Physician and food scientist William Li has highlighted research showing two daily cups of hot dark chocolate can double circulating stem cells in blood within a month.
However, the clinical trial behind the claim relied on a high-potency cocoa drink tested exclusively on 16 heart disease patients, rather than standard supermarket hot chocolate.
Li, a doctor, food scientist, and book author, made the statements during an appearance on episode 562 of Rangan Chatterjee's podcast, which was subsequently shared on Instagram on June 6, 2025.
The assertion originates from a 2010 study published in the Journal of the American College of Cardiology. The research evaluated 16 patients with diagnosed coronary heart disease, who had an average age of 64 years.
Participants completed two distinct 30-day testing periods. In one phase, patients consumed a high-flavanol cocoa drink containing 375 milligrams of flavanols per serving twice daily, while in the other phase, they received a control drink containing only 9 milligrams per dose.
At the end of the high-flavanol phase, researchers recorded a 2.2-fold increase in a specific type of circulating angiogenic cell compared to the low-flavanol control. A second cellular marker expanded eightfold.
Circulating angiogenic cells contribute to the maintenance of the endothelium, the thin cellular layer lining the interior of blood vessels.
The trial also recorded a 47 percent improvement in flow-mediated dilation, an ultrasound assessment that measures how blood vessels expand in response to increased blood circulation.
Trial limitations and cellular findings
While the findings align with scientific interest in heart regeneration, researchers emphasized that the results were limited strictly to the vascular system of a small patient cohort.
The trial represents a separate line of research from cell reprogramming, which seeks to restore youthful traits to adult tissues.
Medical experts note that improved arterial dilation does not equal doubling overall blood flow. Furthermore, a one-month trial on a small group does not guarantee similar health effects for anyone altering their daily breakfast.
Flavanol content versus processing
The difference in flavanol content between the two test preparations was 42-fold, demonstrating that the therapeutic agent was the precise dosage of active cocoa compounds rather than the temperature or appearance of the drink.
Instant cocoa powders often contain substantial sugar and a reduced percentage of raw cocoa, illustrating how ultra-processed foods diverge from laboratory-tested preparations despite sharing similar names.
European Union regulations permit health claims that cocoa flavanols help maintain blood vessel elasticity and support normal blood flow when a product provides a daily intake of 200 milligrams of flavanols.
However, the percentage of cocoa listed on product packaging does not reveal how many flavanols remain after industrial fermentation, roasting, and processing.
Health considerations and practical guidance
Nutrition research on cardioprotective diets indicates that sustained, long-term eating patterns carry far more weight than viewing any single ingredient as a medical remedy.
Choosing pure cocoa without added sugar prevents confusing raw cocoa with sugary prepared mixes, but it does not automatically recreate controlled laboratory interventions.
Consuming two cups of hot chocolate daily also adds calories and provides caffeine and theobromine, which may impact sensitive individuals or those with specific medical conditions.
The 2010 study offers valuable evidence regarding flavanols and endothelial function, but it does not convert hot chocolate into a treatment or replace prescribed medication, targeted diets, or medical advice.
