Posted on June 25th, 2020by RMANY

Ep 25: The Relationship Between Food and Fertility with Dr. Jorge Chavarro

Fertility Forward Episode 25:

Have you ever wondered what the direct impact of what you’re eating has on your chances of getting pregnant? Today’s episode is all about food and fertility, and our guest is an expert in the field. Dr. Jorge Chavarro is the Associate Professor of Medicine at Harvard Medical School and the Co-Director of Epidemiology and Genetics Core at Boston Nutrition Obesity Research Center. His research focuses on investigating the role of nutritional factors in the pathogenesis of diseases affecting reproductive and hormone sensitive organs. He is the co-author of the veritable Bible of fertility nutrition, titled The Fertility Diet, which reveals startling research from the landmark Nurses’ Health Study that shows how the food you eat can either boost or reduce your fertility. Today, we speak to Dr. Jorge, who is a role model on the important nutrients and specific foods for fertility, about the potential dangers of soda, plastics, and the environment and their impact on fertility, as well as current research on health and fertility. We discuss The Fertility Diet and how Dr. Jorge came to write it, and we go into detail about the effects of trans-fatty acids, high glycemic load, and animal protein, including fish and full-fat dairy.

Transcript of Episode 25

Rena: Hi everyone! We are Rena and Dara and welcome to Fertility Forward. We are part of the wellness team at RMA of New York, a fertility clinic affiliated with Mount Sinai Hospital in New York City. Our Fertility Forward podcast brings together advice for medical professionals, mental health specialists, wellness experts, and patients because knowledge is power and you are your own best advocate.
Dara:Dr. Jorge Chavarro is the Associate Professor of Medicine at Harvard Medical School and the co-director of Epidemiology and genetics core at Boston Nutrition Obesity Research Center. Dr. Navarro's research focuses on investigating the role of nutritional factors in the pathogenesis of diseases affecting reproductive and hormone sensitive organs. He is the co author of the bible of fertility and nutrition called The Fertility Diet, which reveals startling research from the landmark Nurses' Health Study, which shows the food you eat can boost your fertility. The book prescribes 10 simple changes in diet and activity that can increase your chances of getting pregnant. Today, we speak to my role model on the important nutrients and specific foods for fertility, the potential dangers of soda, plastics and the environment and their impact on fertility and current research on health and fertility.
Dara:So I am so overly ecstatic to have Dr. Jorge Chavarro today speaking with us. He is the Associate Professor of Medicine at Harvard Medical School and the co-director of Epidemiology and Genetics Core at Boston Nutrition Obesity Research Center and on top of that, he is in my eyes, the researcher on the role of food and nutrition and its connection to reproduction and reproductive hormones. So thank you so much for being here today.
Chavarro: Thank you so much for that kind introduction. It's a pleasure to be here too.
Dara: And I know you're so much more than just a researcher related to nutrition and fertility, but how did you get a start in that passion of research?
Chavarro: It was actually sort of an accident. So when I was in medical school, I already knew I wanted to research. I just didn't know what exactly I wanted to research on. And there was an opportunity to be a research assistant in a study that was about to start recruiting, looking at occupational exposure, seen among agricultural workers as it related to fertility. So it was like, I kind of, Oh, okay. Let's see how this study goes and get an idea of how actual research works. And I did that and I forgot about that. And many years later when I was back in school doing my PhD and struggling to find an interesting research topic for my doctoral dissertation, my advisor, who has a prodigious memory somehow remembered that at some point I had worked on fertility and he suggested that maybe I should take a look on where there was anything going on on nutrition and fertility beyond body weight. So I remember leaving that meeting, thinking that it was going to be a complete waste of time, but that at least I would be done with my thesis. And it's been what, like, uh, almost 15 years later, I'm still doing the same. So obviously it was not a waste of time. There was a lot more than I thought there was going to be when I first started this road.
Dara: Wow. Is that when you were connected with Walter Willett?
Chavarro: Yeah, that's right. So he was my doctoral thesis advisor. So I originally thought that I was going to be working on nutrition on breast cancer, which is his field. And that's why he was assigned to be my thesis advisor initially, but he really enjoys taking side projects and anything related to nutrition. And when these things about fertility came up, he said, Oh, that sounds interesting. I mean, I'll probably never do it again, but it sounds interesting for now. And it was really, really useful to have his insight, his big picture view of nutrition. I was delving into this specific topic of how nutrition might relate to fertility.
Dara: Wow. I mean, I know I'm not sure if you know my story, Dr. Chavarro, but I was a patient first at RMA where I work now and was a dietician, did not specialize in anything reproductive medicine related. And then when I had my own struggles and ended up getting pregnant, that's when I started working here. I said there is a, a need for women to be educated on, you know, their environment, what they're consuming. And I mean, so much more so than that. And then you came into the picture when I went to ASRM for the first time, it must be maybe eight, nine years ago. And really when I was doing research on the connections between nutrition and fertility, your name kept coming up time and time again, you and Walter Willet and The Fertility Diet, this book changed my life. It really did. So let's talk about The Fertility Diet book. I know there's so much more to talk about in terms of research, but how did that come to fruition and, and the research that came from that with the Nurses' Health Study.
