Caffeine and insulin resistance in pregnancy

Consumption of Coffee and Risk of Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis of Observational Studies

Objective: The results from epidemiologic studies on the relationship between intake of coffee and the risk of gestational diabetes mellitus (GDM) remain inconclusive. A meta-analysis was performed to achieve a comprehensive finding regarding the association between intake of coffee and the risk of GDM.

Methods: PubMed, Scopus, ISI Web of Science, and Google Scholar were searched to find articles published up to August 2021. Observational studies that reported risk estimates [risk ratios (RRs), hazard ratios (HRs), and odds ratios (ORs)] for the association of consumption of coffee with the risk of GDM in pregnant women were included. Random effects model was applied to calculate summarized risk estimate and 95% CIs for the highest vs. lowest categories of intake of coffee.

Results: Seven observational studies (three cohort, two case-control, and two cross-sectional studies) with 75,607 participants and 1,625 women with GDM met the inclusion criteria. The meta-analysis of comparing the highest vs. lowest intake of coffee categories showed no significant association between intake of coffee and risk of GDM (summarized risk estimate: 0.89; 95% CI: 0.76, 1.05; I² = 63.4%). Subgroup analysis showed that consumption of coffee had an inverse relationship with GDM in studies conducted in non-Asia countries (summarized risk estimate: 0.75; 95% CI: 0.58, 0.97; I² = 6%).

Conclusion: This study has shown that high consumption of coffee did not decrease the risk of GDM. Furthermore, large-scale cohort studies are required to confirm our findings.

Caffeine and Caffeine Metabolites in Relation to Insulin Resistance and Beta Cell Function in U.S. Adults

The relationship between caffeine and insulin resistance (IR) has been assessed only in terms of caffeine intake, and the association between caffeine and beta cell function (BCF) remains unclear. This study examines the association between urinary caffeine and its metabolites, IR, and BCF in nondiabetic, noninstitutionalized US adults in order to account for the inter-individual differences in caffeine metabolism. Data on urinary caffeine and its metabolites, IR and BCF from adults aged 20 years and older who participated in the 2009–2010 and 2011–2012 National Health and Nutrition Examination Surveys were analyzed (n for caffeine = 994). IR and BCF were assessed using homeostatic model assessment (HOMA) and urinary caffeine and its metabolites were measured using high-performance liquid chromatography-electrospray ionization-tandem quadrupole mass spectrometry. After adjusting for all covariates, increases in urinary 1,3-DMU, 1,7-DMU, 1,3,7-TMU, theophylline, paraxanthine, caffeine, and AAMU were significantly associated with increased HOMA-IR and HOMA-β (HOMA of insulin resistance and beta cell function). Compared with individuals in the lowest quartile of urinary 1,3-DMU, 1,7-DMU, 1,3,7-TMU, theophylline, paraxanthine, caffeine, and AAMU, the regression coefficients for HOMA-IR and HOMA-β were significantly higher among those in the highest quartile. After stratification by prediabetes status, HOMA-IR and HOMA-β showed significant positive associations with urinary caffeine and its metabolites among subjects with normal fasting plasma glucose levels. Our cross-sectional study showed that caffeine and its metabolites were positively related to IR and BCF.

Second-Trimester Maternal Serum Paraxanthine, CYP1A2 Activity, and the Risk of Severe Preeclampsia

OBJECTIVE

To measure the association between second-trimester maternal caffeine intake and caffeine metabolism through the CYP1A2 system and the risk of subsequent severe preeclampsia.

METHODS

This was a nested case-control study of women who had undergone second-trimester screening for fetal aneuploidy and had banked serum available for analysis. The outcome of interest was severe preeclampsia, and exposures were serum paraxanthine (1,7-dimethylxanthine), measured through high-performance liquid chromatography, and CYP1A2 activity, assessed by paraxanthine/caffeine ratios.

