Written by Alexa Heathorn, MS, CNS-c, Science Writer. In two acute randomized, double-blind, placebo-controlled crossover studies, drinking a high-flavanol cocoa immediately before a 2-hour uninterrupted sit did not prevent the sitting-related drop in forward, brain-directed carotid blood flow in young or older adults, but in older adults it appeared to blunt the usual rise in backward (retrograde) flow compared with a low-flavanol control (trend-level effect).

Prolonged sitting is widespread across all age groups, particularly young adults and older adults who average sitting 7 hours/day and 9 hours/day, respectively¹. Greater sitting time is associated with higher risk of cognitive decline and dementia, which is projected to triple by 2050 worldwide¹. Experimental studies show that 1–8 hours of uninterrupted sitting can acutely reduce blood flow, and repeated exposure may contribute to long-term changes in brain structure and function¹. While movement breaks are well supported, dietary strategies to protect the brain during prolonged sitting have been little explored¹. Two recent studies address that gap by testing whether a flavanol-rich cocoa drink consumed before a 2-hour sitting bout can improve blood flow to the brain in young and older adults¹.

Flavanols are a class of bioactive compounds found in plants such as unprocessed cacao, tea, grapes, apples, and berries¹. Prior studies suggest that flavanol-rich diets may help protect against age-related cognitive decline, improve memory, and acutely increase cerebral blood flow and oxygenation¹. While these general brain benefits are described, it remains largely unknown whether flavanol intake can mitigate the immediate, sitting-induced reductions in brain blood flow¹.

These two acute, randomized, double-blind, placebo-controlled cross-over studies included 40 healthy young men (20 high-fit, 20 low-fit) and 20 healthy older adults (13 women, 7 men). Participants attended two visits, consuming either a high-flavanol cocoa (695 mg total flavanols) or a low-flavanol control (5.6 mg) immediately before a 2-hour uninterrupted sitting period. Ultrasound measured blood moving forward toward the brain (anterograde) and backward (retrograde), the gentle “drag” of blood along the artery wall (shear rate), and the artery’s width (diameter) before and after the sitting period.

The results were as followed:

• Two hours of sitting lowered forward blood flow to the brain in both age groups (p<0.001).
  (“Forward” = blood moving toward the brain.)
• Sitting also lowered the gentle “drag” on the artery wall (shear rate) (p<0.001).
• In older adults only, sitting increased backward flow and its shear (p=0.021 and p=0.022).
  (“Backward” = a small reverse push of blood.)
• The high-flavanol cocoa did not stop the drop in forward flow or shear during sitting (p>0.05).
• Signal in older adults: with high-flavanol cocoa, the usual sitting-related rise in backward flow/shear was blunted (interaction ~p≈0.05). In post-hoc tests, backward flow/shear went up after the low-flavanol control (p=0.028; p=0.033) but did not rise after the high-flavanol drink.
• Artery size (diameter) didn’t change in any condition.

Potential limitations include:

• The study population comprised healthy young men and a small sample of healthy older adults; as such, results may not generalize to young women or to individuals with common conditions (e.g., hypertension, diabetes, vascular disease, cognitive impairment).
• The total sample size was modest (n=60 across two cohorts), limiting statistical power and the precision of effect estimates.
• The sitting exposure was limited to a single 2-hour uninterrupted bout, which may not reflect the effects of longer or repeated sitting in daily life.
• This was an acute, single-dose trial with no cognitive outcomes or long-term follow-up; durability and functional relevance of the vascular changes cannot be inferred.
• The mitigation of backward (retrograde) flow in older adults was borderline (interaction p≈0.05), and the studies were not powered primarily for these carotid endpoints.
• The high-flavanol cocoa (~695 mg total flavanols) exceeds typical dietary servings, so results may not translate to common cocoa beverages.

This double-blind, placebo-controlled crossover study offers preliminary evidence that a single flavanol-rich cocoa consumed just before a 2-hour uninterrupted sit may help older adults avoid the usual rise in backward (retrograde) carotid flow, although it did not prevent the sitting-related drop in forward, brain-directed flow in either age group. As such, flavanol-rich foods (natural cocoa/cacao, tea, berries, apples, grapes) can be considered a low-risk adjunct to movement breaks when prolonged sitting is unavoidable. Larger, adequately powered trials should test longer or repeated sitting, include women and people with common conditions, assess cognitive outcomes and direct measures of cerebral perfusion, and define dose–response, timing, and real-world dosing to inform clinical and public-health guidance.

Source: Daniele, Alessio, Samuel JE Lucas, and Catarina Rendeiro. “The Impact of Cocoa Flavanols in Modulating Resting Cerebral Blood Flow During Prolonged Sitting in Healthy Young and Older Adults.” Nutrients 17, no. 13 (2025): 2099.

© 2025 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and
conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Posted September 4, 2025.

Alexa Heathorn, MS, CNS-c, is a clinical nutritionist specializing in metabolic health, hormonal balance, and gastrointestinal restoration through root-cause functional nutrition. She earned her master’s degree in Nutrition from Bastyr University and is currently a Certified Nutrition Specialist (CNS) candidate. Alexa also works as a research writer and functional health consultant, translating complex science into actionable strategies for practitioners and wellness companies. Learn more at www.bloomedwellness.com.

References:

1. Daniele A, Lucas SJE, Rendeiro C. The Impact of Cocoa Flavanols in Modulating Resting Cerebral Blood Flow During Prolonged Sitting in Healthy Young and Older Adults. Nutrients. Jun 24 2025;17(13)doi:10.3390/nu17132099