Chavarro: So that was actually a combination of what was my PhD work and some of my postdoctoral fellow research fellowship work. So Dr. Willett is well known, not only for making very, very important contributions to scientific contributions to the field of nutrition and health in general, but he's also a very good communicator and is very much interested in disseminating as broadly as possible findings from research so that individual people can put these things into practice. And it doesn't just lie on medical journals or research journals. So when I was a postdoctoral fellow working on the work on data fertility in the Nurses' Health Study, he asked me whether I would be interested in writing this as a general audience book, summarizing all the findings from these papers, as a general audience book, because he thought that would be a topic that would be interested to the public.
Dara: For the lay reader. A hundred percent.
Chavarro: Yep. So I said, sure, why not? I mean, I really had no idea what was entailed into that kind of enterprise. In retrospect, I probably should have established stronger connections within the reproductive medicine community before jumping head on to the deep end of the pool. But ignorance was, might have been of the broader field might actually have played to my advantage in retrospect.
Dara: I think it did.
Chavarro: And we went ahead and did it. So it took about a year to write the book at the same time that the papers were on their way out. So by the time we started writing the book, all the papers looking at data fertility within the nurses' health study had been were at some point in the peer review process. Most of them were published, a few of them were still under review, but by the time the book was published, everything was published in peer reviewed journals. And I think we actually ended up delaying the publication of the book by about a month to make sure that everything that was in the book was already published.
Dara: So it was already out to the public?
Chavarro: Exactly.
Dara: And so let's take a step back cause not everyone is familiar with the nurses' health study. And just for the lay listener who has no medical or science background, you know, the magnitude of the nurses' health study. Can you speak a little bit about that?
Chavarro: Sure. So the nurses' health study, is a, is an ongoing study started in 1989 to better understand how lifestyle factors and in particular diet impact the health of women. The main focus of nurses' health study has been identifying risk factors for breast cancer and because reproductive events, including pregnancy, are such important determinants of breast cancer risk, there was a lot of data collected about pregnancy and about fertility within the nurses' health study that nobody had used as a primary outcome. So when I came as a doctoral student, we were able to identify a group of about 20,000 women who've among whom we had collected data on diet and among whom we could completely reconstruct their reproductive careers, whether or not they had been pregnant, how many times they had been pregnant, if they had seen struggles getting pregnant and use that data to try to identify what aspects of diet were related to fertility in particular as it related to an ovulation. And the reason we focused on ovulation were two main reasons. One was a practical reason and it is that we had the data and we had validated the outcome within the nurses' health study. And second, it's one of the most common causes of infertility. So what we decided was like, well, this is something that probably is susceptible to being influenced by environmental factors, including diet, right, as opposed to let's say tubal disease, right? So as you have fallopian tubes or some other mechanical or anatomical problem, that's preventing you from getting pregnant. There's no amount of diet that's going to fix that, or that's going to help you, right? That leads to a completely different course of management. But we found in ovulation and in particular, as it relates to women who may be, may have polycystic ovary syndrome, or who may not completely fulfill the diagnostic criteria for polycystic ovary syndrome, but have some of the features, we thought that there was an opportunity to identify something.
Dara: And 20,000 people. That's a huge sample size.
Chavarro: It is a lot, it's only a small portion of the nurses' health study. So the nurse’s health study too is about 116,000 women. There's only a smaller group. Yeah. It’s still ongoing. So…
Dara: That's great for you in terms of the research.
Chavarro: Yeah. So what has actually become more active on my end is the newer version of the nurses' health study. So the nurses' health study three, which I am the principal investigator of which we started it to some extent actually to follow up on the findings on nurse's health study two. So it was very exciting and we realized that at that moment that there were no other studies where we could replicate our findings. So I said, well, maybe we should start another study to see if we can replicate our findings in a different study. So we've been, this newer study has been going on for a few years now, and that seemed the agenda of things through, with these newer studies.
Dara: Wow. That's great that you're able to build upon that previous research to start something new. And the fact that you're spearheading this is super exciting. So I'm sure things have evolved over the years, but in terms of basics of the fertility diet, I know I'm sure you can speak all day long in terms of kind of your main findings, but perhaps touch upon some of the most important things that, that you discovered at least with that research.
Chavarro: Okay. So I think that the main impetus was that our initial hypothesis was that many of the lifestyle factors that were we knew were predictive of type two diabetes, insulin resistance, would overlap as predictors of infertility due to anovulation specifically. So that's the way we decided to approach the problem. And at the same time, we decided to look more broadly at the literature to see to what extent other nutritional factors might have been suggested in the literature as potential causes for infertility or to be potentially related to fertility. And we identify a handful more. So in the end, this was an effort of about five, six years of worth of work. We identify a few specific that are factors that were related to fertility. So one was intake of transfatty acids. So these are fats that are created during industrial, during commercial baking or commercial frying and they have been decreasing quite substantial in the, in the U S food supply. But that was not the case when we started doing work.
