Digestive System消化系统

Place · Level 3

从口到肛门 · 9 米的化学工厂 · 70% 免疫驻地 · 与微生物共生 · 第二大脑就在这里

Stomach acid

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胃酸 · 化学屏障

Stomach acid (HCl) is the strongest acid in the body — pre-meal pH 1.5-2.0, roughly equivalent to dilute hydrochloric acid in a battery.

It's secreted by parietal cells in the stomach wall, which pump H⁺ against the gradient into the stomach lumen via the H⁺/K⁺-ATPase proton pump. Each round of acid secretion consumes a lot of , which is why acid output drops under severe stress (energy diverted elsewhere).

Three jobs of stomach acid:

Chemical barrier: most bacteria die within seconds at pH < 2 — the first line of defense against foodborne infectionActivate pepsinogen → pepsin: pepsin only works at pH < 4 and breaks proteins into polypeptidesUnlock minerals: reduce Fe³⁺ → Fe²⁺, release B12 from protein, ionize calcium for absorption
The side effects of long-term PPIs (omeprazole and similar acid suppressants) are the inverse of these three: gut infections rise (*C. difficile*), iron deficiency, B12 deficiency, increased fracture risk. That's the mechanistic basis for why acid suppression is not free.

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本站提供科普与一般性建议，不替代医师诊断或处方；有症状或正在服药请咨询合格医师。 Educational content, not medical advice — consult a clinician for diagnosis or treatment.

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Digestive System消化系统

Place · Level 3

从口到肛门 · 9 米的化学工厂 · 70% 免疫驻地 · 与微生物共生 · 第二大脑就在这里

Stomach acid

Stop 1/6

胃酸 · 化学屏障

Stomach acid (HCl) is the strongest acid in the body — pre-meal pH 1.5-2.0, roughly equivalent to dilute hydrochloric acid in a battery.

It's secreted by parietal cells in the stomach wall, which pump H⁺ against the gradient into the stomach lumen via the H⁺/K⁺-ATPase proton pump. Each round of acid secretion consumes a lot of , which is why acid output drops under severe stress (energy diverted elsewhere).

Three jobs of stomach acid:

Chemical barrier: most bacteria die within seconds at pH < 2 — the first line of defense against foodborne infectionActivate pepsinogen → pepsin: pepsin only works at pH < 4 and breaks proteins into polypeptidesUnlock minerals: reduce Fe³⁺ → Fe²⁺, release B12 from protein, ionize calcium for absorption
The side effects of long-term PPIs (omeprazole and similar acid suppressants) are the inverse of these three: gut infections rise (*C. difficile*), iron deficiency, B12 deficiency, increased fracture risk. That's the mechanistic basis for why acid suppression is not free.

Read story

本站提供科普与一般性建议，不替代医师诊断或处方；有症状或正在服药请咨询合格医师。 Educational content, not medical advice — consult a clinician for diagnosis or treatment.