IRA FLATOW, HOST:
This is SCIENCE FRIDAY. I'm Ira Flatow. A growing body of evidence has been hinting that nuts - nuts - are good for us. The popular Mediterranean diet emphasizes nuts but, you know, most Americans only eat nuts on occasion. And I'm talking about, oh, that's less than once a week, except for me. I eat them every day, but that's another story.
A recent study published in New England Journal of Medicine gives a new meaning to the phrase health nut. It showed an association - this is really interesting - an association between regularly eating nuts, and a reduction in your risk of death from a major chronic disease. That's it. Just a handful of nuts, and you can decrease your chances of dying from heart disease, cancer and other diseases.
How is it that nuts affect our health? Should we be putting more nuts into our diet? As I say, I'm a pistachio and toasted almonds fan, so I eat them. Let's get to the story. Charles Fuchs is author of that report. He's also director of the Gastrointestinal Center at the Dana-Farber Cancer Institute, in Boston. Welcome to SCIENCE FRIDAY.
CHARLES FUCHS: Thank you for inviting me.
FLATOW: Now, this is really a very close correlation that you found, correct?
FUCHS: Yeah. It's an impressive result, but it is not without some prior information from other studies suggesting the benefits of nuts.
FLATOW: Tell us what - give us what the correlation is that you found.
FUCHS: Well, what we found is that among these 118,000 individuals followed over 30 years, those who had nuts seven or more times per week had a 20 percent reduction in dying from any cause.
FLATOW: Twenty percent is an awful lot in medicine, is it not?
FUCHS: It's considerable, yes.
FLATOW: And were they all kinds of nuts, or specialty nuts, or what?
FUCHS: We - it's all kinds of nuts. We really didn't see a difference in the nut types. And it actually includes peanuts, which as you technically know, is actually a legume. So if you look at all tree nuts and peanuts, they seem, in our study, to perform similarly.
FLATOW: Hmm. And if you just eat a small amount, can you get some benefit? You know, like Americans are only eating nuts once a week. Is there some benefit there, or do you need to eat nuts every day?
FUCHS: Well, you know, if we look at people who eat it, for instance, once a day - I mean, once a week rather, there is a modest benefit. But there's clearly a dose response - namely, more is better - up into the point of essentially, once a day. But even the folks who had it two to four times per week seemed to have a modest benefit.
FLATOW: You know, as you say - and as I mentioned - there has been a growing body of evidence over the years, has there not been?
FUCHS: Absolutely. And a number of studies previously have shown that people who eat nuts have a reduced risk of heart disease, a reduced risk of Type II diabetes - that is, standard adult-onset diabetes. Some have suggested lower risk of selected cancers. And more recently, some studies have said that there's less obesity in frequent nut eaters.
FLATOW: But yet, there would seem to be some contradiction in people's minds because nuts are high in fat, aren't they?
FUCHS: They are, but they're high in the better fats, namely monounsaturated fats, so that, you know, we think that the variety of substances in nuts - which is a complex food - have health benefits.
FLATOW: Talking with Charles Fuchs, author of a report that's talked about eating nuts; 1-800-989-8255 is our number. Do we know what the mechanism might be for how this works?
FUCHS: We don't, and it's an important question that we're committed to sorting out. If you look at sort of the variety of benefits that nuts offer, it makes you believe - particularly realizing that the nut eaters tend to be leaner, they tend not to get diabetes and not get heart disease or selected cancers. It makes you wonder whether nuts have some effect on metabolism in a very positive way, which may explain that despite the fact that nuts - a serving of nuts is 160 calories, and people eating it once a day don't seem to get heavier. If anything, they're leaner.
FLATOW: Yeah, and as you say, the benefit runs across all kinds of nuts because this study you quoted about diabetes, I'm looking at an article here from April of this year, said walnuts for diabetes, eating walnuts may reduce the risk for Type II diabetes in women.
FUCHS: Yes. And, in fact, a lot of the earlier studies focused principally on walnuts and obviously, those more selected studies are very informative. But at least in this larger study that we just completed, it's not clear to us that walnuts are a superior nut. As I say, it seems to be a class effect.
FLATOW: Mm-hmm. And difference between men and women? Any difference?