Dara: So like Twinkies were very big way back when, and we don't see that as much.
Chavarro: Fortunately for us, you don't have to worry that much about transfats. Although there are still some amount of transfats in the food supply. So that was one. The other thing that we identified as a potential risk factor for infertility was a glycemic load which is a technical way of describing both the amount and the quality of carbohydrates that you consume. So you can have a very high glycemic load if you consume either a lot of carbohydrates or a modest amount of carbohydrates, but most of them are highly processed and refined. So think white bread as opposed to whole wheat bread or white rice as opposed to Brown rice and things like that. So we found that glycemic load was also related to a higher risk of infertility. And looking at different types of protein, we found that the origin of the protein had kind of opposing effects on fertility. So greater intake of protein from animal sources was related to greater risk of infertility. Whereas intake of protein from vegetable sources had the opposite relationship.
Dara: I wanted to touch upon that because I wonder if you have a different thought process now or if we actually retested more specifically protein coming from soy. And I know in your book, you had mentioned that at least with the research that you found, that I believe patients who had more soy had better fertility success, I believe, compared to patients that consumed more animal products, What about environmental toxins or how the soy is prepared?
Chavarro: Sure. So soy, the soy has actually evolved quite a bit since we published that book. So at that time, and I think still there's a much larger literature on the potential negative effect of soy production. Um, so yeah, so if you just search on the internet, you're very likely to find something along the lines of soy is really bad for production, both in men and women because it's a source of estrogen and estrogen-like substances of plant origin. And that is true. So, so it does have a few substances that are chemically very similar to estradiol and actually can bind the estradiol receptors and can have estrogen-like activity both in vitro and in vivo, but whether or not that results in any measurable health effects, including fertility is not that clear.
Dara: You still haven't seen enough?
Chavarro: I think if anything it still looks more favor of soy products than against soy. So since then there has been more work. The biggest concern has actually been on men that it might have a negative impact on sperm counts. So there has been, there have been a few studies, including some of ours looking at soy intake in relation to sperm counts. And it is true that men who consume soy have actually slightly lower sperm counts. So we have observed that. And more importantly, the thing that made me more convinced that this might actually be true, have been studies coming out from East Asian countries, including studies coming out of China…
Dara: Where it’s a big source.
Chavarro: Exactly. Where you think of soy is a much larger proportion of their diet than it is in Western Europe and North America.
Dara: And also, I believe also the quality of the soil is different there than it would be in America.
Chavarro: Correct. Yeah. So there's different ways, different presentations of soy. It's consumed as different food items and much more extensively. And even within the context of East Asian men, you do see that men who consume higher amounts of soy do have slightly slower sperm counts. Now the big question is, does this make any difference in terms of fertility.
Dara: Yes.
Chavarro: Right? So are these men less likely to be able to father a pregnancy and the resounding answer is actually no. So even in our study, the same men who had slightly lower counts, lower sperm counts associated with greater intake of soy, we see absolutely no relationship between their ability to father a pregnancy when they're undergoing treatment with assisted reproduction. And other studies have looked at the same question among couples who without a history of fertility who are trying to get pregnant on their own. And they also see no effect on the priority of fathering a pregnancy. So yes, slightly lower sperm counts, but that doesn't make an enormous difference.
Dara: Even, too, time to get pregnant?
Chavarro: Nothing. Absolutely nothing.
Dara: That's good. That's actually promising.
Chavarro: Yeah. It is promising. So there may be a small effect on sperm counts, but it is, it seems to be of negligible clinical significance as it doesn't impact fertility neither among couples trying on their own nor couples undergoing assisted reproduction.
Dara: And in the same vein I have to say with men, what about fish?
Chavarro: Let’s finish soy and I’ll come back to fish. Okay. So the one thing that I wanted to say about soy in women is that it's like the exact opposite of what you find late literature. So there have actually been a couple of randomized trials with soy extracts with concentrated phytoestrogens, looking at outcomes of infertility treatment and women who are randomized to soy supplements actually do better. Whether it's when women who are randomized placebos whether this is women undergoing IVF or women undergoing IUI, they do better. They have greater clinical pregnancy and live birth rates. And we see something similar in our study among couples on fertility treatment at the mass general hospital women who consume more soy tend to have higher success rates. So I would say that on balance, it looks quite positive for soy. And then moving on to fish, I think that that one has also evolved quite a bit. And that was actually one of the things that I was talking at ASRM and there for a while, especially after 2001, when the EPA and the FDA set an advisory for warning women who are were either pregnant or were likely to get pregnant, to not eat fish. So I think the advisory wants to limit fish consumption to no more than one serving of fish per week. Fish intake among women of reproductive age in the United States came tumbling down. It went really, really low. People really listened to that advice. And this was based mostly on the concern of neuro-developmental effects on the developing fetus’ brain. But the science on neurodevelopment was still limited at that moment. And we actually knew absolutely nothing about the effects on fertility, but since then we know that it actually seems to be quite beneficial in terms of fertility. So on the male end, it seems to improve from counts and pretty much every single aspect of the semen analysis. So both fish, the food and fish oil improve counts and improve motility and morphology. And for men who are not, or do not like fish, we see very similar effects for not consumption. So for consuming shorter chain Omega three fatty acids, which is what you would get in nuts.
