5. Meat avoidance leads to a loss of nutritional robustness [1 of 3]
Diets poor in animal source foods can lead to various nutritional deficiencies, as already described more than a century ago for the case of pellagra (Morabia, 2008 Morabia, A. 2008. Joseph goldberger’s research on the prevention of pellagra. Journal of the Royal Society of Medicine 101 (11):566–8. doi: 10.1258/jrsm.2008.08k010.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), a condition which remains relevant today for poorly planned vegan diets (Ng & Neff, 2018 Ng, E., and M. Neff. 2018. Recognising the return of nutritional deficiencies: a modern pellagra puzzle. BMJ Case Reports 11 (1):e227454. doi: 10.1136/bcr-2018-227454.[Crossref], [PubMed] , [Google Scholar]). Advocates of vegetarian/vegan diets usually admit that these diets must indeed be “well-planned” in order to be successful, which involves regular supplementation with nutrients such as B12. However, realistically , many people are not diligent about supplementation, and will often dip into deficient or borderline-deficient ranges if they do not obtain nutrients from their regular diet. In such cases, general malnutrition (Ingenbleek & McCully, 2012 Ingenbleek, Y., and K. S. McCully. 2012. Vegetarianism produces subclinical malnutrition, hyperhomocysteinemia and atherogenesis. Nutrition 28 (2):148–53. doi: 10.1016/j.nut.2011.04.009.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), poorer health (Burkert et al., 2014 Burkert, N. T., J. Muckenhuber, F. Großschädl, E. Rásky, and W. Freidl. 2014. Nutrition and health – the association between eating behavior and various health parameters: a matched sample study. PLOS ONE 9 (2):e88278. doi: 10.1371/journal.pone.0088278.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), and nutrient limitations (Kim et al., 2018 Kim, S., M. F. Fenech, and P.-J R. Kim. 2018. Nutritionally recommended food for semi- to strict vegetarian diets based on large-scale nutrient composition data. Scientific Reports 8 (1):4344. doi: 10.1038/s41598-018-22691-1.[Crossref], [PubMed] , [Google Scholar]) may be the result, as found in various countries, such as Denmark (Kristensen et al., 2015 Kristensen, Nadja B., Mia L. Madsen, Tue H. Hansen, Kristine H. Allin, Camilla Hoppe, Sisse Fagt, Mia S. Lausten, Rikke J. Gøbel, Henrik Vestergaard, Torben Hansen., et al. 2015. Intake of macro- and micronutrients in danish vegans. Nutrition Journal 14 (1):115. doi: 10.1186/s12937-015-0103-3.[Crossref], [PubMed] , [Google Scholar]), Finland (Elorinne et al., 2016 Elorinne, Anna-Liisa, Georg Alfthan, Iris Erlund, Hanna Kivimäki, Annukka Paju, Irma Salminen, Ursula Turpeinen, Sari Voutilainen, and Juha Laakso. 2016. Food and nutrient intake and nutritional status of finnish vegans and non-vegetarians. PLOS ONE 11 (2):e0148235. doi: 10.1371/journal.pone.0148235.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), Sweden (Larsson & Johansson, 2002 Larsson, C. L., and G. K. Johansson. 2002. Dietary intake and nutritional status of young vegans and omnivores in Sweden. The American Journal of Clinical Nutrition 76 (1):100–6. doi: 10.1093/ajcn/76.1.100.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), and Switzerland (Schüpbach et al., 2017 Schüpbach, R., R. Wegmüller, C. Berguerand, M. Bui, and I. Herter-Aeberli. 2017. Micronutrient status and intake in omnivores, vegetarians and vegans in Switzerland. European Journal of Nutrition 56 (1):283–93. doi: 10.1007/s00394-015-1079-7.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). For example, a substantial number of vegetarians and vegans are in the deficient or borderline-deficient range for B12 (Herrmann & Geisel, 2002 Herrmann, W., and J. Geisel. 2002. Vegetarian lifestyle and monitoring of vitamin B-12 status. Clinica Chimica Acta 326 (1-2):47–59. doi: 10.1016/S0009-8981(02)00307-8.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Herrmann et al., 2003 Herrmann, W., H. Schorr, R. Obeid, and J. Geisel. 2003. Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians. The American Journal of Clinical Nutrition 78 (1):131–6. doi: 10.1093/ajcn/78.1.131.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), despite the fact that the need for B12 supplementation is well-publicized (see also Herbert, 1994 Herbert, V. 1994. Staging vitamin B-12 (cobalamin) status in vegetarians. The American Journal of Clinical Nutrition 59 (5):1213S–22S. doi: 10.1093/ajcn/59.5.1213S.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Hokin & Butler, 1999 Hokin, B. D., and T. Butler. 1999. Cyanocobalamin (vitamin B-12) status in Seventh-day Adventist ministers in Australia. The American Journal of Clinical Nutrition 70 (3):576s–8s. doi: 10.1093/ajcn/70.3.576s.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Donaldson, 2000 Donaldson, M. S. 2000. Metabolic vitamin B12 status on a mostly raw vegan diet with follow-up using tablets, nutritional yeast, or probiotic supplements. Annals of Nutrition & Metabolism 44 (5-6):229–34. doi: 10.1159/000046689.