It is Dangerous for Women to Avoid Fish During Pregnancy
OmegaMatters: Episode 20
Hosts: Drs. Bill Harris & Kristina Harris Jackson
Guest: Dr. Tom Brenna
Background and Key Takeaways:
In this episode, Drs. Harris and Jackson speak with Dr. Tom Brenna about seafood and pregnancy. Dr. Brenna is a professor of pediatrics at the Dell Medical School at the University of Texas at Austin. He received his PhD from Cornell University in Analytical Chemistry and spent 28 years as a professor of human nutrition at Cornell in Ithaca, New York. He’s received several awards from the American Society for Nutrition and served on a number of advisory panels on human nutrition, including being a member of the 2015 Dietary Guidelines Advisory Committee, which is the group that is tasked with updating the US Dietary Guidelines. His work has been in the area of requirements for polyunsaturated fatty acids in the perinatal period and the development of advanced analytical chemical instrumentation and high precision isotope ratio mass spectrometry for anti-doping applications. For more information on OmegaMatters, visit: https://omegaquant.com/omegamatters-broadcasts/
SHOW TRANSCRIPT:
Dr. Kristina Harris Jackson: Welcome to OmegaMatters. I’m Kristina, and this is Bill and this is OmegaMatters, where we talk about all things omega-3s. Today we’re talking with Tom Brenna about seafood and pregnancy. Dr. Brenna is a professor of pediatrics at the Dell Medical School at the University of Texas at Austin. He received his PhD from Cornell University in Analytical Chemistry and spent 28 years as a professor of human nutrition at Cornell in Ithaca, New York. He’s received several awards from the American Society for Nutrition and served on a number of advisory panels on human nutrition, including being a member of the 2015 Dietary Guidelines Advisory Committee, which is the group that is tasked with updating the US Dietary Guidelines. His work has been in the area of requirements for polyunsaturated fatty acids in the perinatal period and the development of advanced analytical chemical instrumentation and high precision isotope ratio mass spectrometry for anti-doping applications. But lucky for you all, we are only focusing on the omega-3 work today. Thank you for joining us, Tom.
Dr. Tom Brenna: Well, thanks for asking me.
Dr. Kristina Harris Jackson: Yes, this is great. So to start off, we’re focusing today on seafood and pregnancy. How did this topic become controversial? And how did we get to a point where women were told to avoid seafood in pregnancy?
Dr. Tom Brenna: Okay, well, that’s a really good opening question. It was in the late 1990s that there was some concern around mercury because it was measurable, and that there may be some health effects. Now we know from poisoning events, that is cases in which, let’s say, there is a release of mercury into a body of water where it would be ingested by pregnant women, that, mercury is a neurotoxin. So between the natural history of mercury, and when I say natural history, I mean, we, we, we don’t do science, in toxins, the way we do in nutrition, we can’t feed people toxins and, and look at the outcome. But what we can do is see what the natural history is. And then we assess the consequences.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: So it was in the late 1990s, that people began to be concerned that the detectable amount of mercury in various fish and how that might have an effect on the developing fetus, in the brain and developing fetus. So I would say that out of an abundance of caution, and very little direct data on the consumption of seafood, that the EPA and FDA issued, let’s say statements of concern that women ought to be careful about the amount of seafood they were eating during pregnancy, in relation to it carrying a neurotoxin (i.e., mercury) and possibly limiting the mental development of their children.
It was probably five years after that, that a committee was constituted — I think it was ’04, but it was probably ’00s sometime where a committee was put together, an advisory committee, to have a look at whatever data were available. And at that time they mostly looked at just the levels of mercury in various fish and listed them from, let’s say, the highest to the lowest levels of mercury, and said, “Well, these are high, and so maybe these top ones you’d wanna stay away from.” But an important caveat to that statement is that they were high relative to other fish, but that doesn’t mean they were high relative to some kind of a biologically relevant level, in other words, no one at that time really knew how much mercury was enough to start to see effects.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: Those were the two major events with respect to regulatory bodies that led us to the concerns over mercury. And then, and then there was a bit of, I don’t know, we call it a meme that got started, and folks said, “Okay, yeah, well, I’m pregnant, so I have to stay away from fish. That’s what they say.”
