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2010-05-13 Mark Messina PhD Health Benefits of Soy Foods: Separating Fact From Fiction

Health Benefits of Soy Foods: Separating Fact From Fiction

An Interview with Mark Messina, PhD

May 13, By Kirkham R. Hamilton, PA-C
© copyright 2010, Prescription 2000, Inc.

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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 HealthyToday Radio, for our free educational services.

Today's show topic is "Common Questions On The Health Benefits Of Soy Foods. Separating Fact From Fiction." Our guest today is Dr. Mark Messina, who holds both masters and PhD degrees in nutrition from the University of Michigan and Michigan State respectively. He is a former director of the Diet and Cancer branch of the National Cancer Institute and presently co-owns Nutrition Matters, Inc. a nutrition education company. He is an adjunct professor at Loma Linda University and he is a chairperson of the Soy Connection newsletter editorial advisory board and a regular columnist.

Welcome, Dr. Messina. Thank you for taking the time out of your busy day to be with us.

DR. MARK MESSINA: Very happy to do so.

KIRK HAMILTON: So one of the reasons I wanted to do this interview is because I have been bombarded, as many of health professionals have been, with the questions of soy and most of these questions actually come from my patients and sometimes I feel adequate explaining them and then sometimes I begin to doubt myself because of all the literature out there. So where you might be biased on the soy side, I think people would say, I think I am kind of balancing the universe because all I get is the anti-soy questions. You know I don't get a good soy question. So with that said why don't we just establish where you are and what ties you have with the soy industry.

DR. MARK MESSINA: Sure. In terms of background, I have a PhD in nutrition and also a Masters in nutrition. And for the past 20 years I have been focused almost exclusively on the health effects of soy foods and soybean components. I began my interest in this field working for the National Cancer Institute and then became so interested in soy I decided to really focus full-time on this one subject. Most of my money comes from industry through consulting. I provide updates on literature to a number of different companies. I also do a lot of speaking. I will say that essentially all of my views are in the peer reviewed literature, so when I make a statement it's pretty easy for me to send anyone who requests the supporting documentation in support of that.

KIRK HAMILTON: So what got you interested in soy in the first place way back when?

DR. MARK MESSINA: Yes. Way back when 20 years ago actually the head of the National Cancer Institute, which is part of the National Institutes of Health, heard a presentation about the potential anticancer effects of components in soybeans called isoflavones. He sent a memo to the branch where I was working, the Diet and Cancer branch, and asked were we doing anything with soy. The secretary of the branch sent me the memo and thought that perhaps I'd be interested because I was already consuming soy foods and I organized a workshop in 1990. About six months after that, the National Cancer Institute funded several million dollars aimed at investigating the potential anticancer effects of soy. And then in the process of reading about soybeans I came to see that they may have a number of benefits in many different fields and so I decided to focus full-time on soy and soy foods.

KIRK HAMILTON: So why do you think that there's such an intense soy debate right now? I mean it is very angry. Let me put it that way, out there when you check out internet sites almost...and so why do you think that has come about?

DR. MARK MESSINA: I agree with your assessment and I think part of it is simply because there is so much research on soy. There's about 2000 soy related papers published each year and a number of claims on both sides of the issue are being made probably without support. And I think people just get very passionate about this one particular food. And to a large extent, one or two groups are really responsible for most of the claims that soy foods are harmful. And there's a lot of disinformation about soy foods on the internet. And because my degree is in nutrition instead of psychology I don't bother to try and analyze the motives of these groups. But I will say that while there in some areas is a legitimate debate about soy in regards as to whether there might be some potential adverse effects, most of the concerns are without any scientific merit. And if you focus on human studies there's no question that you would reach the conclusion that soy foods are safe for everyone except for those who are allergic to soy protein.

KIRK HAMILTON: Well I could see from the other side, let's say, that you have a big agribusiness, the soy industry, and it's reach goes far-reaching. And one of the questions I want to start off with is where is most of the soy bean that is raised, where does it go to? Human consumption or animal consumption?

