¿Debe recomendarse el consumo de leche en dietas vegetarianas?
A continuación hago eco de un artículo inscrito en la revista The American journal of clinical nutrition publicada por la American Society of Clinical Nutrition (¡casi nada!)
Cita:
Should dairy be recommended as part of a healthy vegetarian diet? Counterpoint.
Lanou AJ.
Department of Health and Wellness, University of North Carolina, Asheville, NC, USA. alanou@unca.edu
* Am J Clin Nutr. 2009 May;89(5):1634S-1637S.
Although cow milk has been widely recommended in Western countries as necessary for growth and bone health, evidence collected during the past 20 y shows the need to rethink strategies for building and maintaining strong bones. Osteoporotic bone fracture rates are highest in countries that consume the most dairy, calcium, and animal protein. Most studies of fracture risk provide little or no evidence that milk or other dairy products benefit bone. Accumulating evidence shows that consuming milk or dairy products may contribute to the risk of prostate and ovarian cancers, autoimmune diseases, and some childhood ailments. Because milk is not necessary for humans after weaning and the nutrients it contains are readily available in foods without animal protein, saturated fat, and cholesterol, vegetarians may have healthier outcomes for chronic disease if they limit or avoid milk and other dairy products. Bones are better served by attending to calcium balance and focusing efforts on increasing fruit and vegetable intakes, limiting animal protein, exercising regularly, getting adequate sunshine or supplemental vitamin D, and getting approximately 500 mg Ca/d from plant sources. Therefore, dairy products should not be recommended in a healthy vegetarian diet.
Traducción:
Aunque la leche de vaca ha sido recomendada ampliamente en los países occidentales como necesaria para el crecimiento y la salud de los huesos, las evidencias recogidas durante los últimos 20 años demuestran que la necesidad de reconsiderar las estrategias para desarrollar y mantener los huesos fuertes. Las tasas de fractura ósea osteoporótica son mayores en los países en los que se consume más lácteos, calcio y proteínas animales. La mayoría de estudios sobre el riesgo de fractura ofrecen pocas evidencias, o ninguna, de que la leche o sus derivados beneficien al hueso. Las evidencias que han ido acumulándose muestran que el consumo de leche o productos lácteos puede contribuir al riesgo de cáncer de próstata o de ovarios, enfermedades autoinmunes y algunas dolencias infantiles. Puesto que la leche no es necesaria para los seres humanos después del destete y que los nutrientes que contiene se encuentran fácilmente disponibles en alimentos sin proteína animal, grasas saturadas y colesterol, los vegetarianos pueden lograr resultados más saludables en cuestión de enfermedades crónicas si limitan o evitan el consumo de leche y otros productos lácteos. Los huesos están mejor cuidados si se presta atención al equilibrio cálcico y los esfuerzos se centran en aumentar la ingesta de frutas y verduras, en limitar la proteína animal, practicar ejercicio con regularidad, tomando la cantidad adecuada de sol (o suplementando con vitamina D) y tomando aproximadamente 500 mg de calcio al día de origen vegetal. Por lo tanto, los productos lácteos no deben ser recomendados en una dieta vegetariana saludable.
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El artículo anterior ha sido citado en el extenso artículo de revisión de la prestigiosa revista PEDIATRICS (Vol. 115 No. 3 March 2005, pp. 736-743 (doi:10.1542/peds.2004-0548)) que reproduzco a continuación:
Cita:
Calcium, Dairy Products, and Bone Health in Children and Young Adults: A Reevaluation of the Evidence
Amy Joy Lanou, PhD*, Susan E. Berkow, PhD, CN{ddagger} and Neal D. Barnard, MD*
* Physicians Committee for Responsible Medicine, Washington, DC
{ddagger} SEB Associates, Alexandria, Virginia
Objective. Numerous nutrition policy statements recommend the consumption of 800 to 1500 mg of calcium largely from dairy products for osteoporosis prevention; however, the findings of epidemiologic and prospective studies have raised questions about the efficacy of the use of dairy products for the promotion of bone health. The objective of this study was to review existing literature on the effects of dairy products and total dietary calcium on bone integrity in children and young adults to assess whether evidence supports (1) current recommended calcium intake levels and (2) the suggestion that dairy products are better for promoting bone integrity than other calcium-containing food sources or supplements.
Methods. A Medline (National Library of Medicine, Bethesda, MD) search was conducted for studies published on the relationship between milk, dairy products, or calcium intake and bone mineralization or fracture risk in children and young adults (1–25 years). This search yielded 58 studies: 22 cross-sectional studies; 13 retrospective studies; 10 longitudinal prospective studies; and 13 randomized, controlled trials.
Results. Eleven of the studies did not control for weight, pubertal status, and exercise and were excluded. Ten studies were randomized, controlled trials of supplemental calcium, 9 of which showed modest positive benefits on bone mineralization in children and adolescents. Of the remaining 37 studies of dairy or unsupplemented dietary calcium intake, 27 studies found no relationship between dairy or dietary calcium intake and measures of bone health. In the remaining 9 reports, the effects on bone health are small and 3 were confounded by vitamin D intake from milk fortified with vitamin D. Therefore, in clinical, longitudinal, retrospective, and cross-sectional studies, neither increased consumption of dairy products, specifically, nor total dietary calcium consumption has shown even a modestly consistent benefit for child or young adult bone health.
