Wednesday, March 14, 2012

What Reading that Red Meat and Die Study Actually Told Me

According to the authors, their study was undertaken because prior studies demonstrating risk to red meat consumption were flawed. Some had utilized populations that weren't representative of the average, while others didn't differentiate between unprocessed and processed meats, and where others still had covariates assessed at baseline only.

Here the authors analyzed 28 and 22 years of data respectively (2.96 million person years) from the Nurses Health Study and the Healthy Professionals Follow Up Study involving 37,698 men and 83,644 women who were free of cardiovascular disease and cancer at baseline, and whose diets were assessed by 7 sequential (every 2-4 years) validated food frequency questionnaires. Given dietary recall difficulties, undoubtedly the questionnaires are from from perfect, however unlike the vast majority of other food/risk studies that utilize them (there's not a huge amount of choice but to do so), the data from the questionnaires here were adjusted using the correlation coefficients that separate and published validity analyses (here and here) of their own specific study population's food frequency questionnaires determined were required to at least try to account for their subjects' dietary recall inaccuracies.

The authors also controlled for the following potentially confounding variables:
  • Age
  • Body mass index
  • Ethnicity (though this was weak, white or non white were the only two choices)
  • Smoking status (never, past, current with current being subdivided into 3 quantities)
  • Alcohol intake (4 gradations)
  • Physical activity level (5 gradations)
  • Multivitamin use
  • Aspirin use
  • Family history of diabetes
  • Family history of myocardial infarction
  • Family history of cancer
  • Baseline history of diabetes
  • Baseline history of hypertension
  • Baseline history of hypercholesterolemia
  • Menopausal status
  • Menopausal hormone use
  • Total caloric intake
  • Quintiles of fish consumption
  • Quintiles of poultry consumption
  • Quintiles of nut consumption
  • Quintiles of legume consumption
  • Quintiles of dairy consumption
  • Quintiles of dietary glycemic load
  • Quintiles of dietary cereal fiber consumption
  • Quintiles of dietary magnesium consumption
  • Quintiles of dietary polyunsatured fat consumption
  • Quintiles of dietary trans-fat consumption
Further, they performed a whole bunch of beyond my pay scale statistics when exploring red meat specifically (eg "restricted cubic spline regressions with 4 knots").

When analyzing the data they discovered that men and women with higher intakes of red meat were less likely to be physically active and were more likely to be current smokers, to drink alcohol, to have a higher body mass index, to consume greater total amounts of calories and to have lower intakes of whole grains, fruits and vegetables, but even after controlling for all of those confounders, unprocessed and processed red meat consumption were found to be associated with an increased risk of total mortality, cardiovascular mortality and cancer mortality.

So are you going to die if you eat red meat?

Well you're going to die regardless of what you eat, but this study would suggest that you'll die ever so slightly younger if you eat red meat each and every day of the week, and even younger still if you eat processed red meat each and every day of the week. Did you catch the caveat of each and every day of the week? It certainly wasn't hidden in the study.

So how much younger will you die? According to the study, eat unprocessed red meat daily and your risk of death will be 13% higher than if you don't. Eat processed meat daily and it'll be 20% higher. Those of course are relative risks. In absolute terms your risk of dying younger due to red or processed meat consumption doesn't amount to a huge number, nor do the study authors sensationalize their paper to suggest that it does. The media (and perhaps the study's press release - haven't seen it) did that. But that doesn't change the finding that this study did indeed determine there to be more risk associated to red meat consumption than other protein sources.

As to what it is about red meat that's seems to confer risk? We don't know. Meta-analyses on saturated fat would suggest that ain't it, and that's good news for us butter lovers, but again, that doesn't change this study's findings.

All in all this is a strong study in that there's an incredible wealth of data along with tremendous confounder controls and considerations. We'll never have perfect studies regarding foods and risks because we'll never randomize folks to long term diets differing in single variables and so studies like this one - long term, huge numbers, confounder controlled, thoughtfully considered - are the best we're going to get, and while I'm sure there are variables some axe grinders will wish were included, or analyses they'd love to have seen, to me at least it seems they included all the big ticket issues, and some smaller ticket ones for good measure.

