Coffee May Protect Against Diabetes, But Sugar and Sweeteners Weaken the Effect: Study Reveals

The researchers showed that regular coffee without additives is associated with a 10% reduction in the risk of type 2 diabetes per cup. However, this protective effect significantly diminishes with adding sugar or artificial sweeteners. Adding cream does not impact coffee's protective benefits, while using coffee whitener seems to reduce its effectiveness, though the trend is not as pronounced.

The findings were published online in The American Journal of Clinical Nutrition on January 17, 2025.

Regular coffee consumption has consistently been linked to a lower risk of type 2 diabetes. However, it remains unclear whether the use of additives influences this association. To address this, Frank B Hu, Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, United States, and colleagues aimed to examine the relationship between coffee intake and T2D risk while considering the impact of added sugar, artificial sweeteners, cream, or non-dairy coffee whitener.

For this purpose, the researchers analyzed data from three large prospective cohorts: the Nurses’ Health Study (NHS; 1986–2020), NHS II (1991–2020), and the Health Professionals Follow-up Study (HPFS; 1991–2020). Coffee consumption, additive use, and type 2 diabetes incidence were assessed through validated self-reported questionnaires. To determine the association, time-dependent Cox proportional hazards regression models were applied, calculating hazard ratios (HRs) with multivariable adjustments.

The study revealed the following findings:

• Over 3,665,408 person-years of follow-up, 13,281 new cases of type 2 diabetes (T2D) were recorded.
• After multivariable adjustments, each additional cup of coffee without additives was linked to a 10% lower risk of T2D (HR: 0.90) in the pooled analysis of the three cohorts.
• The inverse association remained unchanged for participants who added cream to their coffee.
• Among those who added sugar (approximately one teaspoon per cup), the protective effect of coffee was significantly weakened (HR: 0.95; interaction term HR: 1.17).
• A similar trend was observed in individuals using artificial sweeteners, with a diminished protective effect (HR: 0.93; 95% CI: 0.90, 0.96; interaction term HR: 1.13).
• The association between coffee consumption and T2D risk was also reduced in participants using coffee whitener, though the interaction was not statistically significant (HR: 0.95; interaction term HR: 1.16).

"The protective effect of higher coffee consumption against type 2 diabetes is significantly reduced when sugar or artificial sweeteners are added, while the use of cream does not impact this inverse association," the researchers wrote.

Reference:

Henn M, Glenn AJ, Willett WC, Martínez-González MA, Sun Q, Hu FB. Coffee consumption, additive use, and risk of type 2 diabetes-results from 3 large prospective United States cohort studies. Am J Clin Nutr. 2025 Jan 18:S0002-9165(25)00017-6. doi: 10.1016/j.ajcnut.2025.01.017. Epub ahead of print. PMID: 39828230.