The importance of balancing protein in diets in different parts of the globe to benefit health and the environment is highlighted in new research that shows nitrogen released into water could be reduced in the US with less protein consumption, whilst in Malawi there is significant deficiency in high quality protein being consumed.
Balancing how much protein you eat with the amount your body needs could reduce nitrogen releases to aquatic systems in the U.S. by 12 percent and overall nitrogen losses to air and water by 4 percent, according to a study led by the University of California, Davis, in collaboration with the University of Nottingham.
Protein consumption in the United States, from both plant and animal sources, ranks among the highest in the world. The study, published in the journal Frontiers in Ecology and the Environment, said that if Americans ate protein at recommended amounts, projected nitrogen excretion rates in 2055 would be 27% less than they are today despite population growth.
The study is the first to estimate how much protein consumption contributes to excess nitrogen in the environment through human waste. It also indicates that coastal cities have the largest potential to reduce nitrogen excretions headed for their watersheds.
"It turns out that many of us don't need as much protein as we eat, and that has repercussions for our health and aquatic ecosystems," said lead author Maya Almaraz, a research affiliate with the UC Davis Institute of the Environment. "If we could reduce that to an amount appropriate to our health, we could better protect our environmental resources."
The human body requires protein. But when a body takes in more protein than it needs, excess amino acids break it down into nitrogen, which is excreted mostly through urine and released through the wastewater system. This brings additional nitrogen into waterways, which can result in toxic algal blooms, oxygen-starved "dead zones" and polluted drinking water.
The scientists estimated current and future nitrogen excretion exports based on U.S. census population data. They saw an upward trend over time, with exports increasing 20% from 2016 to 2055. That increase is associated with population growth, as well as an aging population, which requires more protein to manage muscle loss.
In contrast to this, researchers from the University of Nottingham also led a study, published in Nutrients that estimates that the poorest households in Malawi obtain 80% of their dietary protein from cereal crops, predominately maize, which is known to be poorly digestible and deficient in specific amino acids, in particular lysine. 82% of individuals in the poorest households were at risk of lysine deficiency (compared to only 3% in the richest households). This study, which used data from recent household consumption and expenditure surveys, highlighted the need to diversify the sources of protein available in the poorest areas of the world, and more specifically, to improve access to animal source foods for the most vulnerable.
These two papers highlight the complex nature of the problems we face in moving toward more sustainable food systems. While there is little doubt that reducing excessive consumption of animal-based foods in high-income countries would have both environmental and health benefits, we must remain aware of the large number of vulnerable populations around the world who remain at risk of malnutrition and who are in urgent need of diversification of the types of food available to them. With a growing, and aging, global population, balancing a reduction in the impact of food production on the environment, with ensuring availability of key nutrients to vulnerable populations, represents a major challenge for coming decades.
