Beta-Hydroxybutyrate (BHB / Exogenous Ketones)
The main circulating ketone body — both a fuel and a signalling molecule. The body makes it during fasting, ketosis and exertion. As a supplement (ketone salts/esters) it acutely raises blood BHB; whether that reproduces the benefits of endogenous ketosis is unresolved.
How it works
Beta-hydroxybutyrate is the main ketone body the liver makes from fat during fasting or low-carb eating. It serves as an alternative fuel for brain and muscle and also acts as a signalling molecule, including inhibiting HDAC enzymes, which is anti-inflammatory. Exogenous ketones raise BHB briefly but don't replace metabolic adaptation.
Dosage
Exogenous ketone salts typically deliver 6–12 g BHB per serving and raise blood ketones to ~0.5–2 mmol/L for 1–3 hours. Esters are more potent but taste unpleasant and are expensive. Important: most documented benefits come from endogenous ketosis (fasting, keto diet, exercise) — not from drinking ketones.
Considerations
The molecule's biology is fascinating: BHB is not just fuel but a signalling molecule that inhibits the NLRP3 inflammasome (Youm 2015) and acts as an HDAC inhibitor (Shimazu 2013) — both plausibly linked to inflammaging. The catch: nearly all positive findings concern the state of ketosis that the body generates itself during fasting, a keto diet or exertion. Whether exogenous ketones reproduce these effects in humans is barely established — they raise the level but bypass the fat-burning that may be the actual mechanism. Ketone salts also carry a heavy mineral load (sodium, calcium). Bottom line: an interesting tool for acute cognitive/athletic use and for easing keto-adaptation — but no substitute for the metabolic work of fasting and exercise. If you want ketosis, diet gets you there more cheaply and effectively. With diabetes (especially SGLT2 inhibitors) and in pregnancy, only under medical supervision.
