Soy extracts versus hormone therapy for reduction of menopausal hot flushes: indirect comparison.

OBJECTIVE: The aim of this study was to make an indirect comparison of the results from meta-analyses that evaluated the severity of hot flushes in postmenopausal women exposed to hormone therapy (HT) or soy extracts. METHODS: A systematic review and meta-analysis of HT and soy extracts related to the reduction of hot flushes in postmenopausal women versus the same control (placebo) were conducted. In addition, the combination of the overall results obtained from these two meta-analyses (indirect comparison) was adjusted to the common control (placebo). RESULTS: The indirect standardized mean difference (SMD) obtained from the combination of both individual meta-analyses was calculated by using the following equation: SMD(indirect SOY vs HT) = SMD(soy) - SMD(HT), with a total indirect variance (var) equivalent to the following equation: var(total) = var(soy) + var(HT). These calculations yielded a point estimate of -0.84 (95% CI, -1.33 to -0.35) for the indirect SMD favorable to HT. CONCLUSIONS: HT and soy interventions showed a significant difference in efficacy for the reduction of hot flushes in postmenopausal women when each treatment was compared with placebo. However, using indirect comparison, there is a statistically significant difference between HT and soy extracts in their effects on hot flushes.

Biodisponibilidad del zinc / Zinc bioavailability

La deficiencia marginal de zinc (déficit sub-clínico de zinc) ha sido reconocida como una condición muy prevalente en diferentes regiones del mundo. La absorción intestinal de zinc se efectúa mediante un mecanismo de transporte facilitado, mediado por una proteína de absorción a nivel de la vellosidad intestinal. La carga de zinc por dosis tiene importancia cuando se busca eficacia de la absorción de este elemento. El mecanismo saturable de su absorción explica la existencia de una relación inversa entre las cargas orales de zinc y su absorción intestinal. Las cargas excesivas de zinc por dosis condicionarían una pérdida innecesaria del micronutriente por saturación del mecanismo de absorción, siendo importante fraccionar racionalmente la dosis total diaria para obtener una mayor eficacia en su absorción. Se considera que la fibra a menudo ejerce un efecto negativo en la absorción de zinc; no obstante, este efecto se debe generalmente al hecho que la mayoría de los alimentos que contienen fibra también contienen un importante contenido de fitato. Es bien sabido que los fitatos ejercen un efecto inhibitorio sobre la absorción de zinc. Parece muy poco probable que el calcio per se tenga un efecto negativo en la absorción de zinc y, de igual manera, las cargas habituales de zinc en la, dieta difícilmente afectarían de manera significativa la absorción de calcio. Diferentes estudios han evaluado la interacción de estos dos micronutrientes no encontrando evidencia de algún efecto negativo de uno u otro elemento. La absorción de hierro a partir de una comida estandarizada se reduce significativamente con la ingesta concomitante de carbonato de calcio o de hidroxiapatita; en contraste, la absorción de zinc no se afectó con los suplementos de calcio...

The marginal zinc deficiency (subclinical zinc deficiency) has been recognized as a very prevalent condition in different regions in theworld. The intestinal absorption of zinc is carried out by a facilitated transportation mechanism, through an absorption protein at the level of the intestinal villus. The zinc load per dose is important when effectiveness in the absorption of this element is sought. The saturable mechanism of its absorption explains the existence of an inverse relationship between the zinc oral loads and its intestinal absorption. The excessive zinc loads per dose would determine an unnecessary loss of the micronutrient by saturation of the absorption mechanism, being important to rationally divide the total daily dose to obtain a higher efficiency in its absorption. It is considered that fiber often has a negative effect on zinc absorption; however, this effect is generally due to the fact that most foods containing fiber al so contain a significant level of phytate. It is widely known that phytates exert an inhibitory effect on zinc absorption. It is unlikely that calcium per se has a negative effect on zinc absorption ánd, likewise, the usual zinc loads in the diet would hardly affect calcium absorption. Different studies have evaluated the interaction between these 2 micronutrients, having found no evidence of any negative effect of one or another element. Iron absorption from a standardized meal significantly decreases with the concomitant ingestion of calcium carbonate or hydroxyapatite; by contrast, zinc absorption was not affected with calcium supplements. There is evidence of a clear interaction between iron and zinc when administered at the same time...