Why a splash of milk in your tea keeps teeth white

And milk-drinkers can now rejoice, after a study found adding it to tea can actually stops teeth becoming stained.

It was even more effective than whitening toothpastes, and was as equally good as some bleaching products, researchers found.

'Tea is the second most consumed drink in the world, and the way it's processed affects how teeth are stained,' said Dr Ava Chow, of University of Alberta's School of Dentistry.

'The more the tea is processed or oxidized, the higher its staining properties are.

'But we've found that the addition of milk to tea reduces the tea's ability to stain teeth.'

Tea contains tannins – water soluble compounds that cause the bitter flavour - she explained.

They are dark in colour and can stain the teeth.

Dr Chow found that casein, the main protein in milk, binds to the tannins in tea and prevent staining.

Intially, she designed her study as a way of introducing undergraduate dental hygiene students to research, but was surprised by the results and decided to publish them.

As part of the study, Dr Chow used human teeth that had been extracted, excluding teeth that had fillings, signs of tooth decay, or obvious cracks and fractures.

She analysed the colour of the teeth and recorded them, before putting them through a 'staining process'.

This involved putting the teeth into either a solution of tea, or a solution of tea with milk for 24 hours at 37 C.

At the end of 24 hours she recorded the colour of the teeth again.

The results we found showed that casein is the component of milk that is responsible for the reduction of tea-induced staining,' Dr Chow said.

'The magnitude of the colour change observed in our experiments is comparable to the colour change seen by vital bleaching products and more effective than whitening toothpastes.'

Dr Chow added that before dentists advise their patients to take milk with their tea, they should consider whether milk-drinking is part of the person's culture.

'Adding milk to tea is a culture-specific phenomenon,' she said.

'Some cultures may refuse to add it and others only drink tea with milk.'

The research was published in the journal International Journal of Dental Hygiene.

The news comes after a study found drinking tea reduces the risk of dying from causes unrelated to the heart by a quarter compared with those who don’t drink tea.

The benefits of tea are largely due to the flavonoid content, antioxidant ingredients that are thought to be good for the heart. 

(dailymail.co.uk)