FUCHS: Not really. In fact, when we look at subgroups across these 118,000 people, there seems to be a fairly similar benefit between men and women, older and younger, people who are lean or obese, people who smoke or don't smoke. So across all the things we think about, how we define risk factors for mortality, the benefit is relatively consistent.
FLATOW: Wow. Let's go to the phones, 1-800-989-8255. Nathan, San Jose, welcome.
NATHAN: Hi, yeah. I had a quick question. I have a vegetarian diet, and I eat a lot of nuts and other healthy fats from avocados and things. Just wondering: How much is too much?
FUCHS: That's a great question. And our study really looked up to a maximum of seven or more times per week, realizing that a serving is 1 ounce. And so, you know, I'd say that if you want to focus on results strictly, you say essentially once a day of a 1-ounce serving. Because some have questioned, looked at the data and said, well, if you really go overboard, you might actually get weight gain associated with nuts.
As I say, we don't see that at once a day. These folks are leaner. But I'd say once a day of a 1-ounce serving appears to be the maximum benefit.
FLATOW: Do you know anybody who can eat just 1 ounce of nuts?
FUCHS: Well, you know, people don't realize, 1 ounce is actually not an unreasonable portion. It's about 24 almonds in an ounce. So it's a reasonable number - 18 cashews. So I think it's enough to feel relatively satisfied.
FLATOW: Mm-hmm. And why do you think that the United States has such has such a low consumption of nuts compared to other countries?
FUCHS: Yeah, I think it's cultural, as you point out. The Mediterranean diet is often associated with a relatively high nut consumption; and our study last year, in the New England Journal of Medicine, showed that people who consume a Mediterranean diet with nuts have a lower risk of heart disease, and that same study has only recently reported out even a lower mortality.
So I think it's cultural. And you're absolutely right, namely in our study of Americans, we find that only about 2 1/2 percent of the population were consuming nuts once a day.
FLATOW: Wow. And part of your research was funded by the International Tree Nut Council Nutrition Research and Education Foundation. That didn't affect...
FUCHS: That's right. I mean, the large - the vast majority of the funding for our cohort was actually through the National Institutes of Health, because these folks were followed over three decades. But we also applied to this non-profit foundation for an additional supplement for the analytics. But they had really - well, not - they explicitly had nothing to with the conduct of the study, and we never conferred with them.
FLATOW: Now, can you actually go - now, you have a sample, large sample of people. Can you now analyze what's in their blood to find out how this is working?
FUCHS: We can. We actually have blood specimens on a large subset of these individuals. So we're absolutely committed to saying, OK, among frequent versus rare nut consumers, what goes on in the blood across metabolic pathways, across pathways of inflammation, other things that promote cancer and heart disease and diabetes? So we really do understand what the mechanism is, because you're absolutely right.
It's incumbent on us to understand why this happens, because not only does it tell you how we could leverage this further, but hopefully maybe even further address the causality, because as you pointed out earlier, it's an association, and we want to really drive home that it's real.
FLATOW: Could it also be that people who eat nuts eat healthier?
FUCHS: It's an absolutely good point, and to some extent, yes. And so one might question, well, maybe it's just that the nut eaters are doing lots of other healthy things, and it has nothing to do with nuts. Now, we measured a litany of other health practices in these 118,000 people, and we find that the effect of nuts is independent of all those other practices. So it really does seem to be - at least in our analysis - principally related to nuts.
FLATOW: Wow. Now we're going out to buy some nuts for the holiday. And as you say, it doesn't matter which kind that you get?
FUCHS: That's right.
FLATOW: Choose whatever you like.
FUCHS: Absolutely. It seems to be a class effect, and, you know, I think, you know, people ought to be circumspect about it. But if you look across the compendium of literature, we're not the first. We may be the largest study to find this, but we're not the first.
FLATOW: All right, Dr. Fuchs. Thank you very much.
FUCHS: Well, thank you.
FLATOW: That's good news for the holidays. Charles Fuchs is a author on that report, and he's also director of the gastrointestinal center at the Dana-Farber Cancer Institute in Boston, Mass. Happy holiday to you.
FUCHS: Same to you. Go nuts.
FLATOW: Go nuts. Transcript provided by NPR, Copyright NPR.