¿Viven más años los vegetarianos?

Existen varias razones para hacerse vegetariano o vegano. Motivos medioambientales, éticos, religiosos… Todos ellos altamente respetables. ¿Pero realmente el motivo de mejora de la salud tiene un respaldo sólido? Hace ya años que la idea de que las grasas animales, los huevos y la carne perjudican la salud, y que las dietas vegetarianas son más saludables, han arraigado con fuerza en nuestra consciencia colectiva. Pero a la luz de las evidencias científicas esto no es así.

Las verduras y las frutas son alimentos bastante densos en nutrientes. Sin embargo, las legumbres y los cereales, frecuentemente consumidos por vegetarianos y veganos, no lo son. Esto hace, sobretodo en veganos, que haya determinados nutrientes que sean deficitarios y la dieta desequilibrada. De todos ellos las carencias nutricionales más importantes son las de calcio, hierro, zinc, vitamina B12, A, D y los omega-3 EPA y DHA. Entonces, ¿cómo es posible que los vegetarianos y veganos afirmen que vivan más años? La respuesta, más adelante.

Principales carencias

Vitamina B12. El 68% de los vegetarianos y el 83% de los veganos presentan carencias de esta vitamina frente al 5% de los omnívoros. La carencia de esta vitamina provoca fatiga, anemia, somnolencia, debilidad, pérdida de memoria, síntomas psiquiátricos, etc. En niños, su insuficiencia es especialmente alarmante. Los hijos de padres veganos con déficit de B12, continúan teniéndolo durante años a pesar de añadir una dieta omnívora. Además, los estudios muestran que el déficit de esta vitamina en niños acarrea disminución de la memoria a corto plazo, de la capacidad de resolución de problemas, capacidad de aprendizaje, de la inteligencia fluida y de la habilidad espacial. Parece serio. Y lo es.

Existe una creencia entre los vegetarianos de que pueden obtener suficiente B12 de algas, espirulina, levaduras o soja fermentada. Realmente lo que presentan estos alimentos son cobamidas, que de hecho aumentan la necesidad de esta vitamina.

Calcio. Son los veganos los que presentan mayor prevalencia de carencia de este mineral al no consumir lácteos. Hay verduras ricas en calcio como las espinacas pero los fitatos y oxalatos presentes en ellas hacen que este calcio no pueda ser absorbido por el organismo.

Hierro. Como con el calcio, a pesar de su presencia en determinadas verduras, su disponibilidad está disminuida por la presencia de otros componentes (fitatos, oxalatos, café, té, fibra soluble). La absorción total de hierro está disminuida un 85% en vegetarianos.

DHA y EPA. Estos dos ácidos grasos omega-3 han demostrado su papel profiláctico o terapéutico en situaciones como cáncer, asma, artritis reumatoide, enfermedades cardiovasculares, depresión, problemas autoinmunes, etc.
A pesar que teóricamente es posible la conversión de algunos ácidos grasos vegetales o-3 en DHA y EPA, en el ser humano esta vía es altamente ineficaz. En conclusión, los vegetarianos tienen un 30% menos, y los veganos un 50-60% menos de estos ácidos grasos que los omnívoros.

Vitaminas A y D. Estas vitaminas precisan de la grasa de los alimentos para poder absorberse. Se encuentran en alimentos como mariscos, huevos, vísceras y lácteos. Son necesarias para la función inmune, la fertilidad, la vista y la piel (vit A) y para regular el metabolismo del calcio, la inmunidad, la inflamación y proteger frente a ciertas formas de cáncer (vit D). La vitamina D es un 58% y 74% menor que en omnívoros, en vegetarianos y veganos respectivamente.

20140302-220719.jpg

Existe la idea de que el beta caroteno de las verduras puede convertirse en vitamina A. Sin embargo, esta conversión no es eficaz y son necesarias grandes cantidades de estas verduras para alcanzar concentraciones suficientes.

Entonces, ¿por qué viven más los vegetarianos?

Si bien es cierto que los estudios muestran una esperanza de vida aumentada en vegetarianos y veganos frente a omnívoros, ninguno de estos estudios tiene en cuenta el «sesgo del usuario saludable«. Me explico. Cuando estudiamos causalidad con estudios observacionales, sólo se tienen en cuenta determinadas variables, es este caso la inclusión o no de alimentos animales. Lo que no se tiene en cuenta es que la gran mayoría de los vegetarianos sigue un estilo de vida «saludable», con comportamientos asociados que por su parte también alargan la vida. Comportamientos como el consumo de alcohol, de tabaco, la frecuencia de ejercicio o de pestar más atención a la salud son más frecuentes en personas comprometidas con ello como los vegetarianos. La confluencia de estos factores hace que no pueda atribuirse la mayor esperanza de vida al hecho de no consumir productos animales.

