Study: Red Meat May Increase Risk for Breast Cancer

According to a new study from scientists at Harvard University, eating red meat may lead to an increased risk for breast cancer. The research was published Monday in the Archives of Internal Medicine.

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LYNN NEARY, host:

This is TALK OF THE NATION. I'm Lynn Neary in Washington.

Today, there's new information about risk factors for breast cancer. According to a study from scientists at Harvard University, eating red meat may lead to an increased risk for the disease. The research was published yesterday in the Archives of Internal Medicine, and is no doubt of great interest to women.

Breast cancer is one of the diseases women fear most. But sorting through all the research on risk factors can be difficult. If you have a question of this new research or other risk factors for breast cancer, give us a call at 1-800-989-TALK.

And joining us now is Dr. Deborah Armstrong. She is an associate professor of oncology, gynecology and obstetrics at Johns Hopkins University in Baltimore. And she joins us now from the studios of WYPR in Baltimore. Thanks so much for being with us.

Dr. DEBORAH ARMSTRONG (Oncology, Gynecology and Obstetrics, Johns Hopkins University): You're welcome, Lynn.

NEARY: Now, tell us about this new study. How did the researchers collect their findings?

Dr. ARMSTRONG: Well, this is actually part of a very longstanding study - the Nurses' Health Study II - and actually that's the second part of the Nurses' Health Study. In these studies, nurses every two years fill out fairly detailed information, including dietary information and sometimes send in specimens of toenails and hair. And it's considered very reliable data.

This is a group of women who are very motivated to do the reports. And they, over time, also report any diseases or medical illnesses that they have. So the unique aspects of this study are: number one, that it's prospective, meaning that it's not going back in time and looking at what happened, but it's actually taking women as they go along in time and looking at health effects.

The second is that it's actually looking at a fairly young group of women when we're talking about looking at risk factors for breast cancer. These women were between 26 and 46 when they started doing the questionnaires. And it looked at a specific subtype of breast cancer in this group of patients.

And that's - in particular, the hormone receptor positive breast cancers, which is responsible for a little over half of the breast cancers that we see. And so it was a fairly unique study in the realm of these large dietary and other risk factor studies.

NEARY: Well, can you just tell us specifically what - how big a risk factor is eating red meat? I mean, how does somebody sort this out? I mean, everybody eats red meat, you know - a lot of people do, should they be concerned? Should anyone who eats red meat - any woman who eats red meat be concerned?

Dr. ARMSTRONG: Well, I think the first thing is that number one, there's been a very large number of studies over the past years that have not clearly correlated red meat consumption with breast cancer risk. I think that's the first thing. But, in particular, because they looked at a specific subgroup of women - younger women - and a specific subgroup of cancers, that may explain why this study shows a positive correlation with increasing red meat consumption compared to those other studies.

And what they did was they basically quantified women. Did they eat three or fewer servings of red meat a week? Did they eat somewhere four to five? More than five? Or more than one and a half servings of red meat a day? And they really quantified those into basically five groups and they looked at the breast cancer risk in those groups.

And what they really found was, you know, if you look at kind of a linear progression of risk across those groups, there's a pretty clear cut increase in the risk of breast cancer across that increasing use of red meat.

NEARY: So that - I think so the message is cut out red meat? Is that the message?

Dr. ARMSTRONG: Well, I don't know that it necessarily means cut out red meat. I think like most dietary issues, it's probably not quite as simple as that. I think the issue with red meat is that it's not like it's a medication that you need to take, and if you don't take it there's going to be some negative health effects.

So what I think almost all the studies have persistently shown is that variety is important, not having one type of food that you eat constantly. But I think certainly from this study it would suggest that women should take in three or fewer servings of red meat a week if they are concerned about their risk of breast cancer.

NEARY: All right. Let's take a call now from Jim in Cleveland, Ohio.

JIM (Caller): Yes. Can you hear me?

NEARY: Yes, go ahead.

JIM: Yes. I'm wondering about the link just between animal protein and cancer. That's - you know, studies have been done years ago, and a book like The China Study, you know, covers that quite extensively. And I'm wondering what your take is, you know, on that.

Dr. ARMSTRONG: I think that's actually a good question. You know, one of the reasons that these researchers did this study was because they had previously looked not at meat per se, but they had looked at fat intake. And what they found was that the total fat intake did not appear to be associated with an increased risk of breast cancer. But increased animal fat uptake, which obviously, depending on the type of meat you eat, you will get more or less animal fat.

And that really prompted to do this study. You know, one of the issues when you look at animal protein intake is that if woman, or if anybody, takes in less animal protein, they're usually taking in more of something else, and that may be, for example, plant-based proteins or it may be vegetables. And maybe there's a positive health effect from taking in more of those.

