A recent study from South Korea suggests that drinking black coffee may help improve blood sugar control—especially in women. The research, published in the journal Nutrients, looked at how different types and amounts of coffee affect insulin resistance, a key factor in type 2 diabetes.
Why Insulin Sensitivity Matters
Insulin helps move sugar from the blood into the body’s cells. When someone becomes resistant to insulin, sugar stays in the blood, increasing the risk of type 2 diabetes and other health issues. Improving insulin sensitivity means the body uses insulin more effectively, lowering the risk of diabetes.
Study Looked at Coffee Habits of Over 7,000 Adults
Researchers analyzed health and nutrition data from 7,453 Korean adults between the ages of 19 and 64. Participants were asked how much coffee they drank and whether they added sugar or cream. The study focused on two main groups: people who drank black coffee and those who added extras.
The team used a standard measure called HOMA-IR (Homeostasis Model Assessment of Insulin Resistance) to check how well the body responded to insulin.
Black Coffee Linked to Lower Insulin Resistance
People who drank two cups of coffee a day had a 23% lower risk of high insulin levels. For black coffee drinkers, just one cup or less a day was linked to a 26% drop in insulin resistance and a 21% decrease in fasting insulin levels.
However, drinking more than two cups a day didn’t lead to greater benefits. Adding sugar or cream also did not improve results—and in some cases, it reduced the positive effects.
Women Saw the Greatest Benefits
The effects were even stronger in women. Those who drank two or more cups of coffee per day had a 27% drop in insulin resistance and a 30% decrease in insulin levels. Among women who drank black coffee, insulin resistance dropped by up to 36%.
Researchers believe these differences may be linked to hormones like estrogen, which affects how the body processes sugar. Women are also less likely to smoke or drink alcohol, which may help explain their stronger results.
No Effect on Long-Term Blood Sugar Markers
The study found no link between coffee and long-term blood sugar levels, such as HbA1c, or with beta cell function, which helps produce insulin. This suggests coffee may help the body use insulin better, but not necessarily help it make more insulin.
What’s Behind Coffee’s Health Effects?
Coffee contains natural compounds like polyphenols, which have antioxidant and anti-inflammatory properties. These may help reduce how much sugar the body absorbs or releases. Caffeine and other substances in coffee might also reduce liver sugar production.
While scientists are still studying exactly how coffee works, these findings add to growing evidence that black coffee—without added sugar or cream—can support healthy blood sugar levels.
Bottom Line
Drinking one to two cups of black coffee per day may improve insulin sensitivity, especially in women. These effects may help lower the risk of type 2 diabetes. However, more than two cups a day or adding sugar and cream doesn’t appear to offer added benefits.
