Green tea can increase weight loss, improve our general health and protect us against Alzheimer's disease - and now scientists are beginning to understand why.

The tea helps improve blood flow - especially in people with coronary artery disease - which also allows other nutrients to circulate through the body more efficiently.

The key seems to be a polyphenol known as epigallocatechin gallate (EGCG), which is found in plentiful supply in a cup of green tea. 

EGCG can dramatically improve blood flow, and within just a few hours, as researchers discovered when they tested it on a group of 42 patients with coronary artery disease.

Overall, green tea contains between 30 and 40 per cent of water-extractable polyphenols, antioxidantssuch as EGCG that protect against heart disease and cancers, while standard black tea has just 3 to 10 per cent of them.