Coffee may reduce your risk of type 2 diabetes - but only if you don't add sugar.
A study looked at the coffee consumption of almost 290,000 people, among whom close to 13,000 developed type 2 diabetes, The Dailymail reported.
They found people who drank black coffee had a 10 per cent lower risk of getting type 2 diabetes for each daily cup they consumed.
The benefit was much the same for those who added milk to their coffee.
But people who added sugar saw this benefit halved - their risk of type 2 diabetes was only five per cent lower per cup of coffee.
This was for people adding an average of one teaspoon of sugar to their coffee.
Coffee drinkers are known from previous evidence to gain less weight as they age, which may reduce their risk of type 2 diabetes.
Caffeine and plant compounds found within coffee may also reduce inflammation in the body linked to type 2 diabetes.
However adding sugar increases the chances of gaining weight.
A calorific cup of coffee with sugar doesn't fill people up like sugary foods, so they are unlikely to undo the damage by eating fewer calories in their meals and snacks.
Putting artificial sweeteners in coffee was also found to affect its apparent protection against type 2 diabetes.
The reduction in risk of type 2 diabetes per cup was only seven per cent when these were added.
Dr Matthias Henn, who led the study from Harvard T.H. Chan School of Public Health, said: 'Drinking coffee may help lower diabetes risk, but adding sugar or sweeteners significantly reduces these benefits.'
He added: 'These differences in consumption patterns provided key insights into coffee's potential health effects.
'To maximise coffee's health effects, consider skipping sugar or any artificial sweetener.'
Researchers looked at female nurses and male health professionals involved in three large US health studies.
These people were asked about their coffee consumption every four years as part of a dietary questionnaire.