Dara: Oh good.
Chavarro: So there have been a couple of randomized trials showing that you get essentially the same benefit from consuming nuts than from consuming fish oil
Dara: So men listen to that. It doesn't just have to be nuts. It doesn't have to just be fish if you're not a fan of having, you know, wild salmon or your sardines or anchovies walnuts can still be beneficial.
Chavarro: Walnuts will do the job. Yeah. So one trial was actually with walnuts and the other trial was with mixed nuts. So it was a mixture of walnuts and
Dara: Brazil nuts maybe?
Chavarro: I think it was almonds, walnuts, and something else and pistachios I think.
Dara: Did you see the same for women as men?
Chavarro: So for women there haven't been trials with nuts. For women, for fish, you see, again, something very beneficial, both for women who are trying on their own and as well as for women who were undergoing assisted reproduction and what it is that when we're assessing it as diet questionnaires with pretreatment or preconception diet, looking at time to pregnancy, the biggest benefit is for women who are consuming around, women and men, who are consuming around two servings of fish per week or more.
Dara: I love that you're saying that. I think that's so great. Cause people do fear. A lot of people come into my practice and say, I was told, or I read somewhere that fish isn't great for me. And I always have to let them know that sometimes the things that you read isn't necessarily correct, and there's so much more to it. And the research actually shows that there's more benefit to have it than not to have it.
Chavarro: Exactly. And that is definitely true for fertility. So the greatest benefit, both for couples who are trying on their own and both men and women, we've seen around two servings per week or higher. So we don't have a lot of study participants where we'd more efficient and more than two times per week. So we don't know if there's a ceiling effect beyond that, but I think that's definitely a good target because he also overlaps with targets for general health and prevention of cardiovascular disease and stuff.
Dara: Yeah. There's many benefits besides fertility for consuming good quality fish.
Chavarro: And they, the interesting thing about fish in that in two of the studies, one among couples trying on their own, and one among couples undergoing assisted reproduction, we were able to look simultaneously at both fish intake and mercury, which is the big concern and in the same group of people, we see absolutely no effect whatsoever of mercury in terms of either time to pregnancy or the probability of achieving a live birth through assisted reproduction. But fish intake does have a benefit, which means that at least as it relates to the chance of getting pregnant, there is no concerns of a negative effect of mercury. And the other promising thing is that the literature on the neurodevelopmental effects has evolved too. And it seems today that the greatest concern is really for the large predatory fish and not necessarily for fish in general. So the EPA and the FDA have updated their advisory a few years ago, but the damage of their 2001 advisory seems to be quite lasting.
Dara: It’s still lingering in people’s minds.
Chavarro: So people still talk about oh don't eat any fish. I don't think the correction has really permeated down to the public and to health reform.
Dara: I think there needs to be more public education on that and you know, all fish aren't alike and there is a big window of smaller types of fishes that are great to consume and only a small narrow list of the fish that we really should try to limit or avoid, especially around, you know, when you're trying to get pregnant. And I think…
Chavarro: Exactly.
Dara: I kind of want to take it back and it was so interesting. I didn't know you started in the fertility realm and it makes sense to me that it started with looking at the environment with fertility. I remember clearly, so ASRM is our big reproductive endocrinology fertility conference and when I went years ago, and that's when I met you, we were sitting at a round table, you were having a discussion about your findings. And I clearly remember, and this stuck in my mind, because this was something that I had never even thought of is, and you may not even remember this, but you had spoken about the potential dangers of soda cans. And I always had thought, okay. Yeah. So it is not great for you. It's sugar, not great glycaemic index insulin, but the idea, it wasn't actually what was in, it wasn't the soda itself. It was the can and perhaps the acidic environment.
Chavarro: Yeah. I think it's both
Dara: You're right. I think, I think it's a combination.
Chavarro: So yeah, so definitely the sugared beverages have not fared well in terms of their potential effects on reproduction. So for example,
Dara: And beyond.
Chavarro: A lot of the relations that we have seen before glycemic load with fertility, a lot of that is actually sugary beverages.
Dara: Yes.
Chavarro: But interestingly, in our initial work, in the nurses' health study, when we looked specifically at caffeinated and sugary beverages, so we saw something very similar for sugar and for diet soda in relation to fertility, which should make us when I was like, wow, that's interesting that it's not just the sugary beverages as we had expected, but it's all beverages. And at that time I had started working with an environmental health colleague and it turns out, so I learned at that time that it turns out that many cans use a plastic lining to prevent corrosion of the metal. Right? And this applies not only to soda cans and cans for beverages, this applies to cans,
Dara: Tomato cans.
