Protecting Blood Vessel Health With Flavanols

References to phytonutrients, polyphenols and antioxidants continually show up in posts and articles that we encounter in our daily reading of the news.  Do you know the potential for better health that these nutrients offer?

 

What are Flavanols (1,2,3) ?

First of all, lets clarify a few labels.

• Phytonutrients are natural compounds found in plants that provide a wide range of health benefits, including antioxidant and anti-inflammatory properties.
• Polyphenols are a large family within the group of phytonutrients.
• Flavanols are a type of polyphenol.

Flavanols (also known as flavan-3-ols or catechins) are members of the flavanoid family of polyphenols and are responsible for the bright colours in many plants. They offer a variety of important health advantages.

Flavanols are found in plants including grains, fruits and vegetables, herbs and spices and even flowers.  Foods like legumes; grains such as brown, red or black rice; whole wheat; red and purple potatoes; red and black grapes; apples; strawberries; blueberries; cherries; cocoa; chocolate; cinnamon; green and black tea; hops and beer; and red wine are all rich in flavanols.

Flavanols provide an abundance of health-giving rewards that stem from their anti-inflammatory, anti-cancer, anti-microbial, anti-viral and anti-oxidant properties as well as their neuroprotective and heart protective characteristics.

In the last few decades, observational and epidemiological studies have suggested that diets rich in polyphenols, and particularly flavonoids, reduce the risk of future cardiovascular disease.  Indeed, randomised controlled trials in humans demonstrate that flavonoid-rich foods such as berries and cocoa improve the function of blood vessels.  (4)

 

What happens when our modern lives keep us from being active? 

Inactivity is becoming extremely prevalent in modern societies. Behaviors such as commuting to a job, working at a desk, watching TV and playing video games all play a part in reducing active time. Canadian adults spend an alarming 9.6 hours per day in sedentary behaviours and prolonged sitting has become a national health emergency, costing the healthcare system $2.2 billion annually while dramatically reducing workplace productivity and quality of life. (5)  Sedentary time is linked to increases in early death from all causes and higher risks of several chronic health conditions such as cardiovascular diseases. (6) Human studies have shown that uninterrupted prolonged sitting has detrimental effects on the function of the endothelium, the inner lining of blood vessels, in young healthy adults. This leads to inflammation, increased risk for the formation of blood clots, the building up of plaque within artery walls and ultimately is linked to cardiovascular diseases such as hypertension, heart failure, heart attacks, strokes, diabetes, and chronic kidney failure.  (7)

  

Recent Research on Flavanols and Their Effects on Blood Vessels (8)

Research published in October 2025 investigated whether consuming flavanols immediately before two hours of sitting could affect blood vessel function in the arms and legs of the participants. Study scientists enrolled forty healthy young men into this study of which 20 had higher levels of fitness and 20 had lower levels of fitness.  Participants consumed either a high-flavanol drink containing 695 mg of total flavanols or a low-flavanol drink containing 5.6 mg of total flavanols followed by two hours of sitting.  The experiment included the testing of a range of vascular measures taken before and after the sitting trial.  These tests included the following;

• FMD (Flow-Mediated Dilation) in the superficial femoral artery and the brachial artery. FMD is a non-invasive procedure using a blood pressure cuff.  The cuff is inflated to restrict blood flow and then deflated to allow blood to rush back into the artery.  This measures the elasticity of the blood vessels.  Greater ability of a blood vessel to expand indicates healthier vessels.
• Resting shear rate and blood flow through the arteries. This measures the force exerted on the blood vessel wall by the flow of blood.  Multiple studies have shown that low shear rates are linked to the initiation of atherosclerosis and progression of atherosclerotic plaques.
• Systolic and diastolic blood pressure
• Oxygen levels in leg muscles

Results showed the following,

• Participants with both lower and higher fitness levels who drank the low-flavanol cocoa before prolonged sitting experienced declines in FMD in their arm and leg arteries (lower elasticity in their arteries) at the end of their sitting period. In addition, they exhibited increased diastolic blood pressure, decreased shear rate, lower blood flow through the arteries and declines in the oxygenation of muscles.
• Participants with both lower and higher fitness levels who drank the high-flavonal cocoa before prolonged sitting did not experience declines in FMD in their arm and leg arteries at the end of their sitting period.

These results indicate that, at least in young healthy men, higher levels of fitness do not provide protection from sitting.  However, consumption of flavanols is protective of the harmful effects of long periods of sitting.  It is likely that further research will find the same results in women.  In summary, regardless of physical fitness levels, consuming flavanols can combat the signifcant negative effects of inactivity on blood vessels.

Responding to this information is not difficult.  First, be vigilant about prolonged inactivity.    When you sit down at your work desk, your TV or your video game console, set a 20-minute alarm to get you up and out of your chair and standing for a few moments.  A short walk around is an even better way to stimulate the movement of blood through your arteries.

A study from 2020 illustrated that 5-minute walking breaks or stair climbing every hour can improve FMD measurements in the superficial femoral artery by 4.5% and in the brachial artery by 2.5% (9).

 Secondly, it is important to take stock of the foods you are eating.  Make sure that you are consuming foods that provide flavanols to your body and add more of them to your eating pattern if you can.  A handful of blueberries or strawberries added to your morning cereal is a flavourful and healthy way to start the day.  Enjoy an apple as part of your lunch.  Choose  brown or red rice to serve with your stews, curries and bowls. Value breads that are high in whole grains. Savour a square of dark chocolate after your evening meal.  These are all strategies that can prevent, delay and even reverse the age-associated degeneration of blood vessels and help to promote lifelong health and vitality.

 

SOURCES:

1  https://health.clevelandclinic.org/what-are-flavonoids

2  https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/flavanols

3  Luo, Y., Jian, Y., Liu, Y., Jiang, S., Muhammad, D., Wang, W. Flavanols from Nature: A Phytochemistry and Biological Activity Review. Molecules. 2022; 27(3):719. https://doi.org/10.3390/molecules27030719

4  Deng, B., Lei, Y., Zhou, R., Ruan, T., Lu, W., Ying, J., Yue, Y., & Mu, D. Effect of blueberry intervention on endothelial function: A systematic review and meta-analysis. Frontiers in Physiology. 2024. 15, 1368892.

5  https://www.fitnessavenue.ca/blogs/post/sedentary-lifestyle-statistics-canada

6  Gao, W., Sanna, M., Chen, Y.-H., Tsai, M.-K., & Wen, C.-P.  Occupational sitting time, leisure physical activity, and all-cause and cardiovascular disease mortality. 2024. Journal of the American Medical Association Network Open, 7(1), e2350680.

7  https://microbenotes.com › endothelial-cells

8  Daniele, A., et al. Dietary flavanols preserve upper‐ and lower‐limb endothelial function during sitting in high‐ and low‐fit young healthy males. The Journal of Physiology. 2025.  Doi.org/10.1113/jp289038.

9  Cho, M. J., Bunsawat, K., Kim, H. J., Yoon, E. S., & Jae, S. Y. The acute effects of