Regular coffee intake may lower T2D risk in women with gestational diabetes

Women with a history of gestational diabetes mellitus (GDM) may benefit from habitual consumption of caffeinated coffee to prevent progression to type 2 diabetes (T2D) and have a more favourable metabolic profile, suggests a study.

“Coffee might be promoted as an alternative to other less healthy beverages and be incorporated into a healthy lifestyle to prevent T2D progression for individuals with a history of GDM,” the researchers said.

A total of 4,522 participants with a GDM history in the Nurses’ Health Study (NHS) II for incident T2D were included in the current study and followed between 1991 and 2017. Every 2‒4 years, data on demographics, lifestyle factors such as diet, and disease outcomes were updated.

Using food frequency questionnaires, participants reported their consumption of caffeinated and decaffeinated coffee. To measure glucose metabolism biomarkers (ie, HbA1c, insulin, C-peptide), the researchers collected fasting blood samples in 2012‒2014 from a subset of participants who were free of diabetes (n=518).

Multivariable Cox regression models were used to calculate adjusted hazard ratios (HRs) and 95 percent confidence intervals (CIs) for the risk of T2D. Least squares mean of glucose metabolic biomarkers were also estimated according to coffee intake.

Of the participants, 979 developed T2D. Caffeinated coffee consumption inversely correlated with T2D risk. Adjusted HRs for ≤1 (nonzero), 2–3, and 4+ cups/d, compared with 0 cup/d (reference), were 0.91 (95 percent CI, 0.78‒1.06), 0.83 (95 percent CI, 0.69‒1.01), and 0.46 (95 percent CI, 0.28‒0.76), respectively (p_trend=0.004). [Am J Clin Nutr 2022;116:1693-1703]

“We did not observe evidence of associations between decaffeinated coffee and T2D risk among individuals with a history of GDM,” the researchers said. “This finding differs from the literature as well as the general population of the NHS II where similar magnitudes of the benefits for decaffeinated coffee were reported as compared with caffeinated coffee.”

Meanwhile, replacing a single serving per day of sugar- or artificially sweetened beverage with 1 cup/day of caffeinated coffee resulted in a 17-percent (risk ratio [RR], 0.83, 95 percent CI, 0.75‒0.93) and 9-percent (RR, 0.91, 95 percent CI, 0.84‒0.99) lower risk of T2D, respectively.

“In line with the 2020–2025 Dietary Guidelines for Americans, given the epidemiological evidence on the detrimental effects of added sugar and the moderately protective associations between low-fat dairy consumption and T2D risk, coffee, when consumed properly at moderate levels (3–5 cups/d), may be considered as a healthier beverage option compared with the other less healthy beverages among individuals with a history of GDM,” the researchers said.

Higher consumption of caffeinated coffee also correlated with lower fasting insulin and C-peptide concentrations (p_trend<0.05 for all). On the other hand, decaffeinated coffee intake showed no significant association with T2D but had an inverse association with C-peptide concentrations (p_trend=0.003).

Of note, one strong confounder for the association between coffee intake and T2D risk is smoking. Both current and past smoking have been shown to increase T2D risk. After adjusting for smoking status in this study, a lower risk of T2D with higher consumption of caffeinated coffee was observed among never smokers, indicating that the inverse association was potentially independent of smoking.