Dr. Tom Brenna: And it just got started that way. I think that’s a reasonable synopsis of early events.
Dr. Kristina Harris Jackson: Yeah, and it kind of spiraled a little bit beyond what the first like regulations and science were. They were trying to give a little warning, but in pregnancy, everything gets heightened. And if there’s any risk at all, people tend to be overly cautious, especially around food. There’s so many weird foods that you end up having to avoid for a variety of reasons. So it feels like it’s something that kind of got out of control. And then we start to learn more about how fish intake impacts pregnancy outcomes in general, not just looking at mercury, but looking at fish and seafood intake. And can you kind of summarize a little bit of that history and where we are now there?
Dr. Tom Brenna: Many of us come to an overall food perspective through, let’s say, study of a nutrient. Rsearchers do that, right?
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: So we’re talking about omegas here and omega-3s. And the omega-3s have been a subject of interest for quite a few decades. Every so often, someone who’s new to it says to me, “Hey, people have been interested in omega-3s recently,” and I say, “Hey, recently is like, I don’t know how many decades.”
Dr. Kristina Harris Jackson: (laughs).
Dr. Bill Harris: (laughs).
Dr. Tom Brenna: So, this idea has been around for a long time. The very first detection of our big omega-3 DHA in any tissue was actually in brain, and that was back in the ’50s. In the ’70s, it was a little more cardiovascular and then, and then it drifted into the brain realm with the matter of premature infants and whether they were getting enough omega-3s.
Dr. Bill Harris: Yeah.
Dr. Tom Brenna: But if I then shift to the fish story. Fish is the major source of omega-3s in the diet — the long chain omega-3s, EPA and DHA. And because of other factors in the diet, that becomes really the major source. And so if you believe that preformed version of DHA is required, then you start looking to fish. Many nutritionists don’t like recommending supplements. I mean, I’ve been around long enough, so I’ve seen it go way towards supplements and then way away from supplements. So I don’t know whether it’s gonna go back again.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: But if you then say, “Okay, well, I want a foods-based approach,” and the dietary guidelines, very specifically addresses only foods, recommending supplements is not part of the mission of that organization and effort. So you say, “Well, okay, so seafood is where you get it from, there’s no place else to get it from,” to speak of that is omega-3s, long chain omega-3s. But the other thing about seafood is that it’s loaded with other nutrients — protein, a nice complement of minerals, which many of us think are really important for development of the brain as well.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: So I began to think, “Well, okay, now how important is this mercury story and how much evidence is there that it’s relevant as a toxin?”
Dr. Bill Harris: Yeah, so a risk-benefit analysis started to come into focus.
Dr. Tom Brenna: Yes, that’s exactly right. A risk-benefit analysis started to come in focus.
Dr. Bill Harris: And who led that? Did somebody actually do a risk-benefit analysis in pregnancy?
Dr. Tom Brenna: The earliest one was really a study in the Seychelles Islands.
Dr. Bill Harris: Oh, okay.
Dr. Tom Brenna: Two toxicologists went to the Seychelles Islands, which is a group of islands are kind of isolated. They are in the Indian Ocean, and they eat 10 times more fish than Americans eat, probably more than that. And they said, “Right, we’re gonna go there, and we’re gonna measure the mercury in a mom’s hair. And then we’re gonna look at the IQ of the kids and those kinds of things, how they do in school, and so on. And we think there’s going to be a real issue with all the mercury they’re eating.” The two that started this were out of the University of Rochester, and those guys are still around — Gary Meyers and Phil Davidson.
Dr. Bill Harris: Okay.
Dr. Tom Brenna: So they did these measurements, starting in probably the late ’80s.
Dr. Kristina Harris Jackson: Wow.
