Existem provas irrefutáveis de que não podemos ser uma espécie vegetariana. Em 1972 a publicação de duas investigações independentes confirmaram isso. [1] [2] Essas investigações diziam respeito a gorduras.
Cerca de metade do nosso cérebro e sistema nervoso é composto, de cadeias de ácidos gordos longos e complicadas.
Estes são também usados nas paredes dos nossos vasos sanguíneos. Sem eles, não nos poderíamos desenvolver normalmente. Esses ácidos gordos não existem em plantas, que contêm apenas ácidos gordos numa forma mais simples. É aqui que os herbívoros comedores de plantas entram.
Ao longo do ano, os herbívoros convertem os ácidos gordos simples encontrados nas gramíneas e sementes, em formas intermediária, mais complicadas. Ao comermos os herbívoros podemos converter as suas reservas desses ácidos gordos para aqueles que necessitamos.
Há cerca de 2,5 milhões de anos atrás, os alimentos de origem animal passaram a ocupar um lugar com cada vez mais destaque nos menus dos nossos antepassados. Molares mais pequenos, músculos faciais menos robustos e alterações na forma dos incisivos a partir dessa época, tudo sugere uma maior ênfase em alimentos como a carne, que exigem menos moagem e mais corte.
Uma crescente proporção de carne na dieta, teria obviamente fornecido mais proteína animal um factor talvez relacionado ao aumento na estatura que parece ter acompanhado a transição do australopitecos através do Homo habilis para o Homo erectus. [3] Mas a maior disponibilidade de gordura animal foi, provavelmente, uma alteração ainda mais importante na dieta.
As ferramentas de pedra permitiram que os primeiros seres humanos pudessem partir ossos e permitiu-lhes o acesso às gorduras do cérebro e da medula a partir de uma ampla gama de animais obtidos pela recolecção ou pela caça. Esta e outras gorduras da carcaça, provavelmente tão valorizada pelos primeiros hominídeos como o são agora pelos modernos humanos caçadores-recolectores. [4]
Não só a presença de mais gordura animal na dieta média proporcionou consideravelmente mais energia, como foi também uma fonte facilmente acessível, de ácidos gordos polinsaturados de cadeia longa, incluindo o ácido arachidónico ômega-6 (AA), ácido docosatetraenóico ómega-3 (DTA) e docosahexaenóico ómega-3 (DHA). Estes 3 ácidos gordos juntos, representam mais de 90% dos ácidos gordos encontrados no tecido cerebral de todas as espécies de mamíferos [5].
O nosso cérebro é consideravelmente maior do que o de qualquer macaco. Verificando os registos desde os fósseis de hominídeos até ao homem moderno, vemos um aumento notável no tamanho do cérebro desde 375-550 ml no tempo do Australopithecus, para os 500-800 ml do Homo habilis, 775-1,225 ml do Homo erectus, e 1350 cc nos humanos modernos (Homo sapiens).
Embora ainda haja alguma especulação sobre porquê disso ter acontecido, em termos fisiológicos, esse aumento no tamanho do cérebro não poderia ter acontecido sem um aumento da ingestão de ácidos gordos de cadeia longa pré-formados, que são um componente essencial na formação do tecido cerebral. [6]
Ou seja, nunca teria ocorrido se os nossos antepassados não tivessem comido carne – com a sua gordura. O leite materno contém ácidos gordos necessários para o desenvolvimento de um cérebro grande, o leite de vaca não. Não é por acaso que, em termos relativos, o nosso cérebro tem cerca de 50 vezes o tamanho do de uma vaca.
De onde vem a energia para o nosso cérebro?
Entre 20% e 25% de toda a energia que usamos, é utilizada pelo nosso cérebro. Isto está em contraste com os grandes macacos cujos cérebros utilizam apenas cerca de 8%. Isso faz com que nossos cérebros sejam muito caros em termos energéticos. Isso significa que o nosso uso de energia em relação ao nosso tamanho corporal deve ser consideravelmente maior do que a de outros animais.
Mas não é. Isto representa uma espécie de enigma: onde é que nós, humanos, obtemos a energia extra para gastarmos nos nossos cérebros grandes? Os investigadores WR Leonard e ML Rodrigues concluiram que a evolução do tamanho do cérebro implica mudanças na qualidade da dieta durante a evolução dos hominídeos.
Eles afirmam que:
Foi provavelmente necessária uma mudança para uma dieta mais calórica, a fim de aumentar substancialmente a quantidade de energia metabólica a ser utilizado pelo cérebro hominídeo. Assim, embora os factores nutricionais não sejam suficientes para explicar a evolução do nosso cérebro grande, parece claro que seriam necessárias algumas mudanças na dieta para que pudessem ocorrer as evoluções importantes do cérebro . [7]
Isto confirma o trabalho de Crawfords. Enquanto o nosso cérebro maior se tornou necessário por nos termos reunido em comunidades mais unidas e com mais pessoas e, portanto, recordar-se de mais indivíduos tornou-se uma necessidade. O que tornou isto possível, foi uma dieta de qualidade suficiente para permitir a expansão do cérebro.
Mas há um outro aspecto. Dois cientistas, Aiello e Wheeler, mediram o tamanho do cérebro e outros órgãos corporais contra o tamanho do órgão em relação às previsões do tamanho corporal. [8] O que eles descobriram foi que o tamanho do cérebro, maior do que o esperado, foi compensada por um tamanho do sistema digestivo menoe do que o esperado.
Medindo os outros órgãos do corpo que gastam energia: o coração, rins, fígado e trato gastrointestinal, já que são estes que despendem mais energia a seguir ao cérebro, e comparando um primata não humano de 65 kg com o tamanho dos órgãos do tamanho médio de um homem de 65 kg, encontraram grandes diferenças entre o tamanho esperado e real do cérebro humano, e intestinos: “os órgãos esplâncnicos [abdominais/intestinais] pesavam aproximadamente 900g menos que o esperado”. Quase toda esta perda se deveu ao facto do nosso tracto digestivo representar apenas cerca de 60% do esperado para um primata de tamanho similar.
Temos um sistema digestivo carnívoro
O nosso sistema intestino não só é menor do que o previsto em comparação com outros primatas, como também está configurado de forma muito diferente. O nosso intestino delgado é o órgão principal para digerir a comida e extrair os seus nutrientes para a absorção pelos nossos corpos. Não é pois surpresa, que representa mais do que 50% do volume total dos nossos intestinos.
