Methionine — Nutrient Deep Dive

An essential amino acid that drives methylation, the body's on/off switch for genes.

At a glance

Covered by protein

Powers methylation Becomes SAM, the body's main methyl donor. why ↓
Feeds glutathione Flows downstream into cysteine and glutathione. why ↓
Needs glycine to stay balanced Glycine offsets the homocysteine rise from too much methionine. why ↓

Strong human evidenceEarly / limited

How to take it

Enough protein covers it: beef, salmon, eggs, chicken thigh
Pair heavy muscle-meat eating with glycine or collagen

Watch out

Restriction diets for longevity are still experimental

Functions

Mechanism

Methionine → SAM (S-adenosylmethionine) → SAH → homocysteine, which then branches into either remethylation back to methionine or transsulfuration toward cysteine and glutathione.

Intake

No single "optimal" intake target — aim for adequate protein intake. Methionine restriction protocols (used in longevity research) are experimental and not standardized for human use.

Deficiency effects

As an essential amino acid, insufficient protein intake can contribute to poor growth and tissue repair; outright deficiency is uncommon with adequate dietary protein.

Cross-reference: methionine load and glycine

Methionine restriction extends lifespan in multiple model organisms, and glycine offsets a specific cost of methionine overload — it suppresses methionine-induced hyperhomocysteinemia. See Glycine / Collagen for the citations behind that connection. (Animal–in-vitro)

Top foods

Source page has no linked citations for this entry — the functions and mechanism above are from the page's own summary text, not individually sourced.