Eating high levels of flavonoids including anthocyanins and other compounds found in berries, tea and chocolate could offer protection from type 2 diabetes, according to research from the University of East Anglia (UEA) and King’s College London.
The findings, published on 20 January 2014 in the Journal of Nutrition, showed that high intakes of these dietary compounds were associated with lower insulin resistance and better blood glucose regulation.
A study of almost 2,000 people also found that these food groups lowered inflammation, which, when chronic, is associated with diabetes, obesity, cardiovascular disease and cancer.
“Our research looked at the benefits of eating certain sub-groups of flavanoids,” said Professor Aedin Cassidy from UAE’s Norwich Medical School and leader of the research. “We focused on flavones, which are found in herbs and vegetables such as parsley, thyme and celery, and anthocyanins, found in berries, red grapes, wine and other red or blue-coloured fruits and vegetables,” she said.
“This is one of the first large-scale human studies to look at how these powerful bioactive compounds might reduce the risk of diabetes,” Professor Cassidy said. “Laboratory studies have shown these types of foods might modulate blood glucose regulation — affecting the risk of type 2 diabetes,” she said.
“But until now little has been known about how habitual intakes might affect insulin resistance, blood glucose regulation and inflammation in humans,” Professor Cassidy said.
Study method
The researchers studied almost 2,000 healthy women volunteers from TwinsUK who had completed a food questionnaire designed to estimate total dietary flavonoid intake as well as intakes from six flavonoid subclasses. Blood samples were analysed for evidence of both glucose regulation and inflammation. Insulin resistance, a hallmark of type 2 diabetes, was assessed using an equation that considered both fasting insulin and glucose levels.
“We found that those who consumed plenty of anthocyanins and flavones had lower insulin resistance,” Professor Cassidy said. “High insulin resistance is associated with type 2 diabetes, so what we are seeing is that people who eat foods rich in these two compounds — such as berries, herbs, red grapes, wine — are less likely to develop the disease,” she said.
The researchers said their findings showed that those who ate the most anthocyanins were least likely to suffer chronic inflammation, which is associated with many of the most pressing health concerns including diabetes, obesity, cardiovascular disease and cancer.
“And those who consumed the most flavone compounds had improved levels of a protein (adiponectin) which helps regulate a number of metabolic processes, including glucose levels,” Professor Cassidy said. “What we don’t yet know is exactly how much of these compounds are necessary to potentially reduce the risk of type 2 diabetes,” she said.
Professor Tim Spector, research collaborator on the study and Director of the TwinsUK study from King’s College London said the findings were “exciting”.
“This is an exciting finding that shows that some components of foods that we consider unhealthy like chocolate or wine may contain some beneficial substances,” Professor Spector said. “If we can start to identify and separate these substances we can potentially improve healthy eating,” he said.
“There are many reasons, including genetics, why people prefer certain foods, so we should be cautious until we test them properly in randomised trials and in people developing early diabetes,” Professor Spector said.
Researchers at UAE are now seeking local men and postmenopausal women to help investigate whether blueberries could improve aspects of health linked to heart disease and diabetes. The new six-month study will test if daily consumption of one or two portions of freeze-dried blueberries improves heart health and insulin action in people with metabolic syndrome — a condition characterised by a larger waistline and raised blood sugar, blood fats and blood pressure, and which is found in more than a quarter of UK adults.