Dr. Tom Brenna: And, lo and behold, when they looked at hair mercury in mom, and how the kids were doing, they found almost no relationship, they even found a little bit of a positive relationship, where mom’s hair mercury is higher, and the kids actually are smarter.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: I remember listening to this the first time, I listened to one of those descriptions and before they got to that point, I thought to myself, “I wonder whether actually mercury is gonna look good.”
Dr. Kristina Harris Jackson: Yeah.
Dr. Tom Brenna: And it did.
Dr. Bill Harris: So how they explain that connection between higher mercury and better outcomes?
Dr. Tom Brenna: Just correlation. I mean, mercury was a, was a marker for fish consumption.
Dr. Bill Harris: Oh, okay.
Dr. Tom Brenna: And the more fish ate, the more mercury they had. That was the explanation. And that’s what made sense to me. That’s why I was sort of smiling when I was listening to it, thinking, “I bet you they’re gonna be surprised what they find. It isn’t gonna be downward, it’s gonna be upward.”
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: It’s slightly upwards. That’s what they found.
Dr. Bill Harris: At least it wasn’t downward.
Dr. Tom Brenna: That’s correct. At least it wasn’t downward. That’s exactly correct.
Dr. Tom Brenna: There was another study that’s very relevant. There were various other studies around, but there was another one that was sort of in the ’90s in the Faroe Islands. The Faroe Islands are in the North Sea, north of Scotland. I guess they’re between Scotland and Iceland, or somewhere like that.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: And in that study, those folks had very high levels of mercury in their blood, and in their hair. And the reason is because they consume pilot whale. They have a traditional pilot whale hunt every so often, I don’t know, twice annually, I don’t know. And their cultural food is basically pilot whale meat and blubber. And their levels of mercury, and I’m going from memory, but I think there’s something like 20-fold, 20 times higher than, let’s say, a reference level in the United States. So if mercury was a problem there, you’d expect to see huge effects, wouldn’t you?
Dr. Kristina Harris Jackson: Yeah.
Dr. Tom Brenna: You’d expect to see real problems, lots of people whose biology can’t handle it. I mean, we do know about nutritional conditions that cause problems with brain development, the classic one that comes to mind is iodine deficiency, w hich you could say causes retardation. So you’d almost say, “Okay, well, if it’s 20-fold higher on the Faroe Islands, maybe we should see things that look like that.” And you don’t see anything like that.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: You see, maybe a little effect. But again, that’s pilot whale. It’s not seafood. And there are some explanations why there may be a difference between pilot whale and actually fin fish and shellfish.
Dr. Tom Brenna: You got a big dose issue there, too. You said the 20-fold intake is vastly higher than just maybe eating 12 ounces of seafood a week?
Dr. Tom Brenna: Absolutely.
Dr. Bill Harris: Right.
Dr. Tom Brenna: From a scientific point of view, forget about a humanity point of view, it’s kind of a nice experiment because you say, “Okay, well, those guys are eating so much to get 20 times as much” and you don’t see major problems. So that was a bit of a clue that maybe mercury is not as important at the levels that Americans would get it in commercial seafood.
Dr. Bill Harris: Yeah.
Dr. Tom Brenna: And we’re not talking about isolated bodies of water that might actually be polluted. That’s, that’s something else, right?
Dr. Kristina Harris Jackson: Right.
Dr. Bill Harris: You know, the lake down the road here where the coal plant dumps its crap into it, you know, that we’re not talking about that fish from that lake.
Dr. Tom Brenna: Yeah, that’s exactly right. I mean, you actually do see some mercury and that can be associated with those pollutants, and then there are there are places like gold mines… where mercury comes with gold and when it’s smelted it’s just mercury all over the place. And then mercury dumped into the streams, none of the United States that I know of, but I know there are places in Africa where you have that.
Dr. Bill Harris: Wow.
Dr. Kristina Harris Jackson: Mm.
Dr. Bill Harris: So with those two studies, Seychelles and Faroe Islands, both kind of singing the same song in a way, it still seemed like there was a huge uphill climb to get the federal regulations to get off this mercury scare.