Chavarro: Canned tomatoes, canned vegetables, canned everything. So they do have a lining of a plastic to extend the shelf life of the can essentially. And these plastic is the famous BPA that has been related to a large number of reproductive problems, both on the male and the female end. And so BPA got a lot of attention, maybe about five, six years ago to the point that some manufacturers started retiring BPA away from some applications.
Dara: But they're putting in something new, which I believe you did some research that it could be equally as harmful. Is that correct?
Chavarro: Correct. That's exactly where I was headed. So it's not when you replace a chemical that's used in millions and millions of products and it’s used in the orders of millions of pounds a year, you just don't stop using it. You're going to replace it with something. So bisphenol A ended up being replaced with other bisphenols, bisphenol A and bisphenol S and we recently, uh, one of our junior colleagues recently published a paper looking at these other phenols, especially bisphenol S which has been the main replacement in relation to semen quality. And we see the exact same thing for bisphenol S that we had seen a few years ago for bisphenol A. Yeah so many of these things that are now saying BPA free, they probably are BPA free but that doesn't mean that they're free from the bisphenols in general. So they were replaced with something.
Dara: It’s interesting. We have to be careful with packaging and labels because I think labels can be quite deceiving on so many levels, but even in something as simple as you know, Oh, a BPA, we heard how bad it was, BPA free, but it's not necessarily educating us on what the alternative they're using and it's potentially equally or even more harmful for our bodies.
Chavarro: Correct. And like one example of labeling was when I started working on these, I started working on fertility, the one thing that was their label to pay attention to was the transfat label, which is fortunately something that we don't have to worry about that anymore. That much anymore. And maybe the way in which the labeling laws were written it allowed you to label something that's transfat free if it had less than five grams per serving, I'm sorry, less than half a gram, 0.5 grams for a serving size, which means that if you just decide that the serving size is smaller, right.
Dara: So, it’s kind of hiding it's going around the truth.
Chavarro: Right. And some people did do that. And I was like, Oh, well, if we make our serving size slightly smaller, then we're actually transfat free. And we don't even have to reformulate anything.
Dara: But who eats just the serving size? Most people, or, you know, most Americans consume much larger portions than the serving size that they actually recommend on the box and the label.
Chavarro: So anyway, so because transfats are truly on their way out now, especially after the FDA moved them from the general guide safe list, then that's definitely less of a concern fortunately for everybody's health and everybody's fertility for sure.
Dara: Yes, but let’s talk about other environmental toxins. So in terms of the pesticides in our crops, do you think that is something that we're going to look into and there'll be more research done?
Chavarro: I know for a fact there will be more research on it because we're doing it.
Dara: Yes. I'm so happy. I was hoping you would say that.
Chavarro: Yeah. So a few years ago I had a very hardworking, uh, doctoral student who was interested in this question of pesticide residues in the food supply, which I thought at the time was a very interesting topic but I honestly believed it was going to be that was going to be something that was not going to be anything useful because it was going to be so hard to quantify. B she was very persistent and she decided to prove me wrong. And she did. So she came up with this very clever classification system to try to classify foods according to their known pesticide residues in the US food supply based on a surveillance system that the USDA has for monitoring pesticides in the US food supply and using that classification system, we were able to look at fruits and vegetables separately according to how much pesticide residues they usually have in relation to different markers of fertility. So she was able to publish, looking at pesticide residues in fruits and vegetables, which are the main sources of, of pesticide residues.
Dara: Did she look at the dirty dozen and the clean 15, according to the EWG?
Chavarro: So funny story there. So when we started, we say, well, why don't we go to EWG? And we just asked them to share with us their methodology.
Dara: Yeah. And that's an environmental working group for people who are not familiar.
Chavarro: Right. So when we actually emailed the environmental working group and we told them, look, we really like your classification. We want to know whether or not your classification can predict any health events. Would you share your methodology with us? So how do you classify foods to come up with the dirty dozen and clean 15 so we can use it for research. And they said, Oh, we're looking for your question, we'll be right back with you.
Dara: You didn’t hear back from them?
Chavarro: They took forever. And eventually they said that after long internal discussions, they had decided not to share with us their methodology. So I was like, Oh, that's interesting.
Dara: You need to come up with your own methodology,
Chavarro: I was like, well, I don't understand why but we'll have to come up with our own thing. That's where my former student ended up making a tremendous contribution coming up with this new classification system. Interestingly, when we compare our classification system to the dirty dozen, clean 15, there's a lot of concordance between what we find to be high pesticide residue and low pesticide residue. What they do not publish that we really wanted to know is what happens in between, right? So they're only published the extremes, but if we were going to use it for research, we had to know not only the extremes, but we have to know everything else what's going on with everything in between.
Dara: So true.
Chavarro: So with that classification that my student developed, whereas we have looked at markers of male reproductive potential so looking at semen quality in both men undergoing men at fertility centers and young men, reproductive hormone levels and then ART outcomes. So when we see that higher intake of high pesticide residue, fruits and vegetables is related to lower sperm counts.