If there's criticism to be had it's in the study's reporting, where the distinction of eating red or processed meat daily is lost in the hype, and where the reporting leaves readers thinking they can never safely enjoy a burger, a steak or a hot dog.

That's certainly not what the study or its authors said. In fact one of the authors, Harvard's Frank Hu stated,
"A moderate consumption, for example one serving every other day, I think is fine."
While the study's lead author An Pan told the LA Times whose headline ran, "All Red Meat is Bad For You" that he eats two servings of red meat a week.

And this isn't really news. Basically the study's take home message is that proteins come in both healthy and unhealthy packaging.

And that's where my Internet confusion comes in. Just as ridiculous as the all encompassing, "All Meat is Bad" chant that came from the mass media was the, "this study is terrible" chant of the Internet, a chant generally coming from those same people who will readily agree that there are less and more healthful carbohydrates (and fats). Seems to me a careful read of the paper would have perhaps toned down both the media's reporting and the Internet's rhetoric, whereas relying on press releases and newspaper reports, well that fuels misinformation, and apparently in this case, what comes off like frank anger.

I adore red meat. I also adore processed red meat. But ultimately this study just adds more weight to what the bulk of the literature has already concluded - processed and unprocessed red meats aren't my best protein choices and if consumed daily, carry risks, albeit absolutely small ones, that other protein sources seemingly don't.

Now maybe my read of the paper is off, and admittedly my stats days are long behind me so please feel free after actually reading the paper to weigh in if you think I've missed something, but for me, for now, yes, burgers are still on my menu this weekend (Mmmmmm, burgers), they're just not on it every day this week.

Pan, A., Sun, Q., Bernstein, A., Schulze, M., Manson, J., Stampfer, M., Willett, W., & Hu, F. (2012). Red Meat Consumption and Mortality: Results From 2 Prospective Cohort Studies Archives of Internal Medicine DOI: 10.1001/archinternmed.2011.2287

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26 comments:

  1. Sounds to me like it's a wash, unless you REALLY eat a lot of red meat. I wonder, just out of curiosity, if the slight negative effects of eating red meat would still be there if the study was done on people who only eat, say, grass-fed beef and bison? I don't suppose there are many people who have ONLY eaten those kinds of red meat throughout their lives, so it might be impossible to do.

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    1. Hi Jennifer,

      I'd be willing to wager that in North America there's a huge number of people eating red and/or processed meat daily for whom this message would in fact be important.

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    2. I had the same thought. There's a huge quality difference between conventionally raised cows and grass-fed, organic cows. It makes sense to have a slightly increased mortality rate if you're consuming many more hormones/anti-biotics than you should be. Just a thought!

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    3. Very few people can afford to eat grass-fed beef or bison every day, and those who can probably wouldn't want to. People who eat that type of super-expensive meat it once or twice a week at most, and usually in small quantities.

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    4. As Michael Pollan would say, pay more and eat less. Hopefully greater demand will keep bringing the price down. The nutritional content of grass fed beef is very different from that of industrial cattle (omega 3 fatty acid content, for instance). The Maasai in Africa had very little heart disease eating meat every day before sugar and processed flour showed up.

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    5. Sorry, but the Maasai business makes me a bit buggy.

      Their life expectancy was between 42-45 years old, and they spent their entire day wandering and hunting (aka exercising).

      Go figure they didn't develop heart disease. They were tremendously fit and died too young to get it.

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  2. I think one message that gets lost in these studies is the potential increase in morbidity - diseases that may occur and decrease the quality of life. I would prefer to live a healthy life without health complications but die younger.

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  3. Nice review! I think an important "take-home" message from the study is that it's important to consider what you're getting along with the protein you're eating - e.g., some alternatives have fiber (legumes) & potentially protective compounds (fatty fish=omega 3's; plant proteins=phytochemicals). The study found that people who replaced one serving of red meat with alternative sources of protein decreased their risks of premature death. Choosing chicken and other poultry decreased the risk by 14 percent, fish decreased the risks by 7 percent and legumes decreased the risk by 10 percent.