Recientemente se ha publicado un estudio que compara la mortalidad durante 17 años de personas que compraban en tiendas de comida sana (vegetarianos y omnívoros) frente a población que no lo hacía.

Los resultados muestran que los que compraban en tiendas «sanas» vivían más años que la población general, y que dentro de éstos no había diferencias entre vegetarianos y omnívoros.

Así pues, y como conclusión, no parecen existir evidencias científicas a favor de la superioridad de las dietas vegetariana y vegana frente a la omnívora saludable. En contraposición estas dietas pueden llevar a déficits nutricionales que en el caso de los niños puden tener consecuencias importantes. Fuera de motivos éticos, religiosos o medioambientales, la eliminación de los productos animales de la dieta no aporta ningún beneficio aparente a la salud, incluso puede llegar a perjudicarla.

One thought on “¿Viven más años los vegetarianos?

  1. http://www.ncbi.nlm.nih.gov/pubmed/19562864
    https://unilife.curtin.edu.au/local/docs/MFS_Resources_Veg_ADA_PP_VegetarianDiets.pdf
    “It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes”

    NHS
    http://www.nhs.uk/Livewell/Vegetarianhealth/Pages/Vegetarianhealthqanda.aspx
    “As long as they get all the nutrients they need, children can be brought up healthily on a vegetarian or vegan diet.
    A varied and balanced vegetarian or vegan diet can provide enough nutrients for you and your baby during pregnancy.
    A vegetarian diet can be very healthy
    With good planning and an understanding of what makes up a healthy balanced vegetarian and vegan diet, you can get all the nutrients your body needs to be healthy without the need for supplements.
    You don’t need a special diet for exercising if you’re a vegetarian or vegan. The advice for vegetarians who exercise is the same as the advice for non-vegetarians who exercise regularly.
    Most vegetarians have enough protein in their diet for the body to grow and repair itself.”
    http://www.nhs.uk/news/2011/04April/Pages/vegetarian-diets-prevent-heart-problems.aspx
    “Vegetarians ‘have lower heart risk’
    “Veggie diet cuts heart attack risk by a third,” The results come from a small study that looked at how different dietary patterns related to the prevalence of metabolic syndrome. Metabolic syndrome is a cluster of disorders, including raised blood pressure, cholesterol and blood sugar, which increase the risk of cardiovascular disease and diabetes.”

    http://www.ncbi.nlm.nih.gov/pubmed/?term=Dietary+pattern+analysis%3A+a+comparison+between+matched+vegetarian+and+omnivorous+subjects
    Dietary pattern analysis: A comparison between matched vegetarian and omnivorous subjects.
    “Our results indicate a more nutrient dense pattern, closer to the current dietary recommendations for the vegetarians compared to the omnivorous subjects. Both indexing systems were able to discriminate between the vegetarians and the non-vegetarians with higher scores for the vegetarian subjects”

    http://www.ncbi.nlm.nih.gov/pubmed/24899080
    Nutritional profile of Indian vegetarian diets–the Indian Migration Study (IMS).
    “Overall, Indian vegetarian diets were found to be adequate to sustain nutritional demands according to recommended dietary allowances with less fat”

    http://www.ncbi.nlm.nih.gov/pubmed/24910231
    Prevention and management of type 2 diabetes: dietary components and nutritional strategies.
    Lancet.
    With an emphasis on overall diet quality, several dietary patterns such as Mediterranean, low glycaemic index, moderately low carbohydrate, and vegetarian diets can be tailored to personal and cultural food preferences and appropriate calorie needs for weight control and diabetes prevention and management.

    http://www.ncbi.nlm.nih.gov/pubmed/?term=Comparison+of+Nutritional+Quality+of+the+Vegan%2C+Vegetarian%2C+Semi-Vegetarian%2C+Pesco-Vegetarian+and+Omnivorous+Diet
    Comparison of nutritional quality of the vegan, vegetarian, semi-vegetarian, pesco-vegetarian and omnivorousdiet.
    “The vegan diet received the highest index values and the omnivorous the lowest for HEI-2010 and MDS.
    The score for the more prudent diets (vegetarians, semi-vegetarians and pesco-vegetarians) differed as a function of the used indexing system but they were mostly better in terms of nutrient quality than the omnivores.”

    http://www.ncbi.nlm.nih.gov/pubmed/17175567
    IQ in childhood and vegetarianism in adulthood: 1970 British cohort study
    “Higher scores for IQ in childhood are associated with an increased likelihood of being a vegetarian as an adult.”