Dara: I'm not surprised.
Chavarro: Yeah. So, and it's actually quite dramatic. So it's lower counts and lower motility.
Dara: So both motility and number.
Chavarro: Both motility and number. And right now we're actually working on what might be the effect on the chances of fiber in a pregnancy based so that's ongoing work. But among women, we did look at what are women's pretreatment intake of fruits and vegetables based on pesticide residues had anything to do with their ART outcomes. And what we see is that higher intake of high pesticide residue fruits and vegetables is related to a greater chance of pregnancy loss during both, uh, chemical and clinical losses, um, and therefore a lower chance of live birth. So we do see that and we're working on a, what might be other reproductive events and other reproductive phenotypes that might be affected by these. So at ASRM last week we showed results for endometriosis.
Dara: Yes.
Chavarro: So it's not related to endometriosis.
Dara: OK.
Chavarro: Good about that so that’s good.
Dara: What about Fiber? I know you'd also done research on fiber and endometriosis.
Chavarro: We've done fiber and endometriosis and you just stumped me because I can not remember
Dara: That’s ok. All I know is that I believe there was a, it showed positive, you know, with higher fiber consumption, I believe I'm not sure exactly what it was, but it was something beneficial for people with endometriosis.
Chavarro: That sounds about right. And I think that was part of what we presented at ASRM last week, if not before. But fiber, we did look at fiber and intake of whole grains in relation to ART outcomes and we do see that women who have a greater consumption of whole grains have a greater chance of having a successful treatment outcomes.
Dara: Dairy was the other interesting, I mean, really what you, what I read in the book on dairy consumption and it makes total sense, but the idea of choosing full fat dairy for women and the basis behind it all is because of the fat is where the female hormones are, the estrogen.
Chavarro: Yeah. So there is a fascinating story. And it's one of the ones that, where there has been the unfortunate that the least consistent evidence has been for dairy. So we included dairy among the things we wanted to look at in our self study, because it was similar to soy, right? So there was a lot of lay literature essentially saying dairy is terrible. Don’t drink milk if you’re trying to get pregnant. So that was the main story for dairy 15 years ago. If you look at the literature, most of them there, there was hardly any data in humans. So there was one paper in humans looking, comparing data across countries. So comparing fertility rates among high dairy consumption countries and fertility rates in low dairy consumption countries, which suggested that fertility rates were higher in countries where women with a lower per capita milk consumption. But of course, per capita milk consumption is related to hundreds of other different things.
Dara: Well I’m sure and so you can’t necessarily point to just the dairy?
Chavarro: That's interesting, but not something that you would change your mind and change your action just on that evidence. More strongly, there was evidence from animal models. So there was this very popular animal model for premature ovarian failure, where what he did was they fed, uh, female rodents galactose. So galactose is one of the sugars in milk, right? So lactose is one molecule of galactose and one molecule of glucose. So they would feed these rodents pure galactose. And if you feed, apparently if you feed rodents enough galactose they actually do go into premature ovarian failure. So that was probably the, the, the strongest evidence. Yeah, but the problem was that these were animals that were being fed roughly 50% of their older galactose.
Dara: So huge diet that was predominantly made from milk or galactose.
Chavarro: Exactly so that, that actually doesn't even translate to anything an adult human would ever eat. Right? If you think about it, it would be equivalent to drinking fat free milk only as your only source of food.
Dara: So it’s too extreme it’s not realistic? Not translatable to humans?
Chavarro: For sure. That's for sure. And then so, but there were several studies looking at these galactosemia model. And then the last thing was a study done among farmers in the Midwest. And this study actually suggested that milk was related to better fertility. So as we read the literature at the moment, I was like, well, there's really, it could go any direction. Really. So what we found was that as it related to infertility due to ovulation, we found that high fat dairy, so and most high fat dairy in our population was whole milk, was related to a lower risk of infertility due to an ovulation, whereas intake of low fat dairy and most of low fat dairy in our population was skim milk was related to a higher risk of infertility due to ovulation relation and what we suggested the mechanisms might be where that on the low fat dairy of things, we know that low fat dairy is a very strong stimulus for the production of a hormone called insulin like growth factor one, which has been tied to the polycystic ovary syndrome, which is known for anovulation.
Dara: You took the words right out of me.
Chavarro: So that was what we thought the link was. And then on the high fat dairy end, the concern is really the naturally occurring hormones in dairy, right? So cows will only make milk if they're pregnant or lactating and most commercially available milk in the United States and in the West comes from cows that are milked throughout the pregnancy. So if you've ever seen a cow’s placenta, you will get an idea of how much progesterone and estradiol and testosterone is being produced by this enormous organ and all steroid hormones freely cross into the milk. So, and we know from other studies from studies in the dairy science world, that whole milk and dairy fat does have much higher that was of steroid hormones and that these are biologically active. So we were like, well, maybe some of the progesterone is helping with your things that are showing, being coded as solitary, but maybe something like this defect or something we don't really know.