O nosso cólon (intestino grosso) desempenha umapequena parte no processo de digestão: é usado principalmente para extrair e, desta forma, conservar a água. Por esse motivo, ele representa apenas cerca de 20% do volume dos nossos intestinos. Em contrapartida, os rácios noutros primatas são exactamente o oposto: o intestino delgado dos orangotangos e chimpanzés, os quais desempenham um papel menor na digestão, representam cerca de 25% do volume do intestino, e os seus dois pontos, onde as bactérias são usadas para fermentar a fibra das plantas e onde a maior parte da digestão ocorre, representa cerca de 53% do volume [9].
Esta não é a única medida que interessa. Até agora eu só comparei o nosso sistema digestivo ao dos nossos primos primatas que ingerem principalmente alimentos vegetais. Se nós também o compararmos com os dos grandes carnívoros, iremos verificar que nosso intestino é realmente muito parecido com o deles. As comparações são feitas com relação ao peso corporal, o peso está intimamente relacionado com as necessidades de energia metabólica de um animal.
Essa relação, conhecida como Lei de Kleiber, expressa a relação entre massa corporal (peso) e os requisitos metabólicos de energia do corpo. O tamanho de qualquer órgão, que está directamente relacionado com o volume de gasto metabólico, deve respeitar o a lei de Kleiber. Se medirmos o tamanho destes e os mesmo estiverem em conformidade com a lei de Kleiber, o quociente de cada parte gastrointestinal (GI) deve ser 1,00. Um GI superior a 1,00 significa que o órgão é maior que o esperado, e um GI inferior a 1,00 indica um tamanho menor que o esperado.
No intestino, é a área da superfície de várias partes do trato digestivo, que determina a sua capacidade relativa de absorção. Um teste de grandes áreas do trato digestivo humano foi publicado em 1985 com os seguintes resultados: [10]
| Quociente do estômago | 0,31 |
| Quociente do intestino delgado | 0,76 |
| Quociente do ceco | 0,16 |
| Quociente do cólon | 0,58 |
Como esses valores são consideravelmente menores do que 1,00, isso só pode significar uma coisa: para que a absorção de energia e de nutrientes sejam suficientes para o corpo poder funcionar correctamente, os alimentos devem ser muito densos em energia e nutrientes. A gordura da carne é o único alimento de classe universal que se enquadra nesta categoria, e assim sendo, não pode haver dúvida de que os seres humanos estão incluídos na classe dos carnívoros.
Quociente do cérebro
O nosso intestino não é a única parte do nosso corpo a ser analisada desta forma. É o tamanho do nosso cérebro e a inteligência elevada que faz com que nós, seres humanos, sejamos únicos. Em relação ao nosso tamanho corporal, os nossos cérebros são realmente enormes. Se medirmos o nosso quociente do cérebro da mesma forma que fizemos para os intestinos, poderemos ter uma ideia do quão grande realmente é.
Para medir a chamada encefalização, foram desenvolvidos modelos estatísticos que comparam o tamanho do cérebro com o tamanho do corpo numa ampla gama de espécies. Isto permitiu uma estimativa precisa do tamanho do cérebro de uma dada espécie com base na sua massa corporal.
Isto é importante porque permite o estudo quantitativo e a comparação do tamanho do cérebro entre as diferentes espécies, ajustando automaticamente para o tamanho corporal. Por exemplo, os elefantes, que se alimentam de plantas, e as baleias, sejam elas herbívoras ou carnívoras, têm cérebros maiores que o ser humano – mas eles também têm um corpo muito maior.
Neste exercício, foi observado que o tamanho do cérebro destes animais também segue a Lei de Kleiber.
Quando este teste foi realizado em humanos, ele colocou o homem mesmo no topo da escala dos primatas. O nosso quociente de encefalização foi um incrível 28,8.
Com um cérebro tão fora de proporção em relação ao resto do nosso corpo, não é surpreendente que ele usa uma proporção tão grande da nossa energia total. Como o tamanho do cérebro e o uso de energia é tão elevado, e o tamanho dos nossos intestinos tão pequeno, a quantidade de energia disponível para o cérebro é dependente não só sobre a forma como o orçamento da disponibilidade energético total é repartida entre o cérebro e outros órgãos e sistemas que utilizam energia de forma intensiva, mas também da capacidade dos nossos intestinos extraírem energia suficiente a partir dos nossos alimentos. Isso também confirma que, o tipo de dieta que devemos seguir deve conter ter uma elevada densidade de nutrientes, tais como os encontrados em alimentos como a carne e gordura.
Os nossos cérebros estão a encolher
Com um intestino tão pequeno com o qual absorver todos os nutrientes e energia que o nosso corpo necessita, uma dieta moderna, baixas em calorias, com baixo teor de gordura, rica em fibras, baseada em vegetais, é manifestamente insuficiente como fonte de energia para o nosso sistema sedento de energia poder funcionar com a máxima eficiência. E já começamos a observar sinais dessa.
Desde o advento da agricultura, tem havido uma tendência preocupante, a de que o nosso cérebro diminuiu de tamanho. Um estudo recentemente actualizado e rigoroso sobre as mudanças no tamanho do cérebro humano, verificou que o tamanho do cérebro dos nossos antepassados atingiu o seu auge com os primeiros seres humanos anatomicamente modernos de há cerca de 90.000 anos atrás.
Que depois se manteve constante por mais 60.000 anos. [11] Ao longo dos próximos 20 mil anos, houve uma ligeira diminuição no tamanho do cérebro de cerca de 3%. Desde o advento da agricultura, há aproximadamente 10.000 anos atrás, no entanto, esse declínio acelerou significativamente, de modo que agora os nossos cérebros são cerca de 8% menores.
Isso sugere algum tipo de deficiência histórica recente de alguns aspectos da nutrição humana em geral. A mudança mais óbvia e de grande alcance na dieta durante os últimos 10.000 anos, é claro, a enorme queda no consumo de alimentos ricos em energia, e ricos em gordura de origem animal que representavam, provavelmente, mais de 90% da dieta, para um consumo de apenas 10% nos dias de hoje, juntamente com um grande aumento no consumo de cereais, menos densos em energia [12] Este padrão ainda persiste, e ainda é defendido nos dias de hoje:. ele é a base da chamada dieta “saudável”.
A vitamina B-12
Se é necessário mais provas de que somos uma espécie carnívora, existe um outro nutriente essencial que não é encontrado em nenhum alimento vegetal. Esse nutriente é a vitamina B-12.
