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For people without diabetes, coffee may help reduce the risk of developing diabetes.

Caffeine has been shown in the short term to increase both glucose and insulin levels. Because of this, people with diabetes should be cautious when consuming coffee.

Once sweetener is added to coffee, it removes the benefits of diabetes prevention. It can actually increase your risk of developing diabetes.

Coffee also cuts the risk of having a stroke, research suggests.

Every cup reduces the stroke threat by 8 per cent — and the risk of developing heart failure by 7 per cent.

However, scientists believe the benefits plateau and previous studies suggest that a maximum of three cups a day can be beneficial. 

It is also not clear how long the benefits of each cup lasts. 

Watch: How to brew better coffee at home in 5 easy steps

The latest research, presented at an American Heart Association conference in California, bolsters evidence that coffee benefits the circulatory system.

Scientists believe the antioxidant plant compounds in the drink — rather than caffeine — are responsible for the benefits.

The research by the University of Colorado School of Medicine used a computer model to calculate the benefit of each coffee, based on previous long-running health studies.