Researchers have recommended that people incorporate 2-4 cups of unsweetened tea into their daily diet as a source of flavonoids, which are largely responsible for these beneficial effects.
Leading scientists in the field of tea research recently gathered virtually at the Sixth International Scientific Symposium on Tea and Human Health to discuss the current state of knowledge and gaps in understanding the benefits tea. Researchers discussed many topics at the symposium, including the potential beneficial effects of tea on cardiovascular health, and cognitive function,
Here is an analysis of the main research results on the benefits of tea
Types of tea and flavonoids
Tea is the second most consumed drink in the world, after water. The four main types of tea are white tea, green tea, Oolong tea and black tea. These four teas are made from the same plant, Camellia sinensis, but differ in how they are processed after harvest. Tea contains a wide range of components with biological activity, including flavonoids, L-theanine and caffeine. Many of the beneficial effects of tea are due to the high levels of flavonoids, such as catechins, which have antioxidant and anti-inflammatory properties.
Differences in the manufacturing process can influence the chemical makeup and beneficial effects of different types of tea. For example, green tea is roasted before it oxidizes and therefore contains higher levels of catechins. In contrast, black tea can oxidize and contains fewer catechins. Additionally, black tea contains higher amounts of other flavonoids called thearubigins and theaflavins, which also have antioxidant properties.
Cognitive function and cognitive decline
A number of observational studies suggest that tea consumption is associated with improvements in cognitive function. A few small randomized controlled trials have suggested that drinking tea may lead to short-term improvements in attention. Each cup of tea contains around 35-60 mg of caffeine, which may contribute to the increased alertness and improved mood that some people experience after consuming the tea. The tea also contains theanine, which has been suggested to improve attention while reducing anxiety and stress. Researchers believe that the presence of theanine and caffeine can potentially produce a simultaneous sense of calm while improving attention. Additionally, limited evidence suggests that taking theanine and caffeine together may result in a greater increase in attention than either component taken separately.
The flavonoids found in tea may also exert protective effects against common age-related cognitive decline and dementia. Several large, long-term, prospective cohort studies have recently explored the relationships between tea consumption and the consumption of flavonoids found in tea and dementia outcomes. The two main types of dementia are Alzheimer’s disease and vascular dementia. Flavonoids are components of tea that are thought to play an important role in the prevention of vascular disease.
Other studies have shown that higher tea consumptions, starting from a single cup and up to 5-6 cups per day, are associated with a reduced risk of dementia. Moderate consumptions of flavonoids found in ~2-4 cups of tea are associated with reduced risk of dementia, and that for both tea and its flavonoids, maximum benefit can be obtained from moderate consumptions of 2-4 cups per day.
A higher intake of dietary flavonoids is associated with a lower risk of cardiovascular disease and metabolic disorders, including diabetes. According to a meta-analysis summarizing data from 39 studies, daily consumption of each additional cup of tea was associated with a 2% lower risk of a cardiovascular event, a 4% lower risk of stroke and a 4% reduction in the risk of death from cardiovascular disease. These positive effects of flavonoids on cardiometabolic health are associated with decreased inflammation and oxidative stress, better regulation of blood sugar and lipid levels, healthier gut microbiome, and protective effects on vessels. blood. Thus, tea consumption may be particularly beneficial for people whose diets are deficient in flavonoids, including whole grains, fruits and vegetables.
Tea and immune function
Drinking tea may also improve immune health, with studies suggesting a potential role for green tea in preventing bacterial and viral infections. For example, a number of human studies, including randomized controlled trials, suggest that drinking green tea may reduce the risk of incidence of influenza infection.
Immune system: two categories of benefit
The first is the protective effect against infection. Current research shows that tea/tea catechins can act directly on a variety of viruses and bacteria to prevent them from attaching and thereby block their entry into host tissues, inhibit their replication and limit their spread. Tea/tea catechins can also enhance the anti-pathogen response of host immune cells to help fight pathogens and eliminate infection,” he explained.
Second, the antioxidant and anti-inflammatory properties of green tea may also help prevent tissue damage caused by excessive inflammation in response to infection. Given its anti-inflammatory properties, green tea may also help alleviate symptoms of autoimmune diseases, such as inflammatory bowel disease and rheumatoid arthritis.
Autoimmune disease represents a disturbed immune balance, and it is characterized by a host’s immune cells attacking its own tissues. Tea/tea catechins have been shown to modulate complex immune cell function in ways that help correct this disorder, perhaps by suppressing the overactive response and promoting tolerance. However, most of these findings are based on cell cultures and animal studies, and further studies assessing the impact of green tea on immune function in humans are needed.
Beneficial Properties of Green Tea Catechins
Exploring the potential of black tea based flavonoids against hyperlipidemia related disorders
Tea Drinking: A Systematic Review of Randomized Controlled Trials Focusing on Human Cognition, Mental Wellbeing and Brain Function
Dose–Response Relation between Tea Consumption and Risk of Cardiovascular Disease and All-Cause Mortality: A Systematic Review and Meta-Analysis of Population-Based Studies
Anti-Influenza with Green Tea Catechins: A Systematic Review and Meta-Analysis