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2010-03-11 David J.A. Jenkins MD PHD DSc - Diabetes and Lipid Control Using The Dietary Portfolio

An Interview with David J.A. Jenkins, M.D., PhD, DSc

March 11, By Kirkham R. Hamilton, PA-C
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KIRK HAMILTON: Hi, my name is Kirk Hamilton, your host of Staying Healthy Today, and our mission is simple: To provide you credible usable health information from interviews and our educational resources to help you Stay and Be Well in the busy modern world. Please take a few moments before or after listening to this interview to browse through the Prescription2000.com website, the home of Staying Healthy Today Radio, for our free educational services.

Our show topic is "Learn How Soy Foods And The Dietary Portfolio Can Effectively And Safely Lower Cholesterol, And How Nuts Can Play An Important Role In The Prevention And Management Of Diabetes."

Our guest today is Dr. David Jenkins, MD, PhD and Doctor of Science. Who is the Director of the Risk Factor Modification Center at St. Michael's Hospital, University of Toronto in Toronto, Canada. Dr. Jenkins is world renown for his creation of the Glycemic Index and research on the role of plant based diets, or Dietary Portfolio, to prevent and treat diabetes, lipid disorders, heart disease, obesity and chronic disease.

Welcome, Dr. Jenkins. Thanks so much for taking time out of your busy day to be with us.

DR. DAVID JENKINS: Thank you.

KIRK HAMILTON: Well you have three interesting articles I want to take little snapshots of, and the first one is a paper you did in Metabolism in 2010 and the title is "The Effect on the Blood Lipid Profile of Soy Foods Combined With a Prebiotic: A Randomized Control Trial." And I think the first thing that popped in my mind is why did you decide to put together soy foods and a prebiotic for lipid management?

DR. DAVID JENKINS: Well we thought that the prebiotics have not been very consistently helpful in terms of cardiovascular risk reduction. And the question arose as to whether that was because some other components of the diet, that they might interact with usefully, were present in some diets and not in others, which gave an inconsistent effect.

KIRK HAMILTON: What is a prebiotic, because people hear about probiotics but I don't think they really know what a prebiotic is.

DR. DAVID JENKINS: Well the probiotic is giving the bug, and hoping that gets through to the colon. And the prebiotic is giving the food to the bug. So if you take the food for the bug, and the food gets to the colon, then you're going to stimulate that sort of bug, even if you haven't given it in capsule form. If there are some of sort of bugs in the colon they'll get stimulated.

KIRK HAMILTON: What is the biochemistry of probiotics that would help in lipid management?

DR. DAVID JENKINS: Well, of probiotics, as opposed to pre-, probiotics for example, bifidobacteria, tend to accumulate cholesterol in their "coats." And so the theory could be that they may take cholesterol out of the body.

KIRK HAMILTON: Then the prebiotic helps enhance the number of probiotics. Is that how it works?

DR. DAVID JENKINS: So that's right. So the prebiotic will help enhance the number of the native, or probiotic bacteria.

KIRK HAMILTON: So literally the bug kind of sucks up the cholesterol, is that the simplest way to say it?

DR. DAVID JENKINS: That's the simplest way that's been suggested for bifidobacteria, not all bugs do it.

KIRK HAMILTON: Okay. Now how does soy lower lipids?

DR. DAVID JENKINS: Well, soy we think lowers cholesterol by its effect on the liver. It's a sort of mild inhibitor of HMG-CoA (reductase). It's like you take an HMG-CoA reductase inhibitor and what we're saying with that is that it inhibits the synthesis of cholesterol. The soy probably also helps to reduce the synthesis of cholesterol.

KIRK HAMILTON: Okay, so we have two components of this then. We have reduction of the production and then we have some absorption of the cholesterol before it gets absorbed I guess from the intestinal tract.

DR. DAVID JENKINS: Yeah. I mean that's right. You've got things that stop production and things that stop absorption.

KIRK HAMILTON: Is it the isoflavone component of soy, or is it just something else in the soy protein that has this effect?

DR. DAVID JENKINS: Well that's where the story of isoflavones comes in. We think there are two things. We think the soy protein and possibly the components of soy protein, the amino acids, the peptides, etc., which may be important for plant proteins and soy in particular. And then we have the so-called isoflavones. Some people call them phytoestrogens. And these foods, or these components of the food rather - they're not foods in themselves, are part of the sort of chemical composition of soy.

