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The prevalence of type 2 diabetes continues to reach epidemic proportions worldwide, with no sign of abating. 1 On a positive note, clinical trials show that lifestyle interventions can reduce the risk of progression from impaired glucose tolerance to type 2 diabetes by about 60%. 2 Lifestyle interventions that reduce the risk of diabetes have emphasised reduced intake of total and saturated fat; increased intake of vegetables, fruit, and wholegrain cereals; and increased physical activity. All of these interventions contribute to weight loss, which is the major determinant of a successful outcome. 3
Given the potential of such a lifestyle package to reduce other illnesses associated with obesity it is hardly surprising that it forms the cornerstone of programmes worldwide aimed at reducing the risk of chronic diseases. However, surprisingly few dietary factors have been convincingly established as independent risk factors for type 2 diabetes.
Because fruit and vegetables are rich in dietary fibre, antioxidant nutrients, and magnesium they are prime candidates for protecting against diabetes. However, epidemiological studies have generated mixed results. The linked systematic review by Carter and colleagues (doi: 10.1136/bmj.c4229 ) looked at six large prospective studies from the United States, China, and Finland. 4 The review found that a higher intake (highest v lowest quarter) of green leafy vegetables was associated with a 14% (summary relative risk 0.86, 95% confidence interval 0.77 to 0.97) reduction in the risk of developing type 2 diabetes. Fruit, vegetables, or fruit and vegetables combined were not significantly associated, although the result for fruit bordered on significance.
However, given the limited number of studies it may be too early to dismiss a small reduction in risk for overall fruit and vegetable intake and too early for a conclusion regarding green leafy vegetables. Few studies have reported results for specific fruit and vegetable items, so it is not known whether other specific fruits and vegetables may play a role...