DR. MARK MESSINA: These are really important points and questions that you raised because I also hear that comment being made, that the soy industry is extremely powerful. And while there are an awful lot of soybean farms in this country - there's about 600,000 - we grow about half the world's soybeans, nearly all the soybeans, probably 90+% are actually used for animal feed. And so the soy lobby is not what's it's made out to be. There are many large companies involved in this field, but most of the beans are actually sold for animal feed. So the soy industry itself actually is quite small. The budget - and I'm not part of this group - but the budget for the trade association is tiny, tiny compared to the budgets for you know the dairy industry or the meat industry. So and there's actually very little research funded by the soy industry. So it's really at a very competitive disadvantage relative to other commodities.

KIRK HAMILTON: So your interest, though, would obviously more be with human consumption, correct?

DR. MARK MESSINA: Completely.

KIRK HAMILTON: So one of the statements that I've heard, and again this is one what kind of bent my head a little bit, but that there's more soy consumed per capita in the United States, and not just in whole soy foods, the regular ones we think about, you know, edamame, tofu, tempeh, etc, but in derivatives of that, and so we are consuming more soy product and its derivatives in the West or United States than let's say in Asia or China. Is that true?

DR. MARK MESSINA: No. Well if you - what you really want to do is focus on the amount of soy protein that is consumed and the per capita intake of - daily per capita intake of soy protein in this country. It's hard to get accurate data because it's so small, but it's generally thought to be about 1 to 1 ½ grams per day. That's of soy protein. And in Japan and places like Shanghai where we have quite a bit of data, you find that the average soy protein intake is about 10 grams per day. And furthermore in those countries you also have a number of individuals who are at the say upper quartile or quintile of intake consuming 15 to 20 grams of soy protein per day, and that have almost never is seen in this country even amongst vegetarians.

KIRK HAMILTON: So when you talk about soy food - well first of all, is it true that soy is in things like hamburgers and other just basic commodities unbeknownst to us?

DR. MARK MESSINA: Absolutely. It's added not for nutritional reasons but mostly for functional reasons meaning for moisture retention or an antioxidant effect. And you can even find it in products like Wonder Bread. It's not always there, but on occasion it might be used in a product like that. And so people are consuming soy foods or soy when they consume a wide variety of different foods that are commonly available on the supermarket shelves but the amounts are miniscule. And so as I said before, when you add it all up you're only getting about a gram or so of soy protein per day.

KIRK HAMILTON: Well, maybe I got one question clarified. Or one answer clarified. So it's a reasonable assumption to say that if all of a sudden everybody became vegetarian on the planet, true vegetarians, that we'd wipe out a lot of the soy produced. Correct? Because it wouldn't be fed to animals?


KIRK HAMILTON: Now do you care whether soy is organic or nonorganic? And then the next question to that is GMO versus non-GMO?

DR. MARK MESSINA: The answer is pretty much no and no. And I think these, I have to say it's - both of these questions are somewhat outside my area of expertise, but from the data that I've read I don't see any nutritional advantage to consuming non-GMO products or soybeans versus genetically modified soybeans and organic versus nonorganic. And there may be other issues, and certainly there are other issues surrounding genetically modified foods and organic foods, you know agricultural issues, economic ones, political ones, but that's outside my area of expertise. But from a strictly health perspective I'm not seeing evidence that it matters. But I certainly think it's fortunate that in this country there are a wide variety of products available and so for those individuals who want to consume organic products and non-genetically modified soybean products you know I certainly encourage people to do so. But from the published data, I don't see evidence that they would - that it would matter.

KIRK HAMILTON: Okay, here's another common question that I get. Traditional soy societies, they only consumed fermented soy products that were somehow protected, broke down the enzymes and the enzyme inhibitors such as tempeh, miso. But not tofu and edamame and soy milk. Now aren't those all traditional Asian foods? And do they have any difference in their nutritional content?

