Methionine is an amino acid that humans and farm animals must derive from food. This metabolite, a tightly regulated resource in ecosystems, has become a mass commodity in the global economy, with well over 1 million tons being produced annually from petroleum to fortify livestock feed. Viewed from the standpoint of planetary health, anthropogenic methionine synthesis is an important enabler of low-cost animal protein production, with interdependent but unexamined effects on human health and ecosystems.
Like any other essential amino acid, we have to obtain it from the diet by all means. Otherwise, we will suffer the consequences of its deficiency, right?
Thus, methionine is an amino acid that we need to consume in order to survive. But why do we insist on this aspect so much?…
The essential amino acid methionine, or Met, is critical for genetic regulation, protein production, cell metabolism and DNA repair. Unlike noncancerous cells, most cancer cells cannot recycle Met efficiently; instead, cancer cells rely on a continuous supply of methionine from external sources for growth. This vulnerability is known as Met dependence, or Met stress sensitivity.
Methionine restriction—best achieved through a plant-based diet—may prove to have a major impact on patients with cancer because, unlike normal tissues, many human tumors require the amino acid methionine to grow.
T helper cells import the amino acid methionine to synthesize new proteins and to provide the methyl groups needed for the methylation of RNA and DNA that drives T cell proliferation and differentiation.
Think protein foods, and you will likely find methionine.
Met is ESSENTIAL in the dietary sense – you need to get it from food because you can’t make it. But thanks to Met, its sulfur sister Cysteine is non-essential – methionine can be used to make cysteine. There’s something else special about Methionine – It’s each protein-to-be’s ticket to the peptide wedding chapel!
The numbers... are estimates of methionine content in common foods.
Methionine can be converted to cystine but cystine cannot be converted back to methionine. Cystine can satisfy at least 50% of the total need for sulfur amino acids. Methionine can meet the total need for sulfur amino acids (methionine + cystine) in the absence of cystine.