Japanese researchers at Kyoto Prefectural University of Medicine conducted a study to investigate the potential of various foods and ingredients in inactivating the Omicron subvariants of SARS-CoV-2 responsible for COVID-19.
Their findings revealed that green tea (such as Japanese sencha), matcha, and black tea demonstrated effective inactivation of specific Omicron subvariants. Moreover, saliva produced after consuming candies containing green tea or black tea exhibited virus-inactivating properties in vitro, reducing the virus's contagiousness.
Since COVID-19 primarily spreads through infected individuals' saliva, including those who are asymptomatic, understanding how to inactivate the virus in saliva is crucial for prevention. The researchers previously discovered that polyphenols found in green and black tea could reduce the virus's infectivity in human saliva in vitro by binding to the spike protein, preventing cell infection.
Published on October 3 in Scientific Reports, the study involved experiments with healthy volunteers consuming candies containing tea components. Saliva collected immediately after consumption showed high concentrations of tea polyphenols, including epigallocatechin gallate (EGCG) and theaflavin digallate. This saliva, when mixed with the early Omicron virus strain, demonstrated rapid inactivation. However, this effect gradually diminished after candy consumption ceased.
The study suggested that consuming candies containing green or black tea might be useful in inactivating the virus, reducing virus load in oral and gastrointestinal tracts, and preventing spread to non-infected individuals.
Additional experiments involved steeping tea in hot water and mixing with virus suspension, resulting in a significant reduction in infectivity. Both freshly brewed and store-bought green tea beverages demonstrated virus-inactivating effects against specific Omicron subvariants.
However, it's worth noting that different Omicron subvariants showed varying sensitivity to tea polyphenols. For example, EGCG at a certain concentration effectively inactivated certain viruses, while others remained infectious.
In addition to rendering the virus inactive, tea polyphenols, particularly catechins, were found to inhibit virus replication and improve immune response. Animal studies conducted by researchers at National Taiwan Normal University revealed that a certain concentration of catechins could inhibit an enzyme associated with virus replication. Human consumption data showed that maintaining sufficient levels of immune-related CD8+ T cells can inhibit virus replication.
However, it's important to consider that the dosage of catechins required for this effect might be higher than what is typically obtained from drinking green tea. The catechins used in experiments were extracted using specialized techniques and were caffeine-free, differing from commercially available green tea.
EGCG also demonstrated inhibitory effects on various viruses, including HIV, hepatitis B, and influenza viruses.
Apart from their antiviral properties, tea leaves are rich in essential nutrients that support overall health and immune function. Vitamins A, C, D, and E, along with minerals like iron and zinc, play crucial roles in enhancing the immune system.
When choosing between black and green tea, it's important to consider their properties according to traditional Chinese medicine. Green tea, which undergoes minimal oxidation, tends to have a cooling nature, making it suitable for individuals with a “heaty” body constitution.
On the other hand, black tea, which undergoes oxidation, has a warmer nature and may be better suited for those with a cooler body constitution. Women should be cautious about excessive green tea consumption during their menstrual period.
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