“Over the last 10 years, or even 15 years, the evidence has been building to the point where I think we have what I would suggest are very clear data that support tea consumption,” beyond the current recommendations in the current Dietary Guidelines for Americans, said Mario Ferruzzi with the Arkansas Children’s Nutrition Center University of Arkansas for Medical Sciences.
He explained at the recent Sixth International Scientific Symposium on Tea and Human Health that systematic research conducted in the past 20 years offers “very definitive data” that “true tea” from the Camellia sinensis plant has the potential to modify risk for several chronic and degenerative diseases, including cardiovascular, diabetes and neurodegenerative processes.
He also noted that many Americans confuse ‘true tea’ from the Camellia Sinensis plant, with herbal tisanes, which may also deliver health benefits, but for which the research around Camellia sinensis does not apply.
To ensure that consumers get the benefits of tea and distinguish it from other tea-like beverages, such as herbal infusions, he argued that clear dietary guidance is necessary. Updating the Dietary Guidelines for Americans to include a recommendation for tea also would help establish a standard for generating products that consistently support the benefits outlined in clinical and other analysis.
Such a change would be a significant shift for the DGA, which are in the early steps of being updated for 2025-2030. The current dietary guidelines for Americans primarily discuss tea in terms of the amount of added sugar that is frequently consumed in the beverage and which can lead to excessive calorie consumption, Ferruzzi notes.
No established dietary reference intakes for tea
While this is important, he argues the guidelines should also address the benefits of unsweetened tea, including the beneficial relationship between non-nutritive bioactive compounds found in the beverage, such as flavonoids, with long-term health outcomes.
This may be easier said than done, however, because even though research supporting the health benefits of flavonoids in tea is mounting, there is still no established dietary reference intakes, which is “absolutely critical” for creating guidelines, he said.
“We have some evidence to suggest based on meta-analysis of randomized clinical trials, as well as some of the observational studies, that a DRI for tea in the 200 to 400 to 600 milligram range, which translates roughly to one to two cups of tea conducted by standard brewing practices” could be beneficial, he said.
Even if establishing a DRI is not in the cards in the short term, Ferruzzi argued, “using that process can help guide us in a direction where we can build additional recommendations that are more accurate and relevant for consumers in the context of a diverse range of tea products that we have out on the market.”
Growing research supports health benefits of tea
Among the research that supports consuming two cups of unsweetened tea daily for health benefits is an umbrella review of 39 large population studies slated for publication this spring that examines the extent to which daily tea consumption is inversely associated with adverse cardiometabolic outcomes, Taylor Wallace, principle and CEO of the Think Healthy Group and a professor in the Department of Nutrition and Food Studies at George Mason University, said at the conference.
He explained that the studies are “all very consistent” in showing tea intake reduces the risk of all-cause mortality on average by 1.5%, including a 4% reduced risk of cardiovascular disease mortality, 2% lower risk of CVD events and 4% lower risk of strokes.
While this shift “might not seem that huge,” Wallace noted that it is the impact of “just one component of the diet. We like to think of nutrition science as a reductionist approach, but people don’t just consume tea. They also have a whole host of other dietary patterns that can accumulate and have large effects.”
Antioxidant, anti-angiogenesis and anti-inflammatory mechanisms
In addition, he said, smaller randomized control trials “allude to” tea’s “influence over several biological mechanisms in the body, so what we call flow mediated dilation, which is the elasticity of the veins and arteries and how blood can easily flow through the body.”
He also noted “there might be some effects on certain lipids and blood pressure,” and “cross communication proteins that regulate inflammation in the body,” which is important in the context of the COVID-19 pandemic.
Other research shows potential benefits of tea in preventing cancer, 30-40% of which could be prevented by modifiable risk factors, such as increasing physical activity and following a healthy diet, said Raul Zamora-Ros with the Nutrition and Cancer Unit at the Catalan Institute of Oncology at Bellvitge Biomedical Research Institute.
‘It is time to recommend one to two cups of tea per day’
He explained that there is evidence that tea flavonoids may act via antioxidant, anti-angiogenesis and anti-inflammatory mechanisms as well as modifying the gut microbiota profile.
Further evidence presented at the symposium by Dayong Wu at the Human Nutrition Research Center on Aging at Tufts University suggests including tea in a healthful food patterns could increase the body’s resistance to illness.
He noted green tea and catechins decrease pathogens’ ability to infect hosts and improve autoimmune disorders by promoting self-tolerance and suppressing autoantigen-inducing inflammatory attacks.
He explained this could be possible by green tea and green tea catechins’ ability to inhibit viral absorption, penetration, membrane fusion and replication in the upper respiratory tract, enhance clearing of virus and reduce tissue damage by scaling back inflammation and oxidative effects.
Do no harm
For all the beneficial correlations of tea and health, the beverage also does not pose any risk – as long as it is consumed unsweetened, noted Wallace.
“There is no adverse events and no harm from consuming tea as long as you are consuming unsweetened tea that doesn’t provide a lot of added sugar to the diet,” he said, adding, “So, from a public health standpoint it is time to recommend one to two cups of tea per day, in my opinion.”