KIRK HAMILTON: Well what did you find out about your study and how did you merge them together? Did you take them in a product mixed together or were they separate? Just some soy food like-

DR. DAVID JENKINS: Well I think the soy foods take them separately, and then the prebiotic also taken in a beverage separately.

KIRK HAMILTON: And what kind of lipid modulation occurred?

DR. DAVID JENKINS: Well we tended to get somewhat lower LDLs, but most importantly we got higher HDLs.

KIRK HAMILTON: Is that a surprise?

DR. DAVID JENKINS: Well that's gratifying. It's gratifying.

KIRK HAMILTON: So how much soy would someone have to eat to get this effect?

DR. DAVID JENKINS: I think we'd be talking in terms of about 30 grams a day.

KIRK HAMILTON: Do you have any idea how much that is, like a chunk?

DR. DAVID JENKINS: It's about an ounce.

KIRK HAMILTON: An ounce. Okay. While we're on the subject of soy, because I've had this conversation with many people. Out in the internet world and actually part of the real traditional medical world, there's a lot of - or alternative medical world - there's a lot of people who are really "anti-soy." And I am wondering your opinion about soy in a concentrated form versus food? Or do you think it's harmful or does it even matter to you?

DR. DAVID JENKINS: Well I think it matters a great deal. We've been agonizing over this for years wondering whether it sort of feminizes boys and kills girls with breast cancer. Yeah, I'm not sure that this is really, I'm not sure, growth abnormalities and developmental abnormalities and increased cancer risk is really being borne out by any of the literature in humans. Now if you take laboratory animals then you get different data. Data which quite convincingly that soy is the worst thing on earth. But on the other hand if you look at the data, from say the Shanghai Breast Cancer Study, or the 2006 Journal of the National Cancer Institute meta-analysis of soy (JNCI, 2006 98(7):459-471), and subsequent analyses of soy, if anything they tend to be protective for breast cancer. If anything, they tend to be protective for prostate cancer. And they don't have necessarily as big a cholesterol reduction as we used to see in the old days. But they certainly cause a modest 4% or so reduction in cholesterol. And more important than, that they actually displace the foods you don't want. In other words, the burger, the shake and whatever can be displaced with soy meats and soy dairy, and you'll do a lot better.

KIRK HAMILTON: Do you have any concerns about genetically modified soy versus nongenetically modified soy?

DR. DAVID JENKINS: I don't think that the concerns that one has relate to human health, but - and I think this is probably the big thing that one wants to stress nowadays. Eating has become really an environmental catastrophe in terms of human's destruction of the planet. We've already got rid of 30% of all the fish stocks in the ocean by eating them. We've transformed large tracts of land into desert-like material. And we've caused the loss of innumerable species. So I think that I would say that if GMO has any negative environmental impact, I think maybe just pollen going from the field where the genetically modified organisms are, to organism on the grass by the side of the field or in the hedge, do you know what I mean? If that ends up transforming those in some way, then I think we've done tremendous disservice. Because, I mean many people will say, well you know so we just lost the Monarch butterfly, but what does the Monarch butterfly do for me? I think that's the sort of attitude we - you know it's a cavalier sort of attitude that I don't think we can afford to have. It's just aesthetically rather appalling. So I think that from a nutrition point of view, if that's what one's looking at, I don't know of any ill effects. But as I say, I remain sort of open minded for any environmental effects, and if these exist then I think we've really got to stop doing what we're doing. Now, there may be different forms of genetic modification - do you know what I mean? In other words, if you genetically modify someone to put a toxin in the food that will prevent weevils or whatever from surviving, then I mean that's one thing. You'd better prove that the thing's fairly harmless. If on the other hand you genetically modify a thing by putting in a bit of vitamin A into rice or whatever, do you know what I mean, then I don't see that that's going to be harmful either to the rest of the animal world, and may be of benefit to us. So I think certain sorts of genetic modification may be fine. Do you see what I mean?

KIRK HAMILTON: Yeah. Well let me keep going. I've got your point and I am always gathering - I like gathering expert's opinion on that particular issue because it's going to be around for a while.

I wanted to shift to another article that you co-authored in the Proceeding of The Nutrition Society and it was entitled "A Dietary Portfolio For The Management And Prevention Of Heart Disease - What Is The Concept Of A Dietary Portfolio?" And I know this is one we've talked about before and I am wondering if you can just name the foods in your dietary portfolio and why you chose those and actually that unique name.

