October 29, 2025

expert reaction to study looking at dietary flavanols and blood vessel function following uninterrupted sitting in men

A study published in the Journal of Physiology looks at dietary flavanols and blood vessel function in sitting men. 

Prof Naveed Sattar, Professor of Cardiometabolic Medicine/Honorary Consultant, University of Glasgow, said:

“Sadly, this study will not make me drink cocoa as the trial is not convincing and the blood vessel function measure used is not robust and no one uses it ever to make clinical decisions.  I would suggest other evidence-based advice to eat more fibre rich foods in particular for which the evidence remains super strong.”

Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:

“This study reports that consuming a cocoa-based drink high in flavanols improves blood flow during sitting.  It is already known that the consumption of flavanols improves measures of endothelial function but it is already known that this effect is transient and only last a few hours following consumption when blood flavanols levels are high.

“The limitations of this study include that it was conducted in healthy individuals without impaired endothelial function.  While this study demonstrated increased blood flow this does not necessarily mean it would translate into longer term protection of blood vessels.  Impaired endothelial function is commonly associated with diabetes, hypercholesterolaemia, and smoking/vaping and this study provides no evidence that it would reverse change in these groups.”

Dr Ian Johnson, Nutrition researcher and Emeritus Fellow, Quadram Institute, said:

“This is a well-designed, rigorous study showing a potentially beneficial effect of a cocoa flavonoid extract on human endothelial function, in a context, that of prolonged sitting, which is highly relevant to health.  For many people, prolonged sitting is unavoidable and therefore validated dietary strategies to mitigate some of the potentially adverse effects on vascular health would be welcome.  It should be borne in mind however that these results have been achieved using a relatively high dose of a well-defined cocoa extract, previously shown to have beneficial effects on endothelial function and blood pressure in humans.  Achieving similar results using more conventional plant foods, such as berries and teas, may be more difficult, due to their variable flavonoid content and bioavailability.  As the authors themselves acknowledge, further research will be necessary to translate these encouraging results to everyday diets.”

‘Dietary flavanols preserve upper- and lower-limb endothelial function during sitting in high- and low-fit young healthy males’ by Alessio Daniele et al. was published in the Journal of Physiology at 08:00 UK time on Wednesday 29 October 2025. 

Declared interests

Prof Naveed Sattar: “NS has consulted for and/or received speaker honoraria from Abbott Laboratories, AbbVie, Afimmune, Amgen, AstraZeneca, Boehringer Ingelheim, Carmot Therapeutics, Eli Lilly, GlaxoSmithKline, Hanmi Pharmaceuticals, Janssen, Menarini-Ricerche, Merck Sharp & Dohme, Metsera, Novartis, Novo Nordisk, Pfizer, Sanofi, and Roche; and received grant support paid to his University from AstraZeneca, Boehringer Ingelheim, Novartis, and Roche.  No shares in any medical areas.”

Prof Tom Sanders: “I have received grant funding for research on vegans in the past.  I have been retired for 10 years but during my career at King’s College London, I formerly acted as consultant for companies that made artificial sweeteners and sugar substitutes.

I am a member of the Programme Advisory Committee of the Malaysia Palm Oil Board which involves the review of research projects proposed by the Malaysia government.

I also used to be a member of the Scientific Advisory Committee of the Global Dairy Platform up until 2015.

I did do some consultancy work on GRAS affirmation of high oleic palm oil for Archer Daniel Midland more than ten years ago.

My research group received oils and fats free of charge from Unilever and Archer Daniel Midland for our Food Standards Agency Research.

I was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain.

Member of the Science Committee British Nutrition Foundation.  Honorary Nutritional Director HEART UK.

Before my retirement from King’s College London in 2014, I acted as a consultant to many companies and organisations involved in the manufacture of what are now designated ultraprocessed foods.

I used to be a consultant to the Breakfast Cereals Advisory Board of the Food and Drink Federation.

I used to be a consultant for aspartame more than a decade ago.

When I was doing research at King’ College London, the following applied: Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks.  In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011.  This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof Hough at the Queen Elizabeth College (QEC), which merged with King’s College London.  The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar.  Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006.”

Dr Ian Johnson: “No current conflicts of interest.  In the past I have advised the food industry on the physiological effects of cocoa and other flavonoids.  I have previously advised Barry Callebaut on research studies related to the physiological effects of cocoa and other flavonoids”