New research into the health benefits of nuts for people with type 2 diabetes suggests that all nuts grown on trees can help reduce and stabilise blood sugar levels.
For this latest study, which appears online in the journal PLOS ONE, researchers in Canada reviewed 12 clinical trials involving a total of 450 predominantly middle-aged diabetic participants.
During the trials, each participant ate nearly two daily servings (56g or roughly half a cup) of tree nuts, which include almonds, Brazil nuts, cashews, chestnuts, coconuts, hazelnuts, pecans, macadamia nuts, walnuts, pine nuts and pistachios. The notable nut exclusion was peanuts, which are defined as legumes.
The research team found this daily intake of tree nuts led to improvements in both fasting blood glucose and HbA1c, both important markers for diabetes control.
Dr John Sievenpiper, a physician and researcher in the Clinical Nutrition and Risk Factor Modification Centre of St. Michael's Hospital, Toronto, said the best results were reported when tree nuts were used as a replacement for refined carbohydrates, rather than saturated fats, in participants' diets.
Nuts, particularly tree nuts, are high in healthy unsaturated fat, Dr Sievenpiper explained, adding that while they can also be high in calories, no weight gain was reported among the trial participants.
"Tree nuts are another way people can maintain healthy blood sugar levels in the context of a healthy dietary pattern," he concluded.
Commenting on the study, Dr Richard Elliott, of charity group Diabetes UK, warned that the findings were based on short clinical trials, "many of which were of low quality."
He added: "Owing to these limitations, further research will be needed to find out whether or not tree nuts carry particular benefits for people with type 2 diabetes."
Earlier this month, research published in the Journal of the American Heart Association found that two servings of pistachios a day could help people with type 2 diabetes manage stress and, in the longer term, lower their risk of heart disease.