Nutrition consultant Elizabeth Ward, MS, RDN says there is evidence that tea drinkers have a lower BMI, but only if it’s drunk straight – no milk or sugar. And what is an optimal amount to drink? She suggests two to three cups a day.

“Green tea has less caffeine than coffee and, as a part of a balanced diet, may reduce the risk for high blood pressure, heart disease, cancer, and type 2 diabetes, in addition to supporting brain health and immunity,” says the creator of Better Is the New Perfect.

A study published in the British Journal of Nutrition suggests tea may help lower blood pressure. The Cambridge University study analysed random controlled trials and discovered long-term tea consumption lowered blood pressure. After 12 weeks, blood pressure was down 2.6mmHg systolic and 2.2mmHg diastolic. Green tea had the best results, followed by black tea.

The researchers noted that this would be expected to reduce the risk of stroke by 8 percent and coronary artery disease mortality by 5 percent.

It is thought that tea offers endothelial protection by helping blood vessels relax, allowing blood to flow more freely.

One of the compounds found in green tea has a powerful ability to increase regulatory T cells that play a key role in immune function and suppression of autoimmune disease, according to research from the Linus Pauling Institute at Oregon State University. Pharmaceutical drugs are available that perform similar roles and have been the subject of much research, researchers said.

"This appears to be a natural, plant-derived compound that can affect the number of regulatory T cells, and in the process improve immune function," said Emily Ho, an LPI principal investigator and associate professor in the OSU Department of Nutrition and Exercise Sciences. "When fully understood, this could provide an easy and safe way to help control autoimmune problems and address various diseases," Ho said.

The findings were published in Immunology Letters.

The polyphenols in green tea are attributed to the ability to inhibit tooth decay. The National Library of Medicine in India cites that green tea is particularly rich in health-promoting flavonoids (they account for 30 percent of the dry weight of a leaf) and this reduces inflammation, preventing bone resorption and limiting the growth of certain bacteria associated with periodontal diseases.