Public health pitfalls in a vegan future?

As a somewhat unusual combination of psychologist and nutritionist, I read the cover-story articles in the January 2021 issue on various psychological aspects of veganism with interest. It is refreshing to read about psychological research into eating behaviour of any sort, as historically this essential, everyday and life-shaping behaviour has been relatively neglected by academic psychologists, despite much of 20th century psychological science being based on the responses of rodents and pigeons to various manipulations of their diet.

The articles provided useful, if primarily social psychological perspectives on research into barriers and opportunities for both vegans and non-vegans to adopt a vegan diet, and of course the publication timing is apposite given the apparently exponential growth in veganism, and that approaching half a million people in the UK are expected to try a vegan diet during 'Veganuary 2021'. Moreover, January is traditionally the month when many people attempt to diet to lose the 'Christmas kilos': these attempts are mostly futile, not least because winter weight gain may well be both normal and a natural response to colder weather, so instead one could just hang on for salvation in the spring (Davis & Levitan, 2005; Mehrang et al., 2016).

The message from these articles is by and large that we should all at least strive to become vegans to achieve full planet-saving self-actualisation, for example by overcoming the apparently misguided beliefs that eating meat is 'Nice, Normal, Necessary and Natural' (Piazza, 2021) – surely as powerful a quartet of cognitive horsemen to sustain habitual behaviour, like sex for example, as ever there was. Cole and Stewart (2021) consider the impact of our increasing separation from the natural world and in particular agricultural use of animals. I agree this is concerning, and it was brought home to me vividly on overhearing a trainee student teacher exclaim, "Are you telling me that pork comes from pigs?!". Even so, it seems to me that a lack of connection to livestock farming is as likely to be permissive of veganism as it is to meat eating (vegan farmers?), particularly when information is distorted by the imperfect prism of social media.  

Still, I don't intend to debate the merits or otherwise of vegan and other diets for animal welfare, biodiversity or environmental sustainability in this space: some of the arguments were laid out by Carmichael (2021), though agricultural science and policy is moving at pace now, such that even beef production could substantially reduce its methane output through developments in 'breeding and feeding', not to mention the environmental benefits of local sourcing. Rather, I would like to provide some reflections on the vegan diet from a more nutritional and public health behavioural perspective.  

My first concern is the tendency of the articles to conflate 'vegetarian' with 'vegan', explicitly ('veg*n', Dhont & Stoeber, 2021) and implicitly, whereas nutritionally the two are very different (though I accept this conflation is common practice even in nutrition research, likely due to limited studies on strict vegans only): typical 'lacto-ovo-vegetarian' diets, i.e. including consumption of dairy and eggs, are far less likely to present nutritional concerns than the restrictive vegan diet. Moreover, according to the Vegan Society, veganism is a lifestyle philosophy (with legal rights equivalent to a religion) that seeks to avoid animal exploitation or use of animal-derived products not just for food and drink, but for clothes, cosmetics, household goods, medicines and more. Thus, the vegan diet is determined by this philosophy and any consequences for health, good or bad, are coincidental: few nutrition professionals would advocate adopting a vegan diet purely for health reasons, as opposed to other 'plant-based' diets such as lacto-ovo-vegetarian, or indeed arguably the healthiest option, a pescatarian diet.

Incidentally, if like me you are somewhat confused as to what 'plant-based' means, you are not alone: a recent survey by the British Nutrition Foundation (2020) found that only 10% of respondents understood that plant-based diets were not simply equivalent to vegetarian or vegan diets (i.e. they are mostly but not only based on plants). Indeed, even the most committed advocates of sustainable eating are calling for a reduction in meat eating, not its abolition (Willett et al., 2019). To split hairs, vegan diets also rely on fungi, yeasts and algae, which are not strictly plants. I would prefer to use 'plant-rich' (or 'animal-reduced' anyone?), but I suspect the 'plant-based' ship has already sailed.

Of course, no dietary regime guarantees perfect nutrition in its imperfect disciples, and there are plenty of malnourished omnivores, including among the otherwise 'overfed'; yet, for vegans in particular, avoiding animal products increases the risk of deficiencies in n-3 (omega-3) essential fatty acids, vitamin A, vitamin B12, vitamin D, calcium, iron, zinc, iodine, selenium, and potentially amino acid imbalance. Compared to animal products, plants do not give up these nutrients easily, but with care and attention, these risks can be overcome by taking supplements, or supplemented foods, or deploying various 'nutrient hacks' such as using n-3-rich rapeseed oil, sprinkling on chia seeds, combining cereals and pulses, or avoiding tea within an hour either side of a meal.

However, these strategies need nutritional knowledge – so the finding from a large French study that vegans are less educated than omnivores or vegetarians may be important (Allès et al., 2017) – and usually come at a cost, especially financial and/or temporal, and potentially cognitive. There has long been evidence, particularly from the work of the late Mike Green, that attempting a (new) diet without good support leads to deficits in cognitive performance (as tested in a lab at least) independently of nutritional status, possibly due to working memory load (Green & Elliman, 2013; Green et al., 2005).  