Dara: It’s so interesting.
Chavarro: So the same mechanism was actually concerned for male-factor right?
Dara: In the opposite direction, correct?
Chavarro: Exactly. So we're thinking, well, these might actually be the exact opposite for men because for men, you actually wouldn't want steroid hormones, especially not a estradiol or progesterone being absorbed freely and because the background levels of estradiol in men are much lower compared to background levels in an adult woman then it might actually be a bigger concern among men. But we've looked at dairy in relation to semen quality in three separate studies now, and we see three different things. So I'm not, yeah. So I'm not sure. I mean, the theory is really fascinating
Dara: But the verdict is still not out.
Chavarro: It’s still not out and other groups have looked into dairy.
Dara: I think we need to do more research.
Chavarro: Yeah I think so too. I think it's really fascinating what I think actually I think the group that would be most interesting to study are children because among children pre pubertal children, that's where the background level of steroid hormones is nonexistent and where you would actually expect to see the greatest if there is an effect you would expect to see any effect to be the greatest among pre-pubertal children.
Dara: And there's a couple of areas of research that I would love in terms of dairy to see, you know, the quality that we're getting in America versus the quality that we're getting perhaps in Europe, that's one. And then the second area where I feel like there is a lot of potential I wish we could do more research is perhaps dairy in relationship to PCOS and in relationship thyroid conditions or any type of autoimmunity. I think there's so much more we can do to kind of see if there's any negative or positive because I have so many women coming to see me with PCOS or with thyroid conditions that say, should I not be having it? Isn't dairy potentially pro-inflammatory?
Chavarro: Yeah. Those things are definitely on our docket.
Dara: Great. I’m so happy. I’m counting on you, Dr. Chavarro.
Chavarro: Definitely PCOS because I do think that what we may have observed in the nurses' health study is related to PCOS. And the reason it hasn't replicated well is because most of the studies that have come after ours have looked at time to pregnancy, which is really a composite outcome of not only people who may or may not have. So it doesn't relate exclusively to our three function, but on everything going well. So if it only has a modest effect on population, but no effect on anything else, unless you have an enormous study, you probably will not see any effect. And that's kind of what has happened so far. I think.
Dara: So we need more research on that.
Chavarro: I think that as it relates specifically to ovulation problems, and as I said, as it relates specifically to PCOS, there might be more than what we know.
Dara: So that's so interesting. I hope there is more research and good quality research, but I wanted to ask you, is there anything you're a researcher and I know you're so much more, you’re professor and you're very involved in this world. What do you think we can do as people in the healthcare world to best support our patients or the research that we need to do on our hand to hopefully get more answers to better serve our patients? I know it's a big question.
Chavarro: Yeah, no, no, it's a good question, but I think it's a very practical one, right? So I guess another way to rephrase it is yes, sure. There's still a lot of things to do and things that are not clear, but given what we know today, what can I do for my patients? Right? And I think the answer is relatively straightforward and it is that based on what we know today, the same recommendations that you would give somebody for the prevention of chronic diseases, such as prevention of cardiovascular disease, most of those recommendations overlap substantially with what you would recommend for someone who is interested in becoming pregnant, because they're interested in preconception care and they don't have any history of infertility or couples who are presenting to fertility centers and are seeking to change their diet ahead of treatment. So the overall recommendations would apply just as well for prevention of heart disease, as they apply for a potential improvement of fertility. And then the tweaks are relatively minor, right? So you probably don't need to focus on measuring sodium because we don't have any documented benefits or harms of sodium.
Dara: Actually, there could be a little bit of benefit, you know, depending you know if people are doing an IVF cycle, actually some sodium could potentially be beneficial.
Chavarro: Yeah. And then the other big tweak is making sure that people are getting their and B12 on one carbon metabolism, vitamins. So you make those two tweaks and you're probably doing everything that you need to do.
Dara: Yeah. So, you know, maybe the education before people are trying to get pregnant, as opposed to, you know, we often seek help when we're struggling, but perhaps getting that knowledge and education. I mean, I always think like we need the knowledge and education to our children in schools. So it's one thing that they can hopefully help, you know, have good relationships or knowledge on the importance of food, the environment to make our bodies work as efficiently as possible, which I think is a tough thing to do to, you know, start that early on. But the idea of, you know, not always fixing the problem afterwards, but kind of looking at it ahead of time to perhaps lower the potential risks.
Chavarro: Yep. That I completely agree with you
Dara: Anything that you want to add? I feel that there's so much, you're really, you're a wealth of information.
