There is wide scale concern about the effects of red meat on human health and climate change. Plant-based meat alternatives, designed to mimic the sensory experience and nutritional value of red meat, have recently been introduced into consumer markets. Plant-based meats are marketed under the premise of environmental and human health benefits and are aimed appeal to a broad consumer base.
Most humans generally follow an omnivorous diet: they satisfy some nutrient requirements better from plant foods, while needs for other nutrients are met more readily from animal foods. Animal foods also facilitate the uptake of several plant-derived nutrients (zinc and iron), while plant nutrients can offer protection against potentially harmful compounds in cooked meat. Thus, plant and animal foods operate in symbiotic ways to improve human health. The mimicking of animal foods using isolated plant proteins, fats, vitamins, and minerals likely underestimates the true nutritional complexity of whole foods in their natural state, which contain hundreds to thousands of nutrients that impact human health.
Novel plant-based meat alternatives should arguably be treated as meat alternatives in terms of sensory experience, but not as true meat replacements in terms of nutrition. If consumers wish to replace some of their meat with plant-based alternatives in the diet (a “flexitarian approach”) this is unlikely to negatively impact their overall nutrient status, but this also depends on what other foods are in their diet and the life stage of the individual.
Fortifying Foods to Mimic the Natural Food Source
A recurring concern is that natural whole foods are extremely complex and the reductionist approach of trying to “mimic” whole food sources (whether it be meat or other foods) by combining several isolated nutrients likely underestimates the true complexity and health benefits of eating whole foods. In particular, fortification of a low-meat diet with zinc and other minerals found in meat did not result in similar zinc status as when these minerals were provided in the diet as part of the natural matrix of meat.
Moreover, adequate intakes of zinc, copper, and vitamins A and D were associated with decreased risk of cardiovascular disease and all-cause mortality when obtained from foods, but not from supplements, in a recent large population-based study. Similarly, carotenoid-containing foods are associated with a decreased risk of various cancers, retinopathies, and cardiovascular disease. However, the results of interventional and epidemiological studies suggest that carotenoid and/or vitamin A supplements do not decrease the risk of cancer or cardiovascular disease and might even raise the risk for some sub-populations.
Similar findings have been made in studies of calcium that show a potential for increased cardiovascular disease risk with supplementation but not when calcium is obtained from food. Finally, similar findings have been made for vitamin C and selenium supplements that show no benefits on mortality in a systematic review of randomised controlled trials (RCTs) comprised of nearly 300,000 individuals. Thus, it appears that simply ingesting these nutrients outside of their natural food matrices may not be an optimal solution for promoting health. Thus, obtaining nutrients from whole food sources as opposed to supplemental forms is emphasised regardless of the individual's diet.
The Ecological Impacts of Plant-Based Meat vs. Meat Consumption
The plant vs. meat controversy takes on other dimensions when assessing environmental degradation and climate change, both of which adversely affect human health and are crucial considerations when making recommendations on diets for livestock and humans. Meeting requirements of nutrients with plant foods (e.g., folate, manganese, thiamine, copper, and β-carotene) may come at a lower environmental footprint (i.e., less greenhouse gas emissions or GHGEs) than when these nutrients are met with animal foods. Nonetheless, it has been suggested that similar amounts of protein, iron, and vitamin A can be obtained from carefully selected plant-based diet at a lower carbon footprint when compared to omnivorous diets/animal foods.
The lower carbon footprint of plant-based meat alternatives is touted as a main reason for choosing plant alternatives over beef. While meat alternatives may have a lower environmental impact when compared to feedlot-finished beef, well-managed pasture-based livestock systems fix at a minimum all the GHG they emit (and sometimes more) even when considering all aspects of the production. Pastured beef systems that use land management practices such as rotational grazing—where lands are allowed to properly recover after a grazing period—and/or cover crop grazing suggest that the amounts of carbon sequestered in the soil more than offsets the ruminants' GHGE, resulting in a net negative carbon footprint. By having livestock participate in carbon cycling by spending their lives on well-managed pastures—grooming and fertilising vegetation and soil—such production systems have the potential to help mitigate climate change (or in the very least not exacerbate it further) while ensuring a degree of food security.
