Descubren el mecanismo por el cuál la dieta mediterránea alarga la vida (parte 2)

La dieta mediterránea es bien conocida por sus grandes beneficios para la salud, con reducción de la mortalidad y reducción del riesgo de padecer enfermedades crónicas, entre ellas las enfermedades cardiovasculares. Hasta ahora no se conocía su mecanismo, pero la semana pasada, el 3 de diciembre 2014 se hizo pública una investigación que, sin duda, revolucionará a los conocimientos de nutrición:

El BMJ-British Medical Journal publicó el estudio que relaciona la longitud de los telómeros de los cromosomas con la dieta mediterránea, evidenciando que la fidelidad a esta dieta preserva los telómeros (estructuras protectoras de los cromosomas) y prolonga así la vida.

¿Qué son los telómeros?

Nuestro material genético, el ADN, está empaquetado en los cromosomas de nuestras células (en la imagen de color azul). Para expresarlo de manera simple, los telómeros son las puntas finales (en la imagen de color rojo) que protegen los extremos de los cromosomas. Cuando aún estudiaba ya se hablaba de los telómeros, pero aún no habían demostrado su importancia en relación a la logevidad.

Descubrimiento de la protección de los cromosomas contra la degradación

En el año 2009 los investigadores Elisabeth H. Blackburn, Carol W. Greider y Jack W. Szostak recibieron el Premio Nobel de Fisiología y Medicina por su estudio «How chromosomes are protected by telomeres and the enzyme telomerase» («Cómo los cromosomas están protegidas por telómeros y el enzima telomerasa»).

Demostraron que la disminución de longitud de los telómeros lleva al envejecimiento y a la muerte de la célula y que una mayor longitud de los telómeros está relacionada con una mayor longevidad.

El enzima telomerasa «teje» las puntas finales del cromosoma, el telómero. Si la actividad de la telomerasa es baja, los telómeros disminuyen y el cromosoma queda desprotegido.

Si la actividad de la telomerasa es alta se mantiene la longitud de los telómeros y junto con las proteínas forman una especie de funda protectora alrededor de los extremos de los cromosomas, evitando que se dañen y, con ello, la célula tarda más en envejecer.

La investigación más novedosa: La dieta mediterránea es capaz de preservar los telómeros y alargar la vida

Los investigadores que obtuvieron el Premio Nobel de Medicina en el año 2009, aún no sabían cómo impedir el acortamiento de los telómeros. Ahora, 5 años más tarde, se descubre la relación entre la dieta mediterránea, telómeros más largos y mayor esperanza de vida.

La dieta mediterránea se caracteriza por un alto consumo de frutas, verduras y legumbres, como guisantes, habas y lentejas, cereales sin refinar y frutos secos, un alto consumo de aceite de oliva, pero pocas grasas saturadas, una ingesta de pescado moderadamente alta, pero pocos productos lácteos, poca carne y aves de corral. La dieta se acompaña con un consumo moderado de vino en las comidas.

Las frutas, verduras y frutos secos tienen efectos antioxidantes y antiinflamatorios, por lo que un equipo de investigadores americanos dirigido por Immaculata De Vivo, profesora del Brigham and Women’s Hospital y de Harvard Medical School, quería examinar si la fidelidad a la dieta mediterránea estaba asociada con una longitud mayor de los telómeros.

En las personas sanas, los telómeros se acortan progresivamente a lo largo de la vida. Desde la infancia a la edad adulta se acortan a la mitad y a los ancianos solamente les queda un cuarto de la longitud original. Los telómeros cortos se relacionan con una menor esperanza de vida y un mayor riesgo de enfermedades crónicas relacionadas con la edad.

El estilo de vida, la obesidad, el tabaquismo, el consumo de bebidas azucaradas, el estrés oxidativo y la inflamación han sido relacionados con telómeros más cortos de lo que correspondería a una persona con una edad determinada en comparación con otras personas de la misma edad.

El estudio

Se analizaron los datos de 4.676 mujeres sanas de mediana edad en un estudio de seguimiento de la salud de más de 120.000 enfermeras estadounidenses que se había iniciado en el año 1976. Los participantes completaron cuestionarios alimentarios detallados y se les sometía a un examen de sangre para medir la longitud de los telómeros. Se puntuaba la dieta de cada participante en un intervalo de 0 a 9 puntos, teniendo la puntuación más alta una dieta parecida a la dieta mediterránea.

