#good #reasons #drink #tea #daily
Researchers have recommended that people incorporate 2 to 4 cups of unsweetened tea into their daily diet as a source of flavonoids, which are largely responsible for these beneficial effects.
Des scientifiques de premier plan dans le domaine de la recherche sur le thé sont récemment réunis virtuellement lors du sixième symposium scientifique international sur le thé et la santé humaine in order to discuss the current state of connaissances et des lacunes dans la comréhension des bienfaits tea. The 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 beverage 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 biologically active components, 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 composition 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 be oxidized and contains less catechins. Additionally, black tea contains higher amounts of other flavonoids called thearubigins and teaflavins, which also have antioxidant properties.
Cognitive function and cognitive decline
Several 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 about 35 to 60 mg of caffeine, which may contribute to 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 may simultaneously produce a 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.
Flavonoids found in tea may also exert protective effects against common age-related cognitive decline and dementia. Recently, several large, long-term prospective cohort studies have explored the relationships between tea consumption and intake 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 believed to play an important role in preventing vascular disease.
Other studies have shown that higher tea consumption, from just one cup and up to 5-6 cups per day, is associated with a lower risk of dementia. Moderate consumption of flavonoids found in ~2-4 cups of tea is associated with a reduced risk of dementia, and for both tea and its flavonoids, maximum benefit can be obtained from a moderate consumption of 2-4 cups per day.
cardiovascular benefits
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 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, a healthier gut microbiome, and protective effects on blood vessels. Therefore, 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, several 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 blocking their entry into host tissues, inhibiting their replication and limiting their spread. Tea/tea catechins can also enhance the antipathogenic response of host immune cells to help fight pathogens and clear infection,” she explained.
Second, green tea’s antioxidant and anti-inflammatory properties may also help prevent tissue damage caused by excessive inflammation in response to infection. Given its anti-inflammatory properties, green tea can also help relieve symptoms of autoimmune diseases, such as inflammatory bowel disease and rheumatoid arthritis.
Autoimmune disease represents a disturbed immune balance and is characterized by the host’s immune cells attacking their 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 culture and animal studies, and more studies are needed to assess the impact of green tea on immune function in humans.
Sources
Beneficial properties of green tea catechins
Exploring the potential of black tea-based flavonoids against hyperlipidemia-related disorders
Drinking tea: a systematic review of randomized controlled trials focused on human cognition, mental well-being, and brain function.
Dose-response relationship between tea consumption and the risk of cardiovascular disease and all-cause mortality: a systematic review and meta-analysis of population-based studies.
Anti-influenza with green tea catechins: systematic review and meta-analysis