A vitamina B-12 é única entre as vitaminas, já que embora seja universalmente encontrada em alimentos de origem animal, onde é obtida, em última análise, a partir de bactérias, não existe vitamina B-12 activa em nada que cresça a partir do chão. Só se encontram vestígios fortuitos de vitamina B-12 em plantas que são contaminadas por certas bactérias do solo. E mesmo isso é perdido, já as plantas são cuidadosamente lavadas antes de as comermos.
As bactérias presentes no cólon humano produzem quantidades enormes de vitamina B-12. Infelizmente, isso é inútil, pois não é absorvida através da parede do cólon. Dra. Sheila Callender conta como trata veganos com deficiência severa de vitamina B-12, produzindo extractos a partir das suas fezes, com os quais depois os alimenta, produzindo assim uma cura. [13] Uma seita vegana iraniana, involuntariamente, também faz uso deste facto.
Os investigadores não conseguiam entender como os membros desta seita se mantinham saudáveis, até que as investigações mostraram que eles produziam os seus produtos hortícolas no esterco humano. – E depois comiam os vegetais, sem serem demasiado exigentes com a sua limpeza [14].
Para permitir a sobrevivência dos veganos, na Grã-Bretanha, a vitamina B-12 é acrescentada artificialmente aos cereais de pequeno-almoço e podem ser comprados em forma de suplemento. Isto dificilmente poderia ser considerado uma forma natural de obter alimentos, e, em muitos casos, é auto-destrutivo. Ao contrário da maioria de outras vitaminas, a vitamina B-12 ocorre como uma série de análogos, muito poucos dos quais são activos para os seres humanos.
Ao recolher fezes humanas para análise, o Dr. Victor Herbert constatou que de cada 100 microgramas de vitamina B-12 extraiu, apenas a 5 microgramas eram análogos activos para os seres humanos. [15] Assim, até mesmo na mais prodigiosa fonte de vitamina , 95% era composto de análogos que eram inúteis.
Vários produtos fermentados como tempeh, um produto derivado da soja e spirulinas, usados por vegetarianos estritos, como fonte de vitamina B-12, ou não contêm quantidades significativas de vitamina ou contêm análogos da vitamina, que não são activos para os seres humanos.[ 16]
Mais da metade dos adultos de uma comunidade macrobiótica testados na Nova Inglaterra tinham baixas concentrações de vitamina B-12. As crianças eram de pequena estatura e com um peso baixo. A comunidade contava com as algas para a obtenção dessa vitamina.
Esta confiança nas fontes vegetais dá uma falsa sensação de segurança e pode na verdade exacerbar os sintomas da deficiência B-12 com ainda maior rapidez.
A quantidade de vitamina B-12 que nós precisamos é pequena: cerca de 1 micrograma por dia. Uma ingestão superior a isso irá aumentar uma reserva corporal que temos. Quando uma pessoa se torna um vegana, essas reservas esgotam-se -, mas apenas gradualmente. Assim sendo podem-se passar vários anos antes do início dos sintomas. Na Inglaterra, um estudo realizado cuidadosamente realizado em veganos mostrou que eventualmente, todos eles acabaram por se tornar deficientes em vitamina B-12 [17].
Encolhimento do cérebro entre os vegetarianos
Mas, voltando ao tamanho do cérebro, o declínio que começou com o advento da agricultura e do nossa maior consumo de alimentos de origem vegetal, agravou-se de forma ainda mais significativa significativamente naqueles que têm adoptado uma dieta vegetariana “saudável”.
Cientistas do Departamento de Fisiologia, Anatomia e Genética, da Universidade de Oxford, descobriram recentemente que a mudança para uma dieta vegetariana pode ser prejudicial para os nossos cérebros. – Sendo que aqueles que seguem uma dieta livre de carne têm seis vezes mais probabilidades de sofrer um encolhimento do cérebro [18]
Através de testes e exames do cérebro de voluntários residentes na comunidade, com idade entre os 61 e 87 anos, sem problemas cognitivos ao início dos testes, mediram o tamanho dos cérebros dos participantes. Quando os voluntários foram testados novamente cinco anos depois, os cientistas descobriram que aqueles com níveis mais baixos de ingestão de vitamina B12 foram as mais susceptíveis de sofrer atrofia do cérebro.
Não surpreendentemente, os vegetarianos que evitam todos os alimentos de origem animal, sofreram a maior diminuição do cérebro. Isso confirma pesquisas anteriores que mostram uma ligação entre a atrofia do cérebro e os baixos níveis de vitamina B12.
Os veganos são os mais susceptíveis a tornarem-se deficientes, porque as melhores fontes dessa vitamina são a carne, especialmente o fígado, leite e peixe.
A confirmação disso foi apresentado no ano seguinte por um outro estudo realizado pelo “Oxford Project “para investigar a memória e o envelhecimento, do Departamento de Fisiologia, Anatomia e Genética, na Universidade de Oxford, Reino Unido [19].
Observando que a deficiência de vitamina B-12 está frequentemente associada aos défices cognitivos, os investigadores reviram os dados de que a cognição nos idosos também pode ser seriamente afectada com concentrações de vitamina B-12 acima dos níveis tradicionais de deficiência. A sua sugestão é que os idosos em particular, devem ser encorajados a manter uma boa, ao invés de apenas adequada, ingestão de vitamina B-12, por meio da dieta.
Conclusão
É óbvio que temos de começar a comer mais, e não menos carnes e alimentos de origem animal.
Se os vegetarianos – e especialmente os veganos – o repreenderem por ‘assassinar’ e comer animais, por favor, sejam compreensivos com eles. Pois quase de certeza que estão a sofrer de atrofia cerebral auto-infligida, e compreendem mal os danos que estão fazer a si mesmos e os danos que estão a infligir aos outros que seguem os seus conselhos.
Fonte! / Referências:
[1]. Crawford M, Crawford S. The Food We Eat Today. Spearman, London, 1972.
[2]. Leopold AC, Ardrey R. Toxic Substances in Plants and Food Habits of Early Man. Science 1972; 176(34): 512-4.
[3]. McHenry HM. How big were early hominids? Evol Anthropol 1992; 1: 15-20.
[4]. Stefansson V. The fat of the land. MacMillan, New York, 1960. 15-39.
[5]. Sinclair AJ. Long-chain polyunsaturated fatty acids in mammalian brain. Proc Nutr Soc 1975; 34: 287-91.
[6]. Crawford MA, Cunnane SC, Harbige LS. A new theory of evolution: quantum theory. In: Sinclair A, Gibson R, eds. Essential fatty acids and eicosanoids. American Oil Chemists Society, Champlaign, Ill, 1992. 87-95.