DR. MARK MESSINA: Well a couple of things. First, the first soy foods that were consumed a couple thousand years ago actually were fermented, but there are historical records showing that tofu was consumed in Japan at least 1000 years ago. And when you actually look at the current soy industry intake in Japan, a little bit more than half comes from non-fermented soy foods, primarily tofu. And a little bit less than half comes from fermented soy foods such as miso. In China it varies depending on the region, but in the regions where we have quite a bit of good dietary intake data most of the soy is consumed in non-fermented forms. Now of course that's current intake. We have, you know, pretty good records going back 40 or 50 years, and most of those people are consuming a very traditional diet. So I think in Japan it's relatively mixed and China tends to be more the non-fermented stuff. From a strictly nutritional standpoint, I love fermented foods. I was in - I love tempeh, I like miso. I was actually in Indonesia recently, the home of tempeh, and it was fascinating because it is a cottage industry there. It was fascinating to see it being made. And I think we should consume more tempeh in this country actually. But nutritionally, you know, the protein, the ability to digest protein from non-fermented foods is extremely high, not fermented soy foods. So protein digestibility from soy milk and from tofu and isolated soy proteins, well over 90%, so there's not a problem there. So I'm not seeing any significant advantages whatsoever when I compare fermented versus non-fermented soy foods. So I think it's just a matter of personal choice.

KIRK HAMILTON: Is soy milk a traditional food? I actually read something from Eden Soy that said they found soy milk way back when.

DR. MARK MESSINA: Oh, yeah, it's a very traditional food. It's not consumed very much in Japan, most in China.

KIRK HAMILTON: Got it. Sometimes when I step back either when the internet is confusing to me or I don't understand the literature - I mean I look at the Okinawan centenarians, the 25 year Centenarians Study, and I was going through the book again last night and they were one of the highest consumers of soy products. And if it was so devastating, I don't know. I mean, I don't know what else they'd be eating in their diet to counteract the soy, so that was always where I scratch my head.

DR. MARK MESSINA: Yeah. I don't think, you know for scientists and for nutritional professionals, those kinds of observational data are not very credible. I think they're interesting and they often can generate hypotheses, but I think it's more useful to study for example people in Japan. The health status of people in Japan according to their soy intake. And so you actually have a wide range of soy intake in Japan and in China so that you're able to compare the health status of Japanese women or men who consume say two plus servings of soy per day versus those who consume a serving or less. And from those kinds of studies if you are actually able to conjecture at least that soy foods are linked with reductions in the risk of a number of chronic diseases. So that the Asian study suggested high soy consuming men have about a 30% lower risk of developing prostate cancer. There's many studies showing that high soy consumers in Asia have decreased risk of heart disease and there's two studies, the only two studies that actually have been conducted - one was in Shanghai and one was in Singapore - showing that high soy consumption was associated with a decreased risk of fracture, about a one-third reduction in the risk. Now those are all epidemiologic studies. They're observational studies so you can't make conclusions about causality. Those are just associations. And then you take the observations from those studies and test them in the clinical setting and that's really where you have to base your conclusions.

KIRK HAMILTON: Well let's go to one hot topic - soy and breast cancer. You know I heard your discussion (Plant-Based Diets In Clinical Practice April 10, 2010), but could you give like a little summary of what your conclusions are about either prevention of breast cancer and/or if someone has breast cancer do you recommend soy?