And so it's sometimes hard to say is it really decreasing eating less red meat, or is the fact that when you eat less red meat you may eat more of other things that have a positive health benefit. And I think those remain a little bit difficult to tease out.

NEARY: All right. Thanks for your call, Jim.

JIM: Okay, thank you.

NEARY: Now this risk factor joins a list of other risk factors that have been known about for some time. First, maybe you could remind us what the other risk factors are, and how does this fit in with them? How does a woman make a decision about what's the most serious one for her?

Dr. ARMSTRONG: Sure. Well, first is that breast cancer is a disease of aging; and as women get older, their risk of breast cancer goes up. Family history also definitely contributes to breast cancer risk. There are some genes that people can inherit that put them at very high risk. That's not responsible for a lot of breast cancer, but it's responsible for probably somewhere around 5 to 10 percent of breast cancer.

Most of the other risk factors appear to be pretty clearly hormonal risk factors. And what they basically have shown is sort of the longer you are exposed to the normal female hormones that are produced by the - normally produced by the ovaries, the higher the risk of breast cancer.

So starting your menses early in life, going through menopause later in life, essentially extending the period of hormonal exposure by taking hormone-replacement therapy at menopause, are risk factors. And in fact it may be that these dietary issues really are indirect measures of hormonal exposure.

One of the things that we know is that when meat is well cooked, that some of the compounds that formed actually stimulate hormone production in women. So really this may be another form of a hormonal risk for breast cancer.

NEARY: Interesting. All right. We're going to take another call now from Lisa(ph) in San Francisco. Hi, Lisa.

LISA (Caller): Yes, hello.

NEARY: Go ahead.

LISA: My sister was diagnosed two weeks ago with breast cancer.

NEARY: Oh, I'm sorry. How is she doing?

LISA: She's doing all right, she is. But my question to you is if you could just speak a little bit more about family history. You did just speak about it.

NEARY: Sure.

LISA: And you said that it has to do with 5 to 10 percent. I'm not terribly articulate.

NEARY: That's okay.

LISA: (unintelligible) take a second.

Dr. ARMSTRONG: Well, Lisa, you sound young. How old is your sister?

LISA: Well, I'm 45, and my sister is 48 years old, and…

Dr. ARMSTRONG: The things that we know about, Lisa, about familial breast cancer are usually that there will be early onset breast cancer, and we consider below the age of 50 early onset.

LISA: Okay.

Dr. ARMSTRONG: There will usually be multiple cases in the family that span multiple generations, but in small families you might not see that.

LISA: Right.

Dr. ARMSTRONG: There's also an association with ovarian cancer. So if there's ovarian cancer in the family, that might prompt concern about this. And it's also associated with male breast cancer, which I think, as most of us know, men don't get breast cancer very often. But when there's male breast cancer in a family with early-onset breast cancer in women, it's one of those red flags.

And what one can do is you can - a patient who may be in a family like this can actually see a genetic counselor and consider testing for some of the genes that we know put people at risk, and these can be done by a blood test. And this is most effective when the person who's been diagnosed with cancer is the person who gets testing first.

So at some point in time - I mean, your sister has many things that she has to think about right now.

LISA: Yes.

Dr. ARMSTRONG: But at some point in time in the next few months, that may be something that her physicians would recommend to her. And then that information can potentially be useful to you and to other family members.

NEARY: Okay, thanks…

LISA: Could I also just ask - is there a book, a pretty definitive book that you could recommend off the top of your head, just sort of a beginning point, because there's so much information out there and it's really overwhelming.

Dr. ARMSTRONG: One of the issues with books about medical care is that books become pretty obsolete pretty quickly. By the time it's published, frequently the data is not particularly good. Nancy Brinker, who founded the Susan G. Komen Foundation, has written a book that kind of talks about a variety of issues, including families with breast cancer, her experience with breast cancer. And I think that's a very helpful book.

Susan Love has also written a book that really has a very kind of broad discussion about breast cancer, including risk and screening and treatments. And I think those are two good places where you might potentially start.

LISA: Thank you very much for speaking with me today.

Dr. ARMSTRONG: Good luck, Lisa.

NEARY: Good luck, Lisa.

LISA: Okay.

NEARY: Thanks for your call. All right, we're going to take another call now. We're going to go to Darden(ph), and she's calling from Ohio. Darden, go ahead.

DARDEN (Caller): Hi, yes. My question is years ago, there was some question about the link between breast cancer and birth control. And I have a 15-year-old daughter who has irregular periods and they're recommending to put her on birth control, and I don't know what the latest research is along those lines.

