Nuts and heart health

{***Pause/Music***}

{***Amie***}

Coming up on Harvard Chan: This Week in Health….Nuts and heart health.

{***Marta Guasch Soundbite***}

(We found that people who regularly eat nuts, including peanuts, walnuts, and tree nuts, have a lower risk of developing cardiovascular disease.)

In this week’s episode, a closer look at new research on the health benefits of nuts—including ways that you can include more in your diet.

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{***Amie***}

Hello and welcome to Harvard Chan: This Week in Health. It’s Thursday, December 7, 2017. I’m Amie Montemurro.

{***Noah***}

And I’m Noah Leavitt.

This week we’ll be looking at two new studies out of the Harvard Chan School.

Later in the episode—we’ll tell you about research examining the effectiveness of strategies to increase physical activity on a large scale.

{***Amie***}

But first—nuts and heart health.

In one of the largest studies to date about nuts, researchers found that eating several small servings of nuts each week may significantly lower your risk of heart attack or stroke.

{***Noah***}

Researchers analyzed data from more than 210,000 health professionals over as many as 32 years—and specifically looked at the effects of different kinds of nuts.

We spoke about the findings—including how many nuts you should be eating each week—with one of the study’s authors, Marta Guasch, a research fellow in the Department of Nutrition.

{***Amie***}

And just a note before we dive into this interview…you will hear us talking a lot about peanuts—which are technically a legume. But researchers say peanuts are nutritionally similar to other nuts.

{***Noah***}

And I began our interview with Marta Guasch by asking her what differentiates this study from previous research on nuts.

{***Marta Guasch Interview***}

MARTA GUASCH: Previous evidence has shown that the frequent nut consumption is associated with reduced risk of cardiovascular disease, and also cardiovascular risk factors, including type 2 diabetes, dyslipidemia, metabolic syndrome. But most of these previous prospective studies have focused on total nut consumption in relation to the risk of cardiovascular disease. So the effect of specific types of nuts, such as walnuts and peanuts and also peanut butter, with cardiovascular disease and specific types of cardiovascular disease, such as stroke or coronary heart disease, was unclear. So we thought that analyzing the effect of several types of nuts, including total nuts, peanuts, walnuts, and tree nuts, and the relation with cardiovascular disease, stroke, and myocardial infarction could be of particular interest.

NOAH LEAVITT: And so what were some of your key findings in that regard?

MARTA GUASCH: So, yeah, briefly, in the three large prospective cohort studies, with up to 32 years of follow-up, we found that people who regularly eat nuts, including peanuts, walnuts, and tree nuts, have a lower risk of developing cardiovascular disease, and also coronary heart disease, compared to people who never or almost never consume nuts. And we found a consistent inverse association with total nut consumption and total cardiovascular disease of 14% lower risk for those consuming five or more times per week of total nuts, and 20% lower risk of coronary heart disease. And also, we find the specific benefict for consuming walnuts one or more times per week, and also for peanuts and tree nuts, both for cardiovascular disease and coronary heart disease.

NOAH LEAVITT: So people who were eating more nuts had a lower risk of cardiovascular disease.

MARTA GUASCH: Yes. Exactly.

NOAH LEAVITT: And so you just touched on there, you know, one or more times a week. So when we talk about regular nut consumption, what types of quantities of consumption are we talking about?

MARTA GUASCH: So in our study for total nuts, we observed the greatest benefits for those people who consume a handful of nuts, which is equivalent to 28 grams, or one ounce, five or more times per week had the lowest risk of cardiovascular disease and coronary heart disease compared to those who never consume nuts. But we also observed the beneficial effects on those consuming two or four times per week of nuts.

And actually, when we evaluated the nut consumption as a continuous variable, which means that we show the effects for 28 grams increase in nuts consumption instead of the categories, we observed that each 28-gram increase in nut consumption was associated with 6% lower risk. So for peanuts and tree nuts, which are like specific types of nuts, consuming them at least two times per week, we observed a benefit. So probably, I’d say that consuming four to seven servings per week of nuts, of any types of nuts, in a context of a healthy diet would be a good amount of nuts to consume.