DR. MARK MESSINA: Sure. Both important questions, and I actually entered the field specifically because of my belief at the time, 1990, that soy reduced the risk of prostate cancer. I mentioned that I was working for the National Cancer Institute. Unfortunately, I no longer believe that adult soy intake reduces breast cancer risk. I think the data are relatively unimpressive in that regard. I do, however, think that soy reduces breast cancer risk but to derive that proposed benefit in my opinion one needs to consume it during childhood and/or adolescence. So it's a very exciting hypothesis especially because the studies are showing reductions in risk ranging from about 25 to 50% so that's a huge impact. And secondarily the amount of soy associated with these protective effects is very modest. Basically about a serving, such as a cup of soy milk, to a serving and a half seems to be all that is needed to derive this proposed benefit. Now it is still speculative at this point because we need to get some clinical data which will be difficult to obtain. Nevertheless, because the benefit is so great and the amount of soy needed to be consumed so modest, again about a serving per day and it's a very nutritious food. It's high quality protein, low in saturated fat, high polyunsaturated fat. I currently do recommend and encourage mothers to encourage their daughters to consume at least one serving of soy foods per day. If it turns out that the hypothesis is not confirmed certainly nothing has been lost and everything is still being gained because it's a very nutritious food. On the other side of the picture, there is a legitimate debate. This is where there is one of these legitimate debates about whether these plant estrogens in soy might stimulate the growth of existing estrogen-sensitive tumors, breast tumors, or perhaps increase risk of breast cancer in high-risk women. So for a long time I thought it was totally appropriate to take a very cautious approach, especially because it's a very serious situation, and I had - although I might disagree with oncologists who made this recommendation, I certainly understood why some oncologists would want their patients to avoid all soy. I just recently co-authored an editorial on this subject in which we - the other two people are oncologists in California working at universities - and we've now evaluated the data and reached the conclusion that because of the data that's been published within the last two years or so, all of which has supported the safety. That if a breast cancer patient wants to consume soy for whatever reason, or is already consuming soy, perhaps they're vegetarian, that there's no longer a basis for the oncologist advising that patient not to do so. If anything, the data are starting to suggest that soy foods may actually improve the prognosis of breast cancer patients. That's still speculative so we're not quite at the point where oncologists would be justified in saying or recommending to their patients that they actually begin to consume soy solely for the purpose of improving prognosis. But I do think we're clearly at a point where oncologists are no longer justified in advising their patients not to consume soy.

KIRK HAMILTON: So if I can re-review that, in your opinion, to get the benefits of soy as a protective agent brings up one of the fears of many people starting soy intake too early because you're going to somehow harm the child. And you're saying that the benefits appear to be if you consume soy early in life that's where you get the protective benefit against breast cancer. Correct?

DR. MARK MESSINA: That's correct, and not to interrupt the second part of your summary, but this whole idea or notion that soy may reduce breast cancer risk if consumed early in life is consistent with this school of thought which continues to gain support that early life events have a profound impact on later risk of developing breast cancer. So higher vitamin D exposure seems to be protective. A number of early pregnancies actually is protective. And you can't certainly recommend that teenagers become pregnant so I recommend soy is a better option than having a baby certainly.

Because I have a 2-year-old granddaughter, and that was the first thing you know that came up and I just say well do what Asians do but I - that is a very big concern for a lot of lay people or professionals so -

DR. MARK MESSINA: Oh absolutely. Now the studies actually have only - there was one study that looked at soy intake between the ages of 5 and 11 and it showed a very protective effect. It was a small study so I think one has to be cautious about the interpretation of the findings, but really we haven't looked yet at the relationship between consuming soy when you're 2 years old and risk of breast cancer later on in life. There was one letter to the editor that had a little bit of data suggesting that actually women who consume soy formula as an infant has a much lower risk of developing breast cancer, but it was actually not an official study. So at this point I would not make any conclusions about 2-year-olds consuming soy and their risk of breast cancer. This really applies, as far as we know at this point based on the data, to children a little bit older than that and then teenagers.

KIRK HAMILTON: So I would assume - are you saying the same for prostate cancer then and soy?

DR. MARK MESSINA: No. Well first of all, I think soy is protective against prostate cancer. Still speculative - but the evidence suggests that both actually, the clinical studies and the epidemiologic studies, although proving diet/cancer relationship is very, very difficult, it is much harder than proving diet and heart disease relationships for many reasons. The evidence does suggest that soy is protective, but it's not clear that one has to consume soy early in life to derive the protection. There's a number of lines of evidence to indicate that for prostate cancer, although early life events may also be important, that you can fortunately modify your risk even very late in life.

KIRK HAMILTON: How about if I eat soy and you ate soy, are we going to be able to have a non-demented conversation down the road? Are we going to you know -

DR. MARK MESSINA: Well I eat soy and hopefully I'm not sounding very demented.

