Déficit nutricional de hierro y zinc

Las dietas basadas en plantas pueden producir deficiencias de minerales (por ejemplo, hierro y zinc) por su elevado contenido en fitatos, conocidos inhibidores de la absorción de minerales. Una forma de evitar esas deficiencias es asegurar un consumo mínimo de productos cárnicos, cuyos minerales no sólo se absorben mejor sino que ayudan en la absorción de los minerales de las plantas.

Las dietas basadas en plantas son una moda implantada por motivos políticos e intereses económicos, no por cuestiones de salud. Y es un experimento no exento de riesgo. Salvo que haya razones ideológicas que lo “impidan” (razones respetables pero totalmente fuera de lugar cuando de lo que se habla es de salud), lo prudente es consumir carne/pescado como parte de la dieta. Y digo carne/pescado, no productos de origen animal, porque la leche o los huevos no tienen el mismo efecto que la carne/pescado en la absorción de nutrientes.

Si tu dieta está basada en plantas, extrema las precauciones (fuente).

Presento a continuación algunas citas. No las traduzco, pero el mensaje es claro: es bueno consumir carne/pescado a efectos de no tener déficit de hierro y zinc, y una dieta basada en plantas es un potencial peligro por su alto contenido en bloqueadores de absorción (i.e. fitatos).

Hierro

Plant-based diets in low-income countries (LICs) have a high content of phytic acid (myo-inositol hexaphosphate [InsP6]) and associated magnesium, potassium, and calcium salts. Together, InsP6 acid and its salts are termed “phytate” and are potent inhibitors of iron and zinc absorption. […] In LICs, poor absorption from high-phytate diets is a major factor in the etiology of iron and zinc deficiency (fuente)

Heme iron which comes from hemoglobin and myoglobin, is absorbed directly as the intact iron porphyrin complex, and its iron is freed in the intestinal mucosal cell (10-13). The proportion of heme iron which humans usually absorb from their diet is high in comparison with nonheme iron […] Analysis of a variety of foods has shown that approximately 30 to 40% of the iron in pork, liver, and fish and 50 to 60% of the iron in beef, lamb, and high chicken is in the form of heme (16). The nonheme iron pool consists of iron from other foods such as vegetables, grains, fruits, eggs, and dietary products as well as from the nonheme iron of meats, poultry, and fish and from soluble iron supplements. (fuente)

The absorption of nonheme iron depends not only on the general composition of the meal but along with heme iron is further affected by the iron status of the individual. Absorption of nonheme iron in the deficient individual may be as much as 20% when enhancers are abundant (to be contrasted with about 35% heme iron absorption). A much greater difference is observed in the iron replete subject with a meal lacking enhancers and/or with high levels of blocking substances, where nonheme absorption is about 2% as contrasted to about 15 % heme iron absorption. […] Present evidence indicates that the nature of the meal has little or no influence on the amount of heme iron absorbed (fuente)

Nutrition may be improved by increasing either the amount of iron in the diet or its availability. (fuente)

Dietary factors which dramatically increase the absorption of nonheme iron, as much as four fold, are ascorbic acid and a “meat factor” present in meat, poultry , and fish […] While […] milk, cheese, and eggs do not increase and may decrease iron availability (fuente)

Dietary iron bioavailability is low in populations consuming monotonous plant-based diets with little meat. […] red meats high in hemoglobin are excellent nutrient sources of iron. […] The enhancing effect of meat, fish, or poultry on iron absorption from vegetarian meals has been shown (fuente)

The inhibitory effect of phytic acid on iron absorption is also dose-dependent [34], and occurs even at very low phytate concentrations. (fuente)

Zinc

Marginal zinc deficiency and suboptimal zinc status have been recognized in many groups of the population in both less developed and industrialized countries. Although the cause in some cases may be inadequate dietary intake of zinc, inhibitors of zinc absorption are most likely the most common causative factor.(fuente)

The adverse effect of phytate on zinc absorption follows a dose-dependent response [29], and there is no threshold for the inhibitory effects of dietary phytate zinc bioavailability (fuente)

In the future, dietary modification/diversification, although long term, may be the preferred strategy because it is more sustainable, economically feasible, culturally acceptable, and equitable, and can be used to alleviate several micronutrient deficiencies simultaneously, without danger of inducing antagonistic micronutrient interactions. Appropriate dietary strategies include consumption of zinc-dense foods and those known to enhance zinc absorption, reducing the phytic acid content of plant based staples via enzymic hydrolysis induced by germination/fermentation or nonenzymic hydrolysis by soaking or thermal processing. (fuente)

Zinc absorption can be enhanced by the increased consumption of foods such as cellular animal proteins (meat, poultry and fish) (fuente)

NOTA: aunque he visto en algún artículo (supuestamente) científico que existe un riesgo de déficit de hierro y zinc en Europa por la mala calidad de los vegetales (fuente), yo no me creo que con una dieta que incluya carne vaya a haber ningún riesgo de nada en un país occidental. Me parece sólo un argumento ad hoc para hacer avanzar una cierta agenda política. 

NOTA: algunos autores afirman que las deficiencias de minerales son reales al seguir dietas basadas en plantas pero que no causan problemas de salud (fuente,fuente).

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