November 29, 2013

Will eating nuts save your life?

One of the more eye-catching ways to promote a food or a medicine is to calculate the total reduction in deaths among those consuming the wonder product. 

Statistician Andrew Gelman blogs:
Jeff sent me an email with the above title and a link to a press release, “Nut consumption reduces risk of death,” which begins: 
According to the largest study of its kind, people who ate a daily handful of nuts were 20 percent less likely to die from any cause over a 30-year period than those who didn’t consume nuts . . . Their report, published in the New England Journal of Medicine, contains further good news: The regular nut-eaters were found to be more slender than those who didn’t eat nuts, a finding that should alleviate fears that eating a lot of nuts will lead to overweight. . . . 
For the new research, the scientists were able to tap databases from two well-known, ongoing observational studies that collect data on diet and other lifestyle factors and various health outcomes. The Nurses’ Health Study provided data on 76,464 women between 1980 and 2010, and the Health Professionals’ Follow-Up Study yielded data on 42,498 men from 1986 to 2010. . . . 
Sophisticated data analysis methods were used to rule out other factors that might have accounted for the mortality benefits. For example, the researchers found that individuals who ate more nuts were leaner, less likely to smoke, and more likely to exercise, use multivitamin supplements, consume more fruits and vegetables, and drink more alcohol. However, analysis was able to isolate the association between nuts and mortality independently of these other factors. . . . 
The authors noted that this large study cannot definitively prove cause and effect; nonetheless, the findings are strongly consistent with “a wealth of existing observational and clinical trial data to support health benefits of nut consumption on many chronic diseases.” . . . 
The study was supported by National Institutes of Health and a research grant from the International Tree Nut Council Nutrition Research & Education Foundation. 
The press release did not link to the study—what’s with that, anyway, how hard would it be to include a link???—but a quick google led to this article, “Association of nut consumption with total and cause-specific mortality,” by Ying Bao, Jiali Han, Frank Hu, Edward Giovannucci, Meir Stampfer, Walter Willett, and Charles Fuchs.

Similarly, back in the mid-1990s, my doctor said my cholesterol was too high so I should take a statin. An affable detail man had just given him a box of free Mevacor pills. (Mevacor had been the first statin on the market when introduced in 1987.) So my doctor gave me a fistful and wrote a prescription. But I looked up statins on the new-fangled Internet and found that the hot new statin was Lipitor, which went on to become the biggest moneymaking pill in the world in the 2000s.

The most striking Lipitor study was one from Scandinavia that showed that among middle-aged men over a 5-year-period, the test group who took Lipitor had a 30% lower overall death rate than the control group. Unlike the nuts study, this was an actual experiment.

That seemed awfully convincing, but now it just seems too good to be true. A lot of those middle-aged deaths that didn't happen to the Lipitor takers didn't have much of anything to do with long-term blood chemistry, but were things like not driving your Saab into a fjord. How does Lipitor make you a safer driver? 

I sort of presumed at the time that if they had taken out the noisy random deaths, that would have made the Lipitor Effect even more noticeable. But, of course, that's naive. The good folks at Pfizer would have made sure that calculation was tried, so I'm guessing that it came out in the opposite direction of the one I had assumed: the more types of death included, the better Lipitor looks. Apparently, guys who took Lipitor everyday for five years were also good about not driving into fjords and not playing golf during lighting storms and not getting shot by the rare jealous Nordic husband or whatever. Perhaps it was easier to stay in the control group than in the test group?

Here’s how I would approach claims of massive reductions in overall deaths from consuming some food or medicine:

Rank order the causes of death by how plausible it is that they are that they are linked to the food or medicine. For example:

1. Diabetes
2. Heart attacks
3. Strokes
4. Cancer
5. Genetic diseases
6. Car accidents
7. Drug overdoses
8. Homicides
9. Lightning strikes

If this nuts-save-your-life finding is valid, then the greater effects should be found in causes of death near the top of the list (e.g., diabetes). But if it turns out that eating nuts only slightly reduces your chances of death from diabetes but makes you vastly less likely to be struck by lighting, then we’ve probably gotten a selection effect in which nut eaters are more careful people in general and thus don’t play golf during thunderstorms, or whatever.

40 comments:

Anonymous said...

Walter Willett is the Eric Turkheimer of nutrition.

Anonymous said...

But if it turns out that eating nuts only slightly reduces your chances of death from diabetes but makes you vastly less likely to be struck by lighting, then we’ve probably gotten a selection effect in which nut eaters are more careful people in general and thus don’t play golf during thunderstorms, or whatever.

This might be the case. I like nuts, and I'll gladly eat them if they're around the house or if I'm visiting someone and they're available as snacks. But I've never regularly bought and consumed them. Maybe on road trips at rest stops I'll pick them up. But not normally. The people I do know who always buy and eat nuts tend to be health and exercise nuts. They go hiking a lot, buy lots of trail mix, etc.