DR. DAVID JENKINS: Well, you have to remember that we chose the name at the turn of the century. In those days, bankers were on the roll and finance was the name of the game. So a financial portfolio could be, as it were, morphed into a nutritional or dietary portfolio. In other words - spreading your chance of getting success over a wider range of items or investments. And so the concept of "Portfolio" therefore was to gather together a number of useful cholesterol lowering foods and put them into one diet. In other words one "Portfolio." And I think it worked well. I mean we used soy, we used nuts, we used sticky types of fiber and we used plant sterols, all of which have between 5 and 10% reductions in serum cholesterol by themselves. And we embedded them in a diet which was low in saturated fat and low in dietary cholesterol.

KIRK HAMILTON: Did this approach come close to the statins?

DR. DAVID JENKINS: Yes. This was the approach that we published in JAMA and AJCN and a few other journals and Metabolism showing that we could get possibly about 20 to 25% of our group - we could get a statin-like effect when they self-selected their diet. If we actually provided all the food then the average was as good as a statin.

KIRK HAMILTON: Well I'm looking at your general approach here and one of the things I want to bring up is most of your dietary portfolio was plant based food. I don't see a lot of animal foods.

DR. DAVID JENKINS: Absolutely. The whole thing is designed to be vegan.

KIRK HAMILTON: And that is because?

DR. DAVID JENKINS: That's because we believe that two things. One, you can get major health advantages. But two and equally important, we believe that plant based from the ecological point of view, environmental, humanitarian point of view, are the way of the future. Now we tended to laugh at these things in the past and just talk about the straight science. So I think the straight science is still there, but I think we can no longer laugh at humans' feeding habits simply because there are so many of us on the face of the planet.

KIRK HAMILTON: That brings up a - I had an interview with T. Colin Campbell who wrote - co-authored the China Study, and one of the things we talked about was you know people talk about free range animals and hormone free animals, etc., etc., and so even if we assume that it was healthier, and that was debatable, what would happen if the world keeps up with its dramatic increase in meat consumption, let's say in China and India, and it was all free range animals. There wouldn't be any land mass...

DR. DAVID JENKINS: There would be no other species allowed to live except those that fed us. In other words, I think basically we've become very egocentric and very selfish as a species. And I think that you know our time on this planet hopefully will be short if we're this short-sighted, because we'll destroy everything. So I think that the great appeal of the plant based diet is that you know you can eat a bad plant based diet or a good plant based diet. So I'm not saying that just a plant based diet per se is healthy. But you can eat a healthy plant based diet, and I think to the best of our ability we've got a duty to do so.

KIRK HAMILTON: We're talking with Dr. David Jenkins, who is an MD., PhD, Doctor of Science, and Director of the Risk Factor Modification Center in St. Michael's Hospital at the University of Toronto, in Toronto, Canada, and probably most famous for two things, the Glycemic Index and the Dietary Portfolio. And I want to go from what you just said obviously about the big picture of plant-based diets, but we have a healthcare reform debate in this country, and in my mind it's really the world, but the chronic diseases - heart disease, cancer, diabetes - if we applied your Dietary Portfolio to those chronic diseases, which are really the diseases taxing the economies of not only my country but the world, wouldn't that not dramatically take away the healthcare reform issue? I mean because those diseases would be dramatically reduced.

DR. DAVID JENKINS: I agree with you. And I wouldn't just say our diet. I would say, you know I would say the plant based diets generally which we - eaten in a healthy fashion, with lowering the glycemic index of the diets, too, and making sure that you have your cholesterol - lowering components, combine that with exercise, which we're now advised to do at the rate of possibly even 1, it's now gone 1.5 I understand, for weight reduction, moderate to vigorous exercise per day. Give that - you can flavor that with a fair allowance of sleep of eight hours if you can. And then possibly some time for social and intellectual activities of another nature. I think we'd be a saner and much healthier species, and I think as you say, the whole healthcare issue would be seen in a very different perspective.

KIRK HAMILTON: There's two more dietary factors I would like to talk about. One was in one of your more recent articles entitled "Health Benefits of Nuts and the Prevention and Management of Diabetes" and most of the time people talk about carbohydrates and diabetes and excess calories. Tell me how you got interested in using nuts in the diabetic condition.

DR. DAVID JENKINS: Well we've been interested in using nuts, and so using them in every chronic disease situation, because I think they seem to have - nuts and seeds generally have been with us evolutionally for a very long time and we haven't really been exploring them, and exploiting them to any extent recently. So we really want to start exploring their use. There would be potential benefits as vegetable proteins, high monounsaturated fats. These are all aspects of sort of nutrition, that on the face of it would have advantage for chronic disease.

