Ketone esters

In people, ketone esters reliably raise blood ketones. A single dose of the monoester reached about 3.3 mM of beta-hydroxybutyrate within 1 to 2 hours [1], and across 43 trials exogenous ketones lowered blood glucose by about 0.5 mM [2]. Healthy adults who drank the monoester three times a day for 28 days showed no changes in weight, blood lipids, glucose or kidney function, and nausea was rare [3].

For exercise, an early series of studies in elite athletes found better endurance and a shift in fuel use [4], but a pooled analysis of 13 randomized trials found no effect on performance for esters or salts [5], and a diester made professional cyclists about 2% slower in a time trial, with gut discomfort [6]. In 24 people with type 2 diabetes and heart failure with preserved ejection fraction, two weeks of a ketone ester raised cardiac output slightly [7].

Claims for brain health and aging rest mainly on animals, such as less amyloid, less tau and less anxiety in a mouse model of Alzheimer's disease [8]. No trial has tested whether ketone esters slow aging or prevent disease in healthy people, and safety data cover weeks, not years. No ketone ester is an approved medicine; they are sold as foods and supplements.

• Ketone esters are sold as foods and supplements. No ketone ester is an approved medicine, and none is shown to slow aging.
• Nausea, stomach upset and diarrhea are the common side effects, more so at high doses and with diesters.
• Many products are based on 1,3-butanediol. Dom D'Agostino reported that his liver enzymes rose after two weeks of high doses, and he suggests healthy users keep the dose low.
• They lower blood glucose a little, so people with diabetes or who take insulin or other glucose-lowering drugs should ask their doctor first.
• They have not been tested in pregnancy, breastfeeding or children, and safety data in healthy adults cover weeks, not years.