Scientists have used quantum mechanics to work out why green tea is good for you. The health benefits of the brew are all down to a quirk of the quantum world known as tunneling, they say.

Green tea is traditionally associated with good health and long life - benefits linked to chemicals known as catechins, which act as antioxidants. These polyphenolic flavonoid compounds disrupt the damaging chain reaction between free radicals and lipids.But no one understood how catechins work at micromolar concentrations in the body. Now, Àngels González-Lafont and colleagues at the Autonomous University of Barcelona in Spain have modelled the chemical reaction that allows green tea catechins to zap radicals.

The reaction involves the catechin losing a hydrogen atom to a reactive free radical. The scientists found that in this process the radical and catechin were bound together tightly, leading to very small energy changes as the reaction proceeds.

The compact structures and narrow energy profile revealed by González-Lafont’s calculations allows for a huge tunneling effect in the hydrogen transfer step. This makes the transfer much faster than the free radical’s reaction with the body’s vulnerable lipids, so the radicals are trapped before they can do harm.

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