Animal and Plant Protein – Leucine and Telomeres

Leucine is an amino acid that is much more prevalent in animal-based diets than plant-based diets. The leucine is found in the high concentrations, measured in grams per kCal of energy, in beef (0.021), egg white (0.021), isolated soy protein (0.020), poultry (0.018) fish (0.018), spirulina (0.017), lamb (0.014) parmesan cheese (0.010), tofu (0.008), soy beans (0.007). 1

Aglets are the caps on shoelaces that stop them from unraveling. Our chromosomes have telomeres that perform the same function – they stop our chromosomes from unravelling. The longer they are, the longer the cells survive and the longer we live. An animal-based diet results in shorter telomeres than those on a plant-base diet. Leucine is the amino acid responsible for this. 2

Another 2013 paper also implicates leucine in the aging process because of the effect it has on our telomeres. 3

Caloric restriction is the most reliable intervention to prevent age-related disorders and extend lifespan. The reduction of calories by 10-30% compared to an ad-libitum diet is known to extend the longevity of many species including yeast, worms, fruit flies, cows, dogs, rhesus monkeys as well as humans. 4

Caloric restriction is not very popular. We get hungry and grumpy.

An easier way to achieve the same effect is protein restriction – or at least limit the amount of protein from the 16% of total energy that is consumed in the average US diets. More specifically, it is the restriction of leucine that is mostly responsible for this result. 5

A 2011 paper implicates leucine in the development of diabetes and an increased risk of “various” cancers”. 6

A 2012 paper implicates leucine in the development of diabetes and obesity. 7


  1. U.S. Department of Agriculture. (n.d.). USDA Food Composition Databases.
  2. Shreeram, S., Ramesh, S., Puthan, J. K., Balakrishnan, G., Subramanian, R., Reddy, M. T., & Pereira, S. L. (2016). Age associated decline in the conversion of leucine to β-Hydroxy-β-Methylbutyrate in rats. Experimental Gerontology, 100(80), 6–11
  3. Johnson, S. C., Rabinovitch, P. S., & Kaeberlein, M. (2013). MTOR is a key modulator of ageing and age-related disease. Nature, 493(7432), 338–345.
  4. Lee, S.-H., & Min, K.-J. (2013). Caloric restriction and its mimetics. BMB Reports, 46(4), 181–187.
  5. Gallinetti, J., Harputlugil, E., & Mitchell, J. R. (2013). Amino acid sensing in dietary-restriction-mediated longevity: Roles of signal-transducing kinases GCN2 and TOR. Biochemical Journal, 449(1), 1–10.
  6. McCarty, M. F. (2011). MTORC1 activity as a determinant of cancer risk–rationalizing the cancer-preventive effects of adiponectin, metformin, rapamycin, and low-protein vegan diets. Medical Hypotheses, 77(4), 642–648.
  7. Melnik, B. C. (2012). Leucine signaling in the pathogenesis of type 2 diabetes and obesity. World Journal of Diabetes, 3(3), 38.

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