Conclusion. Scant evidence supports nutrition guidelines focused specifically on increasing milk or other dairy product intake for promoting child and adolescent bone mineralization.
Traducción de la conclusión (no tengo tiempo para más hoy, sorry).
Conclusión: No hay apenas evidencias que respalden las recomendaciones nutricionales que se centran específicamente en el aumento del consumo de leche o de otros productos lácteos para estimular la mineralización ósea ni en niños ni en adolescentes.
Por otro lado, en el siguiente artículo, se demuestra que un exceso de calcio no mejora la salud ni la densidad del hueso. Es decir que "no sólo de calcio vive el hueso" y que hay muchos más factores implicados (como la proteína animal). Por eso los vegetarianos a pesar de consumir menos calcio tenemos un menor índice de osteoporosis y fácturas. Tener más calcio no es tener mejores huesos, sino "tener más calcio" y probablemente más riesgo de padecer otras enfermedades relacionadas con este exceso.
Cita:
Effects of calcium supplementation on bone density in healthy children: meta-analysis of randomised controlled trials
Tania Winzenberg, musculoskeletal epidemiologist1, Kelly Shaw, specialist medical advisor2, Jayne Fryer, statistics fellow1, Graeme Jones, head, musculoskeletal unit1
1 Menzies Research Institute, Private Bag 23, Hobart, Tas 7001, Australia, 2 Department of Health and Human Services, Hobart, Tas 7000, Australia
Objectives To assess the effectiveness of calcium supplementation for improving bone mineral density in healthy children and to determine if any effect is modified by other factors and persists after supplementation stops.
Design Meta-analysis.
Data sources Electronic bibliographic databases, hand searching of conference proceedings, and contacting authors for unpublished data.
Review methods We included randomised placebo controlled trials of calcium supplementation in healthy children that lasted at least three months and had bone outcomes measured after at least six months of follow-up. Two reviewers independently extracted data and assessed quality. Meta-analyses predominantly used fixed effects models with outcomes given as standardised mean differences.
Results We included 19 studies involving 2859 children. Calcium supplementation had no effect on bone mineral density at the femoral neck or lumbar spine. There was a small effect on total body bone mineral content (standardised mean difference 0.14, 95% confidence interval 0.01 to 0.27) and upper limb bone mineral density (0.14, 0.04 to 0.24). This effect persisted after the end of supplementation only at the upper limb (0.14, 0.01 to 0.28). There was no evidence that sex, baseline calcium intake, pubertal stage, ethnicity, or level of physical activity modified the effect.
Conclusions The small effect of calcium supplementation on bone mineral density in the upper limb is unlikely to reduce the risk of fracture, either in childhood or later life, to a degree of major public health importance.
Traducción de la conclusión:
Conclusiones: No es probable que el bajo efecto de la suplementación de calcio sobre la densidad mineral ósea en las extremidades superiores reduzca el riesgo de fracturas, ni en la infancia ni en edades más avanzadas, hasta un grado como para que tenga una importancia de salud pública primordial.
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Espero que imprimiedo esto, a alguna persona adulta, o madre de niños, o a algún adolescente le sirva de ayuda en algún momento (léase en la consulta de un médico cuyo último artículo leído date del 57).
Si creéis que resulta interesante o que existe poca información sobre esto en el foro, comentadlo para añadir más información, porque en Pubmed hay mucha sobre este tema, y lo más importante en ciencia, muy reciente.
Relacíonan un aumento del riesgo de cáncer de próstata con el consumo de lácteos
Dairy Products Linked to Prostate Cancer
A long-term study suggests an association between consumption of dairy products and the risk of prostate cancer. Researchers tracked more than 20,000 male physicians for 11 years and found a moderate elevation in prostate cancer risk associated with higher intake of five dairy products, including milk, cheese, and ice cream.1
Men who drank more than six glasses of milk per week had lower levels of vitamin D, which has been shown to protect the prostate. Milk-drinking also raises the amount of insulin-like growth factor (IGF-1) in the blood, which is linked to cancer risk.
Consumption of animal foods, protein, and calcium in relation to risk of prostate cancer was studied as part of the European Prospective Investigation into Cancer and Nutrition (EPIC). Researchers found a high intake of dairy protein was associated with an increased risk of prostate cancer. An estimated 35 gram per day increase in consumption of dairy protein was associated with a 32 percent increase in the risk of prostate cancer. Calcium from dairy products was also positively associated with risk, but not calcium from other foods. These results support the hypothesis that a high intake of protein or calcium from dairy products may increase the risk for prostate cancer.2
1. Chan JM, Stampfer MJ, Ma J, et al. Dairy products, calcium, and prostate cancer risk in the Physician's Health Study.
2. Allen NE, Key TJ, Appleby PN. Animal foods, protein, calcium and prostate cancer risk: the European Prospective Investigation into Cancer and Nutrition. Br J Cancer. 2008;98(9):1574-1581.