NOAH LEAVITT: And so you’ve got that kind of context of healthy diet, I’m sure people are sitting there thinking, OK, well, nuts are great, but they have a lot of calories or a lot of fat. So I guess could you put people at ease and say, you know, I guess kind of give some perspective in terms of including nuts as part of a healthy diet. You know, what is a healthy amount, and should we be concerned about weight gain or anything like that.

MARTA GUASCH: Yeah, that’s a good question. Despite nuts being an energy dense food and the belief that they can increase weight gain, there is no scientific evidence supporting the associations between weight gain and nut consumption. And indeed, there have been some results showing that nut consumption is associated with lower weight gain, or lower risk of obesity. And that’s probably because they can increase satiety and fullness. And this may potentially reduce the consumption of other unhealthy snacks.

NOAH LEAVITT: So kind of one of the additional benefits is that handful of nuts might make you a little more full, so maybe you’re less likely to go eat– chips are kind of a less healthy snack. So, you know, I’m in the supermarket, I see all the nuts in front of me– the almonds, the walnuts, the peanuts. I mean, are there any kind of nuts that you found were more beneficial than others?

MARTA GUASCH: Well actually, in our study, not really. We have observed benefits for total nuts, peanuts, tree nuts, and walnuts. They were all associated with lower risk of cardiovascular disease and coronary heart disease. And the intake of peanuts and walnuts was additionally associated with lower risk of stroke. However, what we observed was that peanut butter was not significantly associated with cardiovascular disease. This doesn’t mean that it’s harmful, it’s just that we didn’t observe an official association. So probably more studies on this line need to be done.

We believe that one of the reasons why we didn’t observe significant associations is because usually peanut butter is consumed with unhealthy foods, such as white bread or other processed foods with high amount of sugar. And this unhealthy pattern associated with the peanut butter consumption may have obscured some of the potential benefits of peanut butter.

NOAH LEAVITT: And so that’d kind of be a good piece of advice, too. I mean, people might see nuts, and they might see a trail mix filled with peanuts and candies. I mean, So it’s kind of important to– I guess maybe the important point is that, if you’re eating nuts, they should just be nuts on their own. I’m guessing unsalted nuts might be best.

MARTA GUASCH: Yeah, that’s really a good question. Actually, that’s one of probably our limitations of the study, because we were unable to differentiate between the type of nuts, so the preparation of nuts, just the total amount of nuts. But we believe that the consumption of raw or roasted nuts is beneficial for health, but if the nuts are covered in chocolate or have high amounts of sugar or high amounts of sodium, they are probably not as good.

NOAH LEAVITT: And so I know this was a really large study, I think 210,000 people. But as you just kind of hinted at, there are some limitations. So I guess what would be kind of further questions that you or other researchers would want to address with regards to nut consumption and cardiovascular disease?

MARTA GUASCH: So I think that one of the questions is understanding more of the mechanisms which explain these associations between nut consumption and cardiovascular disease, for example with novel techniques, such as metabolomics, genomics, or other techniques that can help us understand these underlying mechanisms. Also, another important thing could be to evaluate the differences among these preparation methods that we’ve just talked about, like the different types of nuts, and maybe also to further elucidate the effects of peanut butter on health could be another line that could be interesting, too.

NOAH LEAVITT: And so you just kind of hinted at mechanisms there. So I mean, do we know a lot about why nuts might be beneficial, or is that still not exactly clear?

MARTA GUASCH: I think that one of the main reasons why we believe that nuts can be beneficial for health are because they are high in unsaturated fatty acids, also dietary fiber, minerals, vitamins, and other bioactive compounds. And there’s some evidence that has shown that nuts can improve blood lipids, they can attenuate inflammation, they can be also beneficial for endothelial function and decreased insulin resistance or glucose intolerance. So all these mechanisms can explain the lower risk on cardiovascular disease that we have observed because they are strong risk factors of cardiovascular disease.

NOAH LEAVITT: How do these findings fit into larger nutritional advice, especially with regards to I think there’s now this awareness that healthy fat consumption is a good thing, but also maybe reduced consumption of animal proteins can be positive. So how do your findings fit into this kind of larger nutritional context?

