Are Humans “Supposed” to be Herbivores, Carnivores, or Omnivores?
Humans are considered omnivores, as evidenced by our physiological attributes.1 For example, whereas the teeth of herbivores have physical characteristics specific to gnawing, scraping, and grinding plant matter and the teeth of carnivores are specific to incapacitating and tearing apart animals for food, a set of human teeth typically comprises a wide variety of shapes and sizes suitable for consuming a wide variety of food, both plant and animal.2 Another physical attribute of humans that suggests our evolved omnivorous tendency is our intestines, which, in terms of length, fall somewhere in between a carnivore’s typically short intestinal tract and an herbivore’s typically long intestinal tract.1 However, these physical attributes do not definitively signify that humans should eat meat or should only eat plants; rather, they are indicative of the human body’s digestive adaptability, which evolved over thousands of years, allowing prehistoric man to survive off of whatever food he could find in the natural world, which might be plant, animal, or insect, as he roamed place to place, season to season.1
Modern man’s diet (and ultimately survival) is no longer limited to whatever food can be found in his immediate natural environment; today, we have the luxury of choice when it comes to how we nourish our bodies, including whether to consume animal-based foods.
What are the Pros of a Vegetarian/Vegan Diet?
Modern research has consistently shown that consumption of red meat and, in particular, processed meat is negatively associated with range of health conditions3 and that reducing meat intake and increasing the intake of vegetables and other plant-based foods is linked to a number of health benefits.4 Research has also demonstrated that greater exclusion of animal-based foods from the diet is associated with reduced intake of saturated fat, cholesterol, and sugar and higher intake of dietary fibers, beta carotene, and vitamins E and K.4 As a result of these and other nutritional differences, vegetarians and vegans may be at reduced risk of a variety of health conditions, including ischemic heart disease, hypertension, Type 2 diabetes, and certain cancers.5 The gut microbiota varies according to dietary habits, and exposure to animal-based foods may facilitate an intestinal environment that can trigger systematic inflammation and insulin resistance-dependent metabolic disorders.6 Similarly, research has shown that vegetarians have a better antioxidant profile than omnivores.7,8 Body weight, body mass index values, and body fat percentages also tend to be lower in flexitarians, vegetarians, and vegans* than in omnivores.4
Important Nutritional Considerations of a Vegetarian or Vegan Diet
When moving from an omnivore diet to a vegetarian or even vegan diet, one must keep in mind what is lost when choosing to avoid different animal products. Foremost is the need to find alternative sources of protein, which include dairy products (if vegetarian), legumes, nuts, and seeds. Additionally, while animal products alone provide all nine essential amino acids, complementary plant foods, such as rice and beans, may need to be combined together to achieve complete proteins, especially for individuals who avoid all animal-based foods, including dairy. Levels of certain minerals, such as calcium (if avoiding dairy products), iron, zinc, and iodine, may also be reduced in vegetarians and vegans,9–11 and deficiencies of vitamins B6 and B12 are a concern.10,11 Similarly, the intake of the omega-3 fatty acids—eicosapentaenoic acid and docosahexaenoic—were found to be low in vegetarians and nearly absent in vegans.12
Research has shown that limiting or avoiding altogether the consumption of animal-based foods has many health benefits; however, obtaining complete sources of protein and some other essential nutrients typically sourced from animal-based foods may be challenging to vegetarians and, in particular, vegans. Consulting with a licensed healthcare professional or nutritionist who can work with you to develop a nutritional plan based on your individual preferences and healthcare needs would be prudent prior to making any drastic changes to your diet.
*Flexitarian: someone who primarily consumes plant-based foods, but occasionally consumes meat and/or fish or animal-based foods (e.g., dairy); vegetarian: someone who consumes plant-based foods and some animal-based foods (e.g., dairy), but avoids the consumption of meat or fish altogether; vegan: someone who strictly consumes plant-based foods, avoiding the consumption of meat or fish or any animal-based foods (e.g., dairy) altogether
- Deneen S. Body of evidence: were humans meant to eat meat? 2002. https://www.thefreelibrary.com/Body+of+evidence% 3A+were+humans+meant+ to+eat+meat%3F-a082352627. Accessed 26 Jul 2022.
- Yashoda. Difference between herbivores and carnivores teeth. 16 Sep 2015. https://www.differencebetween.com/difference-between-herbivores-and-vs-carnivores-teeth/. Accessed 3 Aug 2022.
- Richi EB, Baumer B, Conrad B, et al. Health risks associated with meat consumption: a review of epidemiological studies. Int J Vitam Nutr Res. 2015;85(1–2):70–78.
- Dawczynski C, Weidauer T, Richert C, et al. Nutrient intake and nutrition status in vegetarians and vegans in comparison to omnivores—the Nutritional Evaluation (NuEva) Study. Front Nutr. 2022;9:819106.
- Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: vegetarian diets. J Acad Nutr Diet. 2016;116(12):1970–1980.
- Franco-de-Moraes AC, de Almeida-Pititto B, da Rocha Fernandes G, et al. Worse inflammatory profile in omnivores than in vegetarians associates with the gut microbiota composition. Diabetol Metab Syndr. 2017;9:62.
- Szeto YT, Kwok TCY, Benzie IFF. Effects of a long-term vegetarian diet on biomarkers of antioxidant status and cardiovascular disease risk. Nutrition. 2004;20(10):863–866.
- Rauma AL, Mykkänen H. Antioxidant status in vegetarians versus omnivores. Nutrition. 2000;16(2):111–119.
- Eveleigh E, Coneyworth L, Zhou M, et al. Vegans and vegetarians living in Nottingham (UK) continue to be at risk of iodine deficiency. Br J Nutr. 2022;1–46.
- Dagnelie PC. Nutrition and health—potential health benefits and risks of vegetarianism and limited consumption of meat in the Netherlands [article in Dutch]. Ned Tijdschr Geneeskd. 2003;147(27):1308–1313.
- Schüpbach R, Wegmüller R, Berguerand C, et al. Micronutrient status and intake in omnivores, vegetarians and vegans in Switzerland. Eur J Nutr. 2017;56(1):283–293.
- Saunders AV, Davis BC, Garg ML. Omega-3 polyunsaturated fatty acids and vegetarian diets. Med J Aust. 2013;199(S4):S22–S26.