Los resultados del estudio

Después de ajustar otros factores potencialmente influyentes, los resultados muestran que la dieta mediterránea está asociada con telómeros más largos. Por cada punto menos en la puntuación de la dieta se observa un envejecimiento de los telómeros de 1,5 años. Sin embargo, ninguno de los componentes individuales de la dieta se asoció con la longitud de los telómeros, lo que subraya la importancia de los hábitos alimentarios en su conjunto.

Los investigadores del estudio manifiestan: «Este es el mayor estudio poblacional que aborda la asociación entre la dieta mediterránea y la longitud de los telómeros en mujeres sanas de mediana edad. Nuestros resultados apoyan aún más los beneficios de la dieta mediterránea para la promoción de la salud y la longevidad.»

Opiniones de la comunidad científica

El profesor Peter Nilsson de la Universidad de Lund, Suecia, opina que la dieta mediterránea es la piedra angular de asesoramiento dietético en la prevención de enfermedades cardiovasculares, y el hecho de que también se vincula con un biomarcador del envejecimiento más lento es tranquilizador.

A continuación añadimos el link a los opiniones de otros expertos (fuente Australian Science Media Center):

Rosemary Stanton is a nutritionist and a Visiting Fellow at the School of Medical Sciences at the University of New South Wales

“This latest study adds to the long line of evidence showing that adherence to the Mediterranean diet is linked to lower all-cause mortality, reduced incidence of major cardiovascular diseases and other chronic diseases, and greater health and well-being in people who survive to older ages.

It also shows the futility (when looking at associations between diet and health) of looking at individual nutrients and the wisdom of assessing the whole dietary pattern.

The Mediterranean diet pattern is characterised by a high intake of fruits, vegetables, grains [not highly refined], fish, nuts, legumes and olive oil, moderate alcohol consumption (with meals) and a low intake of highly processed foods, red meats and foods high in saturated fats. It is not the only dietary pattern associated with health and longevity, but it is the most studied. This particular study had a large number of participants and corrected the data for confounding factors.

It adds greatly to our knowledge and supports the messages of Australia’s Dietary Guidelines.”

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Professor Vlado Perkovic is the Executive Director of The George Institute for Global Health and a Professor of Medicine at The University of Sydney

“People eating a Mediterranean diet have been known to have reduced rates of vascular diseases like heart attack, and a number of studies have suggested it may be a method of preventing cardiovascular events and other poor outcomes. The mechanism by which any benefit might occur is unknown. The present paper shows a relationship between adherence to the Mediterranean diet and telomere length, a marker that has been linked to longevity. It is proposed that benefits of the Mediterranean diet on outcomes might occur through this mechanism.

It is a large and carefully conducted study that puts forward an interesting hypothesis. There are a number of issues: the study identifies an association, which does not prove causation and this needs to be prospectively assessed to be more robust. For example, those who followed the diet were also less likely to smoke and more likely to be physically active which may confound the results.

In addition, the effects of the Mediterranean diet on mortality (and even cardiovascular outcomes) has not yet been well proven, so the importance of this mechanism remains somewhat uncertain. Finally, it is not clear which aspects of the diet might be important.

Having said that, the results highlight the importance of diet in driving length and quality of life, and suggest that following a sensible healthy diet, many aspects of which are part of what is described as a Mediterranean diet, is likely to improve health for all Australians.”

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Associate Professor Margaret Allman-Farinelli is an Associate Professor of Nutrition and Dietetics in the School of Molecular Bioscience at the University of Sydney

“It is great to see that what diet and health population surveys have shown for some time is now coupled with biological evidence. The typical Mediterranean diet, characterised by generous intakes of fruit, vegetables, nuts, legumes, olive oil and fish has been associated with longevity. What this study adds is the measurement of telomere length. Telomeres are the end caps that protect the integrity of our chromosomes that contain our genetic information. The Noble prize winner, Elizabeth Blackburn, showed that shortening of telomeres leads to aging and hasten death. It is very exciting to see that something as simple as making some dietary changes can lengthen lifespan as found in the US Nurses’ Health study. It is perhaps unfortunate that the typical Australian diet is low in fruit and vegetables and legumes with more saturated than unsaturated fat, as found in the olive oil.”

