Coffee and blood sugar: what happens after drinking it? The expert answers

When it comes to wellness and nutrition, a question related to our metabolic health may arise: does coffee raise blood sugar levels, or is it safe to drink even for those who need to monitor their blood sugar levels? It's a common question, but the answer isn't as simple and unequivocal as we might think: it all depends on several factors, such as the amount of caffeine consumed throughout the day, the time of day when you drink the coffee, and how it's consumed (for example, whether it's unsweetened, sweetened, or with the addition of cream or flavored syrups).

With the help of biologist and nutritionist Simone Gabrielli, we'll explore the true effects of coffee on blood sugar levels, the role this alkaloid plays in metabolic processes, and whether it's safe to drink if you have diabetes or insulin resistance. Finally, we'll offer some practical tips for enjoying this beloved "black gold" while minimizing its impact on blood sugar.

What are the effects of coffee on blood sugar?

Before analyzing the relationship between coffee and blood sugar, it's important to clarify a key point: in a healthy individual, a temporary increase in blood sugar after consuming food or drinks is a completely normal and efficient physiological response. "Blood sugar management, however, becomes a real clinical priority for those suffering from metabolic diseases, such as type 2 diabetes or insulin resistance," explains Gabrielli.

Coffee's effect on blood sugar levels presents an apparent paradox between the short and long term: acutely, or in the short term, caffeine can cause a temporary and mild increase in blood sugar levels or a momentary reduction in insulin sensitivity; chronically, or therefore in the long term, epidemiological studies demonstrate that habitual coffee consumption (both regular and decaffeinated) is associated with a reduced risk of developing type 2 diabetes.

This is likely due to the presence of antioxidants and polyphenols, natural compounds essential for health, which improve glucose management and protect pancreatic cells over time.

Contrary to popular belief, blood sugar levels can experience a slight, temporary spike even when drinking unsweetened coffee without sugar or other additives (such as cream or syrup). This happens not because coffee contains carbohydrates—it contains virtually none—but because of caffeine's effect on the nervous and hormonal systems:

• Release of adrenaline and cortisol: Caffeine stimulates the adrenal glands to produce stress hormones (adrenaline and cortisol). These hormones signal the liver to release its glucose reserves into the blood (glycogenolysis) to provide immediate energy for the body, making it available to the muscles and brain;
• empty stomach effect: when fasting, this hormonal peak is more marked, causing a slightly more visible rise in blood sugar levels than when it is taken at the end of or within a meal;
• Excess caffeine: Drinking too many cups of coffee in a row amplifies the adrenergic response, keeping cortisol high and temporarily reducing the cells' ability to absorb glucose.

Can you drink coffee if you have diabetes?

"Yes, people with diabetes can drink coffee, but with some precautions based on their individual response," reassures Gabrielli. Although chronic coffee consumption protects against the onset of diabetes, high doses of caffeine can temporarily make it more difficult to manage postprandial blood sugar levels in those who already have it. However, it's also important to note that caffeine tolerance varies greatly from person to person: some diabetics don't notice any significant changes, while others experience small increases in blood sugar.

For those with diabetes, the best choice is to opt for decaffeinated coffee or limit caffeine intake to 1-2 cups a day, without added sugar, preferably during or after balanced and macronutrient-rich meals.

Some tips for drinking coffee without affecting blood sugar levels

To enjoy your coffee while minimizing its impact on your glucose levels and avoiding unnecessary empty calories, here are some practical tips from a nutritionist.

These are the "smart" ingredients you can add and with which you can create strategic functional combinations:

• Ground cinnamon; adding a pinch of cinnamon instead of sugar gives it a delightful aroma and a delicate, barely perceptible sweetness. This spice, among the most studied in the nutritional field for its properties in managing carbohydrate metabolism, contains polyphenolic compounds that support insulin sensitivity;
• bitter cocoa powder (100%): provides flavonoids and antioxidants without adding free sugars and gives the coffee an intense note;
• Milk or plant-based drink without added sugar (in small doses): The protein and fat content of milk (or an almond/soy drink without added sugar) slows gastric emptying, attenuating the acute hormonal response. It's essential to check the label for sugar-free status because even if it says "without added sugar," it may still contain sugar.
• pairing with a full meal: drinking coffee at the end of a meal (especially if rich in fiber and protein) cancels out the isolated adrenaline rush that occurs on an empty stomach.

These are the additions to avoid:

• sugar (white, cane, honey, or syrups); transforms a zero-calorie drink into a source of ultra-fast-absorbing free sugars;
• whipped cream or industrial creams: they add a high load of saturated fats and calories without any nutritional benefit;
• Artificial sweeteners used extensively: although they do not directly raise blood sugar levels, maintaining an extremely sweet taste alters the perception of natural flavors and the habituation to the bitter taste.