Dr. ARMSTRONG: That's actually - it's an excellent question. What we know about birth control pills, which actually the way birth control pills work is they mimic being pregnant and so they suppress ovulation. And what happens for women who take birth control pills is there's a very, very small increase in the risk of breast cancer while women are taking the pill.

Now most women who are taking birth control pills are not at an age where they're at very high risk. So what we call the attributable risk, meaning the fraction of breast cancer that can be attributed to the use of oral contraceptive, is very, very small. And in a teenage girl, I think if she - if there are other medical reasons why it was being recommended, I would not be particularly concerned about breast cancer risk.

DARDEN: Okay, thank you very much.

Dr. ARMSTRONG: Good luck.

NEARY: We are talking with Dr. Deborah Armstrong about risk factors for breast cancer. If you'd like to talk with Dr. Armstrong, give us a call at 989-8255. And you're listening to TALK OF THE NATION from NPR News.

You know, it's so hard, Dr. Armstrong, for people to sort through these risk factors, and I wonder if you have any advice about that.

Dr. ARMSTRONG: Well, I think it's hard for all of us who are trying to look at the field. I think one of the issues that we certainly recognize is that, first of all, you know, the milieu that we look at for people today is very different from what it was 20 years ago or 100 years ago. We can say that about diet, we can say that about exercise, we can say that about reproductive factors. And so it sometimes is very hard to know, you know, what of the many, many things that have changed over the decades is the thing that we can sort of put our finger on.

I think the biggest issue is, you know, what are the things that we can put our finger on that we can do something about? You know, we can't do something about, for example, our family history, and most of us are not going to make decisions about having children based on breast cancer risk. But for - this study, for example, provides us with some information that women who want to be proactive, that there is something potentially that they can do that, frankly, really doesn't have much of a downside: By reducing the amount of red meat that you eat in your diet, that you may have a positive impact and reduce your risk of breast cancer.

NEARY: All right, let's take a call now from Brianna(ph) in…

BRIANNA (Caller): Hi.

NEARY: Hi.

BRIANNA: I'm a new mom. And having been to La Leche League meetings and finding out all these wonderful things about continuing to nurse your baby, I was wondering if there has been any research on length of time that women do nurse their children versus an increased risk of breast cancer, either for themselves or for their children.

Dr. ARMSTRONG: Well, the question about children becomes even more complicated, and that one's a difficult one. What we do know is that breast-feeding and increased duration of breast-feeding has a small effect on breast cancer risk, but it's a positive one.

One of the issues in the United States, though, is that when we're talking about long-duration breast-feeding, we're usually talking about on the order of months. And this is quite different than women, for example, in the developing world, where very commonly they might nurse their children for years. It may be the main source of nutrition for a young child. So it's quite different for the United States than it is in other areas of the world.

NEARY: All right, we're going to see if we're going to get one more phone call in here. Let's go to Diana(ph), and she is in Ithaca, New York. Hi, Diana.

DIANA (Caller): Hello.

NEARY: Go ahead.

DIANA: Hi. I'm a naturopathic doctor and a certified midwife, and I'm specially trained in a program called the Healthy Breast Program for breast cancer prevention. And I live in an intentional community, and we do organic farming. And I'm wondering if you looked at the quality of the meat, being that the pesticides in the feed and the hormones that are given to the animals can affect the quality of the meat and also increase the risk of breast cancer, as well as the quality; it changes the amount of omega-3 fatty acids in ratio with arachidonic acid, which is pro-inflammatory.

Dr. ARMSTRONG: I think that's an excellent question, and the authors of the study were very quick to point out that they could not sort of tease out those kinds of issues. They basically clumped red meat - they did look at some sub-group analyses of, you know, more processed meats like, you know, sausages and bacon, but they really could not tease out the data on more organic types of meat.

You know, we think that potentially this red meat exposure is a hormonal factor. And is that because the meat does something to change the normal hormone production in a woman, or is that because of hormones that could be in the meat? And this study unfortunately doesn't answer that question. But I think it actually remains something that people are very actively investigating.

NEARY: So more research is going to be done on this link.

Dr. ARMSTRONG: Absolutely.

NEARY: And you mentioned something about bacon and sausage. Are there some kinds of meat that are worse than others?

Dr. ARMSTRONG: You know, they were not able to find any clear-cut correlation between the types of red meat items and the risk factors.

NEARY: All right. Well, thanks so much for being with us today, Dr. Armstrong.

Dr. ARMSTRONG: It was my pleasure.

NEARY: Dr. Deborah Armstrong is an associate professor of oncology, gynecology and obstetrics at Johns Hopkins University in Baltimore. This is TALK OF THE NATION from NPR News. I'm Lynn Neary.

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