Well-managed grasslands, especially in more mesic (moisture-rich) areas, can act as carbon sinks in a variety of geographical locations worldwide and depending on geographical locations, may be more reliable carbon sinks than forest. It must be noted that the two (forests and livestock) are not mutually exclusive to begin with, as demonstrated by successful implementation of silvopastoralism—a type of agroforestry integrating trees, forage, and livestock—in forested areas across the globe as a strategy to enhance carbon sequestration, soil health, and food security for those inhabiting such areas. Thus, considerations regarding livestock-production systems should be tailored to fit the geophysical landscape instead of attempting—often at great expense—to change the environment to fit the production system. For example, it would be suitable to practice silvopasture techniques with locally adapted animals in landscapes such as the Amazon rather than attempting to convert its forests to pasturelands.
It must be noted though that not all pasture-based (grass-fed) operations are per se regenerative or neutral, and depending on management practices, grass-fed beef systems can have a higher carbon footprint than some feedlot systems. It is also important to highlight that the amount of carbon sequestered with well-managed grazing of livestock on carbon-depleted soils is initially more rapid and diminishes over time as soil health is restored, which is not surprising once equilibrium of ecological systems are reached.
The ecological impacts of human diets are not as simple as plant vs. meat discussions might suggest. The global food system is far too diverse and contingent on unique environmental and socioeconomic circumstances to allow for one-size-fits-all policy recommendations. As the latest IPCC (Intergovernmental Panel on Climate Change) Report points out, mixed plant farming-livestock grazing systems can heal damage done by years of continuous arable cropping reliant on mechanical and chemical inputs. In the process, we may increase the number of animals grazing phytochemically rich landscapes that nurture animals, soil, plants, and people, and provide food that is biochemically richer and arguably more nourishing for Homo sapiens and the planet.
Conclusion
Humans satisfy requirements for certain nutrients much better from plant foods, while needs for other nutrients are met more readily from animal foods. Plant nutrients (i.e., phytochemicals) often protect against potentially harmful compounds in cooked animal foods while animal foods also facilitate the uptake of several plant nutrients (e.g., zinc and non-haem iron). Thus, plant and animal foods interact in symbiotic ways to improve human health.
While plant-based diets are being promoted for human and environmental health reasons, this may put large portions of the population at greater risk for nutrient deficiencies and accompanying health issues. This may especially be the case for vulnerable populations such as children, elderly, and nursing mothers who are at increased risk for nutritional deficiencies. Some suggest that in order to meet requirements for several key nutrients with plant foods (vitamins A, B3,6,12, choline, zinc, iron, and selenium), more plants should be ingested to overcome their reduced bioavailability and supplements should be taken if deficiencies arise (vitamin B12 would have to be supplemented regardless). However, intra-individual differences in nutrient metabolism may preclude portions of the population to thrive on vegan/vegetarian diets, regardless of how well the plant-based food or diet may be “designed.”
Many scientists are concerned about the reductionist approach of simply adding isolated forms protein, vitamins, and minerals to foods, or diets in general, and designating them as nutritionally adequate. As whole foods contain hundreds-to-thousands of compounds that act synergistically to impact human health, adding synthetic nutrients to food sources often does not confer similar benefits compared to when these nutrients are ingested as phytochemically and biochemically-rich whole foods—whether it be plant or animal foods.
Scientists who operate in the realms of nutrition and ecology, those in companies that produce plant-based meat alternatives, and the general public arguably share similar concerns about the influence of agriculture on climate change. Where groups differ is in their solution to the challenge. There are many whole-foods dietary options that could substantially improve human and ecological health - whether they be vegetarian, pescatarian, or omnivorous. An omnivorous diet rich in whole foods, produced using sustainable agricultural practices that integrates plants and animals in agroecological ways (i.e., in harmony with natural systems), is most likely to benefit human and ecological health.
At present, novel plant-based meat alternatives should arguably be treated as meat alternatives in terms of sensory experience, but not per se as true nutritional replacement for meat. If consumers wish to replace some meat in their diet with plant-based alternatives (a “flexitarian approach”), this is unlikely to negatively impact their overall nutrient status; however, this also depends on what other foods are routinely consumed and the life stage of the individual (e.g., infancy, pregnancy, or advancing age). That said, it is important for future work to compare human health outcomes in response plant-based vs. animal meat consumption. Such studies can ensure, and potentially improve, the healthfulness of plant-based meat alternatives and meat itself, as it is likely that both will have a have a significant role to play in our future food supply.
Reference
van Vliet S, Kronberg SL and Provenza FD (2020) Plant-Based Meats, Human Health, and Climate Change. Front. Sustain. Food Syst. 4:128. doi: 0.3389/fsufs.2020.00128
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