Nuts have had a reputation of being healthy for a while, and of being the healthy snack option for people who exercise a lot and are always active. The people who eat them may be more healthy and active already. Fat people prefer chips to nuts.

Anonymous said...

If it is a nutritional effect why is it the same for peanuts as tree nuts ? Are they nutritionally that similar ?

AKAHorace

agnostic said...

My hunch is that nuts are a substitution for even more harmful snack foods with more starch and sugar, not that they're very healthy per se.

Why are they shaped, packaged, and put on display exactly like candy bars?

They're loaded with phytates, which bind to minerals and make them unavailable. Animals adapted to nuts produce phytase, the enzyme that undoes them (like amylase for starch-eaters), but human beings do not. Eating nuts is an easy way to become deficient in the minerals that phytates bind to.

A lot or most nuts are goitrogens too, things that interfere with thyroid functioning.

bobby said...

"But if it turns out that eating nuts . . . makes you vastly less likely to be struck by lighting . . . "

That's just common sense.

When I eat nuts, I tend to drop lots of them.

Which causes me to spend more time kneeling on the ground trying to find and pick up the dropped nuts.

The more time I spend kneeling on the ground, the lower my chance of being struck by lightening.

But there's a trade-off.

The more time I spend kneeling on the ground, the more transitory radon I inhale, which increases my chances of cancer.

So I made a six-foot-long snorkel which I breathe through as I creep along the ground picking up my nuts.

This reduced my radon exposure back to the low levels I had experienced while standing.

But, sadly, I had made my first snorkel out of metal pipe which, as I now understand, tends to attract lightening strikes.

I'm now considering just giving up nuts altogether when I get out of the hospital.

ironrailsironweights said...

Nuts are a chore to chew and swallow. People in very poor health may not be up to the task.

Peter

V said...

The paper's Table 3 is great at evaluating the list you have (though you have a lot of categories they don't have; everything after cancer probably got lumped into "Other Causes" or the specific place the genetic disease is from.

You can find some analysis here, but the basic finding is that nuts almost definitely reduce heart disease (sensible), probably reduce diabetes (hmm), definitely reduce cancer (for tree nuts mostly) and definitely reduce other causes (hmmmm).

So it looks to me something like healthiness -> nut eating -> heart disease, with a healthiness -> heart disease link also. You probably ought to eat tree nuts (which, in this study and others, are noticeably better than peanuts), but you shouldn't expect the full all-cause mortality reduction.

JayMan said...

I have covered this nut study over at my blog. Yes, the fundamental problem is that this is an observational study, and hence incapable of demonstrating causation by its very nature. Nuts are now the newest fad food based on nonsense correlational studies. See:

Nuts Over Nuts | JayMan's Blog

Readers might be interested in the one strong link to lifespan we have: IQ.

IQ and Death | JayMan's Blog

Anonymous said...

Nuts

Auntie Analogue said...


bobby: delightful comment you made (above). Thanks for the laugh!

And I must say that his study makes me feel much better about my youth in which I devoured bags and bags of BEER NUTS.

Anonymous said...

I wish they'd shut up about nuts, blueberries, and other foods. Every time they release stories like this, it causes a rush on said product which causes the price to shoot up. Nuts are already expensive, and this is not going to help.

aisaac said...

In medical trials the experimenters are supposed to prespecify the outcomes they're looking for - if you can just take data and mine it for correlations you can make any drug/procedure look good, and people who understand this stuff are well aware of that. Presumably the Scandinavian experiment you referred to had prespecified outcomes. Sometimes a drug will fail to meet its prespecified goal, and the company will mine the data for something that looks good, but savvy investors/regulators see through that.

bjdubbs said...

Willett is the guy who got MickeyD's to switch over to transfats, at great expense. The FDA just outlawed transfats. In other words, he is personally responsible for the public health equivalent of Pearl Harbor, except that he was leading the attack.

Orlando Gibbons said...

Jayman is right - in the field of nutrition, observational studies have a very poor track record in predicting the outcome of controlled experiments. The published results on cholesterol, dietary fiber, and salt are obvious examples. Medical epidemiologists think they can establish causation, but experiments continually prove them wrong; causation turns out to be more complex and counterintuitive than they think.

The brutal truth is that there is no way to know what causes heart disease, strokes or cancer, and almost nothing can be done to prevent them. As doctors could not reliably prevent infections prior to the germ theory of disease, so we cannot prevent strokes and heart attacks without a more complete understanding of physiology and the pathophysiology of chronic disease. But that truth is so terrifying that it is rarely uttered. Bogus science serves the same role as religion - to give people a sense of control amid daunting uncertainty.