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Professor Emeritus Brian Morris is from the School of Medical Sciences and Bosch Institute at the University of Sydney

“As people age their telomeres shorten. The discovery of telomeres and the enzyme that protects telomeres from shortening (telomerase) led to the Award of the Nobel Prize to Australian Elizabeth Blackburn in 2009. When these repeated sequences reach the critical ‘Hayflick limit’ the cell dies. It is loss of telomeres in stem cells that is ultimately the cause of death of anyone who avoids all other age-related causes of death.

This new study based on over 30,000 women in the Nurses’ Health study found that a traditional Mediterranean diet high in vegetables, olive oil and low in meat and processed foods, reduces telomere shortening and ageing. The protective effect was similar to being a nonsmoker vs. smoker or to an active vs. a sedentary person. The women on the diet lived 4.5 years longer. The Mediterranean diet reduces inflammation, which is a major cause of telomere shortening. Because it is low in saturated fat, refined carbohydrates and animal protein it reduces the risk of common diseases of ageing, making it good for individuals, health budgets and the environment, as shown is a recent study in Nature.”

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Professor Mark Wahlqvist is Emeritus Professor of Medicine at Monash University and Director, Fuli Institute, Zhejiang University, China

“As a co-author of the original paper published in the British Medical Journal in 1995 ( BMJ 311: 1457-1460) that showed that the Greek (Cretan) form of the Mediterranean diet predicted longer life expectancy better than any one nutrient or food, I welcome further evidence, now overwhelming, that dietary diversity is a critical approach to long and healthy lives. It matters not what the mechanism is, but it may well be that telomere length is part of the story. Moreover, it is not that the diet is Mediterranean, but that it is biodiverse, a characteristic of successful eating patterns elsewhere as well, including North-East Asia and Australia. Australia has benefited from cultural, and with it food, diversity, but this is now threatened by climate change and the inevitable consequences for our food system. This is when it is now most important.”

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Dr Alan Barclay is an accredited practicing dietitian and nutritionist, chief scientific officer for the Glycemic Index Foundation Ltd

“This is an interesting study investigating cross-sectional associations between Mediterranean diet score and telomere length. It’s strength is the number of people in the analysis and the quality of the food frequency questionnaire used to determine the Mediterranean diet score. Cross-sectional analyses do not prove causality but the results are interesting and consistent with the observation that people consuming a traditional Mediterranean diet have a longer lifespan than average. We must not forget that other eating patterns – like the Okinawan diet – are also associated with longevity. Therefore there is more than one healthy pattern of eating and we don’t all have to follow the Mediterranean diet to live a long and healthy life – taking into account personal and cultural food preferences is important as these affect social interactions and quality of life.”

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Professor Linda Tapsell is the Discipline Leader of Nutrition and Dietetics in the School of Medicine at the University of Wollongong

“The Mediterranean Diet was determined by applying a score for choosing foods that characterise the diet – mostly vegetables, fruits, nuts, legumes (beans, lentils) and grains (mainly wholegrain) balanced with moderate amounts of fish, dairy foods and lean meat while using olive oil as a culinary adjunct. It’s not so much a ‘diet’ as a deliberate preference for a particular combination of foods in reasonable amounts. These align with the current Australian Dietary Guidelines. It’s great to see further scientific evidence supporting this food choice pattern. The foods can be combined in many ways to produce all sorts of ‘diets’ – it’s the principles of ‘the Mediterranean Diet’  that count.  The research confirms it’s not just common sense. We are all singing from the same page!”

Referencias

1. M. Crous-Bou, T. T. Fung, J. Prescott, B. Julin, M. Du, Q. Sun, K. M. Rexrode, F. B. Hu, I. De Vivo. Mediterranean diet and telomere length in Nurses’ Health Study: population based cohort study. BMJ, 2014; 349 (dec02 5): g6674 DOI:10.1136/bmj.g6674
2. P. M. Nilsson. Mediterranean diet and telomere length. BMJ, 2014; 349 (dec02 8): g6843 DOI: 10.1136/bmj.g6843