[7]. Leonard WR, Robertson ML. Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. Am J Human Biol 1994; 6: 77-88.
[8]. Aiello LC, Wheeler P. The expensive tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology, 1995; 36: 199-221.
[9]. Milton K. Primate diets and gut morphology: implications for hominid evolution. In: Food and Evolution: Toward a Theory of Food Habits, eds. Harris M, Ross EB; Temple University Press, Philadelphia, 1987, 93-115.
[10]. Martin RD, et al. Gastrointestinal allometry in primates and other mammals. In: Size and Scaling in Primate Biology. Jungers WL ed., Plenum Press, New York, 1985, 61-89.
[11]. Ruff CB, Trinkaus E, Holliday TW. Body mass and encephalization in Pleistocene Homo. Nature 1997; 387: 173-176.
[12]. Eaton, S Boyd, Eaton, Stanley B III. Evolution, diet and health. Presented in association with the scientific session, Origins and Evolution of Human Diet. 14th International Congress of Anthropological and Ethnological Sciences, Williamsburg, Virginia, 1998.
[13]. Callender ST, Spray GH. Latent pernicious anaemia. Br J Haematol 1962; 8: 230.
[14]. Halstead JA, et al. Serum and tissue concentration of vitamin B 12 in certain pathologic states. N Eng J Med 1959; 260: 575.
[15]. Herbert V. Vitamin B-12: plant sources, requirements and assay. Am J Clin Nutr 1988; 48: 852.
[16]. Miller DR, et al. Vitamin B-12 status in a macrobiotic community. Am J Clin Nutr 1991; 53: 524-9.
[17]. Chanarin I, O’Shea AM, Malkowska V, Rinsler MG. Megaloblastic anaemia in a vegetarian Indian community. Lancet 1985; ii: 1168.
[18] Vogiatzoglou A, et al. Vitamin B12 status and rate of brain volume loss in community-dwelling elderly.Neurology 2008; 71(11): 826-32
[19] Smith AD, Refsum H. Vitamin B-12 and cognition in the elderly. Am J Clin Nutr 2009; 89: 707S-11S
[2]. Leopold AC, Ardrey R. Toxic Substances in Plants and Food Habits of Early Man. Science 1972; 176(34): 512-4.
[3]. McHenry HM. How big were early hominids? Evol Anthropol 1992; 1: 15-20.
[4]. Stefansson V. The fat of the land. MacMillan, New York, 1960. 15-39.
[5]. Sinclair AJ. Long-chain polyunsaturated fatty acids in mammalian brain. Proc Nutr Soc 1975; 34: 287-91.
[6]. Crawford MA, Cunnane SC, Harbige LS. A new theory of evolution: quantum theory. In: Sinclair A, Gibson R, eds. Essential fatty acids and eicosanoids. American Oil Chemists Society, Champlaign, Ill, 1992. 87-95.
[7]. Leonard WR, Robertson ML. Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. Am J Human Biol 1994; 6: 77-88.
[8]. Aiello LC, Wheeler P. The expensive tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology, 1995; 36: 199-221.
[9]. Milton K. Primate diets and gut morphology: implications for hominid evolution. In: Food and Evolution: Toward a Theory of Food Habits, eds. Harris M, Ross EB; Temple University Press, Philadelphia, 1987, 93-115.
[10]. Martin RD, et al. Gastrointestinal allometry in primates and other mammals. In: Size and Scaling in Primate Biology. Jungers WL ed., Plenum Press, New York, 1985, 61-89.
[11]. Ruff CB, Trinkaus E, Holliday TW. Body mass and encephalization in Pleistocene Homo. Nature 1997; 387: 173-176.
[12]. Eaton, S Boyd, Eaton, Stanley B III. Evolution, diet and health. Presented in association with the scientific session, Origins and Evolution of Human Diet. 14th International Congress of Anthropological and Ethnological Sciences, Williamsburg, Virginia, 1998.
[13]. Callender ST, Spray GH. Latent pernicious anaemia. Br J Haematol 1962; 8: 230.
[14]. Halstead JA, et al. Serum and tissue concentration of vitamin B 12 in certain pathologic states. N Eng J Med 1959; 260: 575.
[15]. Herbert V. Vitamin B-12: plant sources, requirements and assay. Am J Clin Nutr 1988; 48: 852.
[16]. Miller DR, et al. Vitamin B-12 status in a macrobiotic community. Am J Clin Nutr 1991; 53: 524-9.
[17]. Chanarin I, O’Shea AM, Malkowska V, Rinsler MG. Megaloblastic anaemia in a vegetarian Indian community. Lancet 1985; ii: 1168.
[18] Vogiatzoglou A, et al. Vitamin B12 status and rate of brain volume loss in community-dwelling elderly.Neurology 2008; 71(11): 826-32
[19] Smith AD, Refsum H. Vitamin B-12 and cognition in the elderly. Am J Clin Nutr 2009; 89: 707S-11S
Artigo original:
Vegetarians have smaller brains
If you want to get ahead, get a brain
There is overwhelming evidence that we can not be a vegetarian species. In 1972 the publication of two independent investigations confirmed this.[1] [2] They concerned fats. About half our brain and nervous system is composed of complicated, long-chain, fatty acids. These are also used in the walls of our blood vessels. Without them we cannot develop normally. These fatty acids do not occur in plants, although fatty acids in a simpler form do. This is where plant-eating herbivores come in. Over the year, the herbivores convert the simple fatty acids found in grasses and seeds into intermediate, more complicated forms. By eating the herbivores we can convert their stores of these fatty acids into the ones we need.
About 2.5 million years ago animal foods began to occupy an increasingly prominent place in our ancestors' menus. Smaller molar size, less robust facial muscles and alterations in incisor shape from that time all suggest a greater emphasis on foods such as meat that require less grinding and more tearing.
