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Three cups of coffee a day could help keep diabetes away, scientists say


Drinking more coffee may slightly reduce your risk of diabetes, and people who drink three or more cups appear to be at the lowest risk of all, an American study has suggested.

Researchers at Harvard University’s School of Public Health analysed data on more than 120,000 people’s coffee consumption over several years. They found that those who increased their intake by more than a cup a day over a four-year period had an 11 per cent lower chance of developing diabetes in the following years.

Those who had consistently higher coffee consumption – of three or more cups a day – had a risk which was 37 per cent lower than people who consistently drank one or fewer cups a day, researchers found.

The study is the latest to suggest a possible link between coffee and reduced diabetes risk and while the researchers behind the paper said that bigger, clinical trials would be required to confirm their findings, they believe that existing evidence of coffee’s benefit is “well established”.

However, experts in the UK said that it was still not clear that coffee was directly responsible for the lower risk scores shown in the study.

Dr Shilpa Bhupathiraju, from Harvard School of Public Health’s department of nutrition, who co-led the study, said that while exercise and maintaining a healthy diet were by far the best ways to cut the risk of type 2 diabetes, there were also “biologically plausible” theories as to why coffee might also help.

“Coffee has a lot of bio-active compounds, including chlorogenic acid, which we know improves glucose metabolism when tested in animals,” she said. “Coffee is also a rich source of magnesium, which is known to be associated with a  lower risk of type 2 diabetes. The biological plausibility is actually very strong.”

People with type 2 diabetes face problems regulating sugar levels in the body because they cannot produce enough of the hormone insulin, or the cells in the body do not react with insulin. Raised sugar levels can lead to damage to the blood vessels and organs. Being overweight or obese is a major risk factor for type 2 diabetes, but people over 40 and people of South Asian, Afro-Caribbean and Middle Eastern origins are also at higher risk.

Current health advice suggests that around 400mg – roughly four mugs of instant coffee – is the safe limit for caffeine consumption, although pregnant women are advised to consume half that amount. The cups of coffee referred to in the study had roughly 100mg of caffeine. The association with diabetes risk was not observed for decaffeinated coffee drinkers, nor for tea drinkers.

One of the authors of the new study, Dr Frank Hu, also of Harvard, sits on the USA’s Dietary Guidelines Advisory Committee, which is understood to be considering public recommendations on the benefits of moderate coffee consumption for people at a high risk of developing type 2 diabetes. 

However, Dr Richard Elliott a spokesperson for the charity Diabetes UK said that while the findings, published in the journal Diabetologia today, suggested a connection between coffee and diabetes, it was still not certain that increasing coffee intake could really reduce a person’s risk.

“Even if people who drank more coffee did tend to have a lower risk of type 2, it does not necessarily follow that coffee consumption was directly responsible,” he said.

“Other factors that this study has not identified could also be involved and it is even possible that being at high risk of type 2 diabetes encourages people to reduce their coffee intake. What we do know is that the best way to reduce your risk of type 2 diabetes is to maintain a healthy weight by eating a healthy, balanced diet and by being regularly physically active.”