Where do You Get Your Protein

“Where do you get your protein?” (or iron of calcium) is a frequent question for those on a vegan diet. Well, the same place as gorillas, elephants, the grumpy extinct aurochs, brontosaurus and Argentinosaurus- the largest ever land animal weighing more than 15 elehants. From eating plants.

Milks are complex lipid emulsions in water containing protein, fat, lactose, vitamins and minerals, as well as enzymes, hormones and immunoglobulins which provide initial immunity functions.

There is approximately 5,500 species of mammals which initially supply their young with milk. There are vast differences in milk composition among the mammal species.

Mammals have evolved over millions of years to provide nutrition for their infants in the first stage of life. There are significant difference between species depending upon factors such as rates of growth.

Proteins in human milk provide sufficient nourishment to sustain infants for the first six months without any additional food, as well as establishing a suitable environment for the growth of healthy intestinal bacteria.

Human milk has the lowest protein content of any mammal. Human milk is supplied to babies when the need for protein is at the greatest. Babies double in size during the first 6 months of our lives. The ideal food for a baby is mum’s milk where 5% – 6.5% of the energy requirements is obtained from protein.

This should offer reassurance that as long as we a consuming an adequate diet, we do not need a high protein diet.

Proteins are comprised of amino acids. There are 21 amino acids found in foods, although 20 is commonly given as a number. Two contain sulphur (methionine, cysteine) with selenocysteine containing selenium instead of sulphur.

Dr. William Rose of the University of Illinois, working in the 1940s, found that 10 amino acids were essential for a rat’s diet.

According to these rat studies, wheat and rice are lacking in lysine and corn is lacking in tryptophan.

The following table shows that one serving of a several foods provide ample protein. One serving (250 ml) of brown lentils provide all our protein and amino acid requirements.

The Recommended Daily Intake (RDI) is 2 standard deviations above the average requirement. That is, the RDI meets or exceeds the requirements of at least 97.8% of the population. You do not need to take additional protein “just to be safe“. ¹

The following table shows a selection of common vegetables showing that there is ample protein available – irrespective of age or physical activity. ²

However, human protein requirements are different from humans. Rats double in size in 4-5 days and become adults in 6 months. It takes 6 months for a baby human to double in size and 17 years (maybe) for a human to become an adult.

Of all of these mammals, human milk has the lowest protein content (6%) compared with cows (20%), rat (24%), guinea pig (41%) and kangaroo (57%). ³

Lysine is a dietary indispensable amino acid.

Lysine is the first limiting amino acid in most grain and cereal-based diets so it also defines the protein required to meet the amino acid requirements.

David Kritchevsky was one of the early investigators of the relationship of cholesterol and heart disease in the 1950s. He linked different types of proteins to heart disease, determining that protein of animal origin leads to an increase of cholesterol in the blood. ^{4 5}

Casein is a protein found in all milk from mammals.

The addition of lysine to soy protein, sufficient to change its normal lysine/arginine ratio to that of casein, significantly increases its atherogenicity – the buildup of fatty deposits in the artery walls which causes inflammation and narrowing of the arteries.

Addition of arginine to casein to lower its lysine/arginine ratio to that of soy protein decreases its atherogenicity.

Foods high in lysine include meat, poultry, fish, cheese, yoghurt and eggs. Wheat and oats are relatively low in lysine.

Another 1997 study suggests that low lysine diets as measured by the low lysine to arginine ratio “exert hypocholesterolemic effects” – that is, cholesterol is lowered. ⁶

Russell Henry Chittenden was professor of physiological chemistry at Yale from 1882 to 1922. He was not convinced that the current protein requirements of 120g per day was correct and determined that 50-60g per day was more appropriate. As Chittenden explained back in 1904: ⁷

Last updated on Saturday 4 July 2026 at 08:45 by administrators

1. SDA ERS (2018) USDA ERS – Food Availability (Per Capita) Data System. Available from: https://fdc.nal.usda.gov/food-search?type=Survey%20(FNDDS) (Accessed 5 March 2018).
2. Food Standards Australia New Zealand (2026) Food Detail – Australian Food Composition Database. Available from: https://www.foodstandards.gov.au/science-data/food-nutrient-databases/afcd/search.
3. Hurley, W. L. (2009) Milk Composition – Species Table. Available from: http://ansci.illinois.edu/static/ansc438/Milkcompsynth/milkcomp_table.html (Accessed 2 January 2017).
4. Kritchevsky, D. (1990). Protein and Atherosclerosis. Journal of Nutritional Science and Vitaminology, 36(5), 81–86.
5. Kritchevsky, D., Tepper, S. A., Czarnecki, S. K., & Klurfeld, D. M. (1982). Atherogenicity of animal and vegetable protein: Influence of the lysine to arginine ratio. Atherosclerosis, 41(2–3), 429–431.
6. Rajamohan, T., & Kurup, P. (1997). Lysine: Arginine ratio of a protein influences cholesterol metabolism. Part 1—Studies on sesame protein having low lysine: Arginine ratio. Indian Journal of Experimental Biology, 35(11), 1218–1223.
7. Chittenden, R. H. (1904). Physiological economy in nutrition, with special reference to the minimal protein requirement of the healthy man. An experimental study. Frederick A. Stokes Company.