KIRK HAMILTON: How would - does it have - well nuts a low glycemic food I take it.

DR. DAVID JENKINS: Yes.

KIRK HAMILTON: Are you ever concerned about nut consumption? I know, for example, Dr. Esselstyn who wrote "Prevent and Reverse Heart Disease" he goes on a no-fat regimen, and because the average American takes, when they eat nuts they sit down on a couch and they eat handfuls, and they're a little excess fat there. So you would take that in the context of still keeping people overall lean obviously.

DR. DAVID JENKINS: Yes.

KIRK HAMILTON: Let's -

DR. DAVID JENKINS: But one of the things we found is that nuts aren't the things that are increasing body weight.

KIRK HAMILTON: Well talk about that because that's a very important concept that I sometimes say incorrectly. How do you use nuts in a beneficial way that doesn't add extra calories, because the fat calorie is two and a half times that of a carbohydrate or protein?

DR. DAVID JENKINS: Absolutely it is. Well what we've found, we give people some very modest advice to say, you know, remember that nuts have some calories. Eat them as much as you can, but don't eat excessive of carbohydrate foods in addition. And people find that very congenial. They find it easy to do. In other words, they substitute the nuts almost reflexly for other calories in the diet, gain the advantage in terms of LDL and HDL, and possibly even lose weight.

KIRK HAMILTON: So nuts have - do they have an additional satiety effect?

DR. DAVID JENKINS: I think they probably do have it. I think they must have because they seem to be very well received in what we call an isocaloric diet.

KIRK HAMILTON: You know you're famous for the Glycemic Index and I think that index got used in inappropriate ways and then it got people completely off all carbohydrates. I mean that's how some people used it.

DR. DAVID JENKINS: Yeah, well we're never - that was never our intention. Our intention was mainly to choose carbohydrates that had a lower glycemic index and that were more slowly released and slowly absorbed.

KIRK HAMILTON: Would it be putting words in your mouth if I said that when you eat generally - I know there's exceptions - carbohydrates in their whole state, unrefined state, that they have a lower glycemic index than a white flour or a refine carbohydrate?

DR. DAVID JENKINS: That unfortunately is not always the case.

KIRK HAMILTON: Uh-huh.

DR. DAVID JENKINS: You can get white flour breads that are not a lot different from the whole wheat flour breads. So simply being whole wheat or being white does not say how rapidly you rise. But I think the important thing is that whole wheat has other values. It tends to be lower calorie. It's got more magnesium, and in cohorts that it seems to relate for freedom from heart disease. Having said that, if you can have pasta that will raise your blood glucose half as much as even whole wheat bread. So what's the answer to that? Well I think the answer to that is, have your pasta whole wheat. Do you see what I mean?

KIRK HAMILTON: Uh-huh.

DR. DAVID JENKINS: In other words, there are some foods that have a lower glycemic index - beans, peas, lentils, pasta, these sort of things. And certain breads, specialty breads have lower glycemic indices than the routine. And I think that the aim that you should have is to pick healthy foods which are rich in fiber. And they - if you have the chance between choosing a healthy food which is rich in fiber and is low glycemic index, choose that over the one which is high glycemic index. And you may say well surely no foods that are high glycemic index are healthy or rich in fiber. Well they are. And I wouldn't worry about that. I mean even very sort of very light textured whole wheat breads may be sort of fluffy, quite high glycemic index, but still healthy.

KIRK HAMILTON: Well Dr. Jenkins, this was perfect. I will let you get back to work. I really appreciate you coming on. I got what I wanted to get. You speak very eloquently, and one thing that just comes into my mind very powerfully is not just eating for nutrition but also the way we eat affects the ecology of everything else. You make that, you drive that point -

DR. DAVID JENKINS: Absolutely. You've got to eat for the planet.

KIRK HAMILTON: Well with that, I think we'll -

DR. DAVID JENKINS: Eat for the planet, and I say don't neglect the legumes, the beans, peas, lentils and chickpeas...

KIRK HAMILTON: Alright. Thanks so much Dr. Jenkins for being on the show today.

DR. DAVID JENKINS: You're very welcome.

KIRK HAMILTON: And I want to thank you, the audience today, for being on this edition of Staying Health Today Radio. And remember until next time, Stay and Be Well.

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