Chavarro: I think that the other thing it's important to rethinking their fertility world is body weight, right? So like, do you know quite well? We have known for a long time that women who are overweight or obese have a hard time getting pregnant on their own. And when they are under grinding for, to have treatment and assisted reproduction, they have lower success rates. So for the longest time of everyone involved in the care of fertility patients has been advising women who were overweight or obese to lose weight. And in the last couple of years, we've had two randomized trials suggesting that these may not be these helpful. So now the question is, well, what do you do now? And so the interesting thing is that even in these studies, that show that there's actually, there doesn't seem to be a benefit of short term weight loss immediately before treatment. We do see that baseline weight is still predictive, meaning that the way you have going in still matters, right? And second in two trials, they also show that even though there's no effect on the treatment once women get to assisted reproduction, there is an increasing in spontaneous conceptions for women immediately before undergoing treatment, right?
Dara: Who've lost weight, you’re saying?
Chavarro: So women who are randomized to losing weight, to, to weight loss intervention. And then they happened to get pregnant before they start treatment for fertility. So my overall read of the literature is that weight loss is still probably useful in a subset of women. And these are going to be the overweight PCOS women who we have known for a long time that weight loss and insulin sensitizers improves ovulatory function. So these women are probably still good candidates for weight loss immediately for treatment, but not with the goal of improving treatment outcomes, but with the goal of achieving a spontaneous conception to avoid treatment.
Dara: OK and then what about, even for me, it's also about pregnancy. There’s definitely higher risk with pregnancies too.
Chavarro: Yeah. Right. So you may not change their chance of getting pregnant, but it definitely does change the health of the pregnancy. And we do know that we have also known that for awhile, including from weight loss and weight maintenance trials among overweight women. So I think that while we still know that weight going into treatment is important and it's very, very important. It is probably okay to have overweight women not worry so much about the weight by the time that the best option is to undergo assisted reproduction and maybe focus on the quality of their diet and focus on something else.
Dara: I agree because I think that's, you know, people often worry, like, do I wait and try to lose the weight? Is that going to increase my chances? And the problem is, is I think we still don't have that answer, but the idea of maybe taking weight out of the equation or that number out of the equation and looking more about your diet and the quality of the diet, no matter what weight you're going into a potential pregnancy. And the same goes, I always say for patients who are underweight, I think we often, yes, because America, we definitely have an obesity epidemic, but I still always like to point out anyone outside that extreme, whether they be overweight, obese, or even underweight can potentially have a negative impact in trying to get pregnant.
Chavarro: That's correct. And women who are underweight tend to be overrepresented at fertility clinics. So that's definitely a population dieticians and physicians in the fertility world would definitely run into and the other kink about body weight is that we have concentrated forever on BMI BMI is pretty good, but it's not perfect.
Dara: And you agree with me! I feel wholeheartedly the same thing that we always look at that number.
Chavarro: Yeah. So the question is we know that the majority of people who present at fertility centers are people who are going to be in the middle range of BMI, right? So you do have some overweight, obese women, but not as much as in the general population, but you do have more underweight women than you would see in the general population. And, but you do have a lot of women who fall within the normal range of BMI. And one thing that we haven't paid a lot, attention is waist circumference . And we've published earlier this year, showing that among women within the norm of what women are going for to a treatment within the normal body weight range, we tend to normal BMI range, waist circumference is actually quite important.
Dara: I'm happy that you brought that up. Cause I do think that is, I think, where we're moving towards that. It's not necessarily the BMI, but it's, you know, the waist to hip ratio perhaps.
Chavarro: Yeah so I think that what we're trying to get at is the same. But the difference is that among young women BMI doesn't give us as much information as it gives us in the broader population. And we need to also pay attention to waist circumference.
Dara: It's a snapshot. I think there's so much more to it. So I'm happy that you actually brought that up. I think that's wonderful. I feel like we can talk all day long. There is so much more research that you've done. Really, please check out his research online. I saw that you have over like hundreds of research that you've contributed to over the years. And really, I mean, over the past 15 years, you really have made such a positive impact in the world of fertility and health. So thank you so much. We always close our sessions with one last question. And the question is, what are you grateful for today?
Chavarro: So I think not necessarily only today, but I am incredibly grateful that I get to spend my days doing what I love to do. So I started in medicine and I found out pretty quickly that I didn't really like practicing that much. I am grateful that I can do something that I really enjoy and that I can help people still within the health field, but doing something that I truly truly enjoy every single day of my life.
Dara: Dr. Chavarro, I agree with that. I can not like I can clearly see your passion and really you've paved the way for an area that I think was really untapped, you know, before those 15 years. And what I'm grateful for today is you like really, you are my role model, my inspiration, and really I've been in this world for, you know, at least the fertility realm just over 10 years now. And I really get excited every time I see new research that you have been involved with and cannot wait to see where it leads in the future. So thank you so much for speaking to everyone today, speaking to myself, and we would love to have you back down the road, if you will have us.
Chavarro: Of course. Thank you so much for your kindness, it's been a pleasure participating today.
Dara: Can't wait. Thanks.
Dara: Thank you so much for listening today. And always remember, practice gratitude. Give a little love to someone else and yourself. And remember, you are not alone. Find us on Instagram @fertility_forward. And if you're looking for more support, visit us at and tune in next week for more Fertility Forward.

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