October 23, 2023, by pczmj

Time to diversify rather than demonize our dietary protein sources

This blog is by Professors Andrew Salter and John Brameld.

Andrew Salter is an Emeritus Professor of Nutritional Biochemistry, School of Biosciences at the University of Nottingham. John Brameld is a Professor of Nutritional Biochemistry at the School of Biosciences, University of Nottingham

Global protein consumption trends

Consumption of protein of appropriate quality, in terms of both indispensable amino acid (IAA) composition and digestibility is essential across our lifecycle.  In infancy this can be met entirely by breast milk but after weaning we are dependent on dietary sources. The contribution of different proteins sources varies substantially across the world. Details about global population protein supply and intake, are available within this FAO Food Balance Sheet 2020.

In high-income regions, much of the population significantly exceed their protein requirement through the consumption of a combination of animal and plant-based foods.  Meat, fish, dairy products and eggs are all sources of highly digestible protein of appropriate amino acid composition.  For those who choose to avoid animal-derived foods, requirements can be met by consumption of a variety of plant-based foods which, while individually may be of lower quality, in combination can also meet requirements.  Protein consumed in excess of requirements can be used as a source of energy.  In lower income countries, meeting requirements is more challenging, particularly when protein is largely obtained from poor quality plant sources.  For example, we recently showed that in Malawi, there is a high dependency on maize as the primary protein source, which is low in some IAAs and poorly digested.  As a result, 20% of households were estimated to be in danger of protein deficiency. Historically, as poorer countries become more economically stable, the risk of protein deficiency has been alleviated by incorporating more animal-derived food products into the food chain.  However, increasing concerns over both health and environmental impacts of animal products, particularly red and processed meat, have led to calls for alternative solutions.

The pros and cons of meat

Meat represents a major source of protein and many other essential nutrients for a large proportion of individuals in most high-income countries.  Over the last century, agricultural practices, including selective breeding, precision nutrition, husbandry, and in some cases, use of growth promoters, have all contributed to ensuring widespread accessiblity to affordable meat products.  As a result, in general, protein deficiency is relatively rare in such regions.  However, there is increasing recognition of potential health impacts of excessive consumption, particularly of red and processed meat. Diets rich in such products tend to be more energy dense, and as such can lead to obesity and related conditions such as type 2 diabetes.  Red meat also represents one of the major sources of saturated fatty acids in the diet, which are known to increase plasma low density lipoprotein (LDL) cholesterol, and as such increase the risk of cardiovascular disease.  Red and processed meat have also been increasingly associated with colorectal cancer.  In addition to health effects, meat production has also been associated with negative impacts on the environment.  Methane production by ruminant animals, such as cows and sheep, has been linked with global warming.  On the other hand, through the action of microbes in their digestive system, such animals are able to ‘fix’ nitrogen to synthesize amino acids, while consuming low quality forage -based diets.  By contrast, monogastric animals, including pigs and poultry, require relatively high -quality dietary protein (often from human-edible crops) that is relatively inefficiently incorporated into their body tissues.  This requires vast amounts of land and water which could be utilized directly for producing crops to be consumed by humans. You can check here for the relatively high inefficiencies by which protein used to feed livestock is ultimately consumed by humans.

Health, environmental, and for some, ethical considerations have all led to increasing calls for such populations to reduce their meat consumption.  While there is little doubt that many individuals could achieve this without any adverse nutritional impact, caution should be taken with some demographics, including adolescents, who already have a potential risk of micronutrient deficiencies; the elderly, who are increasingly recognised as requiring higher protein intakes than younger people; as well as those who are most economically compromised and as such may not have access to, the often more expensive, high quality plant protein sources.  Furthermore, in low income regions, including large parts of Africa, where populations are growing most rapidly and who are currently reliant on low quality cereal protein, some increase in consumption of meat or other animal products could alleviate the risk of protein-energy malnutrition.

