MORE GREENS PLEASE. I FEAR DIABETES

For many years now, since the DASH diet has shown that green veges and fruits prevent and lower hypertension, medical practitioners all over the world had encouraged the eating of more vegetables and fruits. We know that green leafy veges and fruits are very good for healthy living. At least 5 portions daily, is what is recommended.
The latest issue of the British Medical Journal, carried a piece of research by the researchers from Leicester University, on the good effects of green leafy veges on the prevention of T2 Diabetes Mellitus. They took 6 large scale studies where diet and the effects on diabetes were studied, analysed them ( meta-analysis ), and came to their conclusion. The meta-analysis included 220,000 subjects, who had filled in questionaires about their diet and their medical status. The researchers found that eating one and the half portions of green leafy veges like cabbage and spinach, reduced the incidence of diabetes by 14%. That is significant. One portion of veges is about 80 grams. ( in UK, their veges come packed by portions ). 80grams is not very much. The diabetic association, still recommend the consumption of 5 portions of green leafy veges daily, though.
We are not certain why this is so? Is it because of the vitaminC, or the potassium, or the magnesium, or other minerals, but it seem to work. There is obviously no downside side-effects? Is that true?
Well some of my patients have gone on to organic, or hydrophonic veges, because of the fear of chemicals and other pesticides or insecticides, that are often sprayed on the veges, to prevent their destruction by the pest. Well, there is a small risk of pesticide poisoning. The risk that these pesticide and insecticides may be carcinogenic, has also been raised.
I suppose we should eat more green leafy veges, but wash them well before consumption. I supose cooking them should also make them safe, though not so healthy.