Green and Black Tea May Lower Blood Pressure, Study Finds

Compounds in green and black tea relax blood vessels, which may help lower blood pressure, according to a study in Cellular Physiology and Biochemistry.

Researchers from the University of California, Irvine pinpointed two specific flavonoid compounds that affect a type of protein found in the smooth muscle that lines blood vessels.

When this protein, called KCNQ5, is activated, that prompts the blood vessels to relax and allows for better blood flow. In turn, that lowers your blood pressure.

These findings should encourage individuals to drink more tea but may also aid in the development of new anti-hypertension medications.

There's a Need for More Remedies

As many as one-third of the world’s adult population has hypertension, according to a research review published in Nature Reviews Nephrology in early 2020, and it’s considered the leading cause of cardiovascular disease and premature death. Those researchers noted that risk factors for hypertension include:

• High sodium intake
• Low potassium intake
• Obesity
• Alcohol consumption
• Physical activity
• Stress
• Unhealthy diet

Prevalence of hypertension has been particularly notable in low- and middle-income countries, the study noted, and this is made more problematic by lower levels of hypertension awareness and treatment.  

That’s why something as affordable and widely available as green and black tea may be promising as an option that provides small but consistent improvements, according to the recent study’s co-author Geoffrey Abbott, Ph.D., professor of physiology and biophysics at the University of California Irvine School of Medicine. Also, he added, the identification of KCNQ5 could make that protein a candidate for development of hypertension medicines in the future.

“The action of tea is consistent whether the beverage is iced or hot,” he says. “Simply by drinking it, we can activate its beneficial, hypertensive properties.”

Nutritional Advantages of Tea

Although there is evidence to support the health benefits of many types of tea, including herbal options, green tea has the highest levels of antioxidants, Abbott says. Previous research suggests in addition to reducing hypertension, green tea also inhibits carcinogenesis—the formation of normal cells into cancer cells.

A major part of this is traced to catechins, the natural antioxidants that prevent cell damage by stopping free radicals, which are molecules that cause chemical reactions in the body called oxidation.

Black tea has similar benefits and can activate KCNQ5, but the effect was dampened by milk in Abbott’s lab. That seems like it would be a complication for lowering blood pressure since black tea is often paired with milk, but Abbott believes that you don’t need to skip the milk when preparing your tea.

“We’re confident that the environment in the human stomach will separate the catechins from the proteins and other molecules in milk that would otherwise block catechins’ beneficial effects,” he says.

Other Beneficial Compounds

As efficacious as KCNQ5 might prove to be, it’s not the only blood-pressure-lowering compound in black and green tea that’s been singled out recently. A study in Scientific Reports found that compounds called flavanols also have a beneficial effect for hypertension.

These are not the same compounds as flavonols, although both types fall under the family of compounds known as flavonoids. Flavonols, which also have numerous advantages, are found in foods like onions, scallions, kale, and broccoli.

In that study, people who drank tea and had foods rich in flavanols had lower blood pressure than those who didn’t consume these options. Foods include:

• Red wine
• Grapes
• Apples
• Berries
• Cocoa

"The results of the study are exciting," study co-author Gunter Kuhnle, Ph.D., in the Department of Food and Nutritional Sciences at the University of Reading in the UK. "For the first time, we can show that there was a statistically significant, meaningful difference in blood pressure between those high- and low-flavanol intake."

In addition to drinking tea and having other flavanol-packed food and beverage choices, there are other ways to lower blood pressure as well:

• Reduce stress
• Get more quality sleep
• Exercise regularly
• Lose weight if needed

Also, be sure to get your blood pressure checked at your annual physical, no matter what your age. As the American Heart Association notes, there are often few, if any, symptoms of high blood pressure, which is what makes it so dangerous.