by Jenn
Answer by Dr. Albana Greca, MD, MMedSc
Hi Jenn,
Caffeine and coffee are not the same thing. Caffeine can have a short-term effect that makes insulin work less efficiently, while habitual coffee drinking has been associated with a lower long-term risk of type 2 diabetes in population studies.
Yes, temporarily. Controlled studies have found that caffeine taken before a glucose load can reduce insulin sensitivity and increase the glucose and insulin response. The effect varies between people and may be more noticeable in those who already have diabetes or difficulty controlling glucose.
Caffeine blocks adenosine receptors and can increase stress hormones such as epinephrine. These changes may promote liver glucose release and make muscle cells less responsive to insulin for several hours.
Read more about what insulin resistance means.
Current evidence does not show that ordinary coffee consumption causes type 2 diabetes. In fact, long-term observational studies have associated both caffeinated and decaffeinated coffee with a lower risk of developing type 2 diabetes.
This apparent contradiction may be explained by the difference between an immediate caffeine effect and the long-term effects of the whole beverage. Coffee contains chlorogenic acids and other compounds that may influence inflammation, the liver, the gut microbiome and glucose metabolism. However, observational studies cannot prove that drinking more coffee prevents diabetes.
It may be. For most adults, the FDA cites 400 mg of caffeine per day as an amount not generally associated with negative effects. The caffeine in coffee varies widely. A 12-ounce brewed coffee may contain approximately 113–247 mg, while decaffeinated coffee usually contains much less.
Ten cups could therefore greatly exceed 400 mg, particularly if the cups are large or the coffee is strong. Too much caffeine may cause palpitations, anxiety, tremor, headaches, stomach upset, higher blood pressure and poor sleep.
Poor sleep can itself make glucose regulation more difficult. If you reduce caffeine, do it gradually over one or two weeks to lessen withdrawal headaches and fatigue.
Decaffeinated coffee is a reasonable alternative if caffeine raises your glucose, affects sleep or causes palpitations or anxiety. It is not completely caffeine-free, but it usually contains far less caffeine than regular coffee.
Decaf retains many of coffee’s non-caffeine compounds, and observational studies have also linked it with a lower risk of type 2 diabetes. This does not prove that decaf prevents diabetes, but it makes it a practical choice for someone trying to reduce caffeine.
The healthiest option is the one that keeps total caffeine moderate and does not add large amounts of sugar or saturated fat.
Because responses differ, compare glucose under similar conditions. If you have been advised to monitor, check before coffee and again about one to two hours after the same breakfast on two or three days. Then repeat the experiment with decaf, without changing the meal.
Do not diagnose insulin resistance from symptoms or home readings alone. Follow the laboratory instructions for fasting glucose, HbA1c or an oral glucose tolerance test. For a fasting test, drink only water unless the laboratory tells you otherwise.
Our guides to symptoms of insulin resistance and blood tests for diabetes explain what the results can show.
Do not assume that coffee caused your possible insulin resistance, but ten cups a day is more than I would recommend. Check the caffeine content and gradually reduce toward no more than 400 mg daily, and possibly lower if you have high glucose, anxiety, palpitations, high blood pressure or poor sleep.
Try replacing several cups with decaf or water. Once your test results are available, discuss them with your doctor before making conclusions about insulin resistance.
Hope this helps.
Dr. Albana Greca
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