Dr. Tom Brenna: Well, I’m not even sure we’re off it yet.
Dr. Bill Harris: Okay.
Dr. Tom Brenna: What people did and when I say people, it’s the company I keep, but what researchers did was they started looking at this question asking, “How much seafood does a pregnant mom consume, and what is the consequences for the neuro-development of their kids?”
Dr. Bill Harris: Mm-hmm.
Dr. Tom Brenna: And one of the o- one of the, let’s say, that, that… those studies started to really be published in earnest in the, in the 2010s, let’s say.
Dr. Bill Harris: Okay.
Dr. Tom Brenna: The federal government around this period, did a study to find out how much seafood a mom would consume of various species, and the benefits for the Omega-3s just swamped any, what I call hypothetical harms. The reason I call it hypothetical harm is because the only way you can even quantify it is by doing a, what we science guys call, a regression analysis. And so you assume there’s a little harm, you say, “Okay, well, if there is a little harm all the way down to zero and, and even a little bit, then we can ascribe a little bit of harm to mercury.” But I’m not even sure that’s accurate, to be perfectly honest.
It a multiple regression, and you’re extracting something, but nobody has been fed mercury, and showing harm and I just cited those other two cases. And we do have ways of dealing with mercury, it comes off the hair. So it was in preparation for the 2020 dietary guidelines that a group of us got together and said, “Right, what is the actual evidence around seafood consumption?” Not Omega-3 consumption, not mercury consumption, no nutrients, specifically, just seafood consumption. What’s the evidence around that and child development?
Dr. Bill Harris: Mm. Yeah.
Dr. Tom Brenna: And we chose to replicate, as best we could, the procedures that the dietary guidelines would rely upon that are actually developed by the USDA.
Dr. Bill Harris: Right. Right.
Dr. Tom Brenna: And so in a manner of speaking, we decided that we would find out what they were gonna get when they did the analysis.
Dr. Bill Harris: You’re right.
Dr. Tom Brenna: Indeed, and I would also point out that the USDA and FDA who are responsible for the dietary guidelines like to say that the methods they use are transparent, meaning you can replicate them.
Dr. Bill Harris: Mm-hmm.
Dr. Kristina Harris Jackson: Yeah.
Dr. Tom Brenna: And so if they’re transparent, and they can be replicated, then a group of a dozen senior scientists looking at those procedures ought to be able to replicate them. And it was quite a summer of 2019, as we were on the phone an awful lot with each other, going over research paper after research paper, and we ultimately concluded that seafood consumption, even at the highest level is beneficial. If you, if you take 20-something studies, all measuring many different outcomes so not just IQ, but all sorts of, you know, performance in school kinds of things, you will sometimes just randomly see things that might look negative. We saw hardly any that look negative, and no pattern that made any sense that would make any concern. So the pattern overall was the more seafood mom ate in pregnancy, the better neuro-cognitively that the kids got in school and later.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: And to pretty much a plateau level. And it never came down again. The highest number we had was about 100 ounces a week of seafood.
Dr. Bill Harris: Oh, 100 ounces.
Dr. Tom Brenna: Which is getting to be in the realm of what a shark eats.
Dr. Kristina Harris Jackson: Yeah, (laughs).
Dr. Tom Brenna: So that’s an awful lot. And our recommendation is 12 ounces a week, although the 12 ounces a week. And it’s a long story how people got to that number, but it was certainly not evidence-based.
Dr. Bill Harris: Yeah, right.
Dr. Tom Brenna: It was pulled out of a hat.
Dr. Kristina Harris Jackson: Yeah.
Dr. Tom Brenna: But that 12 ounces a week is kind of the reference level. And so we got to pick a number. So we picked 12 and 12 is okay.
Dr. Kristina Harris Jackson: Yeah. Yeah.
Dr. Tom Brenna: So this is up to 100.
Dr. Kristina Harris Jackson: Yeah.