KIRK HAMILTON: So that study -

DR. MARK MESSINA: I'm getting at the age where that's possible. I understand the concern. It was based on the Honolulu Heart Study published in 2000. It's important to recognize it. That study actually was focused on heart disease and the cognitive end point was added much later on about 30 years after the study actually started. And when you look at the data overall it's really not possible to reach any conclusions about whether soy is having any beneficial or harmful effects. The most interesting epidemiologic study actually showed no relationship between soy intake and risk of dementia. And when you look at the clinical studies - now most of those have been conducted in women - when you look at the clinical studies there's actually quite a bit of reason for optimism. There are about 9 clinical studies and these are studies in which subjects were actually given soy foods, or some plant estrogens from soy foods. These studies are showing improvement in a variety of different aspects of cognition. But I think you have to consider all those results very tentative at this point, because although the studies overall generally are showing benefits, one study might show a benefit in one particular aspect of cognition and another one a completely different aspect. So I think at this point one should not base their soy intake on the effects - proposed effects - on cognition. But there's certainly no justification for not consuming soy because of fear that soy may increase dementia. That's certainly not justified.

KIRK HAMILTON: How about infertility? Male infertility. I have a logical -

DR. MARK MESSINA: The flippant response of course is you know there's over a billion people in China and I don't think - I think it's sort of a facetious remark, but when you actually look at the data and this was just published in the Journal of Fertility and Sterility. There's no effect of soy on testosterone levels, either the total testosterone, which is one measure, or more importantly even the free testosterone, the biologically active form of this sort of male hormone. There's no effect of soy on estrogen levels. Nine studies look at that. In the clinical studies there's no adverse effect of soy on sperm or semen. There's no evidence to suggest that soy would cause erectile dysfunction. So I think that idea that soy may have a feminizing effect is completely without scientific merit. And in fact, in contrast to the concern that soy may be lowering sperm count or concentration, the three studies using very high dose amounts of these plant estrogens in soy - three studies found no adverse effects and one case report published in 2004 actually showed that when a man with low sperm count and concentration who was unable to father a child, and there was nothing wrong with his partner, when he was given isoflavones, these plant estrogens from soy, for three months, his sperm count increased so it was now normal. It was in the normal range. His sperm count and concentration increased, and he was able to impregnate his wife and they had a healthy child. And the authors of that case report actually suggested that the plant estrogens from soy might be a treatment for low sperm count.

KIRK HAMILTON: Well let's go to the world's number one killer heart disease. First soy was recommended as a cardiovascular risk reduction, a healthy heart food, and then it got taken off the list. Can you explain that for me?

