Weight loss:

The use of green tea preparations for weight loss and weight maintenance in overweight or obese adults has been assessed in a Cochrane review (Jurgens et al. 2012), but due to the heterogeneity of the studies no clinical relevant claims could be made for green tea preparations. These products do appear to induce a small, statistically non-significant, weight loss in overweight or obese adults.

Cancer prevention:

A Cochrane review on green tea consumption for cancer prevention assessed all prospective, controlled interventional studies and observational studies that either assessed the associations between green tea consumption and risk of cancer incidence, or reported on cancer mortality. The review concluded that there is insufficient data as yet to make recommendations as to whether green tea has cancer preventative properties (Boehm et al. 2009). Further studies are needed.

Cardiovascular health:

Regular consumption of green tea has been associated with enhanced cardiovascular and metabolic health, but further clinical studies are needed. In a double-blind, placebo-controlled trial with obese, hypertensive subjects receiving a daily supplement of 1 capsule of green tea extract (379 mg) for 3 months, it reduced blood pressure compared to placebo, along with reductions in fasting serum glucose and insulin levels and insulin resistance (Bogdanski et al. 2012). Another study with habitual tea drinkers in China, green or oolong (120 ml/day or more for 1 year) also showed that tea drinking significantly reduced the risk of developing hypertension (Yang et al. 2004). The epigallocatechin-3-gallate (EGCG), the major catechin found in green tea, is thought to be beneficial in insulin resistance and other metabolic parameters (Brown et al. 2009).

Bone health:

Epidemiological evidence has shown an association between tea consumption and the prevention of age-related bone loss in elderly women and men. Tea and its active components may decrease the risk of fracture by improving bone mineral density and supporting osteoblastic activities while suppressing osteoclastic activities (Shen et al. 2009). Green tea polyphenols, in combination with Tai Chi exercise, have been shown to mitigate oxidative damage in post-menopausal women with osteopenia (Qian et al. 2012), but clinical studies remain to be carried out to clarify whether supplementation with green tea is beneficial for maintaining bone mineralisation in osteoporosis.

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