    http://www.ncbi.nlm.nih.gov/pubmed/21771850
    Diet and risk of diverticular disease in Oxford cohort of European Prospective Investigation into Cancer and Nutrition (EPIC): prospective study of British vegetarians and non-vegetarians.
    “Consuming a vegetarian diet and a high intake of dietary fibre were both associated with a lower risk of admission to hospital or death from diverticular disease.”

    http://care.diabetesjournals.org/content/early/2011/03/13/dc10-1221.abstract?sid=a28ee081-f677-46e7-9dd6-49ed5a9e7a57
    Vegetarian Dietary Patterns Are Associated With a Lower Risk of Metabolic Syndrome
    The Adventist Health Study 2
    “Vegetarian Dietary Patterns Are Associated With a Lower Risk of Metabolic Syndrome
    The Adventist Health Study
    A vegetarian dietary pattern is associated with a more favorable profile of MRFs and a lower risk of MetS. The relationship persists after adjusting for lifestyle and demographic factors.”

    http://www.ncbi.nlm.nih.gov/pubmed/23836264
    Vegetarian dietary patterns and mortality in Adventist Health Study 2
    “Vegetarian diets are associated with lower all-cause mortality and with some reductions in cause-specific mortality. Results appeared to be more robust in males.”

    http://www.ncbi.nlm.nih.gov/pubmed/24566947
    Vegetarian diets and blood pressure: a meta-analysis
    “Consumption of vegetarian diets is associated with lower BP. Such diets could be a useful nonpharmacologic means for reducing BP.”

    http://www.ncbi.nlm.nih.gov/pubmed/?term=Vegetarian+nutrition%3A+past%2C+present%2C+future
    Vegetarian nutrition: past, present, future
    “The former prejudices that vegetarianism leads to malnutrition were replaced by scientific evidence showing that vegetarian nutrition reduces the risk of most contemporary diseases.”

    http://www.ncbi.nlm.nih.gov/pubmed/25192735
    Type of vegetarian diet, obesity and diabetes in adult Indian population
    “In this large, nationally representative sample of Indian adults, lacto-, lacto-ovo and semi-vegetarian diets were associated with a lower likelihood of diabetes. These findings may assist in the development of interventions to address the growing burden of overweight/obesity and diabetes in Indian population.”

    http://www.ncbi.nlm.nih.gov/pubmed/16399477
    Vegetarian eating for children and adolescents
    “Well-planned vegetarian diets can satisfy the nutritional needs and promote normal growth of infants and children. Research has highlighted nutritional advantages to vegetarian diets and has indicated that this style of eating can lead to lifelong healthy eating habits when adopted at a young age.”

    http://www.ncbi.nlm.nih.gov/pubmed/22333737
    Restriction of meat, fish, and poultry in omnivores improves mood: a pilot randomized controlled trial.
    “Restricting meat, fish, and poultry improved some domains of short-term mood state in modern omnivores. To our knowledge, this is the first trial to examine the impact of restricting meat, fish, and poultry on mood state in omnivores.”

    http://www.ncbi.nlm.nih.gov/pubmed/23364007
    Risk of hospitalization or death from ischemic heart disease among British vegetarians and nonvegetarians:results from the EPIC-Oxford cohort study.
    “Consuming a vegetarian diet was associated with lower IHD risk, a finding that is probably mediated by differences in non-HDL cholesterol, and systolic blood pressure.”

    http://www.ncbi.nlm.nih.gov/pubmed/?term=Cancer+in+British+vegetarians%3A+updated+analyses+of+4998+incident+cancers+in+a+cohort+of+32%2C491+meat+eaters%2C+8612+fish+eaters%2C+18%2C298+vegetarians%2C+and+2246
    Cancer in British vegetarians: updated analyses of 4998 incident cancers in a cohort of 32,491 meat eaters, 8612fish eaters, 18,298 vegetarians, and 2246 vegans.
    “In this British population, the risk of some cancers is lower in fish eaters and vegetarians than in meat eaters.”

    http://www.ncbi.nlm.nih.gov/pubmed/?term=A+provegetarian+food+pattern+and+reduction+in+total+mortality+in+the+Prevenci%C3%B3n+con+Dieta+Mediterr%C3%A1nea+(PREDIMED)
    A provegetarian food pattern and reduction in total mortality in the Prevención con Dieta Mediterránea (PREDIMED) study.
    “Among omnivorous subjects at high cardiovascular risk, better conformity with an FP that emphasized plant-derived foods was associated with a reduced risk of all-cause mortality. This trial was registered at http://www.controlled-trials.com as ISRCTN35739639.”