In order to cure AIDS, cancer and chronic disease, the fundamental principles of animal physiology must first be fully understood. Medical science is guilty of major errors in this domain which have permeated every level of science education. Look up the work of Gerry Pollack and his lab at UW - he has several fascinating books which will shake your faith in the scientific process and the peer review system.

If you want to do something to cut your risk of heart disease and cancer, I offer one suggestion, at least if you're male: take aspirin. Experiments have found aspirin to protect against an incredible range of diseases. Nothing else comes close in terms of the extent or integrity of confirmatory evidence.

Anonymous said...

"lot of those middle-aged deaths that didn't happen to the Lipitor takers didn't have much of anything to do with long-term blood chemistry, but were things like not driving your Saab into a fjord. How does Lipitor make you a safer driver?"

Hev-eda, Hov-eda. (Bojrk, Borjk!)

DYork said...

A very high percentage of people will eventually die regardless of what they eat.

http://www.youtube.com/watch?v=gs4b3Fm5ymI&hd=1

Mangan said...

"The brutal truth is that there is no way to know what causes heart disease, strokes or cancer, and almost nothing can be done to prevent them."

Absolute nonsense.

David Davenport said...

Since peanuts are legumes, are P-nuts really nuts?

JI said...

Sounds like an approach ready made for Bayesian analysis. I think Pfizer should hire you, Steve, to come up with priors.

JayMan said...

@bjdubbs:

Yes, Willet is behind a lot of the dietary nonsense we've been given these days. Though trans fats are likely yet another boondoggle:

Trans Fat Hysteria and the Mystery of Heart Disease | JayMan's Blog

You think it'd be OK for McDonald's to go back to frying in beef fat.

The situation is very much as Orlando Gibbons describes.

rob said...


Blogger bobby said...

"But if it turns out that eating nuts . . . makes you vastly less likely to be struck by lighting . . . "

...causes me to spend more time kneeling on the ground trying to find and pick up the dropped nuts.

The more time I spend kneeling on the ground, the lower my chance of being struck by lightening.

But there's a trade-off.

The more time I spend kneeling on the ground, the more transitory radon I inhale, which increases my chances of cancer.

So I made a six-foot-long snorkel which I breathe through as I creep along the ground picking up my nuts.


Bobby, that is such a Rube Goldberg solution. I am moved to offer you a much more efficient strategy that works for me.

I keep my nuts in a sac. I call it a nutsack, and I always have them handy. They haven't fallen off yet!

Mr. Anon said...

"DYork said...

A very high percentage of people will eventually die regardless of what they eat.

http://www.youtube.com/watch?v=gs4b3Fm5ymI&hd=1"

Ah, the 70s - back when Woody Allen was funny.

"Everyone you knew is dead."

"How could they be dead? They all ate organic rice!"

Anonymous said...

The best ways to have a long live:

1) Live in a rich country

2) Come from a line of long-lived ancestors

3) Have parents who vaccinated you in childhood

4) Don't smoke

5) Eat reasonably

6) Move around a bit a few times a week

7) Drive with care


Everything else is incredibly expensive (on a population basis) for little gain.

Mr. Anon said...

Nuts, like berries, are expensive. So anyone routinely eating them is probably not among the poorest of people. Also, their health benefits are widely touted in newspaper and magazine articles. So whoever is eating them because they read good things about them is someone who reads.

That said, I can believe that there are tangible benefits to eating nuts - assuming you aren't allergic to them. They are a good source of protein and fat, and they fill you up without a lot of carbohydrates.

Anonymous said...

OT: Remind me again, why can't I donate directly thru Paypal?

I know, I know, it sucks, but it is still the most convenient way to transfer money to (business-wise) strangers.

Yeah, I can transfer money to ISteve in other ways, but it will take 2 minutes. I think that this site is missing out on a lot of potential donations.

Anonymous said...

"That said, I can believe that there are tangible benefits to eating nuts - assuming you aren't allergic to them. They are a good source of protein and fat, and they fill you up without a lot of carbohydrates"


Bacon is also a very good source of protein and fat. Surely, this cannot be the explanation for the health benefits of nuts, if any.

People who eat a lot of nuts everyday unforced are just -different. I eat nuts too, but not everyday, and usually in combination with alcohol.

Peanuts are not nuts in the botanical sense, so their inclusion in this study is puzzling.

Anonymous said...

Peanuts are not nuts in the botanical sense, so their inclusion in this study is puzzling.

Peanuts are fruits containing seeds, so they are nuts in the botanical sense.

Anonymous said...

"Peanuts are fruits containing seeds, so they are nuts in the botanical sense"

Nah.

With your definition, pears would be nuts.

Cashews (yum) are nuts. Walnuts are nuts. Acorns are nuts.

Peanuts are peas (well, legumes.)

