Medical review by Dr. Mike Natter.
If you’re a coffee drinker and live with diabetes, you may be familiar with the surprising difficulty involved with drinking a regular morning cup of joe.
Coffee, all by itself, has nearly zero carbs, so it shouldn’t really have any impact on your blood sugar. Unfortunately, that’s not the experience that many of our readers have. Diabetes can make drinking coffee annoyingly complicated, because lots of us experience surprising blood sugar spikes after our morning mug. So, what’s the deal? What exactly does coffee do to your blood sugars?
This article will outline the effects that coffee has on blood sugar levels and ways you can prepare and guard against any negative side effects from your morning routine.
What Is It About Coffee That Affects Blood Sugar?
First, let’s stick to unsweetened coffee. Coffee itself has nearly zero carbs. If you add a touch of milk or cream, you may be adding a few grams of carbohydrate, but not more than that. Any blood sugar spike should be negligible, or close to it. In theory.
But many people with diabetes see a spike in their blood sugar after drinking coffee. Just check out the Diabetes Daily forums, where this has been a repeated complaint.
Guess what? The science backs them up. This 2018 review of eight clinical trials found that coffee “may lead to unfavourable acute effects” on glucose metabolism. The CDC agrees, listing coffee among other surprising things that can spike your blood sugar.
The primary cause is caffeine. Research shows that caffeine causes blood glucose spikes in patients with diabetes. The reasons are not exactly clear, but it’s worth noting that habitual coffee drinkers still experience the hyperglycemic effect, meaning that this is one response that you probably cannot develop a tolerance for.
The glucose-spiking effect will vary from one person to another. Judging from anecdotes in the diabetes online community, it appears that some people with diabetes can drink as much coffee as they want without seeing a blood sugar spike, while others need to administer insulin for every cup.
Surprisingly, coffee drinking (and caffeine consumption) might have an opposite effect when viewed from the long term. Studies have shown that regular coffee consumption may “improve the glycaemic metabolism by reducing the glucose curve and increasing the insulin response.” This may be one of the reasons why coffee has been linked with a reduced risk of type 2 diabetes.
This relationship has been found in many studies, enough to convince experts that there’s really something to it. Recent research has proposed several complicated mechanisms by which frequent coffee consumption might reduce diabetes risk factors, ultimately by “by preventing the deterioration of liver and beta cell function.”
So it’s possible that your regular morning cup is helping to lower your blood glucose throughout the day, even if it causes a short-term rise.
Beware Added Carbs in Coffee Drinks
Photo credit: Stock
It should go without saying, but it’s important to remember that added sugar in coffee (including natural sweeteners such as honey and agave syrup) can have a big effect on blood sugar. Those simple carbs are just as powerful as the carbs in snacks and other meals.
If you prefer prepared coffee drinks, whether hot or cold, be very careful to check the nutrition facts. Cafes such as Starbucks and Dunkin’ publish their nutrition facts on their websites. These beverages can pack in an amazing amount of sugar.
The difference in carbohydrate counts between one cup of black coffee (0-1 gram) and a Grande Frappuccino from Starbucks (50 grams) is stark and can make all the difference between a “good” blood sugar day and a difficult one. Having coffee beverages that are high in saturated fat and sugar on a regular basis can contribute to both insulin resistance and the progression of type 2 diabetes.
Milk is also a sneaky contributor to coffee carb counts. An extra large latte can have up to 25 grams of carbohydrates, mostly from the sugars found in milk.
Troubleshooting the ‘Coffee Spike’
If you are feeling frustrated with morning glucose spikes after your coffee, consider some of the following potential remedies:
Switch to decaf! This might be the single easiest substitution to make.
Rule out dawn phenomenon. Some people with diabetes experience daily morning blood sugar spikes that have nothing to do with coffee or breakfast.
Combine your coffee with a brisk walk or other light exercise to help bring your blood sugar back into range.
Replace sugar with one of our favorite zero-carb sweeteners.
Replace milk or cream with a lower-carbohydrate plant-based milk or creamer.
Add vanilla extract, cinnamon, or sugar-free syrups to your coffee for extra taste.
Bolus insulin for your coffee. If you use fast-acting insulin before meals, you may find that you need to administer a dose of insulin 10-15 minutes before your first sip. Many people with type 1 diabetes have learned that they need to bolus for the caffeine in coffee as if it were 5-15 grams of carbohydrates. Please consult with your physician before making changes to your insulin usage.
The routine of a morning cup of coffee is practically essential to millions of people around the world. Incorporating some of these strategies can help you mitigate the negative effects on blood sugar, while still allowing you to enjoy what you love! A little planning and preparation can make all the difference. And that’s definitely something to celebrate. Cheers!