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  4. I'm glad you wrote about this today. The overly dramatic headlines and tweets were driving me crazy yesterday! Who eats red meat every day? Not that many people I know. The big question I have is would you have the same risk eating organic, grass-fed beef vs eating the grocery store cuts that may come from cows treated with hormones and antibiotics? Does the TYPE of beef matter?

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  5. I was particularly interested in the characteristics of the quintiles - they found that the more red meat/processed meat people ate, the more likely they were to have a higher BMI, lower physical activity levels, lower fruit, veg, whole grain consumption, etc. After controlling for all THAT, red meat consumption still conferred a risk, but I'm guessing the cumulative risk of all the factors is much higher and red meat consumption is just one of many lifestyle habits one could change.

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  6. Anonymous9:27 am

    I appreciate your adding a "voice of reason" to the hype that is out there.

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  7. A person has to die from something sometime. It doesn't have to be heart disease, cancer, or some other non-communicable disease. It can be old age. However, given the quality of our modern industrialized food supply, most of us are destined to expire early either from the side effects of drugs that are supposed to prolong life or from the ravages of disease itself.

    But why settle for a 13 to 20 percent risk reduction (whatever that means) when the prospect of dying from a non-communicable disease can be nearly eliminated. How does a person do this? Rather simple. Restrict added sugars and omega-6 industrial seed oil consumption, eat high quality whole foods, avoid consuming significant amounts of foods that don't contain supportive nutrition, and choose foods that support your peculiar metabolic make up. This last measure requires some experimentation.

    Likely, the problem with red meat is not the red meat itself but rather lack of some other dietary element or elements required to process it. For example, in rat experiments where the animals were fed a high-fat diet, scientists reported problems for the animals only when the remainder of the diet was deficient in protein and micro nutrients. Here's an excerpt from pages 81-82 of "Nutrition Against Disease" by Roger J. Williams, PhD (1972).

    Rats have been used extensively to study the effects of diet on atherosclerosis. Under ordinary dietary conditions the inclusion of saturated fats in their diet will consistently promote the deposition of cholesterol in their arteries.(50) For 285 days rats were fed a diet containing 61.6 percent animal fat, but highly superior with respect to protein, mineral, and vitamin content, without producing any pathological changes in the aorta or in the heart.(51) The animals did, to be sure, become obese, as much as three to four times their normal weight. Animals fed vegetable fats at the same level fared essentially no better and no worse. These findings were based upon extensive long-term experiments at Yale, using a total of 600 rats, which were observed for as long as two years. There were no findings suggestive that either high animal fat diets or high vegetable fat diets were conducive under these conditions to atherosclerosis.
    These animals represented an extreme condition, since 81 percent of their energy came from fats. Their diets otherwise were extremely good. The protein was of high quality (casin) and was kept at a high level (20 percent); the vitamin levels were double those ordinarily used in this laboratory. The Yale findings were corroborated almost a decade later (1965) at Tufts University School of Medicine.(52)

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  8. References and notes:

    50. Thomas, W.A., and Hartroft, W.S. “Myocardial infarction in rats fed diets containing high fat, cholesterol, thiouracil, and sodium cholate.” Circulation, 19:65, 1959; Taylor, C. B., et al. “Fatal myocardial infarction in rhesus monkeys with diet-induced hyper-cholesterolemia.” Circulation, 20;975, 1959.
    In the above experiments, the investigators found that prolonged feeding of butter or lard to rats resulted in hyperlipemia and finally coronary thrombosis and myocardial infarction with lesions similar to those found in human beings. The diets of these animals were regarded as otherwise “normal” in respect to their intake of supplementary vitamins, minerals, and amino acids. Other data, however (see reference note 52 below) demonstrate that when fat and cholesterol (or animal protein) are increased in the diet, certain nutrients (particularly pyridoxine) must be increased above “average” or “normal” requirements.

    51. Barboriak, J.J., et al. “Influence of high-fat diets on growth and development of obesity in the albino rat.” J. Nutr., 64: 241, 1958.

