Flavonoids: How Certain Foods Can Improve Blood Pressure

High blood pressure is one of the most common health problems Americans deal with on a daily basis. Nearly 50 percent of U.S. adults (116 million) have hypertension, and more than 500,000 deaths in 2019 were caused by hypertension, according to the Centers for Disease Control and Prevention.

While various high blood pressure medications are often viewed as a quick-fix measure, the fact is simple lifestyle changes have been proven to lower hypertension. More recently, researchers have studied the impact nutrients found in certain foods have on lowering blood pressure. For example, plant compounds called flavonoids are the latest trendy topic believed to have heart healthy benefits. We will discuss what flavonoids are, which foods you can find them in and how they may impact blood pressure.

What are flavonoids?

Flavonoids come from the polyphenol family of phytonutrients, which are compounds found in plants. Visually, they give fruits and vegetables their color, but they also play a critical role in cellular defense and repair. They also help filter UV lights, serve as detoxifying agents, have antimicrobial properties and help protect against extreme heat and cold weather.

Since flavonoids are present in so many fruits and vegetables we eat, they are also often called dietary flavonoids due to their potential health benefits — anti-inflammatory, antiviral and anti-tumor properties.

Once eaten, your gut microbial in the intestinal tract breaks down flavonoids into metabolites, a substance made or used when the body processes food. From there, the metabolites are either absorbed or excreted. When absorbed, these compounds have several reported benefits, including protecting the heart. Flavonoids and metabolites are also beneficial to gut health because they can help limit the growth of certain pathogens while also increasing good bacteria that help with digestion and absorption.

While there are many flavonoids, they can be broken down into six main subclasses that carry dietary benefits: 

• Anthocyanidins
• Flavan-3-ols
• Flavanones
• Flavones
• Flavonols
• Polymers

Foods high in flavonoids

The main sources of flavonoids come from fruits and vegetables, tea, cocoa and red wine. Some herbs and spices, such as oregano, parsley, thyme and hot peppers, also contain flavonoids.

Fruits

• Apples
• Oranges
• Lemons
• Grapes
• Berries (raspberries, blackberries, blueberries and strawberries)
• Pears

Vegetables

• Spinach
• Legumes
• Kale
• Broccoli
• Soybeans
• Onions
• Red cabbage

According to the National Health and Nutrition Examination Survey (NHANES), the average adult flavonoid intake is between 200 and 250 mg/day. The research shows the majority (80 percent) of consumption comes from flavan-3-ols, while flavonols (8 percent), flavanones (6 percent), 5% anthocyanidins (5 percent) and isoflavones and flavones (less than 1 percent) account for less.

Foods high in flavan-3-ols include teas, particularly black tea, cocoa, grapes, berries, apples and red wine.

Whole foods should be consumed for maximum benefit and processed versions, such as products containing tea or cocoa, may not carry flavonoid benefits. If either contains dairy, the milk proteins have been shown to weaken the antioxidant properties of flavonoids. In other words, black tea would have more of a benefit than a black tea drink with milk.

Flavonoids and blood pressure

Earlier this year, research published in Hypertension, an American Heart Association journal, found foods high in flavonoids can help lower blood pressure levels.
The study, based out of Germany and conducted by Queen’s University in Belfast, Northern Ireland, examined the dietary habits of 904 participants between the ages of 25 to 82 and then kept track of their systolic blood pressure, diastolic blood pressure and pulse pressure. 

Among the major findings:

• People who ate more foods rich in flavonoids, anthocyanins and polymers displayed lower systolic blood pressure and pulse pressure.
• People who consumed more flavan-3-ols had a lower systolic blood pressure.
• People who ate more foods that contained flavonols and flavones had lower pulse pressure.
• People who ate 1.6 servings of berries per day saw, on average, their systolic blood pressure decrease by 4.1 mm Hg. Anthocyanins, which are present in red- or blue-colored fruits such as berries and grapes, were mainly responsible for this decrease.
• People who drank 2.8 glasses of red wine per week experienced, on average, a 3.7 mm Hg decrease in systolic blood pressure.
• Each individual has a unique microbiome, and up to 15.2% of the correlation between flavonoids found in food and systolic blood pressure was due to gut bacteria.

Note: Systolic blood pressure measures how much pressure your blood creates during a heartbeat, and diastolic blood pressure measures how much pressure your blood creates when the heart is in a resting state. When receiving a blood pressure reading, systolic blood pressure is the first number followed by diastolic blood pressure. For example, with a blood pressure of 120/80, the 120 value is your systolic figure and the 80 value is your diastolic figure.

Systolic blood pressure is important because it gives doctors a glimpse of how much pressure is placed on your artery walls. This number typically rises as you get older as arteries become tighter due to plaque build ups.

Additional research indicates flavonoids in chocolate and tea may help improve systolic numbers. According to the Oregon State University micronutrition information center, various clinical trials have shown dark chocolate and cocoa have reduced systolic blood pressure by 2.77 mm Hg and diastolic blood pressure by 2.20 mm Hg. Other trials also showed green tea consumption over a three-week period reduced systolic blood pressure by 2.05 mm Hg and diastolic blood pressure by 1.71 mm Hg.

While these findings are promising, the research is observational in nature as opposed to experimental. Remember that each individual digests food in their own unique way. One person may benefit from flavonoids, while someone else with a different microbiome may experience little to no changes. 

Talk to your doctor before making any drastic changes to your diet. A nutritionist can also determine which fruits, vegetables, legumes and other heart-healthy foods are best for you. For more news on trending health topics and nutrition, visit the INTEGRIS Health For You blog.