Compound
Lactic acid
Also known as: Lactate, Lactic acid (food)
An organic acid produced by *Lactobacillus* and related bacteria as they metabolize sugars in the absence of oxygen. The principal preservative agent in lacto-fermented foods (sauerkraut, kimchi, yogurt, sourdough, pickles) — its production lowers the pH of the food below the threshold most spoilage organisms and pathogens can survive. Lactic acid is also produced by human muscle cells during anaerobic metabolism, and by the cells of the vagina (where it maintains the protective acidic environment). The same molecule, made by the same biochemistry, in microbial fermentation and in human physiology.
What it is
Lactic acid is a three-carbon organic acid (CH₃CH(OH)COOH). It is produced by the anaerobic metabolism of carbohydrates by Lactobacillus, Lactococcus, Pediococcus, Leuconostoc, and many related bacteria — and by human muscle cells when oxygen is limited.
What it does in food
- Lowers pH — typical lacto-fermented food drops to pH 3.5–4.0, below the threshold pathogens (Clostridium, Salmonella, E. coli, Listeria) can grow
- Preserves nutrients — many vitamins are more stable at low pH; some (B-vitamins, vitamin C) are produced or increased by fermentation
- Increases bioavailability — lactic-acid fermentation breaks down phytic acid and other anti-nutrients, freeing minerals (iron, zinc, calcium) for absorption
- Develops flavor — sour, complex, layered taste that heat preservation cannot produce
What it does in the body
- Muscle metabolism — produced during intense exercise; long misunderstood as the cause of fatigue, now recognized as a useful fuel and signaling molecule
- Vaginal protection — Lactobacillus crispatus and relatives maintain the protective acidic vaginal environment that suppresses pathogenic bacteria and yeast
- Brain fuel — lactate is increasingly recognized as a metabolic substrate the brain prefers under certain conditions
Why this matters
Lactic acid is a cross-domain compound — the same biochemistry preserves your [[sauerkraut|sauerkraut]], protects your reproductive tract, and powers your muscles under load. The microbial world and the human body share metabolic infrastructure; the compounds we encounter through fermented food are the same compounds our own cells produce. Treating fermentation as exotic misses how internal it already is.
See also
Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.
- Subset of: [[lacto-fermentation]]
- Parallels: [[gut-microbiome]]
- Member of: [[compound]]
Sources
- [[the-art-of-fermentation|The Art of Fermentation]], [[sandor-katz|Sandor Katz]]
- Multiple peer-reviewed reviews of fermentation biochemistry
Rooted in life.
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