DR. MARK MESSINA: Well, a little bit. I'd have to correct your sort of opening statement there a little bit. First of all, it's important not to forget that soy foods actually are very high in polyunsaturated fat, and the American Heart Association just came out and emphasized the important role that polyunsaturated fatty acids can have in heart health because they lower blood cholesterol levels. The FDA approved a health claim for the cholesterol-lowering effects of soy protein in 1999. This was a direct effect of the protein, not because soy foods are low in saturated fat and high in polyunsaturated fat. So people are very, certainly very excited about this health claim and about the finding that soy protein directly lowered blood cholesterol levels. In 2006 the American Heart Association questioned the effect of soy protein on cholesterol levels. They didn't question the value of soy foods for heart disease. In fact, they recommended soy foods for heart disease because of their favorable fatty acid profile. The American Heart Association found that soy foods or soy protein lowered cholesterol about 3%. Other I think more sophisticated analyses have shown that soy protein lower cholesterol 4 to 5%. So if you assume that if you split the difference among those various studies and you assume it's about a 4% reduction in LDL cholesterol, the bad cholesterol, that's less than the initial estimates, and the initial reports back around 1995. But even a 4% reduction in cholesterol over time can by itself in theory reduce heart disease risk by about 10%. If soy protein is unlikely, or certainly will not lower cholesterol to the normal range or target goal in people with very high cholesterol levels and then the best way to use soy foods, and the way it's been used experimentally with the best effect is in combination with low saturated fat diets, fruits and vegetables. You know high viscous fiber, soluble fiber, and phytosterols, plant sterols found in a variety of different plants. And these kind of diets have been shown to be able to lower cholesterol from 20 to 30%. So really you need to use soy in combination with other dietary factors that lower cholesterol to get dramatic reductions, but soy foods are perfect for that because they provide high quality protein. You need to get your protein from somewhere, and they're low in saturated fat, high in polyunsaturated fat, and the protein itself does lower cholesterol. It's just not as potent as we initially thought. But even a 4% reduction as I said is clinically relevant certainly from a public health perspective it's very relevant. So I think soy foods are very heart healthy. And if you look at the epidemiologic studies and there are about 7 or 8 of those, what's interesting is that they find that within Asia those individuals who consume about two servings per day have as much as 50% lower risk of developing or having a coronary event, a heart attack or a stroke, in comparison to Asians who consume little soy. So there's quite a bit of evidence, although with one exception is still speculative, that soy foods might be having coronary benefits independent of their effects on cholesterol. So it's not a magic food and you know no food is magic. If it's going to reduce your risk of heart disease, you need to do many, many things. Diet, exercise, lose weight, stop smoking, lower blood pressure, but it's certainly one component of a heart healthy diet.

KIRK HAMILTON: How about thyroid? Is it a goitrogen? Is it something that has an anti-thyroid effects soy?

DR. MARK MESSINA: No. There have now been about 20 clinical studies. So these are studies in which the subjects are actually given soy foods or given the plant estrogens from soy and that's the component of soybeans that has raised concern about thyroid function. There are about 20 studies that show if you are healthy and consuming enough iodine, which is an essential mineral needed for thyroid function that we generally don't have a problem meeting iodine needs in this county because we use iodized salt for the most part. If you give soy to those people there's absolutely no adverse effect on thyroid function. No question about it. And in fact one of the criticisms has been of people that think there may be some anti-thyroid effects of soy is that these studies have not been conducted for a long enough duration. Well there was just two, three-year studies published. And in one of the three-year studies, it was very large and they used very sensitive measures of thyroid function beyond just the traditional measures of thyroid hormone, and they found absolutely no evidence of any kind of adverse effects.

KIRK HAMILTON: How about blocking mineral absorption?

DR. MARK MESSINA: Yeah. Soybeans contain phytate like whole grains do. Phytate inhibits the absorption of several different types of minerals. What's interesting is despite the fact that soybeans contain phytate and another compound oxalate, which inhibits mineral absorption. When you look at the absorption of calcium from a food like calcium fortified milk, it's equal to the - in fact the study was published today literally confirming this - it shows that the calcium absorption from soy milk is equal to that from cow's milk. Secondarily, we thought like other plant foods that the iron absorption from soy was quite poor because it is for most plant foods. However, research published in 2003 and 2005 actually showed that because the iron in soy is in a particular form is extremely well absorbed. And the study, the older studies that reach a different conclusion, that it was poorly absorbed were actually using inappropriate methodology. The zinc, the other key one, is absorbed about 25% less from soy than it would be from a variety of animal foods but soy is not a particularly good source of zinc so I don't see that as a problem. We actually conducted, I was involved with a study that took place recently at Iowa State University, and we showed over a 10 week period in premenopausal women that there were no adverse effects to consuming two to three servings of soy foods per day on iron or zinc status.

KIRK HAMILTON: The last clinical concern is any reduction in immune function? I interviewed a very credible, and I think he's done great work, Nicholas Gonzales, on using pancreatic (enzyme) therapy for cancer treatment. And one of the theories is that proteolytic enzymes help our immune system. They're going around scavenging things. So is there any evidence at all that soy protein consumption inhibits immune function?

