Coffee Before Breakfast Cereal Boosts Blood Sugar, Prof Finds

May 20, 2008 - News Release

Think you're doing your body good by eating a low-sugar cereal in the morning? Not if you're drinking a cup of coffee beforehand, new research by a University of Guelph professor shows.

Prof. Terry Graham is the first to discover that drinking coffee before eating your morning cereal can significantly affect your body's blood-sugar response.

"You may think you've made a healthy choice by eating cereal low in sugar, but if you have a cup of caffeinated coffee before eating that cereal, you are immediately changing the way your body responds to your breakfast without even knowing it," said Graham, who worked on the study with master's students Lesley Moisey and Stia Kacker. "It's the caffeine in the coffee that is altering your body's sugar response."

Using two types of cereal — one with low levels of sugar and one with moderate levels — Graham examined the difference in response when healthy male subjects drank caffeinated and decaffeinated coffee one hour before eating breakfast.

The study, which was published this week in the American Journal of Clinical Nutrition, showed the blood-sugar response was higher for the subjects who drank the caffeinated coffee.

"Caffeine interferes with our body's response to insulin," said the human health and nutritional science professor. "It makes us resistant to insulin which in turn makes our blood-sugar levels go higher."

Blood sugar levels in subjects who ate the low-sugar cereal jumped 250 per cent higher when they drank caffeinated coffee than when they drank decaf.

In fact, combining the caffeinated coffee and low-sugar cereal resulted in higher blood-sugar levels than when the subjects drank decaffeinated coffee before eating the cereal with more sugar, said Graham.

"This shows that the combination of foods you eat affects how your body responds."

Although occasionally drinking a cup of coffee before a meal isn't harmful, it can have adverse health effects if done several times a day every day, said Graham. Most people can handle this nutrition challenge well, but those at risk for Type 2 diabetes should be careful, he added.

"Surges in our body's blood-sugar level three or four times a day are challenging to the system. It will start to induce changes in the tissues of the body that can cause the health effects associated with diabetes."

At the same time, there are many health benefits associated with long-term coffee drinking, he said.

"Coffee contains many compounds in addition to caffeine, and some have very positive effects. If you want the good without the bad, then you should consider drinking decaf."

Terry Graham
Department of Human Health and Nutritional Sciences
519-824-4120, Ext. 56168

For media questions, contact Communications and Public Affairs: Lori Bona Hunt, 519-824-4120, Ext. 53338, or, or Deirdre Healey, Ext. 56982 or

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