Coffee consumption at a level of 1-4 cups of coffee per day is associated with a reduced risk of metabolic syndrome, according to a new report from the Institute for Scientific Information on Coffee.
Coffee is a broadly consumed beverage which has shown beneficial associations not only with cardiovascular disease and type 2 diabetes, but has also been associated with lower all-cause mortality.
Nevertheless, only a small number of prospective cohort studies have addressed the association between regular coffee consumption and the incidence of metabolic syndrome.
“Metabolic syndrome is characterized by a number of components that are associated with accelerated arterial aging and cardiovascular events,” said Dr. Estefania Toledo from the University of Navarra and Dr. Giuseppe Grosso from the University of Catania.
“These include raised blood pressure, dyslipidaemia, raised fasting glucose and central obesity.”
In their report, the two experts explored the research on coffee consumption and metabolic syndrome, discussing data from meta-analyses and research on potential mechanisms.
Dr. Toledo collated information from two meta-analyses, both published in 2016, which suggested that overall coffee consumption is associated with a reduced incidence of metabolic syndrome, although some variability in the results from individual studies was observed.
She presented three longitudinal studies from the meta-analyses, the first being a cohort of 17,000 middle-aged adults in Norway. In that study, the authors suggested that coffee consumption tended to be protective for metabolic syndrome at low and moderate levels of intake (1–4 cups of coffee per day), especially for men. However, coffee consumption greater than 4 cups per day did not appear to be as protective.
Further results from a group of more than 9,000 U.S. adults, aged 45-64 where 40% of the cohort developed metabolic syndrome, concluded that the results showed tendency for coffee to be associated with a reduced risk of metabolic syndrome, however the association was not significant.
In contrast, the Amsterdam Growth and Health study, which found a 10% incidence of metabolic syndrome at age 36, suggested that none of the relationships between coffee consumption and the metabolic syndrome or its components were significant.
Dr. Toledo focused on the SUN cohort, a large prospective cohort study (22,000 people, 91% retention rate) based at the University of Navarra. That study differed from the others discussed as it specifically considered caffeinated and decaffeinated coffee.
The study authors concluded that the consumption of 1-4 cups of coffee per day was associated with a reduced risk of developing metabolic syndrome, however higher intakes were not. This association was reported for both regular and decaffeinated coffee, and when reviewing each type of coffee individually, the association was similar however in both cases the statistical significance was lost.
Dr. Grosso analyzed studies that consider individual aspects of the metabolic syndrome. He also identified the potential mechanisms to describe the associations.
An umbrella review on associations between various diseases and coffee consumption suggested that there was no evidence of increased risk of diseases including heart disease.
Dr. Grosso highlighted a potential protective effect of moderate coffee consumption on some cancers, however, he reported a strong confounding effect of smoking, particularly in relation to cancer mortality. Once this confounding effect was accounted for he suggested that a moderate coffee consumption is associated with a reduction of cardiovascular diseases, cancer and all cause mortality.
In considering type 2 diabetes, the researcher reported that there appears to be a linear association between coffee consumption and a decreased risk of type 2 diabetes.
In relation to hypertension, Dr. Grosso’s own work suggests that long-term coffee consumption is associated with a decreased risk of hypertension. Further work on obesity, another risk factor for metabolic syndrome, suggests a weaker association.
“In summary, not all components of metabolic syndrome are affected by coffee consumption, but some individual elements seem to be inversely related to coffee drinking,” he said.
Dr. Grosso also discussed two cohort studies on metabolic syndrome and coffee consumption, which both suggested an inverse association.
The Polish arm of his work concluded that after adjusting for confounding factors, both higher coffee and tea consumption were negatively associated with metabolic syndrome. In relation to specific symptoms, those who drank more than 3 cups of coffee had lower BMI (body mass index), waist circumference, systolic and diastolic blood pressure, triglycerides, and higher HDL (‘good’) cholesterol than those drinking less than one cup a day.
In his Italian cohort no direct association between caffeine intake and metabolic syndrome or its components was observed, however, coffee consumption was significantly related to reduced risk of metabolic syndrome.
Dr. Grosso gave an overview of potential mechanisms behind the described effects, with particular emphasis on his work on polyphenols.
“In the Polish cohort, coffee was the main source of polyphenols, followed by tea. By contrast, in the Italian cohort the main sources of polyphenols were nuts followed by coffee,” he said.
“Metabolic syndrome is inversely associated with total polyphenol consumption, specifically phenolic acids and flavonoids. Hydroxycinnamic acids were significantly inversely associated with metabolic syndrome, and despite the variability in diets the main source of hydroxycinnamic acids in both the Polish and Italian cohorts was coffee.”
“These striking similarities between both cohorts provide an insight into the potential mechanisms, and although firm conclusions cannot yet be reached, the importance of polyphenols and hydroxycinnamic acid in particular seem to be of note.”
“It is also important to consider individual genetic profiles as this may impact the metabolism of coffee within the body,” he concluded.
Estefania Toledo. Coffee and metabolic syndrome: A review of the research. FENS 19, abstract # S2-CC-10.2
Guiseppe Grosso. Coffee and the metabolic syndrome: A review of the latest research. FENS 19, abstract # S2-CC-10.1