An increasing proportion of meat in the diet would obviously have provided more animal protein, a factor perhaps related to the increase in stature which appears to have accompanied the transition fromAustralopithecines through Homo habilis to Homo erectus.[3] But greater availability of animal fat was probably a more important dietary alteration. Crude stone tools allowed early humans to break bones and allowed them access to brain and marrow fats from a broad range of animals obtained by scavenging or hunting. These and other carcass fats were probably as prized by early hominids as they are by modern human hunter-gatherers.[4] Not only did more animal fat in the diet mean considerably more energy, it was also a source of ready-made, long-chain, polyunsaturated fatty acids, including omega-6 arachidonic acid (AA), omega-3 docosatetraenoic acid (DTA) and omega-3 docosahexaenoic acid (DHA). These 3 fatty acids together make up over 90% of the fatty acids found in the brain matter of all mammalian species.[5]
Our brain is considerably larger than that of any ape. Looking back at the fossil records from early hominids to modern man, we see a remarkable increase in brain size from 375-550 ml at the time of Australopithecus, to 500-800 ml in Homo habilis, 775-1,225 ml in Homo erectus, and 1,350 cc in modern humans (Homo sapiens). While there is still speculation about why this should have happened, this increase in brain size could not have been supported physiologically without an increased intake of preformed long-chain fatty acids which are an essential component in the formation of brain tissue.[6] It would never have occurred if our ancestors had not eaten meat — with its fat. Human breast milk contains the fatty acids needed for large brain development, cow's milk does not. It is no coincidence that, in relative terms, our brain is some 50 times the size of a cow's.
Our brain is considerably larger than that of any ape. Looking back at the fossil records from early hominids to modern man, we see a remarkable increase in brain size from 375-550 ml at the time of Australopithecus, to 500-800 ml in Homo habilis, 775-1,225 ml in Homo erectus, and 1,350 cc in modern humans (Homo sapiens). While there is still speculation about why this should have happened, this increase in brain size could not have been supported physiologically without an increased intake of preformed long-chain fatty acids which are an essential component in the formation of brain tissue.[6] It would never have occurred if our ancestors had not eaten meat — with its fat. Human breast milk contains the fatty acids needed for large brain development, cow's milk does not. It is no coincidence that, in relative terms, our brain is some 50 times the size of a cow's.
Where does the energy for our brain come from?
Between 20% and 25% of all the energy we use, is used by our brain. This is in contrast to the great apes whose brains use only about 8%. This makes our brains very expensive in energy terms. It means that our energy use compared to our body size should be considerably higher than that of other animals. Yet it isn't. This presents something of a puzzle: where do we humans get the extra energy to spend on our large brains? Researchers WR Leonard and ML Robertson concluded that the evolution of brain size imply changes in diet quality during hominid evolution. They say,
'The shift to a more calorically dense diet was probably needed in order to substantially increase the amount of metabolic energy being used by the hominid brain. Thus, while nutritional factors alone are not sufficient to explain the evolution of our large brains, it seems clear that certain dietary changes were necessary for substantial brain evolution to take place.'[7]
This confirms the Crawfords' work. While our enlarged brain was made necessary by our banding together into tighter communities with more individuals and, thus, a necessity to remember more individuals, what made it possible was a diet of sufficient quality to allow that brain expansion.
But there is another aspect. Two scientists, Aiello and Wheeler, measured the sizes of brains and other body organs against organ size relative to body size predictions.[8] What they found was that the larger-than-expected size of the human brain was compensated for by a smaller-than-expected gut size. Measuring the other energy-expensive organs in the body: heart, kidneys, liver, and gastrointestinal tract, as these use the most energy after the brain, and comparing those of a 65-kg non-human primate with the organ sizes of an average 65-kg human, they found dramatic differences between the expected and actual sizes of the human brain, and gut: 'the splanchnic [abdominal/gut] organs were approximately 900g less than expected'. Almost all of this shortfall was due to our gut being only about 60% of that expected for a similar-sized primate.
But there is another aspect. Two scientists, Aiello and Wheeler, measured the sizes of brains and other body organs against organ size relative to body size predictions.[8] What they found was that the larger-than-expected size of the human brain was compensated for by a smaller-than-expected gut size. Measuring the other energy-expensive organs in the body: heart, kidneys, liver, and gastrointestinal tract, as these use the most energy after the brain, and comparing those of a 65-kg non-human primate with the organ sizes of an average 65-kg human, they found dramatic differences between the expected and actual sizes of the human brain, and gut: 'the splanchnic [abdominal/gut] organs were approximately 900g less than expected'. Almost all of this shortfall was due to our gut being only about 60% of that expected for a similar-sized primate.
We have a carnivore gut
Not only is our gut smaller than predicted compared with other primates, it is also configured very differently. Our small intestine is the major organ used to digest food and extract its nutrients for absorption into our bodies. Not surprisingly, it is more than 50% of the total volume of our gut. Our colon (large intestine) plays little part in the process of digestion: it is used mainly to extract and, so conserve, water. For this reason, it represents only around 20% of our gut's volume. In contrast, the ratios in other primates are exactly the opposite: The small intestines of orangs and chimps, which play a minor role in digestion, are around 25% of gut volume, and their colons, where bacteria are used to ferment plant fibre and where most digestion takes place, are around 53% by volume.[9]
This is not the only measurement that matters. So far I have compared our gut to that of our primate cousins which eat mostly plant food. If we also compare them to the great carnivores, we find that our gut is actually very much like theirs. The comparisons are done with respect to body weight as weight is closely related to the metabolic energy requirements of an animal. This ratio, known as Kleiber's Law, expresses the relationship between body mass (weight) and the body's metabolic energy requirements. The size of any organ that is directly concerned with metabolic turnover should comply with Kleiber's law. If we measure the size of these and they are in accordance with Kleiber's law, each part's gastrointestinal (GI) quotient should be 1.00. A GI greater than 1.00 means the organ is larger than expected, and GI less than 1.00 indicates a size smaller than expected.
In the gut, it is the surface area of various parts of the digestive tract which determines their relative absorptive ability. A test of major areas of the human digestive tract was published in 1985 with the following results:[10]
This is not the only measurement that matters. So far I have compared our gut to that of our primate cousins which eat mostly plant food. If we also compare them to the great carnivores, we find that our gut is actually very much like theirs. The comparisons are done with respect to body weight as weight is closely related to the metabolic energy requirements of an animal. This ratio, known as Kleiber's Law, expresses the relationship between body mass (weight) and the body's metabolic energy requirements. The size of any organ that is directly concerned with metabolic turnover should comply with Kleiber's law. If we measure the size of these and they are in accordance with Kleiber's law, each part's gastrointestinal (GI) quotient should be 1.00. A GI greater than 1.00 means the organ is larger than expected, and GI less than 1.00 indicates a size smaller than expected.
In the gut, it is the surface area of various parts of the digestive tract which determines their relative absorptive ability. A test of major areas of the human digestive tract was published in 1985 with the following results:[10]
| Stomach quotient | 0.31 |
| Small intestine quotient | 0.76 |
| Caecum quotient | 0.16 |
| Colon quotient | 0.58 |
As these values are all considerably less than 1.00, it can only mean one thing: for the absorption of sufficient energy and nutrients for the body to function properly, food must be very energy and nutrient dense. Fat meat is the only universal class of food that falls into this category, thus there can be no doubt that humans fall into the carnivore class.
