Cup that cheers... green tea could be a defence against Alzheimer's and cancer

It could also play a vital role in protecting the body against cancer, says a Newcastle University study published in the academic journal Phytomedicine.

A research team led by Ed Okello wanted to know if the protective properties of green tea – previously shown to be present in the undigested, freshly-brewed drink – were still active once the tea has been digested.

Dr Okello, from the university's School of Agriculture, Food and Rural Development, said: "What was really exciting about this study was that we found when green tea is digested by enzymes in the gut, the resulting chemicals are actually more effective against key triggers of Alzheimer's development than the undigested form of the tea.

"In addition to this, we also found the digested compounds had anti-cancer properties, significantly slowing down the growth of the tumour cells which we were using in our experiments."

Digestion provides our bodies with the nutrients we need to survive but vital nutrients are not necessarily absorbed into the body once food is digested.

"It's one of the reasons why we have to be so careful when we make claims about the health benefits of various foods and supplements," Dr Okello said.

"There are certain chemicals we know to be beneficial and we can identify foods which are rich in them but what happens during the digestion process is crucial to whether these foods are actually doing us any good."

As part of the research, the Newcastle team worked in collaboration with Dr Gordon McDougall of the Plant Products and Food Quality Group at the Scottish Crop Research Institute in Dundee, who developed technology which simulates the human digestive system.

It is this which made it possible for the team to analyse the protective properties of the products of digestion.

Two compounds are known to play a significant role in the development of Alzheimer's disease – hydrogen peroxide and a protein known as beta-amyloid.

Previous studies have shown that compounds known as polyphenols, present in black and green tea, possess neuroprotective properties, binding with the toxic compounds and protecting the brain cells. When ingested, the polyphenols are broken down to produce a mix of compounds, which the Newcastle team tested.