Svigor said...

Nuts, like berries, are expensive. So anyone routinely eating them is probably not among the poorest of people.

Yeah, I heard about this on the radio the other day. The first thing I thought was, nuts are expensive, so I wondered if they controlled for wealth; people who can afford to eat a lot of nuts are more likely to be able to afford better health care, too. Then there's the correlation between wealth and intelligence; smart people take better care of themselves.

David said...

> Every time they release stories like this, it causes a rush on said product which causes the price to shoot up. <

I've heard Ec majors say higher demand causes falling prices just as often as I've heard them say it causes rising prices. For perfectly legible reasons, the average person's opinion of economics is that it's epitomized by the loud blur he glimpses on Asia Squawk Box while channel-surfing.

Similarly, I have heard people swear by and against nuts for years. If you live long enough in America, you will see literalIy every form of provender denounced and praised, in cycles. I eat cashews, almonds, and pine nuts because they taste good, and if someone has a problem with this or a theory about it, I don't give a damn.

Bobby, the snorkel's being metal is excellent.

Anonymous said...

Here is my experience eating commercially-available nuts:

Peanut: Not nut.Best eaten roasted in the shell. But it is not even a nut!

Walnuts: completely tasteless except for some vague woodiness. Just go gnaw on a tree.

Macadamia: Seriously, a treat with a frozen-wax texture? I better be in Hawaii.

Pecan: Throw them in a pie. In November. Or December.

Cashew: Yes! But I want heavily salted, and with a beer.

If the choice is between eating nuts or dying 5 years earlier, I choose death.

Anonymous said...

Dude, you are brilliant, but you always fall short when you try to criticize quantitative work. Even Andrew Gelman, who knows what he is doing, comes up with real zingers when criticizing the work of others. Just saying.

David said...

You are what you eat.

Mr. Anon said...

"Anonymous said...

Bacon is also a very good source of protein and fat. Surely, this cannot be the explanation for the health benefits of nuts, if any."

But you ignore the fact that bacon also contains nitrites - cured meats contain a lot of compounds which are probably carcinogens. It's a shame, as they are tasty. However there is nothing wrong with dietary fats, in and of themselves. I have no problem believing that nuts - assuming you are not allergic to them (in which case they are obviously NOT good for you) - are indeed rather good for you.

Mr. Anon said...

"David said...

I've heard Ec majors say higher demand causes falling prices just as often as I've heard them say it causes rising prices."

Maybe Econ majors should study other things besides Econ - like Botony. Nut trees take many years to mature. Even if growers planted more trees in response to higher demand, it would take years for them to produce saleable nuts. Economists think that thier laws supercede physical reality. They don't.

Anonymous said...

Do boiled peanuts count? Because I eat like two cans of those a day.

toomanyspiders said...

It's long been known, or at least stated, that people who regularly eat nuts are slimmer on average, which seems counterintuitive because nuts have a lot of calories-- about 180 calories per 1/4 cup, and nut butters have 100 calories per tbs (the average p&j sandwich probably has 3 tbs of peanut butter). Nuts, though, have a high satiety factor and will suppress appetite which I'd guess is the main reason they keep weight down, if they indeed do. My own experience has borne this out; I eat 2-3 full servings of nuts a day (about 400-600 calories) and I'm very thin. So I'll take the good nut news about longevity.

Matthew said...

"My hunch is that nuts are a substitution for even more harmful snack foods with more starch and sugar, not that they're very healthy per se"

I wonder if this is the case with a lot of "health foods" - it's not that they're especially healthy, but that they're replacing the worse alternatives. If you're eating lots of broccoli, perhaps what's saving your life isn't what's in the broccoli, but the fact that you aren't eating sugar/fat-laden alternatives.

Two known facts suggests this might be the case:

1) The benefits of caloric restriction on longevity.

2) The failure to find any long-term benefits from consumption of multivitamins.

Healthy eating may be more about what you don't eat than what you do eat. The real health benefit from eating broccoli is that it leaves less room for Oreos.

One key to eating healthy is to stay ahead of your hunger. Once your body gets hungry you're more likely to go for junk food, which provides quick energy. Eat fruits, vegetables, and high fiber grains when you're half-hungry and you'll never get to that point.

Matthew said...

"Macadamia: Seriously, a treat with a frozen-wax texture? I better be in Hawaii."

Are you kidding me? Chocolate covered macadamia nuts and white chocolate chip & macadamia nut cookies will be served in Heaven at every meal.

Anonymous said...

"The best ways to have a long live:

1) Live in a rich country

2) Come from a line of long-lived ancestors

3) Have parents who vaccinated you in childhood

4) Don't smoke

5) Eat reasonably

6) Move around a bit a few times a week

7) Drive with care"


Add to that 8) Adequate rest.