Brain quotient
Our gut is not the only part of our bodies to be analysed in this way. It is in our brain size and high intelligence that we humans are unique. Relative to our body size, our brains are truly enormous. If we measure our brain quotient in the same way we did for the gut, we can get some idea of just how big it really is.
In order to measure encephalization as it is called, statistical models were developed which compared brain size and body size in a wide range of species. This allowed an accurate estimation of the brain size for a given species based on its body mass. This is important because it allows the quantitative study and comparison of brain sizes between different species by automatically adjusting for body size. For example, elephants, which are plant eaters, and whales whether herbivores or carnivores, have larger brains than we do — but they also have much larger bodies. In this exercise it was noticed that the brain sizes of these animals also followed Kleiber's law.
When this test was conducted on humans, it put humans right at the very top of the primate scale. Our Encephalization Quotient was an outstanding 28.8.
With a brain so out of proportion to the rest of our bodies, it's not surprising that it uses such a large proportion of our total energy. As brain size and energy use is so high, and our gut size so small, the amount of energy available to the brain is dependent not only on how the body's total energy budget is allocated between the brain and other energy-intensive organs and systems, but on the ability of our gut to extract sufficient energy from our food. That also confirms that the kind of diet we should eat must have the high nutrient density found in foods such as meat and fat.
In order to measure encephalization as it is called, statistical models were developed which compared brain size and body size in a wide range of species. This allowed an accurate estimation of the brain size for a given species based on its body mass. This is important because it allows the quantitative study and comparison of brain sizes between different species by automatically adjusting for body size. For example, elephants, which are plant eaters, and whales whether herbivores or carnivores, have larger brains than we do — but they also have much larger bodies. In this exercise it was noticed that the brain sizes of these animals also followed Kleiber's law.
When this test was conducted on humans, it put humans right at the very top of the primate scale. Our Encephalization Quotient was an outstanding 28.8.
With a brain so out of proportion to the rest of our bodies, it's not surprising that it uses such a large proportion of our total energy. As brain size and energy use is so high, and our gut size so small, the amount of energy available to the brain is dependent not only on how the body's total energy budget is allocated between the brain and other energy-intensive organs and systems, but on the ability of our gut to extract sufficient energy from our food. That also confirms that the kind of diet we should eat must have the high nutrient density found in foods such as meat and fat.
Our brains are now getting smaller
With such a small gut with which to absorb all the nutrients and energy our bodies need, a modern low-calorie, low-fat, fibre-rich, plant-based diet is woefully inadequate as an energy source for our energy-hungry system to function at peak efficiency. That lack has begun to show.
Since the advent of agriculture, there has been a worrying trend as our brains have actually decreased in size. A recently updated and rigorous analysis of changes in human brain size found that our ancestors' brain size reached its peak with the first anatomically modern humans of approximately 90,000 years ago. That then remained fairly constant for a further 60,000 years.[11] Over the next 20,000 years there was a slight decline in brain size of about 3%. Since the advent of agriculture about 10,000 years ago, however, that decline has quickened significantly, so that now our brains are a further 8% smaller. That is a total of 11% smaller than at their peak size.
This suggests some kind of recent historical deficiency in some aspect of overall human nutrition. The most obvious and far-reaching dietary change during the last 10,000 years is, of course, the enormous drop in consumption of high-energy, fat-rich foods of animal origin which formed probably over 90% of the diet, to as little as 10% today, coupled with a large rise in less energy-dense grain consumption.[12] This pattern still persists; it is even advocated today: it is the basis of our so-called 'healthy' diet.
Since the advent of agriculture, there has been a worrying trend as our brains have actually decreased in size. A recently updated and rigorous analysis of changes in human brain size found that our ancestors' brain size reached its peak with the first anatomically modern humans of approximately 90,000 years ago. That then remained fairly constant for a further 60,000 years.[11] Over the next 20,000 years there was a slight decline in brain size of about 3%. Since the advent of agriculture about 10,000 years ago, however, that decline has quickened significantly, so that now our brains are a further 8% smaller. That is a total of 11% smaller than at their peak size.
This suggests some kind of recent historical deficiency in some aspect of overall human nutrition. The most obvious and far-reaching dietary change during the last 10,000 years is, of course, the enormous drop in consumption of high-energy, fat-rich foods of animal origin which formed probably over 90% of the diet, to as little as 10% today, coupled with a large rise in less energy-dense grain consumption.[12] This pattern still persists; it is even advocated today: it is the basis of our so-called 'healthy' diet.
Vitamin B-12
If any more convincing that we have to be a meat-eating species is needed, there is one other essential nutrient that is not found in any plant food. That nutrient is Vitamin B-12.
Vitamin B-12 is unique among vitamins in that while it is found universally in foods of animal origin, where it is derived ultimately from bacteria, there is no active vitamin B-12 in anything which grows out of the ground. Where trace amounts of vitamin B-12 are found on plants it is there only fortuitously in bacterial contamination of the soil. And even that is lost if plants are washed thoroughly before eating them.
Bacteria in the human colon make prodigious amounts of vitamin B-12. Unfortunately, this is useless as it is not absorbed through the colon wall. Dr. Sheila Callender tells of treating vegans with severe vitamin B-12 deficiency by making water extracts of their stools which she fed to them, thus affecting a cure.[13] An Iranian vegan sect unwittingly also makes use of this fact. Investigators could not understand how members of this sect remained healthy, until their investigations showed that they grew their vegetables in human manure — and then ate the vegetables without being too fussy about washing them first.[14]
To enable vegans to survive, vitamin B-12 is added artificially to breakfast cereals in Britain and may be bought in pill form. This is hardly a natural way to get food and in many cases it is self-defeating. Unlike most other vitamins, Vitamin B-12 occurs as a number of analogues, very few of which are active for humans. In collecting human stools for analysis Dr. Victor Herbert found that of each 100 micrograms of vitamin B-12 extracted, only 5 micrograms were analogues active for humans.[15] Thus even in this most prodigious source of the vitamin, 95% was composed of analogues which were useless.
Several fermented products such as tempeh, a soya bean product and spirulinas, used by strict vegans as a source of vitamin B-12, either do not contain significant amounts of the vitamin or contain analogues of the vitamin which are not active for humans.[16] Over half of the adults from a macrobiotic community tested in New England had low concentrations of vitamin B-12. Children were short in stature and low in weight. The community relied on sea vegetables for the vitamin.