DR. MARK MESSINA: No. Not at all. If you look at - it's actually been measured. There was one study that showed an improvement. But for the most part when you're looking at these studies you're seeing no relationship between soy intake and any kind of immune disturbances. And bear in mind that there have been literally hundreds of clinical studies conducted and in most of these studies there - they have to report adverse effects, and they're just not seeing anything so I think it would have shown up if there were any. So I would have to say there's no evidence to support that concern.

KIRK HAMILTON: And lastly, it all makes common sense. I mean this whole debate to me makes common sense if you eat whole soy foods like healthy Asian cultures that you're going to be fine. But I know you create products of extracting the isoflavones, which are components in the soy, and I know they are in short-term, in trials, benefits on certain things. But what is the danger of taking isoflavones long term? Do you have any safety profiles of taking long-term isoflavones for whatever reason to enhance some kind of function?

DR. MARK MESSINA: Yes. A couple of points. First of all, all my degrees are in nutrition. I eat a very healthy diet and if you consume soy foods there's no reason to bother with supplements. The reality is that I think unfortunately most, or many Americans, don't consume any soy. And certain, most Americans don't consume a couple of servings per day which is the amount you need in theory at least to derive many proposed benefits. And also most of the clinical work in the last couple of years has either been done by soy that's soy protein or these isolated - these extracts, these concentrated in isoflavones. So a lot of what we know about soy is actually based on these studies. These products, rather than the traditional soy foods because they're much more difficult to use in clinical studies. I don't have any problem with using the supplements. But I would much prefer that people get their isoflavones from soy foods. But if you're a woman, for example that wants to use soy to alleviate hot flashes, I think the evidence supports that use for that purpose. You need about two servings per day of soy foods to get that benefit to get that relief. If you consume two servings per day, then don't worry about supplements. But on any given day that you might not consume two servings I think it's perfectly reasonable to consume a supplement that would make up the difference in regard to the amount of isoflavones or plant estrogens that you actually need. So clearly the way it should go is that you should focus on traditional minimally processed soy foods first and then I think the more processed soy products do have a role. I think soy burgers are, you know better in my opinion, than hamburgers. And they're a very convenient food that provides excellent protein so I have no problem with using those in the diet. And last, you know if you just don't get enough soy in your diet on any given occasion, I think supplements can be used for specific purposes. They don't provide protein so they're not going to lower cholesterol levels. They don't have all the benefits of soy foods, but if you're using them for something like the alleviation of hot flashes I think that's perfectly reasonable. And long-term studies have been done with these using very large amounts. Now long term, I'm talking three years or so. We don't know beyond that, but we don't know, you know most clinical studies aren't done for more than three years.

KIRK HAMILTON: We're talking to Dr. Mark Messina of Nutrition Matters, an expert on soy. Dr. Messina, thank you so much. How can people - if someone's interested in learning about soy, and again people will say I'm biased and I'm giving them to a pro soy person, but what -

DR. MARK MESSINA: Let me just characterize that. You know I think it's an unfair characterization because I try to just evaluate the data and report what I find. And this is another conversation. But I can show you many instances of where in the peer reviewed literature I have disagreed with my colleagues when they claim that soy has a particular benefit. So I am focused on soy and I try to report the data as they are.

KIRK HAMILTON: Let's say they had a soy question. What source would you recommend they go to? What do you recommend?

DR. MARK MESSINA: I have no good answer to that. What I would recommend is that people try to focus on the human studies. Almost without exception all of the concerns that are being raised are based on animal studies. And when you look at the clinical studies and the epidemiologic studies, but especially the clinical studies, there's just absolutely no basis for concern with the exception of people who are allergic to soy protein, but that's extremely rare.

KIRK HAMILTON: I was going to put a link up with the interview that goes to your slide presentation (Health Effects of Soy Foods) that you did at the Plant Based Diets and Clinical Practice Conference.

DR. MARK MESSINA: Sure. That's fine.

KIRK HAMILTON: Okay. Thanks, Dr. Messina. Thank you for letting me cram a bunch of questions in a short period of time.

DR. MARK MESSINA: Oh sure. My pleasure.

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

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