RESULTS

We identified 51 cases of severe preeclampsia from our population of 3,992 women (1.3%), of whom 33 had sufficient serum for analysis. These were compared with 99 healthy women. Median paraxanthine concentrations were not significantly higher in women in the control group than women in the case group (96.4 ng/mL compared with 38.0 ng/mL, P=.12), and higher serum paraxanthine was not associated with lower odds of severe preeclampsia (odds ratio [OR] 0.72, confidence interval [CI] 0.48-1.08). However, we found a significantly higher paraxanthine/caffeine ratio in women in the control group than women in the case group (0.37 compared with 0.23, P=.02) and a decreased risk of preeclampsia per every log standard deviation increase in paraxanthine/caffeine ratio (OR 0.53, 95% CI 0.31-0.90).

CONCLUSION

Faster caffeine metabolism in the second trimester, assessed by paraxanthine/caffeine ratios, is associated with a reduced risk of subsequent severe preeclampsia.

LEVEL OF EVIDENCE

II.

Absorption of caffeine in fermented Pu-er tea is inhibited in mice

Caffeine is present in a number of dietary sources consumed worldwide. Although its pharmacokinetics has been intensively explored, little is known about complexed caffeine (C-CAF) in aqueous extraction of fermented Pu-er tea. The major components of C-CAF are oxidative tea polyphenols (OTP) and caffeine. Furthermore, the C-CAF can be precipitated in low pH solution. After administering the same amount of total caffeine and comparing the peak level of plasma caffeine with the coffee (contains 0.11 ± 0.01% C-CAF) group, the results showed that the caffeine/OTP (contains 66.67 ± 0.02% C-CAF) group and the instant Pu-er tea (contains 23.18 ± 0.02% C-CAF) group were 33.39% and 25.86% lower, respectively. The concentration of the metabolites of caffeine supports the idea that the absorption of the C-CAF was inhibited in mice. Congruent with this result, the amount of caffeine detected in mice excrement showed that more caffeine was eliminated in the caffeine/OTP group and the Pu-er tea group. The locomotor activity tests of mice demonstrated that the stimulating effect of caffeine in caffeine/OTP and Pu-er tea was weaker than in coffee. Our findings demonstrate that caffeine can be combined with OTP and the absorption of C-CAF is inhibited in mice, thus decreasing the irritation effect of caffeine. This may also be developed as a slow release formulation of caffeine.

First trimester coffee and tea intake and risk of gestational diabetes mellitus: a study within a national birth cohort

OBJECTIVE

Coffee and tea consumption is associated with a decreased type 2 diabetes risk in non-pregnant adults. We examined the relation between first trimester coffee and tea consumption and gestational diabetes mellitus (GDM) risk.

DESIGN

Population-based cohort study.

SETTING

Denmark 1996-2002.

POPULATION

Non-diabetic women with singleton pregnancies in the Danish National Birth Cohort (n = 71,239).

METHODS

Estimated adjusted relative risks (RR) and 95% confidence intervals (95%CI) for the association between first trimester coffee and tea or estimated total caffeine and GDM.

MAIN OUTCOME MEASURES

GDM ascertained from the National Hospital Discharge Register or maternal interview.

RESULTS

Coffee or tea intake was reported in 81.2% (n = 57,882) and 1.3% (n = 912) of pregnancies were complicated by GDM. Among non-consumers, 1.5% of pregnancies were complicated by GDM. Among coffee drinkers, GDM was highest among women who drank ≥8 cups/day (1.8%) with no significant difference across intake levels (P = 0.10). Among tea drinkers, there was no difference in GDM across intake levels (1.2%; P = 0.98). After adjustment for age, socio-occupational status, parity, pre-pregnancy body mass index, smoking, and cola, there was suggestion of a protective, but non-significant association with increasing coffee (RR ≥8 versus 0 cups/day = 0.89 [95%CI 0.64-1.25]) and tea (RR ≥8 versus 0 cups/day = 0.77 [95%CI 0.55-1.08]). Results were similar by smoking status, except a non-significant 1.45-fold increased risk with ≥8 coffee cups/day for non-smokers. There was a non-significant reduced GDM risk with increasing total caffeine.

CONCLUSIONS

Our results suggest that moderate first trimester coffee and tea intake were not associated with GDM increased risk and possibly may have a protective effect.