Britain’s favorite beverage was the subject of the Sixth International Scientific Symposium on Tea and Human Health, which was held virtually yesterday. Tea is notable for containing flavonoids, natural compounds with antioxidant properties. These chemicals can help to neutralize free radicals within the body that can otherwise damage both lipids and genetic material and contribute to disease.
The symposium was chaired by nutrition expert Professor Jeffrey Blumberg of Tufts University, in Massachusetts.
He said: “There is a growing body of research from around the world demonstrating that drinking tea can enhance human health in many ways.
“True teas — which include black, green, white, oolong, and dark — can contribute significantly to the promotion of public health.
“Evidence presented at this symposium reveals results — ranging from suggestive to compelling — about the benefits of tea on cancer, cardiometabolic disease, cognitive performance, and immune function.”
Boosting immune function
According to Tufts University nutritional immunologist Dr Dayong Wu, “tea may help support your immune system and increase your body’s resistance to illnesses.
“In the event you do become sick, tea can help your body respond to illness in a more efficient way by ridding itself of the infection and may also alleviate its severity.”
According to Dr Wu, flavonoids called catechins that are found in green teas have been shown to help one’s body fight against a variety of pathogens — both by boosting the immune system and decreasing the potency of the infection.
They have also been found, he added, to help with autoimmune disorders by promoting self-tolerance, enhancing tissue repair and autoantigen-induced inflammatory attack.
Nutrition and behavior expert Professor Louise Dye of the University of Leeds said: “There is strong evidence that tea and its constituents seem to be beneficial under conditions of stress.
“The most profound cognitive domain that tea seems to act upon is attention and alertness.”
Evidence from randomized controlled trials, she explained, has suggested that drinking tea can improve performance in both attention switching tests and in subjective reports of alertness.
In particular, high doses of an amino acid called L-theanine that is found in both black and green tea as well as a lower dose of caffeine can be beneficial for attention-based tasks.
Prof. Dye added: “With these effects on attention, tea is an optimal beverage of choice during a time of elevated stress and burnout worldwide.”
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Preventing cognitive decline
Researchers have estimated that 40-50 percent of dementia cases could be prevented by means of lifestyle changes — and drinking tea could play a role in this.
Nutrition scientist Professor Jonathan Hodgson of the Edith Cowan University in Australia explained that “there is growing evidence that as little as 1–to-2 cups of tea daily could significantly reduce risk of vascular dementia and potentially Alzheimer’s disease.”
Specifically, data from long-term prospective cohort studies have found that a reduced risk of dementia is associated with the consumption of 1–6 cups of tea daily — peaking at 2–4 cups — with a moderate intake of flavonoids in tea also found to be key.
The strongest protection may come against vascular dementia, one of the most common forms of the syndrome.
Reduced risk of cancer
Various studies have suggested that tea consumption is positively correlated with a reduced risk of some cancers — including biliary tract, breast, endometrial, liver, and oral cancer.
Flavonoids — which have anticarcinogenic properties — may act via a mixture of antioxidant, anti-angiogenesis, and anti-inflammatory mechanisms, as well as serve to modify the profile of the gut microbiota.
Nutrition expert Dr Raul Zamora-Ros of the Bellvitge Institute for Biomedical Research in Barcelona said: “More research needs to be done to determine the exact dosage.
However, he added, “the conclusion we can share is that higher intakes of tea consumption may reduce the risk of some forms of cancer.”
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A cup of cardiovascular health
Cardiometabolic diseases, like diabetes and heart disease, are the number one cause of death worldwide.
However, tea has been associated with improved cardiometabolic outcomes, with studies showing that drinking two cups of unsweetened tea daily can help mitigate both the risk of developing cardiometabolic diseases and its progression.
In fact, research has suggested that each cup of tea consumed daily is associated with an average reduction in all-cause mortality of 1.5 percent, cardiovascular disease mortality by four percent, cardiovascular disease events by two percent and strokes by four percent.
Nutrition expert Professor Taylor Wallace of Virginia’s George Mason University said: “When you look at all the different biomarkers and mechanisms that tea is affecting, this bountiful beverage is one which consumers can easily add to better their diet and create a healthier and longer life for themselves.”
Dietary guidance needed
The researchers said that — especially in the US — clearer dietary guidance is needed around tea drinking to support the growing evidence that tea and other flavonoid-bearing foods carry health-promoting benefits.
Food scientist Professor Mario Ferruzzi of the University of Arkansas said: “There may be other herbals and botanical products that can deliver health benefits, but none of them are as studied as Camellia sinensis – true tea.
“With true teas — white, green, black and oolong — you’re dealing with thousands of years of traditional use, 60–70 years of systematic study.”
In the last 15–20 years, he added, this scholarship “has ramped up to the point where we have very definitive data.”