Estimado Sujal, el tema del hierro , recién ahora está siendo investigado con profundidad.
Pero, a pesar de ciertas investigaciones bastante contundentes, falta mucho para "modificiar" los esqueletos teóricos dogmatizados de la nutrición.
Por ej, yo comencé a poner en duda las ventajas de la aclamada biodisponibilidad del Fe Hem vs el Fe no hem, por que alta biodisponibilidad de algo tan tóxico como el hierro, yo lo veo como algo perjudicial, ya que la alta velocidad de llegada a sus lugares de necesidad bioquimica implica, al menos teóricamente, y de alguna manera hay sustentos fácticos, que los mecanismos de proteccion serían más fácil de ser superados. Es una simple cuestión mecánica y química.
Yo creo que en el futuro, los valores hoy considerados normales, concretametne la ventana normal , va a descender. Pero, es muy importante mas investigacion.
Ya hay varias investigaciones que estan creando una linea de pensamiento que considera al hemo como causa de ciertos cánceres, por ej, colon.
saludos
Heme Iron, Zinc, Alcohol Consumption, and Colon Cancer: Iowa Women's Health Study
Duk-Hee Lee, Kristin E. Anderson, Lisa J. Harnack, Aaron R. Folsom, David R. Jacobs, Jr.
Affiliations of authors: Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis (KEA, LJH, ARF, DRJ); Department of Preventive Medicine, College of Medicine, Kyungpook National University, Daegu, Korea (DHL); Institute for Nutrition Research, University of Oslo, Oslo, Norway (DRJ).
We examined associations among colon cancer incidence and dietary intake of heme iron, a possible prooxidant, zinc, a possible antioxidant, and alcohol, a disruptor of iron homeostasis. During 15 years of follow-up, 34 708 postmenopausal women, aged 55–69 years at baseline who completed a food-frequency questionnaire for the Iowa Women's Health Study, were followed for incident colon cancer. After adjusting for each micronutrient, the relative risks for proximal colon cancer increased more than twofold across categories of heme iron intake (Ptrend = .01) and the corresponding relative risks decreased more than 50% across categories for zinc intake (Ptrend = .01). The positive association with heme iron and the inverse association with zinc intake were stronger among women who consumed alcohol than among those who did not. Zinc intake was also associated with a decreased risk of distal colon cancer (Ptrend = .03), regardless of alcohol or heme iron consumption. Our results suggest that intake of dietary heme iron is associated with an increased risk of proximal colon cancer, especially among women who drink, but that intake of dietary zinc is associated with a decreased risk of both proximal and distal colon cancer.
Heme and Chlorophyll Intake and Risk of Colorectal Cancer in the Netherlands Cohort Study
Helena F. Balder1, Johande Vogel2, Margje C.J.F. Jansen1, Matty P. Weijenberg3, Piet A. van den Brandt3, Susanne Westenbrink1, Roelof van der Meer2 and R. Alexandra Goldbohm1
Background: The evidence for red meat as a determinant of colorectal cancer remains equivocal, which might be explained by differences in heme content. Heme is the pro-oxidant, iron-containing porphyrin pigment of meat and its content depends on the type of meat. Chlorophyll from green vegetables might modify this association.
Methods: The Netherlands Cohort Study was initiated in 1986 when a self-administered questionnaire on risk factors for cancer was completed by 120,852 subjects ages 55 to 69 years. After 9.3 years of follow-up through the Cancer Registry, 1,535 incident colorectal cancer cases (869 men and 666 women) were available. Nineteen of the 150 items in the validated dietary questionnaire related to consumption of specific types of fresh and processed meat. Heme iron content was calculated as a type-specific percentage of the total iron content and chlorophyll content of vegetables was derived from the literature.
Results: Multivariate rate ratios for quintiles of heme iron intake and colon cancer were 1.00, 0.98, 1.04, 1.13, and 1.29 (Ptrend = 0.10) among men and 1.00, 1.31, 1.44, 1.18, and 1.20 (Ptrend = 0.56) among women, respectively. No consistent associations were observed for rectal cancer. Rate ratios for colon cancer increased across successive quintiles of the ratio of heme/chlorophyll among men only (1.00, 1.08, 1.01, 1.32, and 1.43; Ptrend = 0.01). No associations were observed between fresh meat and colorectal cancer.
Conclusion: Our data suggest an elevated risk of colon cancer in men with increasing intake of heme iron and decreasing intake of chlorophyll. Further research is needed to confirm these results. (Cancer Epidemiol Biomarkers Prev 2006;15(4):717–25)
Recordemos: el hemo es la forma sanguinea de transporte del hierro en animales, ademas de estar en otros sistemas bioquimicos. Forma parte de la hemoglobina, un complejo proteico, con una porfirina que acompleja el hierro (hemo). Esta estructura es esencial para el transporte de oxigeno en los animales.
La clorofila, una estructura semejante al hemo, tiene Magnesio en vez de hierro como nucleo del complejo (porfirina mas magnesio, ademas de otras radicales). Es esencial para la vida en la tierra, ya que forma parte de los fotosistemas implicados en la captacion de energia del sol, y es el sistema que permite la transformacion de esa energía luminca en energía quimica nutricional.