One Component of “Five-a-Day” May Help Prevent Diabetes

We’re constantly urged to eat fruit and vegetables - “5-a-day” is the cry – in order to lower our risk of cardiovascular disease and, to a lesser extent, some cancers.  This nutritional benefit has been demonstrated, but an effect on the risk of type 2 diabetes hasn’t.  So University of Leicester researchers in the UK decided to study the effectiveness of different fruit and veggies on diabetes risk.  They published their findings online in the British Medical Journal. 

The scientists searched major English-language medical publication data-bases for prospective studies with an independent measure of intake of fruit, vegetables, or fruit and vegetables, as well as the occurrence of type 2 diabetes.  

They found 6 studies meeting their criteria, with an average follow-up of 13 years.  They covered 220,000 participants aged 30 to 74 years; 4 of the 6 studies provided separate data on the consumption of green leafy vegetables (e.g. lettuce, spinach, kale, cabbage, cauliflower, or Chinese greens). 

In the 4 studies that specifically measured green leafy vegetables there was a 14% reduction in the risk of diabetes between the highest and lowest levels of “greens” consumption.  The intake of fruit or vegetables, either alone or combined, was not, however, associated with a significantly lower risk of diabetes, although a trend in this direction was found for increased consumption of fruit and vegetables.

In trying to explain the benefits of “greens”, the researchers point out the antioxidant effects of beta-carotene, polyphenols, and vitamin C as possible mechanisms.  However, health benefits probably result from eating these substances in foods, as dietary supplements have proven disappointing in clinical trials as preventatives.  So there’s no good way round the maxim “eat your greens”.