Vegetarianism, and particularly its strictest form, veganism, has seen a surge in popularity, especially among young adults in the United States. While some research suggests that a vegan diet (VD) may reduce the risk of cardiometabolic diseases, concerns have been raised about potential adverse health outcomes. This article explores the arguments against a vegan diet, focusing on potential nutritional deficiencies and the impact of veganism on vulnerable populations.
What is vegan diet
Vegetarianism is a broad term encompassing various dietary practices. Vegans follow the most restrictive diet, avoiding all animal-derived foods and by-products. Lacto-vegetarians exclude meat, fish, and eggs but consume dairy. Ovo-vegetarians avoid meat, fish, and dairy but eat eggs. Lacto-ovo-vegetarians exclude meat but consume both eggs and dairy. Pescatarians avoid meat but eat fish and shellfish.
Potential for Nutrient Deficiencies
One of the primary arguments against veganism centers on the potential for micro and macronutrient deficiencies. Vegans may face challenges in obtaining sufficient amounts of certain nutrients that are more readily available in animal products.
Protein Intake
A systematic study found that vegans consumed the least amount of total protein compared to other diet groups, raising concerns about insufficient protein intake, especially when legume, seed, and nut consumption is limited. Plant proteins are also less digestible (50-70%) than animal proteins, and food processing methods like heating may further reduce digestibility. Animal proteins are considered complete proteins with higher biological value and a higher Protein Digestibility Corrected Amino Acid Score (PDCAAS) compared to plant proteins, according to the WHO. Vegans also consume fewer essential amino acids than non-vegans.
Vitamin B12 Deficiency
Low vitamin B12 intake is a significant concern in vegan diets due to the exclusion of vitamin B12-rich foods like meat, poultry, and eggs. Vitamin B12 deficiency can lead to neurologic and hematologic problems, with symptoms appearing gradually over time. High folate levels may mask some hematological manifestations of vitamin B12 deficiency. Inadequate B12 consumption may also contribute to carcinogenesis by impairing DNA synthesis and genomic instability. Studies have linked low B12 levels to an elevated risk of breast, cervical, and gastrointestinal tract malignancies.
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Iron and Zinc Deficiencies
Vegans have greater iron needs than those following other diet patterns because non-heme iron from plant-based foods is less bioavailable. Absorption is hindered by the phytic acid content in whole grains, legumes, and nuts. Vegans also risk zinc deficiency. While meat, dairy, and eggs contain zinc, some zinc-rich plant foods have poor bioavailability due to phytate, which inhibits absorption in the gut. Inadequate zinc consumption may be associated with mental health problems (e.g., depression), dermatitis, diarrhea, and alopecia, which are more prevalent among vegans.
Calcium and Vitamin D Deficiencies
Studies have shown that vegans often consume insufficient calcium and vitamin D due to the absence of dairy products and calcium bioavailability problems in plant-based diets. Vitamin D insufficiency exacerbates calcium shortage due to impaired intestinal absorption. A study reported that vegans had an increased risk of hip fractures and overall fracture incidence compared to meat-eaters. Vegans also had a greater incidence of leg fractures and fractures in other major sites.
Mental Health Concerns
Vegans have a greater prevalence of mental health problems, potentially leading to a poorer quality of life. A systematic review found that meat-free diets were linked with worse psychological health in eleven out of eighteen studies. Meat-avoiders had a higher prevalence of unipolar depressive disorders and anxiety disorders compared to meat consumers. The study highlights the high incidence of mental health problems among vegans, emphasizing the need for increased awareness and early intervention.
Orthorexia nervosa (ON), a fixation on health-conscious eating behavior, can also be a concern. It involves obsessive food decisions, self-imposed anxiety, self-punishment, and increasingly extreme limitations. Individuals develop dietary restrictions, lack of food pleasure, inflexible eating behaviors, and ritual activities surrounding food preparations.
Impact on Vulnerable Populations
The impact of veganism on vulnerable populations, including children, adolescents, pregnant and breastfeeding women, and fetal outcomes in strict vegan mothers, raises specific concerns.
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Children and Adolescents
Adolescents often show a strong preference for VD. A balanced diet is critical for children and adolescents to meet their bodies' rising demands during the growth spurt, rendering the implications of VD in this vulnerable age more intriguing. While some studies suggest no specific nutrient concerns among vegetarian and vegan children and adolescents compared to omnivores, subsequent cross-sectional studies have shown that vegetarian and/or vegan children had a lower bone mineral density (BMD). Vegan children were also found to be shorter than omnivores and had substantially lower vitamin D levels and BMD than omnivores after controlling for body size. Maximizing childhood BMD is suggested to promote peak BMD and reduce the risk of osteoporosis and fracture in adulthood. It does not seem to be ideal to start puberty, a period when bone-specific nutrition requirements are greater, with an already established BMD deficiency.