Furthermore, the observation that vegan diets are most likely to be taken up by young women (British Nutrition Foundation, 2020) raises additional concerns, as this group has been repeatedly shown to be most susceptible to low intakes of many of the same micronutrients that are hard to obtain from plants (Derbyshire, 2018; Public Health England, 2020). This is also the group for whom preconception and pregnancy diet is most important (Stephenson et al., 2018), albeit the biggest concern in this respect seems to be the very high prevalence of deficiency in folic acid in the UK (Public Health England, 2020), which is less likely for plant-based diets.

Furthermore, whereas most people who adopt either vegetarian or vegan diets are likely motivated by concerns about animal welfare and/or health, there is also evidence that some young women are attracted to restricted plant-based diets as a means to lose weight, and that eating disorder patients often dabble with vegetarianism or veganism probably as a guise for dietary restriction (Paslakis et al., 2020; Timko et al., 2012; Zickgraf et al., 2020).

Given that eating disorders, particularly restrictive anorexia nervosa, seem to be rising sharply during the Covid-19 pandemic (Haripersad et al., 2020; Rodgers et al., 2020), clinicians should be alert to the possibility that patients are adopting a vegan diet primarily for restrictive purposes – doubling down on restriction will not end well.

As well as eating disorders, the pandemic is widely acknowledged to contribute to increasing prevalence of other mental health disorders (The Psychologist, 2020): thus, it may be relevant that there is evidence (though not entirely consistent, Medawar et al., 2020) that veganism is associated with risk of depression (Iguacel et al., 2020; Paslakis et al., 2020); however, this cross-sectional evidence cannot discount the possibility that vegans simply wear weaker rose-tinted spectacles than the rest of us, i.e. their bleaker outlook on the world, or ability to eschew pleasure for ethical principles, helps drive them to veganism.

The food industry has responded to the public's increasing attempts to try a vegan diet with a plethora of 'vegan-friendly' foods and ready meals. As with Carmichael's point about caterers needing to offer plant-based meal choices, this is generally to be welcomed as supporting attempts at veganism, as many such foods may be supplemented; however, being labelled as suitable for vegans is not a guarantee of a healthy meal.

All too often they can also be high in fat, sugar and/or salt, the 'dark triad' of nutrition – though this is not so much intentionally nefarious behaviour by industry as a cheap and easy route to the twin holy grails of the food industry, palatability and shelf-life. Nevertheless, this can certainly compromise the healthiness of the vegan diet, which perhaps together with nutrient deficiencies might explain a lack of benefit to all-cause mortality from avoiding meat (Appleby et al., 2016), particularly if the fat is largely saturate-rich coconut or palm oil – the latter with its well-deserved and hard to counter environmentally disastrous reputation.

Another important debate concerns whether children should be brought up on a vegan diet given their developmentally critical periods and greater nutritional needs than adults (Barnard & Leroy, 2020). Despite limited evidence, there is a broad consensus that a vegan diet is not recommended for babies and infants up to two-years-old because of the nutritional knowledge and professional support required, notwithstanding that vegetarians and vegans tend to breastfeed for longer than omnivores (Baldassarre et al., 2020); but beyond that age there are divergent views.

Many European countries have position statements from paediatric or nutrition societies regarding children on vegan or vegetarian diets (again unfortunately conflated), which could be summarised as 'only with careful oversight from a medical or dietetic/nutritional practitioner', yet forming that parent-professional alliance can be fraught (Farella et al., 2020; Rudloff et al., 2019). A particularly complex situation arises when a vegan child has food allergies, as this further restricts dietary options, requiring more supplementation and concerns about meeting basic protein-energy needs (Protudjer & Mikkelsen, 2020).

The Covid-19 pandemic has increased the already rising use of food banks and further exaggerated the stark socioeconomic differences in food security in the UK (The Trussell Trust, 2020; Yau et al., 2020): perhaps surprisingly, European non-meat eaters tend to have lower incomes, though there may be residual confounding due to also being younger and mostly female (Allès et al., 2017; Wozniak et al., 2020).

To many people, despite its nutrient density, meat is already a luxury, and this may well be the future for most of us, especially with the demise of factory farming, however welcome that may be for welfare reasons. Thus, the future may well be more 'flexitarian', and greater uptake of 'plant-based' meals will have clear health benefits, but following a strict vegan diet, with its exclusion of nutrient-rich seafood, dairy and egg products as well as reliance on supplementation, does not look like a solution to these public health problems any time soon.

Dr E. L. Gibson BSc PhD RNutr CPsychol AFBPsS FHEA
Reader in Biopsychology
Department of Psychology
University of Roehampton

References

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