MARTA GUASCH: Yeah. So recently, dietary recommendations have shifted towards diets including higher quantities of plant-based foods over animal foods, with most dietary patterns also including nuts because their association with reduced risk of cardiovascular disease and cardiovascular risk factors because of their unique nutritional composition. So nuts are a good source of healthy fats, including mono-unsaturated and poly-unsaturated fats, and they are also rich in plant-based protein, minerals and fiber. So they can really fit well into healthy diets that emphasize more plant-based foods, specifically because they can help and they can be a good source to substitute for animal foods, such as red meat or other processed meats.

NOAH LEAVITT: Is there any general advice for people looking to get more nuts into their diet, or is it as simple as just maybe keep a jar at work and just take a handful, you know, every day for a snack?

MARTA GUASCH: I think that several things can be done to increase the consumption of nuts. One may be just to use it as a snack, as a healthy snack in, like, the morning or the afternoon. Just a handful of nuts would be a healthy snack compared to eating other things. But they can be also included, like, in salads or with yogurt or with fruit as a way to increase the consumption.

{***Noah***}

That was our interview with Marta Guasch about nuts and heart health.

{***Amie***}

If you’re interested in learning more about her research—and the larger health benefits of nuts, we’ll have some information on our website, hsph.me/thisweekinhealth.

{***Noah***}

And now we shift gears from healthy eating—to another beneficial habit—physical activity.

{***Amie***}

The health benefits of exercise are well-known, but getting people to actually be active is much more of a challenge.

{***Masamitsu Kamada Soundbite***}

(Physical inactivity and a sedentary lifestyle remains highly prevalent globally. So, effective population strategies to promote physical activity are necessary to reduce the global burden of noncommunicable diseases, such as diabetes, cardiovascular diseases, and cancer, stemming from physical inactivity.

{***Amie***}

That’s Masamitsu Kamada, a research fellow in the Department of Social and Behavioral Sciences here at the Harvard Chan School.

{***Noah***}

Kamada and colleagues recently tested one strategy to promote physical activity on a large scale.

And their study was unique for a couple of reasons.

{***Amie***}

Kamada told us that most studies on physical activity interventions are not high-quality enough or long enough to effectively measure what works.

{***Noah***}

That might mean that the population being study isn’t large enough—or researchers weren’t able to follow participants long enough to measure the benefit of an intervention.

{***Amie***}

In this case Kamada and his colleagues conducted a five-year randomized trial of a community-wide intervention in Unnan City, Japan.

It’s a city of about 44,000 people—and more than 4,400 people were involved in the study.

{***Noah***}

They were testing a program that aimed to improve physical activity through social marketing—so informing and educating people about the benefits of physical activity through posters, news reports, and even the use of high-profile influencers.

{***Amie***}

The campaign focused on three types of activities: aerobic, flexibility, and muscle-strengthening.

Questionnaires were then sent to the participants one year, three years, and five years after the study began to measure their level of physical activity.

{***Noah***}

Overall researchers say this intervention was successful at promoting all three types of physical activity.

But the style of messaging was important—the campaign was most successful when it focused on a specific type of activity—as opposed to generally promoting all three.

{***Masamitsu Kamada Soundbite***}

(The intervention was effective for promoting all types of recommended physical activities. That is, aerobic, flexibility, and the muscle strengthening activities. But interestingly, a bundled approach– or in other words, an all-in-one approach– was not effective. This means we failed when we attempted to promote all types of physical activities simultaneously. So maybe the key message is one thing at one time. Dissemination of knowledge doesn’t assure dissemination of behavior. So we need more sophisticated strategies and approaches to change actual behavior or, in this case, physical activity.)

{***Noah***}

Researchers say another key takeaway is that one year was not enough to see an effect—which means that communities do need to invest in long-term interventions.

{***Amie***}

Kamada says that the intervention also does not address the other factors that can affect a person’s ability to be active—such as the built environment or social and psychological factors.

{***Noah***}

Kamada says more research is needed to develop a multi-disciplinary approach to address these factors.

{***Amie***}

That’s all for this week’s episode—a reminder that if you’d like to learn more about either of the studies we discussed in this episode, you can visit hsph.me/thisweekinhealth.

{***Noah***}

A reminder that you can always find older episodes of our podcast on iTunes, Stitcher, and Soundcloud.