Pregnancy and Fetal Outcomes
Optimal fetal growth requires balanced maternal nutrition during pregnancy. Mothers on rigorous VD are at risk of vitamin insufficiency, which can lead to poor fetal outcomes. A study found that a vegan diet was substantially linked with an elevated risk of small-for-gestational-age infants compared to an omnivorous diet. Birthweight in vegans was lower compared to lacto-ovo-vegetarians and omnivores. Vegans also had a lower mean gestational weight gain compared only to omnivores. Maternal B12 status influences their offspring’s B12 levels and is an independent risk factor for neural tube defects (NTD). Studies have shown an association between low B12, low birth weight, and pre-term delivery. Vegan mothers may have poor prenatal nutritional status, resulting in low maternal fat reserves for breastfeeding.
Lifestyle Factors and Selection Bias
While veganism has been shown to decrease the risk of cardiovascular and metabolic syndrome, it is important to consider that vegans often have better socioeconomic levels, live a healthier lifestyle with more physical exercise, and tend to smoke less compared to non-vegetarians. This makes it difficult to isolate the effects of veganism in observational research. Existing research is often skewed by selection bias, with study samples chosen based on prior eating patterns and recruited in environments with a high level of health awareness.
Ethical and Moral Considerations
Arguments against veganism also extend to ethical and moral considerations.
Moral Relativism
Moral relativism, the idea that no behavior is inherently right or wrong and that we must judge people based on the standards of their society, is sometimes used to defend the eating of animals and animal products. However, veganism can be argued to align with most people’s ethics, which involve avoiding unnecessary suffering or death.
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Harm Caused by Plant-Based Agriculture
The argument that plant-based agriculture still causes harm to animals is another point of contention. Modern methods of harvesting plants can result in the deaths of mice and rodents. However, there is a categorical difference between industries that inherently require the suffering/death of animals and industries where that suffering/death is not required but instead is related to the means of implementing that process. It is always possible to continue to refine and improve plant-based processes to make them less harmful, whereas harm and death is, by definition, an inherent part of animal agriculture.
Elitism
The argument that advocating vegan ways of life is elitist or insensitive is sometimes raised. However, most people advocating a vegan way of life are attempting to convince people who have a choice and live in modern areas with many food choices.
Common Anti-Vegan Arguments
Several common arguments are used against veganism, including:
- "Animals eat other animals": Basing our ethics on the actions of animals can lead to problems, as animals engage in behaviors that are not morally justifiable for humans.
- "It's the food chain": Asserting that it is morally justified to eat animals because we are at the “top” of the food chain is an example of the 'might makes right' fallacy.
- "Humane slaughter": The words 'humane' and 'slaughter' are an oxymoron, as there is no nice way to kill someone who doesn't want to die.
- "It's natural to eat animals": There is nothing at all 'natural' about eating animal products in this day and age anyway, as the definition of 'natural' means something that is not man-made.
- "But we're omnivores / We have canine teeth": Having body parts that are simply capable of doing something does not mean that we should do it.
- "Humans have eaten meat for thousands of years / Our ancestors did it": This is an appeal to tradition fallacy, as you could justify just about anything using this logic.
- "What about plants?": It is insane to compare cutting a plant to harming an animal.
- "Those animals are bred for that purpose": Bringing someone into existence for the sole purpose of harming them cannot be justifiable under any circumstances.
- "It's survival": Vegans are living proof that we do not eat animal products for survival purposes.
- "It's the circle of life": This is a quote from Disney’s The Lion King and is used as a thought-terminating cliché to end the argument without having to face the reality.
- "What would happen to all the farm animals if the world went vegan?": The world going vegan is a gradual process, by which the number of people boycotting animal products would increase slowly over time, thus meaning that farmed animals were bred less and less to meet demand.
- "People would lose their jobs if we all went vegan": The livelihoods of those on the side of the oppressor is not worth more than the lives of the oppressed.
- "Your phone parts were made with slave labour / Car tyres contain animal parts": We shouldn't bother minimizing our harm in one area just because we are causing harm in other areas is a complete cop-out.
- "Animals aren't as intelligent as us": It has never been morally justifiable to discriminate against others based on their intelligence.