    http://www.ncbi.nlm.nih.gov/pubmed/?term=Gut+microbiota+and+cardiometabolic+outcomes%3A+influence+of+dietary+patterns+and+their+associated+components
    Gut microbiota and cardiometabolic outcomes: influence of dietary patterns and their associated components.
    “Studies in individuals who consume vegetarian and vegan diets have shown a reduced risk of cardiovascular events and incidence of diabetes.”

    http://ajl.sagepub.com/content/6/3/250.abstract
    Health Implications of a Vegetarian Diet
    A Review
    “There is now a significant amount of research that demonstrates the health benefits of vegetarian and plant-based diets, which have been associated with a reduced risk of obesity, diabetes, heart disease, and some types of cancer as well as increased longevity.”

    http://www.ncbi.nlm.nih.gov/pubmed/21139125
    Nutrition concerns and health effects of vegetarian diets
    “Vegetarians typically have lower body mass index, serum total and low-density lipoprotein cholesterol levels, and blood pressure; reduced rates of death from ischemic heart disease; and decreased incidence of hypertension, stroke, type 2 diabetes, and certain cancers than do nonvegetarians.”

    http://ajl.sagepub.com/content/5/2/135.abstract
    Vegetarian Diets and Diabetes
    “In observational studies, a vegetarian or vegan diet is associated with reduced risk of development of type 2 diabetes and lower risk of complications in those with existing diabetes.”

    http://www.ncbi.nlm.nih.gov/pubmed/24964573
    Health benefits and risk associated with adopting a vegetarian diet.
    “It has been shown that properly applied vegetarian diet is the most effective way of reducing body mass (expressed as BMI), improving the plasma lipid profile and in decreasing the incidence of high arterial blood pressure, cardiovascular disease, stroke, metabolic syndrome and arteriosclerosis. In addition, improved insulin sensitivity together with lower rates of diabetes and cancer has been observed.”

    http://www.ncbi.nlm.nih.gov/pubmed/20222825
    Vegetarian diets and public health: biomarker and redox connections.

    In this review, evidence for health benefits of vegetarian diets is presented from different perspectives: epidemiological, biomarker, evolutionary, and public health, as well as antioxidant. Sufficient scientific evidence exists for public health policy to promote a plant-rich diet for health promotion.

    http://www.ncbi.nlm.nih.gov/pubmed/24716274#
    Vegetarians reduce risk of heart disease by a third.

    http://www.ncbi.nlm.nih.gov/pubmed/25084991
    Key elements of plant-based diets associated with reduced risk of metabolic syndrome.
    “Vegetarian and vegan diets have demonstrated effectiveness in improving body weight, glycemic control, and cardiovascular risk factors, as compared with conventional therapeutic approaches, and are potentially useful in the prevention of metabolic syndrome.”

    http://www.ncbi.nlm.nih.gov/pubmed/21614817
    [Nutritional status, lifestyle and cardiovascular risk in lacto-ovo vegetarians and omnivore].
    “The results of the present study suggest that, although a lacto-ovovegetarian diet is considered healthier due to the lower consumption of total fat, saturated fatty acids and cholesterol, there are no significant differences in nutritional status or anthropometric indicators of cardiovascular risk when lifestyle and total calorie intake are similar.”

    http://www.ncbi.nlm.nih.gov/pubmed/17397638
    [Vegetarian diets; effect on health].
    Some studies have shown beneficial results in obesity, cancer, Parkinson disease, hypertension, type 2 diabetes mellitus and urinary stones, compared with the omnivorous. The possible theoretical benefits in some diseases has been seen in the medical practice (diabetes mellitus, obesity, cardiovascular risk). However more studies are needed in the case of Parkinson’s disease and rheumatoid arthritis.

    Physicians Committee for responsible medicine
    http://www.pcrm.org/search/?cid=262
    http://www.pcrm.org/health/diets/vegdiets/la-comida-vegetariana-poderosa-para-la-salud
    A vegetarian diet, based on nutritious whole foods, is a healthful choice for any pregnant woman
    La dieta vegetariana previene el cáncer. Muchos estudios epidemiológos y clínicos muestran que los vegetarianos tienen un riesgo cincuenta porciento menor de morir de cáncer que los no-vegetarianos.
    Se ha demostrado que los ovo-lacto-vegetarianos son más saludables que los que comen carne, y los vegans lo son más que los ovo-lacto-vegetarianos.
    La dieta vegetariana previene también las enfermedades cardíacas. La carne es la fuente principal de grasa saturada, y casi la única fuente principal de grasa saturada, y casi la unica fuente de colesterol en la dieta. Los vegetarianos evitan estos productos de alto riesgo.

    http://nutritionfacts.org/video/vegetarians-versus-healthy-omnivores/
    Vegetarians Versus Healthy Omnivores.

Los comentarios están cerrados.