Alcohol Metabolism酒精 · Alcohol Metabolism

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Ethanol · the molecule

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乙醇 · 一个化学物

Ethanol (CH₃CH₂OH) is a small, simple, fast-moving molecule. Molecular weight is only 46 g/mol — four times smaller than glucose (180 g/mol). It's also amphipathic, with a water-soluble hydroxyl (-OH) and a fat-soluble ethyl (-CH₂CH₃). Being small and amphipathic means ethanol crosses every membrane in the body without a transporter — stomach, gut, liver, brain, heart, gonads, bone marrow, no exception. It also doesn't need to be digested: blood ethanol is measurable 5–10 minutes after drinking and peaks at 30–60 minutes.

The route into the body is short: about 20% is absorbed directly in the stomach (faster on an empty stomach; food slows gastric emptying), and the remaining 80% in the upper small intestine; from there it enters the portal vein and the first stop is the liver — which is why the liver is always the main battlefield for alcohol metabolism.

There's a caloric trap: ethanol provides 7 kcal/g, sitting between carbohydrate (4), protein (4), and fat (9), but those calories are nearly empty — no vitamins, minerals, or fiber. One US 'standard drink' is 14 g of pure ethanol (the UK uses 8 g and Japan 20 g), roughly 350 ml of beer, 150 ml of red wine (12% ABV), or 45 ml of spirits (40% ABV), all landing around 98 kcal.

In the end, ethanol is a small toxic solvent the body has no metabolic role for and must immediately get rid of. The next four scenes show how the body handles it — and the real damage produced along the way.

Fitnuhealth doesn't moralize about drinking on this island; it just lays out mechanism and evidence clearly. All the latest evidence (GBD 2018 Lancet / Anderson 2022 NEJM) converges on the same conclusion: safe drinking quantity = 0 — any dose carries measurable health cost. So what we're doing here is letting you make your own informed choice after understanding the mechanism.

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