Fiona Atkinson talks to Prof David Jenkins on GI, diet and longterm health
'I recently had a great opportunity to talk to Professor David Jenkins (a professor in the Departments of Medicine and Nutritional Sciences, Faculty of Medicine, University of Toronto, a staff physician in the Division of Endocrinology and Metabolism, and the Director of the Clinical Nutrition and Risk Factor Modification Center, St. Michael's Hospital) to find out where the science of GI started. But we didn’t just cover GI but also other hot topics in nutrition such as vegetarian/vegan diets!'
Professor David Jenkins
FA: Did you have any idea at the time that the implications of your research and the paper Glycaemic index of foods: a physiological basis for carbohydrate exchange would be so far reaching?
DJ: We thought it would be broad because diabetes was linked with heart disease, renal disease, and with blindness. We didn’t want to even speculate how far this was going to go. We thought it was important because it was looking at diet from the physiological point of view and not simply from the chemical point of view.
FA: These days it typically takes 6 months for a paper to be reviewed/amended and then accepted for publication. Were there any challenges getting the study published at the time?
DJ: You’d be surprised, really surprised but Ted Van Itallie, who was editor of AJCN, a really nice guy and well known in terms of his work on obesity accepted the paper we sent him without revision and published it! Never before nor since have I had that treatment. The next surprise was that we got no requests for reprints, it was absolutely unnoticed for the next year. It was accepted without comment and without criticism, it was published and it was ignored.
FA: What did you do to follow up?
DJ: The data in the original publication included many studies, so we broke out many of the things already imbedded in it and started showing that pulses (beans, peas and lentils), were low GI foods; that cereal fibre didn’t necessarily make a difference and wheat fibre only made a small difference, which was again a surprise; and that pasta was different from bread. We must have done some self promotion and we referenced the original paper to make people aware that we made these discoveries before. I think people started to become interested in fibre or pasta or beans and I think that meant that there was a general interest. Out of all the papers that I’ve written and published, it’s had the slowest generation of interest but on the other hand it’s had the most sustained [interest].
FA: What do you see as the short term and long term benefits of adopting a low GI diet to prevent or treat disease.
DJ: I think that keeping glycemia under control stops you from stressing your pancreas, stops you from getting too much free radical damage and stops you from oxidising LDL [cholesterol], and stops you from glycating your haemoglobin. All these things may in the end have adverse consequences. Do I think that it matters that sleek, lean athletes who haven’t got an ounce of fat on their body, who’s blood glucose profile is flat and rarely raises above baseline are people on low GI diets. No – I think they can have high GI foods all the time and they can do what they like in life but in fact they don’t because by definition they’re trained athletes, by definition they’re incredibly disciplined, by definition they eat regularly and they exercise hard – they burn all their calories. So by definition they’re not slouches. But for the rest of us, mere mortals who don’t take any exercise and eat too much, watch too much television and do too much in front of computers and perhaps are driven to smoke – we really need to start thinking about how we are going to look after ourselves. We are becoming increasingly the norm, in fact we are the norm – the human greyhound is the abnormal person now.
FA: If you were going to give someone tips for the best things they could do for their longterm health, reducing disease risk even for the health of the planet and sustainability?
DJ: I think the first tip is focus on plant foods. The next tip is look at higher protein plus or minus the higher vegetable oil/vegetable protein foods such as nuts and legumes. Leafy vegetables are actually high in protein with very little fat and carbohydrate so these are useful. I think fruit is … should be the pleasure in life. Temperate climate fruit have a low GI so if you’re a little more overweight or a little insulin resistant you may have to forgo too many mangoes or too many bananas. Stick to apples, pears, peaches, blueberries, blackberries, raspberries, strawberries – the berries – are generally good, I think that’s important. Obviously if you’re eating well, you must exercise well to the best of your ability – that’s important and often overlooked.
FA: What do you see as the benefit of going meatless?
DJ: I think the benefits are basically on an humanitarian perspective – I used to put that as a sort of rider at the end but I think now it’s becoming the first issue as human beings. Second, I think one has to think of the environmental issues. They always say it’s a ten to one ratio for plant based diet versus an animal based diet in terms of land consumption, water usage, which is obviously a problem in many places, and basically environmental impact and environmental degradation. We cannot afford to have the whole planet geared to feeding cattle that feed us, this seems to be an insanity that we accept because it’s palatable. I think those are really strong reasons. I think that if one is sensible and one watches B12 and one’s diet, one can live very well on a vegetarian or vegan diet.