maize bread is a major component of the diet.
Assuntos
Farinha , Alimentos Fortificados , Ferro/farmacocinética , Zea mays , Absorção , Adulto , Culinária , Fibras na Dieta , Feminino , Farinha/análise , Humanos , Ferro/sangue , MasculinoRESUMO
The iron status of 3228 subjects from the nutrition survey Proyecto Venezuela was studied. The sample included children from 1 to 16 y of age grouped by age and sex. Values for three indicators of iron status were compared: hemoglobin concentration, serum ferritin concentration, and percentage saturation of serum transferrin. In all groups there was a strong overlap in the hemoglobin concentration distribution curves for non-iron-deficient and iron-deficient subjects classified as such according to the other two indexes. The prevalence of iron deficiency ranged from 35% in 1-3 y olds to 10% in adolescent males, the values being almost identical in the nonanemic group compared with the total population. In the different groups, 80-97% of the subjects with abnormal values of at least one of these two indexes were not anemic. The difficulties involved in establishing a state of iron deficiency according to these indexes are discussed.
Assuntos
Anemia Hipocrômica/sangue , Deficiências de Ferro , Adolescente , Fatores Etários , Anemia Hipocrômica/epidemiologia , Criança , Pré-Escolar , Feminino , Ferritinas/sangue , Hemoglobinas/análise , Humanos , Lactente , Masculino , Prevalência , Fatores Sexuais , Transferrina/análise , Venezuela/epidemiologiaRESUMO
Proteins, some minerals and vitamins, play important roles in erythropoiesis and the survival of the red blood cell. This article deals specifically with the physiological requirements and recommended intakes of iron, folate and vitamin B12. A comparison of the physiologic iron requirements according to age and sex, and the amount of iron which is actually absorbed from the diets consumed by the lower socioeconomic strata of the Venezuelan population; indicates that these diets do not satisfy the requirements at all ages. Such disparity is most marked in children below three years of age, in adolescents and in women during their reproductive age. Failure to do so leads to varying degrees of iron deficiency. This low bioavailability of the Venezuelan diet is also observed in other Latin American diets consumed by the same low socioeconomic strata, which explains the high prevalence of iron-deficiency anemia in the vulnerable groups. The low intake of fruits and vegetables by the lower socioeconomic strata of the Latin American population prevents these sectors from consuming an adequate intake of folate, failing to fulfill the daily recommended intake (3.3 - 3.6 micrograms/kg body weight). This situation is aggravated in pregnant and lactating women who require an additional intake of 300 micrograms and 100 micrograms, respectively. Prevalence of folate deficiency in the first stage may be in the order of 30% in some regions. In the second stage of deficiency, characterized by megaloblastic changes in the bone marrow and an erythrocyte folate concentration of less than 50 micrograms/lt, it could be as high as 40% in pregnant women. Nutritional vitamin B12 deficiency does not constitute a health problem in Latin America. Various surveys in the lower socioeconomic strata have reported normal or higher than normal serum B12 concentrations, compared to well-nourished populations.