    52. Naimi, S., et al. “Cardiovascular lesions, blood lipids, coagulation and fibrinolysis in butter-induced obesity in the rat.” J. Nutr., 86:325, 1965.
    In this more recent study, Naimi and his colleagues were directly interested in the effects of a high fat butter-induced obesity on the cardiovascular system of seventeen male Wistar albino rats. Butter constituted 65 percent of the total calories, with 20 percent protein (casin) and generous vitamin and mineral supplements equal to if not superior to those used in the above-mentioned Yale study.
    Under the conditions of their experiment, these investigators found that a high fat butter diet causing obesity in rats did not produce changes in blood cholesterol nor result in cardiovascular lesions, as other data had led them to expect. The authors note, “The absence of such adverse changes, despite, the development of gross obesity in these animals may be significant, since both obesity and animal fats have been considered to be associated with lipemia and vascular lesions. It may be suggested that other dietary factors might have protected the experimental group against such changes. Yet, even if this happens to be the case, it should not detract from the significance of the fact that large amounts of saturated fat and obesity are not necessarily associated with lipemia and vascular lesions.”
    We are confident that other dietary factors did protect these rats, and that only in the absence of sufficient supportive nutrients are obesity and high fat and high cholesterol diets associated with atherosclerosis and heart disease in the human population.

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    1. Thank you for sharing this information. My mama was right when she told us to eat our veggies!

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  9. Anonymous1:39 pm

    I feel dumb today because I'm having a hard time figuring out what counts as "processed red meat." Are we talking deli meat and beef jerky, or something much more common?

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    1. It's not a dumb question.

      In the study "processed" meant: bacon, hot dogs, sausage, salami bologna and other processed red meats (where both deli and jerky would likely quality)

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    2. Anonymous5:17 pm

      Thanks. I never thought of those as red meat; I assumed hot dogs, bacon and sausage were all pork based.

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    3. Pork is considered red meat. But yeah. The first thing that came to my mind was beef, and the first thing that came to my mind thinking about processed red meat was ground beef. I figured the difference was caused by the high saturated fat content. I guess that's not what was meant by it, though.

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    4. Anonymous1:00 pm

      But isn't pork called "the other white meat?"

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    5. Anonymous:

      "The other white meat" was a marketing ploy developed by the National Pork Board in the eighties. They were trying to portray pork as healthier meat product than beef.

      In reality however it is a "red" meat.

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  10. nazgulnarsil2:34 pm

    I have to disagree about emphasizing "each and every day" so much. Yes it is the indication of the study, but the linear dose-response indicates that half a serving a day on average is probably half as bad.

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  11. Those that eat a lot of red meat also do a lot of unhealthy things as shown by this. But how do you know that red meat is the contributor when it could be the other factors.

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    1. Here is some intelligent discussion on that: http://www.marksdailyapple.com/will-eating-red-meat-kill-you/#axzz1p71ow9R7

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  12. Michelle, the Fat Nutritionist, really lays into it here, if anyone's interested.

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  13. The questionnaire used by participants in this study (isn't it really more a "survey"?) is an issue itself (you can see it as a pdf at http://www.channing.harvard.edu/nhs/questionnaires/pdfs/NHSI/2002.PDF)

    Example: it asks respondents how many servings of "pizza, 2 slices" they have eaten with what frequency within the time period (two to four years) since the last survey. Okay...well, is that two tiny slices of plain cheese from little frozen supermarket pizza made in the toaster oven at home or is that two slices, each as big as a sheet of 8.5x11 paper, covered in extra cheese and layered with sausage and pepperoni? There is NO CONTROL in studies such as this; it is completely an observational study that relies on the memories, truthfulness and accuracy of the respondents. It asks how many one-ounce servings of cream cheese were eaten...do you think all 120,000 participants measure and weigh everything they eat and eat only that amount in the anticipation that food x may be asked about on a survey 24 months in the future? Eating a six ounce serving of grilled top sirloin once a week is a lot different than chowing down a footlong steak and cheese sandwich every day.

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  14. Anonymous6:22 pm

    This is a bunch of bull, probably funded by the meat industry, Has anybody read the China Study ? or John Robbins ? This probably won't get published, cause it's the truth.

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