A black brew is thought to raise metabolism as its larger molecules are poorly absorbed in the intestine, which may encourage the growth of weight loss-boosting bacteria, a study found.

Research has previously revealed English breakfast tea only relaxes blood vessels, which leads to improved blood flow, when taken without milk.

The new study also found both black and green tea appear to have weight-loss benefits by reducing levels of intestinal bacteria associated with obesity and increasing those linked to lean body mass, the study found.

Study author Dr Zhaoping Li from the University of California, Los Angeles, said: ‘For black tea lovers, there may be a new reason to keep drinking it.’