Diversifying protein sources in food and feed

The majority of protein in the human diet is derived from cereal crops, meat and dairy products, but in very different proportions according to region. Roughage (largely fresh and preserved grasses) represents the major protein source for ruminants in the European Union, though in many countries this is supplemented with other ingredients to improve performance. Soyabean meal represents the major protein source in monogastric (pig and poultry) feeds.

There is considerable potential for diversifying the protein sources used for food and feed. There have been increasing calls for us to increase consumption of protein-rich plants.  While some of these already represent a significant component of many diets, including peas, a range of beans and ground and tree nuts, others remain relatively underutilized.  One of the primary reasons for this is the relatively poor digestibility of many such sources.  This can be the result of interactions of protein with other components, such as fibre, the physical structure of the protein and/or the presence of anti-nutritional factors, such as tannins, phytic acid and trypsin inhibitors, that interfere with the digestive processes.  Similar problems have also limited their use in animal feeds.  Measuring the digestibility of such sources in vivo is expensive and highly invasive.  However, working with colleagues around the world, we have been developing an in vitro digestion system that can rapidly and affordably determine potential digestibility of each amino acid.  This will allow us to screen large numbers of potential protein sources and to determine the effectiveness of different processing techniques to improve their digestibility.  Several such protein -rich plant sources have been identified that are relatively tolerant to adverse climate conditions.  These have the potential to represent important protein sources in some of the most protein-deficient parts of Africa and Asia.

Single cell organisms, including algae, fungi and bacteria also represent currently underutilized protein sources. Some are already well established in our diets, with one of the most familiar being Fusarium venenatum, a filamentous microfungus that has been used to produce ‘mycoprotein’, the protein -rich ingredient of the meat analogue brand ‘Quorn’.  At Nottingham, we are investigating a range of sources to optimize production, amino acid composition and digestibility of other algal and fungal species.  There is also increasing interest in genetically manipulating organisms such as yeast to produce high value proteins (such as casein and whey) that can be incorporated into products such as ice cream.  Bacteria are also rich in protein, and there is particular interest in developing large scale bioreactors to sustainably produce such protein for incorporation into animal and fish feed.

Insects represent a major source of protein for many wild animals and birds.  They have also been a traditional component of the diet of many populations around the world.  Insect production is much more environmentally friendly than traditional livestock production, in terms of land and water use, greenhouse gas emissions and their ability to grow on relatively poor dietary sources.  While attempts have been made to introduce products containing insect protein into Western diets, there still remains some resistance to consuming what many regard as ‘pests’. However, like bacteria, there is growing interest in insects for use in animal feeds with a number of global companies now producing insects (largely black soldier fly larvae or mealworms) as a dietary component for poultry, fish and even pet food.

A further alternative protein source which is often highlighted in the media is cultured meat.  This is produced by growing animal cells (derived from livestock) in bioreactors and then combining them with ‘scaffold ingredients’ to produce meat-like products.  While such products have been made, at present the technology needs to be refined and scaled to compete with other protein sources, or indeed meat itself, in terms of cost and sustainability.  At Nottingham we are developing novel cell technologies including pluripotent stem cell lines with enhanced stability in long term culture and high differentiation potential, to generate rapidly growing muscle cells.  Ultimately, cultured meat may have the capacity to meet the needs of those in society that continue to demand access to meat.

Challenges for the Future   

There is increasing recognition that our food systems must evolve to provide equitable access to adequate nutrition across the world, while minimizing negative effects on human health and the environment.  In achieving such a transition, we must protect the most vulnerable in society and meet the needs of all demographics.  The Nottingham International Centre for Alternative Proteins firmly believes that this should be achieved by a combination of reducing our dependence on animal-derived foods and improving the sustainability of livestock farming.  With a large proportion of the global population dependent on animal products, and even more who would benefit from increased consumption, as well as many agricultural workers dependent on incomes derived from their production, we do not believe that demonizing their consumption is the way forward.  There is an urgent need for funding of research to enable a much more diverse and sustainable protein economy that will ultimately reduce our dependency on animal-derived foods.

Posted in Alternative ProteinsFood Research