Ketone bodies, such as acetoacetate and β-hydroxybutyrate, are metabolites that are alternative sources of energy to glucose and fatty acids, and utilization of ketones has been shown to be upregulated in diabetes mellitus. A retrospective study performed at a single centre in Japan now indicates that ketone body utilization is reduced under conditions of myocardial ischaemia. Coronary and systemic serum lactate and β-hydroxybutyrate concentrations were measured in 171 consecutive patients with angina who were undergoing an acetylcholine provocation test at Kumamoto University Hospital, Japan. The investigators found that acute coronary lactate production (indicative of increased myocardial anaerobic metabolism) was associated with decreased myocardial β-hydroxybutyrate consumption, particularly in male patients. Further research into the effects of mild ketosis on cardiovascular prognosis is needed.