This reliance on vegetables sources gives a false sense of security and could actually bring on the symptoms of B-12 deficiency more quickly.
The amount of vitamin B-12 we need is tiny: about 1 microgram per day. Eating more than this results in a reserve being built up in the body. When a person becomes a vegan, those stores are depleted — but only gradually. Thus it can be several years before the onset of symptoms. In England a carefully conducted study carried out on vegans showed that they all got vitamin B-12 deficiency eventually.[17]
Vitamin B-12 is unique among vitamins in that while it is found universally in foods of animal origin, where it is derived ultimately from bacteria, there is no active vitamin B-12 in anything which grows out of the ground. Where trace amounts of vitamin B-12 are found on plants it is there only fortuitously in bacterial contamination of the soil. And even that is lost if plants are washed thoroughly before eating them.
Bacteria in the human colon make prodigious amounts of vitamin B-12. Unfortunately, this is useless as it is not absorbed through the colon wall. Dr. Sheila Callender tells of treating vegans with severe vitamin B-12 deficiency by making water extracts of their stools which she fed to them, thus affecting a cure.[13] An Iranian vegan sect unwittingly also makes use of this fact. Investigators could not understand how members of this sect remained healthy, until their investigations showed that they grew their vegetables in human manure — and then ate the vegetables without being too fussy about washing them first.[14]
To enable vegans to survive, vitamin B-12 is added artificially to breakfast cereals in Britain and may be bought in pill form. This is hardly a natural way to get food and in many cases it is self-defeating. Unlike most other vitamins, Vitamin B-12 occurs as a number of analogues, very few of which are active for humans. In collecting human stools for analysis Dr. Victor Herbert found that of each 100 micrograms of vitamin B-12 extracted, only 5 micrograms were analogues active for humans.[15] Thus even in this most prodigious source of the vitamin, 95% was composed of analogues which were useless.
Several fermented products such as tempeh, a soya bean product and spirulinas, used by strict vegans as a source of vitamin B-12, either do not contain significant amounts of the vitamin or contain analogues of the vitamin which are not active for humans.[16] Over half of the adults from a macrobiotic community tested in New England had low concentrations of vitamin B-12. Children were short in stature and low in weight. The community relied on sea vegetables for the vitamin.
This reliance on vegetables sources gives a false sense of security and could actually bring on the symptoms of B-12 deficiency more quickly.
The amount of vitamin B-12 we need is tiny: about 1 microgram per day. Eating more than this results in a reserve being built up in the body. When a person becomes a vegan, those stores are depleted — but only gradually. Thus it can be several years before the onset of symptoms. In England a carefully conducted study carried out on vegans showed that they all got vitamin B-12 deficiency eventually.[17]
Brain shrinkage among vegetarians
But, getting back to brain size, the decline which started with the advent of agriculture and our greater reliance on foods of plant origin has now seen a dramatically greater decline in those who have adopted a 'healthy', vegetarian diet.
Scientists at the Department of Physiology, Anatomy and Genetics, University of Oxford, recently discovered that changing to a vegetarian diet could be bad for our brains — with those on a meat-free diet six times more likely to suffer brain shrinkage.[18]
Using tests and brain scans on community-dwelling volunteers aged 61 to 87 years without cognitive impairment at enrolment, they measured the size of the participants' brains. When the volunteers were retested five years later the scientists found those with the lowest levels of vitamin B12 intake were the most likely to have brain shrinkage. Not surprisingly, vegans who eschew all foods of animal origin, suffered the most brain shrinkage. This confirms earlier research showing a link between brain atrophy and low levels of B12.
Vegans are the most likely to be deficient because the best sources of the vitamin are meat, particularly liver, milk and fish.
There were two other worrying aspects to this trial. The first was at the start of the trial, the biggest brain in a vegan, at 1455 ml, was already smaller than smallest brain of someone on a ‘normal diet’, at 1456 ml.
The other aspect was even more worrying. It was that all participants had Vit B-12 which was within the 'normal' range. This suggests that the normal range is too low - and by quite large margin. I understand that, based on this study, the Japanese have raised their normal level.
Confirmation of the above study was provided the following year by another study by the Oxford Project to Investigate Memory and Ageing, the Department of Physiology, Anatomy and Genetics, University of Oxford, UK.[19] Noting that vitamin B-12 deficiency is often associated with cognitive deficits, they reviewed evidence that cognition in the elderly may also be adversely affected at concentrations of vitamin B-12 above the traditional cutoffs for deficiency. Their suggestion is that the elderly in particular should be encouraged to maintain a good, rather than just an adequate, vitamin B-12 status by dietary means.
Scientists at the Department of Physiology, Anatomy and Genetics, University of Oxford, recently discovered that changing to a vegetarian diet could be bad for our brains — with those on a meat-free diet six times more likely to suffer brain shrinkage.[18]
Using tests and brain scans on community-dwelling volunteers aged 61 to 87 years without cognitive impairment at enrolment, they measured the size of the participants' brains. When the volunteers were retested five years later the scientists found those with the lowest levels of vitamin B12 intake were the most likely to have brain shrinkage. Not surprisingly, vegans who eschew all foods of animal origin, suffered the most brain shrinkage. This confirms earlier research showing a link between brain atrophy and low levels of B12.
Vegans are the most likely to be deficient because the best sources of the vitamin are meat, particularly liver, milk and fish.
There were two other worrying aspects to this trial. The first was at the start of the trial, the biggest brain in a vegan, at 1455 ml, was already smaller than smallest brain of someone on a ‘normal diet’, at 1456 ml.
The other aspect was even more worrying. It was that all participants had Vit B-12 which was within the 'normal' range. This suggests that the normal range is too low - and by quite large margin. I understand that, based on this study, the Japanese have raised their normal level.
Confirmation of the above study was provided the following year by another study by the Oxford Project to Investigate Memory and Ageing, the Department of Physiology, Anatomy and Genetics, University of Oxford, UK.[19] Noting that vitamin B-12 deficiency is often associated with cognitive deficits, they reviewed evidence that cognition in the elderly may also be adversely affected at concentrations of vitamin B-12 above the traditional cutoffs for deficiency. Their suggestion is that the elderly in particular should be encouraged to maintain a good, rather than just an adequate, vitamin B-12 status by dietary means.
Conclusion
It is obvious that we need to be eating more, not less, meat and animal-sourced foods.