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Elmadfa & Singer, 2009 Elmadfa, I., and I. Singer. 2009. Vitamin B-12 and homocysteine status among vegetarians: a global perspective. The American Journal of Clinical Nutrition 89 (5):1693S–8S. doi: 10.3945/ajcn.2009.26736Y.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Gilsing et al., 2010 Gilsing, A. M. J., F. L. Crowe, Z. Lloyd-Wright, T. A. B. Sanders, P. N. Appleby, N. E. Allen, and T. J. Key. 2010. Serum concentrations of vitamin B12 and folate in british male omnivores, vegetarians, and vegans: results from a cross-sectional analysis of the EPIC-Oxford cohort study. European Journal of Clinical Nutrition 64 (9):933–9. doi: 10.1038/ejcn.2010.142.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Obersby et al., 2013 Obersby, D., D. C. Chappell, A. Dunnett, and A. A. Tsiami. 2013. Plasma total homocysteine status of vegetarians compared with omnivores: a systematic review and Meta-analysis. British Journal of Nutrition 109 (5):785–94. doi: 10.1017/S000711451200520X.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Pawlak et al. 2013 Pawlak, Roman, Scott James Parrott, Sudha Raj, Diana Cullum-Dugan, and Debbie Lucus. 2013. How prevalent is vitamin B12 deficiency among vegetarians? Nutrition Reviews 71 (2):110–7. doi: 10.1111/nure.12001.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar], 2014 Pawlak, R., S. E. Lester, and T. Babatunde. 2014. The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature. European Journal of Clinical Nutrition 68 (5):541–8. doi: 10.1038/ejcn.2014.46.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Pawlak, 2015 Pawlak, R. 2015. Is vitamin B12 deficiency a risk factor for cardiovascular disease in vegetarians? American Journal of Preventive Medicine 48 (6):e11–26. doi: 10.1016/j.amepre.2015.02.009.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Woo et al., 2014 Woo, K. S., T. C. Kwok, and D. S. Celermajer. 2014. Vegan diet, subnormal vitamin B-12 status and cardiovascular health. Nutrients 6 (8):3259–73. doi: 10.3390/nu6083259.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Naik et al., 2018 Naik, S., N. Mahalle, and V. Bhide. 2018. Identification of vitamin B12 deficiency in vegetarian indians. The British Journal of Nutrition 119 (6):629–35. doi: 10.1017/S0007114518000090.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). B12 deficiency is particularly dangerous during pregnancy (Specker et al., 1988 Specker, B. L., D. Miller, E. J. Norman, H. Greene, and K. C. Hayes. 1988. Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and identification of an acceptable dietary source of vitamin B-12. The American Journal of Clinical Nutrition 47 (1):89–92. doi: 10.1093/ajcn/47.1.89.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar], 1990 Specker, B. L., A. Black, L. Allen, and F. Morrow. 1990. Vitamin B-12: low milk concentrations are related to low serum concentrations in vegetarian women and to methylmalonic aciduria in their infants. The American Journal of Clinical Nutrition 52 (6):1073–6. doi: 10.1093/ajcn/52.6.1073.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Bjørke Monsen et al., 2001 Bjørke Monsen, A. L., P. M. Ueland, S. E. Vollset, A. B. Guttormsen, T. Markestad, E. Solheim, and H. Refsum. 2001. Determinants of cobalamin status in newborns. Pediatrics 108 (3):624–30. doi: 10.1542/peds.108.3.624.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Koebnick et al., 2004 Koebnick, Corinna, Ingrid Hoffmann, Pieter C. Dagnelie, Ulrike A. Heins, Sunitha N. Wickramasinghe, Indrika D. Ratnayaka, Sindy Gruendel, Jan Lindemans, and Claus Leitzmann. 2004. Long-term ovo-lacto vegetarian diet impairs vitamin B-12 status in pregnant women. The Journal of Nutrition 134 (12):3319–26. doi: 10.1093/jn/134.12.3319.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), childhood (Rogers et al., 2003 Rogers, L. M., E. Boy, J. W. Miller, R. Green, J. C. Sabel, and L. H. Allen. 2003. High prevalence of cobalamin deficiency in guatemalan schoolchildren: associations with low plasma holotranscobalamin II and elevated serum methylmalonic acid and plasma homocysteine concentrations. The American Journal of Clinical Nutrition 77 (2):433–40. doi: 10.1093/ajcn/77.2.433.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and adolescence (van Dusseldorp et al., 1999 van Dusseldorp, M., J. Schneede, H. Refsum, P. M. Ueland, C. M. Thomas, E. de Boer, and W. A. van Staveren. 1999. Risk of persistent cobalamin deficiency in adolescents fed a macrobiotic diet in early life. The American Journal of Clinical Nutrition 69 (4):664–71. doi: 10.1093/ajcn/69.4.664.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Louwman et al., 2000 Louwman, Marieke W. J., Marijke van Dusseldorp, Fons J. R. van de Vijver, Chris M. G. Thomas, Jørn Schneede, Per M. Ueland, Helga Refsum, and Wija A. van Staveren. 2000. Signs of impaired cognitive function in adolescents with marginal cobalamin status. The American Journal of Clinical Nutrition 72 (3):762–9. doi: 10.1093/ajcn/72.3.762.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]).