Dr. Tom Brenna: And so the margin for safety is enormous.
Dr. Kristina Harris Jackson: Yeah. And 12 ounces is two or three servings, depending on how big your fish is.
Dr. Tom Brenna: It’s not very much, you know, in the old idea of two to three, fish meals a week.
Dr. Bill Harris: It’s not bad.
Dr. Tom Brenna : So not a bad guide.
Dr. Kristina Harris Jackson: Good baseline, for sure.
Dr. Tom Brenna: I should also say that after we finished that project, we presented some of that and published that study. Despite all the experience that those researchers had, that all of us had in this world, we were actually surprised that the data were as positive as they were.
Dr. Bill Harris: Yeah.
Dr. Tom Brenna: We thought we might dig in through everything, find something. So we presented some of that stuff to the dietary guidelines. And we were really amazed at how the committee not only accepted much of what we said and that the data that they were handed also was consistent with what we said and they even went further in the recommendations.
Dr. Kristina Harris Jackson: Okay.
Dr. Tom Brenna: Now this was the advisory committee — not all of the recommendations made it into the Dietary Guidelines for Americans. But boy, we went a long way. And then, and then in the following year, the FDA’s job is then to update the advice to consumers from the Dietary Guidelines for Americans. Dietary Guidelines for Americans is more or less for professionals, even though it’s widely reported in the press.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: It’s more or less for registered dieticians and medical professionals. So the FDA updated the advice and we did a couple of listening sessions with them. And they were glad to listen to us, and they did, they did start to emphasize the positive. They started to emphasize in neurocognitive benefits of fish. They still had the mercury story, but they pushed it down low.
Dr. Bill Harris: Great.
Dr. Tom Brenna: I’d like to see them get rid of it.
Dr. Bill Harris: Right. Maybe that’s the next step.
Dr. Kristina Harris Jackson: Yeah.
Dr. Tom Brenna: Maybe next step, we’re making progress. You know, decade after decade, we’re making progress.
Dr. Bill Harris: Decade by decade, right.
Dr. Tom Brenna: I’ve been on the record saying that the danger about seafood and pregnancy is not eating enough, not eating enough seafood.
Dr. Kristina Harris Jackson: Yep.
Dr. Tom Brenna: The danger is not eating enough seafood. Mom should be eating seafood, if they don’t eat seafood that’s dangerous. Yeah.
Dr. Kristina Harris Jackson: Mm-hmm.
Dr. Tom Brenna: Avoiding it is dangerous.
Dr. Tom Brenna: I don’t think it’s productive or even accurate to make demons and say, “You know, there were some bad guys 20 years ago that were going in wrong direction. That’s why I think the abundance of caution view is accurate. I don’t think it’s unreasonable to think that EPA and the FDA said, “Hey, you know, there’s something to this mercury stuff. Maybe we should be careful about it.” But as you said, it kind of spiraled, and really scared women.
Dr. Bill Harris: Yeah.
Dr. Kristina Harris Jackson: Yeah. And it’s a very human story. It’s like when science bumps up into human nature, sometimes it’s not what was intended. The fear factor is really powerful, especially in pregnancy. And so the work that you guys have done to really show like, “This has been looked at, at the extremes, and the mercury in fish is not affecting your kids’ outcomes.”
Dr. Kristina Harris Jackson: It was really good to see how research and policy and all of this kind of comes together when you’re talking about the dietary guidelines and how it affects people’s lives. And so we’ve through like seafood nutrition partnership, been able to kind of see how this process has gone. And we thank you for this work. Hope it keeps going.
Dr. Tom Brenna: Mm-hmm.
Dr. Kristina Harris Jackson: And it’s a pretty major impact. It’s kind of hard to appreciate how big it could be. So thank you so much for joining us. We have a lot of other things we’d love to talk to you about. So maybe we’ll have to pull you back for a completely different topic. But thank you so much.
Dr. Tom Brenna: Always fun to speak with both of you.
Dr. Bill Harris: Great. Thank you, Tom.