This is the first time people with type 2 diabetes (T2D) have been given a drink with ketone esters — a supplement that is meant to plunge your system into ketosis — to monitor the effect on the heart.

Ketosis is the metabolic state where your body is forced to burn fats instead of carbohydrates.

The study was carried out after a new drug treatment, set to lower sugar levels in people with type 2 diabetes, was also found to save people dying from cardiovascular disease, but more research was needed to find out why.

Study author, Dr Maria Perissiou from the University of Portsmouth’s School of Psychology, Sport and Health Sciences, said: “It’s still early days, but these results are promising. We saw an improvement in cardiac efficiency after the participants had the drink with ketones, compared to a placebo drink.”

The trial involved 13 participants who were given a drink with ketones, and then a placebo drink over a week later. Their cardiovascular function was measured 30 minutes later using non-invasive monitoring, similar to an ECG; ultrasound to assess microvascular function, which looks at the health of the vessels; and infrared spectroscopy, which assesses the blood flow into small vessels.

Dr Perissiou said: “In all 13 of the participants, their hearts were working more efficiently after the ketone drink at rest and during moderate intensity exercise, compared to the placebo drink. I’m feeling very positive about the results, but more research is needed because we only assessed participants on the day, which means we have no idea what the chronic impact of drinking ketones would be.”

Dr Perissiou added that the effect of ketones on heart health is a serendipitous finding: “It’s only really by chance that we’ve been able to establish this connection after seeing an improvement in cardiovascular health of patients being treated for diabetes with a drug called sodium-glucose cotransporter-2 inhibitors (SGLT2i).”

Our bodies have two different fuel tanks — glucose and free fatty acids. Healthy people use glucose because it’s more efficient, but people with diabetes tend to use free fatty acids because their bodies are unable to break down glucose into energy due to insulin resistance.

Dr Perissiou said: “For patients with diabetes, glucose can stay in the bloodstream and act like rust — destroying the vessels gradually. And for those with type-2 diabetes, their hearts are using fatty acids and gradually working harder and harder, which means they’re at risk of dying from different cardiovascular diseases.

“The drug SGLT2i was used to lower glucose in patients with diabetes and longitudinal studies were showing that it was inadvertently protecting the heart. The hypothesis was that the drug induces ketosis and the heart was using ketones, which improved heart health, but the evidence for this was limited so our research set out to prove the connection.”