One of the most common questions heard by anyone on a plant-based diet is: “Where do you get your protein?”
The question arises because of a common misconception that protein is only available in meat or other animal products, such as chickens’ eggs or cows’ milk, or that plant-based protein is somehow inferior.
The fact that some of the largest, strongest animals are herbivores or near-herbivores should alert people to the fact that there is plenty of protein available without eating animals. The range of herbivores or near-herbivores includes elephants, rhinoceroses, giraffes, cows, horses and great apes such as chimpanzees, gorillas, and orangutans.
The position is further highlighted by the fact that a 2013 paper from the Institute on the Environment at the University of Minnesota stated :
“The world’s croplands could feed 4 billion more people than they do now just by shifting from producing animal feed and biofuels to producing exclusively food for human consumption”.
Animal feed crops represent 90% of that figure (representing 3.6 billion people), and biofuels only 10%.
The lead author, Emily Cassidy, has been quoted as saying:
“We essentially have uncovered an astoundingly abundant supply of food for a hungry world, hidden in plain sight in the farmlands we already cultivate. Depending on the extent to which farmers and consumers are willing to change current practices, existing croplands could feed millions or even billions more people.”
Similarly, Dr David Pimentel of Cornell University reported in 2003 that the grain fed each year to livestock in the United States could feed 840 million people on a plant-based diet. 
Referring to US Department of Agriculture statistics, Pimentel has also stated that the US livestock population consumes more than 7 times as much grain as is consumed directly by the entire American population.
He and Marcia Pimentel have also reported:
” . . . each American consumes about twice the recommended daily allowance for protein “.
The results cited above reflect, in part, the gross and inherent inefficiency of animals as a food source.
Is it difficult to replace animal protein with plant protein?
The Physicians Committee for Responsible Medicine (PCRM) has stated :
“To consume a diet that contains enough, but not too much, protein, simply replace animal products with grains, vegetables, legumes (peas, beans, and lentils), and fruits. As long as one is eating a variety of plant foods in sufficient quantity to maintain one’s weight, the body gets plenty of protein.”
“It was once thought that various plant foods had to be eaten together to get their full protein value, but current research suggests this is not the case. Many nutrition authorities, including the American Dietetic Association, believe protein needs can easily be met by consuming a variety of plant protein sources over an entire day. To get the best benefit from the protein you consume, it is important to eat enough calories to meet your energy needs.”
PCRM is a US-based non-profit organisation that promotes preventive medicine, conducts clinical research, and promotes higher standards for ethics and effectiveness in research.
The US Department of Agriculture has reported the following protein content for a variety of food products, as shown in Figure 1 .
Figure 1: Protein content of selected foods
Some health implications of consuming too much protein
PCRM has also highlighted some of the health implications of excessive protein intake, including kidney disease and certain types of cancer. Specifically in relation to animal protein, it has referred to osteoporosis and kidney stones, stating :
“Diets that are rich in animal protein cause people to excrete more calcium than normal through their kidneys and increase the risk of osteoporosis. Countries with lower-protein diets have lower rates of osteoporosis and hip fractures.”
I have also commented on some health implications of eating animals in my article “If you thinks it’s healthy to eat animals, perhaps you should think again“.  Amongst the studies referred to was a 26-year study of more than 120,000 people by Harvard University, which found that eating red meat is associated with a sharply increased risk of death from cancer and heart disease. The lead author described the results as “staggering”. 
In addition to contributing significantly to human health problems, by utilising animals as a source of protein and other nutrients, we are causing extreme cruelty to the animals themselves, creating massive environmental problems (including those relating to climate change) and contributing to the malnutrition of more than 800 million people. 
Protein sources in Australia
The following chart shows that 81 percent of protein produced in Australia in 2010/11 came from plants, and only 19 percent from animals.
It includes products that are exported and/or used as livestock feed. The inclusion of the latter means there is some double-counting of protein content. However, given animal agriculture’s relatively low output level, the double-counting does not appear to be significant.
Figure 2: Protein value of Australian food production
The chart is based on: (a) production figures from the Department of Agriculture, Fisheries and Forestry’s “Australian food statistics 2010-11″;  and (b) nutritional information for each product from the United States Department of Agriculture’s (USDA) National Nutrient Database for Standard Reference. . It appeared in my September, 2012 submission in response to the Department of Agriculture Fisheries and Forestry’s National Food Plan Green Paper. 
Despite effective campaigns by powerful interest groups to convince us that animal-based protein is essential to human health, an objective review of the available evidence points strongly in the opposite direction. If we are to improve human health and create a world that is more just and sustainable, we must move away from animals as a food source.
- This article is not intended to represent dietary, nutritional, health, medical or similar advice.
- Figure 1 was updated on 21st February, 2016.
- The comment “Animal feed crops represent 90% of that figure, and biofuels only 10%” added 1st April, 2016.
Author: Paul Mahony
 Cassidy, E.S., West, P.C., Gerber, J.S., Foley, J.A., “Redefining agricultural yields: from tonnes to people nourished per hectare”, Environ. Res. Lett. 8 (2013) 034015 (8pp), doi:10.1088/1748-9326/8/3/034015, cited in University of Minnesota News Release, 1 Aug 2013, “Existing Cropland Could Feed 4 Billion More”, http://www1.umn.edu/news/news-releases/2013/UR_CONTENT_451697.html
 Pimentel, D., Cornell University “Livestock production and energy use”, Cleveland CJ, ed. Encyclopedia of energy (in press), cited in Pimentel, D. & Pimentel M. “Sustainability of meat-based and plantbased diets and the environment”, American Journal of Clinical Nutrition, Vol. 78, No. 3, 660S-663S, September 2003, http://ajcn.nutrition.org/content/78/3/660S.full
 Physicians Committee for Responsible Medicine “The Protein Myth”, http://www.pcrm.org/health/diets/vsk/vegetarian-starter-kit-protein
 PCRM 2013 Consolidated Fiscal Year Report, http://www.pcrm.org/media/good-medicine/2014/winter2014/pcrm-2013-consolidated-fiscal-year-report
 Mahony, P., “If you thinks it’s healthy to eat animals, perhaps you should think again”, 12th February, 2013, https://terrastendo.net/2013/02/12/if-you-think-its-healthy-to-eat-animals-perhaps-you-should-think-again/
 Bakalar, N., “Risks: More Red Meat, More Mortality”, The New York Times, 12 March, 2012, http://www.nytimes.com/2012/03/13/health/research/red-meat-linked-to-cancer-and-heart-disease.html?_r=1&scp=2&sq=red%20meat%20harvard&st=cse#
 Food & Agriculture Organization of the United Nations, “Global hunger down, but millions still chronically hungry”, 1st October, 2013, http://www.fao.org/news/story/en/item/198105/icode/
 Dept of Agriculture, Fisheries and Forestry, “Australian Food Statistics 2010-11”, http://www.agriculture.gov.au/ag-farm-food/food/publications/afs/australian-food-statistics (Link updated 9th July, 2015.)
 Mahony, P., “Submission in Response to Department of Agriculture Fisheries and Forestry National Food Plan Green Paper: The urgent need for a general transition to a plant-based diet” Sep, 2012, pp. 37-38 http://www.daff.gov.au/__data/assets/pdf_file/0011/2211014/Mahony-Paul.pdf