How Does Caffeine Affect Your Blood Sugar?

Whether it’s from coffee, tea, soda, or chocolate, most Americans get caffeine every day. For healthy people, it’s usually a harmless perk-me-up. But if you have type 2 diabetes, caffeine may make it harder to keep your blood sugar in check.

How Does Caffeine Affect Your Blood Sugar?

A growing body of research suggests people with type 2 diabetes react to caffeine differently. It can raise blood sugar and insulin levels for those with the disease.

One study looked at people with type 2 diabetes who took a 250-milligram caffeine pill at breakfast and another at lunchtime. That’s about the same amount as drinking two cups of coffee with each meal. The result: Their blood sugar was 8% higher than on days when they didn’t have caffeine. Their reading also jumped by more after each meal.

That’s because caffeine can affect how your body responds to insulin, the hormone that allows sugar to enter your cells and get changed into energy.

Caffeine may lower your insulin sensitivity. That means your cells don’t react to the hormone by as much as they once did. They don’t absorb as much sugar from your blood after you eat or drink. This causes your body to make more insulin, so you have higher levels after meals.

If you have type 2 diabetes, your body already doesn’t use insulin well. After meals, your blood sugar rises higher than normal. Caffeine may make it tougher to bring it down to a healthy point. This may lead to too-high blood sugar levels. Over time, this may raise your chance of diabetes complications, like nerve damage or heart disease.

Why Does Caffeine Have This Effect?

Scientists are still learning how caffeine affects your insulin and blood sugar levels. But they think it may work this way:

  • Caffeine raises levels of certain stress hormones, like epinephrine (also called adrenaline). Epinephrine can prevent your cells from processing as much sugar. It may also keep your body from making as much insulin.
  • It blocks a protein called adenosine. This molecule plays a big role in how much insulin your body makes. It also controls how your cells respond to it. Caffeine keeps adenosine from doing its job. It can’t clear sugar from your blood as quickly.
  • It takes a toll on your sleep. Too much caffeine can keep you awake. Lack of sleep may also lower your insulin sensitivity.

Continued

How Much Caffeine Is Too Much?

It only takes about 200 milligrams of caffeine to affect your blood sugar. That’s the amount in about one or two cups of brewed coffee or three or four cups of black tea.

You may be able to handle more or less caffeine. People can have different reactions to the drug. Your response depends on things like your age and weight.

How much caffeine you usually get may also play a role. People with diabetes who are regular coffee drinkers don’t have higher blood sugar levels than those who aren’t. Some experts think your body gets used to that amount of over time. But other research shows that caffeine could still cause a spike, even if you always start your day with a cup of joe.

To find out if caffeine raises your blood sugar, talk to your doctor or a dietitian. You might test your blood sugar throughout the morning after you have your usual cup of coffee or tea. Then you’ll test after you skip the drink for a few days. When you compare these results, you’ll know if caffeine has an impact.

What About the Caffeine in Coffee?

There’s another twist to the story. Studies show that coffee may lower your odds of getting type 2 diabetes in the first place. Experts think that’s because the drink is high in antioxidants. These compounds reduce inflammation in your system, which can raise your chance of having the disease.

If you already have type 2 diabetes, this may not hold true. The caffeine in a cup of java makes it tougher to control your blood sugar. If yours spikes after your morning cup, you may want to switch to decaf. Even though this drink has a tiny amount of caffeine, it doesn’t have the same effect on your blood sugar or insulin.

WebMD Medical Reference Reviewed by Michael Dansinger, MD on April 13, 2017

Sources

SOURCES:

FDA: “Medicines in My Home: Caffeine and Your Body.”

Diabetes Care: “Acute Effects of Decaffeinated Coffee and the Major Coffee Components Chlorogenic Acid and Trigonelline on Glucose Tolerance,” “Caffeine: A Cause of Insulin Resistance?” “Caffeine Can Decrease Insulin Sensitivity in Humans,” “Caffeine Increases Ambulatory Glucose and Postprandial Responses in Coffee Drinkers With Type 2 Diabetes,” “Coffee, Caffeine, and Type 2 Diabetes.”

Mayo Clinic: “Caffeine Content for Coffee, Tea, Soda and More,” “Caffeine: Does It Affect Blood Sugar?” “Diabetes: Complications,” “Nutrition and Healthy Eating.”

Joslin Diabetes Center: “What Is Insulin Resistance?”

American Diabetes Association: “Type 2.”

Sacha Uelmen, director of nutrition, American Diabetes Association.

Journal of Clinical Investigation: “Epinephrine-induced Insulin Resistance in Man.”

Nature Review Endocrinology: “Adenosine signalling in diabetes mellitus -- pathophysiology and therapeutic considerations.”

Annals of Internal Medicine: “Impaired Insulin Signaling in Human Adipocytes After Experimental Sleep Restriction: A Randomized, Crossover Study.”

European Journal of Clinical Nutrition: “The Evaluation of Inflammatory and Oxidative Stress Biomarkers on Coffee -- Diabetes Association: Results From the 10-year Follow-up of The ATTICA Study (2002–2012).”

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