Balancing the global protein economy is more than just switching from animal-based to plant-based foods
from sewage in the USA, protein quality in Malawi to vulnerable older people here in the UK
There has been increasing recognition that the production of dietary protein is having deleterious impacts on the environment. In addition, there is evidence that high consumption of some animal-based protein sources, particularly red and processed meat, impact on risk of developing various chronic diseases, particularly colorectal cancer. These concerns were reflected in Henry Dimbleby’s recommendations for a national food strategy, published last year1, which referred to ‘a protein transition’ which included:
· Investment in technology to reduce methane production in ruminants
· Investment in alternative proteins that can replace some animal products
· Nudging consumer behavior through industry action and public sector procurement.
In June, the UK government’s response to Dimbleby’s recommendations2 highlighted ongoing investment in alternative protein research, the value of British grown pulses and beans and briefly mentioned non-traditional livestock protein sources. Such a response perhaps under-estimates the scale of the transition needed, with the most recent NDNS data3 showing that UK adults (19-64y old) currently on average obtain 59% of their protein intake from animal sources, 24% from cereals and only 8% from vegetables (the remaining 9% coming from ‘other’ sources)’.
It is also important to consider global issues in protein production and consumption. Two recent publications have highlighted very different issues in different parts of the globe, one of excess quantity of protein intake (and environmental impact) and one of inadequate protein quality (and health impact).
The first study shows nitrogen pollution of water supplies could be reduced in the United States with lower protein consumption4. Protein consumption in the United States, from both plant and animal sources, ranks among the highest in the world. When a body takes in more protein than it needs, excess amino acids are used as an energy source and their nitrogen-based breakdown products excreted in urine, which are released through the wastewater system.
The second study estimates that in Malawi the protein consumed is often of relatively low quality, associated with a high risk of lysine deficiency in the poorest households5. The study showed that the poorest households in Malawi obtain 80% of their dietary protein from cereal crops, predominately maize, which is known to be relatively poorly digestible, with low concentrations of specific essential (indispensable) amino acids, in particular lysine.
But what about the situation in the UK? Closer to home, there are also potential problems in providing sufficient high-quality protein for our ageing population. There is increasing recognition that as we age, protein requirements increase. Deficient intakes, coupled with reduced exercise, increase the likelihood of muscle wasting and sarcopenia. The reference nutrient intake (RNI) for adults currently stands at 0.75 g/kg body weight per day which equates to 56 g/day and 45 g/day for men and women (assuming body weights of 75 and 60kg respectively). NDNS data indicates that mean protein intake in 75+ year-old males is 68.8g/d and for females 59.2/g.
However, recent research is suggesting that intake should be considerably higher in older age groups and, even in healthy individuals, intake should be increased to between 1.0-1.2 g/kg6. Taking a value of 1.1 g/kg, this would equate to an increase in requirements of this age group to 82.5 g/d and 66.0 g/d for men and women respectively, both (particularly for men) above the average current intakes in this age group. The wide range of current intakes, including low intakes, is also noteworthy in this context. Furthermore, a shift from animal- to plant-derived protein sources, without access to a wide range of plant sources with complementary indispensable amino acid profiles, may decrease the overall quality of the protein consumed in terms of both indispensable amino acid consumption and digestibility. With the 75+ age group, which currently obtains 62% of protein from animal-derived foods (and a further 24% from cereals), set to increase by 75% by 20507 in the UK (with similar rises in many high -income countries), this highlights the caution that must be taken in ensuring any transition of our food systems is mindful of the needs of the most vulnerable in our societies.
The Academy of Nutrition Sciences (ANS) recognizes the need to diversify our choice of protein sources and reduce our dependence on animal products as a primary source of protein. For some individuals this could simply mean consuming less meat (with little need to replace this with anything else as protein intakes are already adequate). However, the ANS is acutely aware that the high-quality-protein provided by meat, and other animal derived foods – milk and dairy products, fish and eggs - will remain a vital part of the diet of vulnerable individuals, within both low- and high-income countries, and that in the poorest parts of the world consumption is likely to increase. Therefore, in addition to changing human diets to better align them with both healthy eating and sustainability guidelines, further efforts are required to improve the environmental impact of livestock production. In addition to the methane reductions highlighted by Dimbleby, other strategies include replacement of human-edible crop sources of protein (such as wheat, maize and soya) as ingredients of animal feed, which represents almost 50% of global production, with alternative and more sustainable protein sources such as single-cell organisms and insects. While industries producing these are appearing, there is an urgent need for further research to ensure the safety, affordability and sustainability of such alternatives.
Our food systems need to change, and this includes a reduction in our dependence on animal-derived foods, in high-income societies in particular. However, the issues highlighted above demonstrate that this should be done cautiously, with due regard to the most vulnerable. While recent years have seen significant shifts toward vegan and vegetarian diets, 86% of individuals still eat meat in the UK. There needs to be a realistic acknowledgement that animal products will remain a fundamental part of our diet for decades to come, but much could be done to improve the sustainability of livestock production. It is not simply a case of swapping beef burgers for plant burgers.
1) https://www.nationalfoodstrategy.org/
2) https://www.gov.uk/government/publications/government-food-strategy/government-food-strategy
4) https://esajournals.onlinelibrary.wiley.com/doi/10.1002/fee.2531
5) https://www.mdpi.com/2072-6643/14/12/2430
6) https://www.mdpi.com/2072-6643/10/3/360/htm
7) https://population.un.org/wpp/
Professor Andy Salter, University of Nottingham