If vegetarians — and vegans in particular — berate you for 'murdering' and eating animals, please be kind to them. They are almost certainly suffering from self-inflicted brain atrophy, and have little recognition of both the damage they are doing to themselves and the harm that are doing to others who follow their advice.
If vegetarians — and vegans in particular — berate you for 'murdering' and eating animals, please be kind to them. They are almost certainly suffering from self-inflicted brain atrophy, and have little recognition of both the damage they are doing to themselves and the harm that are doing to others who follow their advice.
References
[1]. Crawford M, Crawford S. The Food We Eat Today. Spearman, London, 1972.
[2]. Leopold AC, Ardrey R. Toxic Substances in Plants and Food Habits of Early Man. Science 1972; 176(34): 512-4.
[3]. McHenry HM. How big were early hominids? Evol Anthropol 1992; 1: 15-20.
[4]. Stefansson V. The fat of the land. MacMillan, New York, 1960. 15-39.
[5]. Sinclair AJ. Long-chain polyunsaturated fatty acids in mammalian brain. Proc Nutr Soc 1975; 34: 287-91.
[6]. Crawford MA, Cunnane SC, Harbige LS. A new theory of evolution: quantum theory. In: Sinclair A, Gibson R, eds. Essential fatty acids and eicosanoids. American Oil Chemists Society, Champlaign, Ill, 1992. 87-95.
[7]. Leonard WR, Robertson ML. Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. Am J Human Biol 1994; 6: 77-88.
[8]. Aiello LC, Wheeler P. The expensive tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology, 1995; 36: 199-221.
[9]. Milton K. Primate diets and gut morphology: implications for hominid evolution. In: Food and Evolution: Toward a Theory of Food Habits, eds. Harris M, Ross EB; Temple University Press, Philadelphia, 1987, 93-115.
[10]. Martin RD, et al. Gastrointestinal allometry in primates and other mammals. In: Size and Scaling in Primate Biology. Jungers WL ed., Plenum Press, New York, 1985, 61-89.
[11]. Ruff CB, Trinkaus E, Holliday TW. Body mass and encephalization in Pleistocene Homo. Nature 1997; 387: 173-176.
[12]. Eaton, S Boyd, Eaton, Stanley B III. Evolution, diet and health. Presented in association with the scientific session, Origins and Evolution of Human Diet. 14th International Congress of Anthropological and Ethnological Sciences, Williamsburg, Virginia, 1998.
[13]. Callender ST, Spray GH. Latent pernicious anaemia. Br J Haematol 1962; 8: 230.
[14]. Halstead JA, et al. Serum and tissue concentration of vitamin B 12 in certain pathologic states. N Eng J Med 1959; 260: 575.
[15]. Herbert V. Vitamin B-12: plant sources, requirements and assay. Am J Clin Nutr 1988; 48: 852.
[16]. Miller DR, et al. Vitamin B-12 status in a macrobiotic community. Am J Clin Nutr 1991; 53: 524-9.
[17]. Chanarin I, O'Shea AM, Malkowska V, Rinsler MG. Megaloblastic anaemia in a vegetarian Indian community. Lancet 1985; ii: 1168.
[18] Vogiatzoglou A, et al. Vitamin B12 status and rate of brain volume loss in community-dwelling elderly.Neurology 2008; 71(11): 826-32
[19] Smith AD, Refsum H. Vitamin B-12 and cognition in the elderly. Am J Clin Nutr 2009; 89: 707S-11S.
[2]. Leopold AC, Ardrey R. Toxic Substances in Plants and Food Habits of Early Man. Science 1972; 176(34): 512-4.
[3]. McHenry HM. How big were early hominids? Evol Anthropol 1992; 1: 15-20.
[4]. Stefansson V. The fat of the land. MacMillan, New York, 1960. 15-39.
[5]. Sinclair AJ. Long-chain polyunsaturated fatty acids in mammalian brain. Proc Nutr Soc 1975; 34: 287-91.
[6]. Crawford MA, Cunnane SC, Harbige LS. A new theory of evolution: quantum theory. In: Sinclair A, Gibson R, eds. Essential fatty acids and eicosanoids. American Oil Chemists Society, Champlaign, Ill, 1992. 87-95.
[7]. Leonard WR, Robertson ML. Evolutionary perspectives on human nutrition: the influence of brain and body size on diet and metabolism. Am J Human Biol 1994; 6: 77-88.
[8]. Aiello LC, Wheeler P. The expensive tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology, 1995; 36: 199-221.
[9]. Milton K. Primate diets and gut morphology: implications for hominid evolution. In: Food and Evolution: Toward a Theory of Food Habits, eds. Harris M, Ross EB; Temple University Press, Philadelphia, 1987, 93-115.
[10]. Martin RD, et al. Gastrointestinal allometry in primates and other mammals. In: Size and Scaling in Primate Biology. Jungers WL ed., Plenum Press, New York, 1985, 61-89.
[11]. Ruff CB, Trinkaus E, Holliday TW. Body mass and encephalization in Pleistocene Homo. Nature 1997; 387: 173-176.
[12]. Eaton, S Boyd, Eaton, Stanley B III. Evolution, diet and health. Presented in association with the scientific session, Origins and Evolution of Human Diet. 14th International Congress of Anthropological and Ethnological Sciences, Williamsburg, Virginia, 1998.
[13]. Callender ST, Spray GH. Latent pernicious anaemia. Br J Haematol 1962; 8: 230.
[14]. Halstead JA, et al. Serum and tissue concentration of vitamin B 12 in certain pathologic states. N Eng J Med 1959; 260: 575.
[15]. Herbert V. Vitamin B-12: plant sources, requirements and assay. Am J Clin Nutr 1988; 48: 852.
[16]. Miller DR, et al. Vitamin B-12 status in a macrobiotic community. Am J Clin Nutr 1991; 53: 524-9.
[17]. Chanarin I, O'Shea AM, Malkowska V, Rinsler MG. Megaloblastic anaemia in a vegetarian Indian community. Lancet 1985; ii: 1168.
[18] Vogiatzoglou A, et al. Vitamin B12 status and rate of brain volume loss in community-dwelling elderly.Neurology 2008; 71(11): 826-32
[19] Smith AD, Refsum H. Vitamin B-12 and cognition in the elderly. Am J Clin Nutr 2009; 89: 707S-11S.
1 comentário:
Achei estranho que o site divulgue esse artigo. Acha realmente que a espécie humana não deve ser vegetariana? É contra o vegetarianismo?
Ou eu li muito rapidamente e não entendi?
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