Here we go again with the latest “Meat Kills!” study.  You may have already seen it reported in the news with headlines like Vegetarians cut heart disease risk. Here are some quotes from that article:

Vegetarians are nearly a third less likely than meat-eaters to die or be hospitalized from heart disease, British researchers report this week in another study supporting a plant-based diet.

Vegetarians have lower blood pressure and cholesterol levels, weigh less and are less likely to have diabetes, as well, the researchers report in the American Journal of Clinical Nutrition.

The study, which covers 45,000 people over an average of 11 years from the 1990s through 2009, shows that vegetarians were 28 percent less likely to develop heart disease over that time.

Well, that’s it, then.  Drop the burger, pick up the tofu meat substitute, and save your heart.

Nawww, let’s read on:

“The results clearly show that the risk of heart disease in vegetarians is about a third lower than in comparable non-vegetarians,” said Tim Key, deputy director of the Cancer Epidemiology Unit at the University of Oxford.

The researchers said they accounted for age, smoking, drinking, exercise, educational level and socioeconomic background in making their calculations. Over the 11 or so years, 1,235 of the volunteers were diagnosed with heart disease, and 169 died of heart disease – the No. 1 cause of death in both Europe and the United States.

In the disclosures section of the full study, Tim Key (quoted above) is listed as a member of the Vegetarian Society, United Kingdom.  That makes me a wee bit suspicious … although Chris Gardner of Stanford is also a vegetarian, and he conducted the clinical trial of four different diets that found the Atkins dieters lost the most weight and showed the greatest improvements in their cardiovascular risk factors.  Dr. Key isn’t necessarily biased just because he promotes vegetarian diets.

So let’s look at this particular study and ask ourselves some Science For Smart People questions:

Q: Is this a clinical study or an observational study?

A: It’s an observational study based on questionnaires and medical records.  We can’t make conclusions about cause and effect from observational studies, but at least in this case the researchers aren’t asking the study subjects to accurately remember everything they ate during the past several years.  Most people can surely give an accurate answer to the question “Have you been a vegetarian for at least the past five years?”

That being said, comparisons of vegetarians versus non-vegetarians are always likely to produce skewed results for the simple reason that vegetarians tend to be more health-conscious than the population as a whole.  That means they’re different in all kinds of ways.  Not eating meat is just one of them.

Q: Did the researchers control their variables?

A: Not really, no.  In the full text of the study, the researchers admit that the participants are not a representative sample of the British adult population.  In fact, both the vegetarians and non-vegetarians in the study population had lower-than-usual rates of heart disease.  Then there’s this little issue:

Risk factors such as hypertension, hyperlipidemia, and diabetes may be mediating factors through which vegetarianism affects the risk of IHD; therefore, the analyses were not adjusted for these variables.

In other words, since we believe meat-eating causes hypertension, hyperlipidemia and diabetes, we didn’t adjust for any of them.  When I read that sentence, I scoured the study to see if rates of diabetes were reported.  Yup … and the non-vegetarians (let’s just call them meat-eaters from here on) had more than double the rate of diabetes.

Now … since diabetics are three times more likely to die of heart disease than non-diabetics, do you think maybe we have a confounding variable here?  If you believe eating meat causes diabetes (as the vegetarian researcher probably does), then yes, you could choose to ignore that as a variable.  But if you believe diabetes is caused by excess sugar consumption, you can’t.

Since clinical studies have shown that low-carb, meaty diets can control and often reverse diabetes, I seriously doubt eating meat causes diabetes.  So what we’re likely seeing here is that the vegetarians consume less sugar than the meat-eaters – once again, comparing health-conscious people to the population as a whole.

Then there’s the age problem.  Here’s the breakdown of the study participants with their average ages at the time they were enrolled:

6,831 non-vegetarian men, average age = 49.5
22,610 non-vegetarian women, average age = 46.3

3,771 vegetarian men, average age = 41.8
11,349 vegetarian women, average age = 38.4

With a little Excel magic, I determined that the overall average age of the meat-eaters at the beginning of the study was 47 years old.  The overall average age of the vegetarians at the beginning of the study was 39 years old.

The researchers compared their medical records 11 years later.  At that point, the average meat-eater was 58 years old and the average vegetarian was 50 years old.  Now take a look at the chart below, which shows CDC figures on heart-disease deaths rates by age bracket.

The heart-disease death rate in the 55-64 year-old-bracket is more than double the rate in the 45-54 year-old-bracket.  The meat-eaters were far more likely to fall into the age group where the rate of heart-disease death more than doubles.

Ahhh, but the researchers assured us they adjusted the data for age, gender, BMI and smoking status.  Perhaps, but I have my doubts.  Those “adjustments” are where a lot of mathematical manipulations occur, as Dr. John Ioannidis has pointed out in his criticisms of observational studies.

Here’s part of the reason I have my doubts:  in the study, the researchers made this statement:

On the basis of the absolute rates of hospitalization or death from IHD, the cumulative probability of IHD between ages 50 and 70 y was 6.8% for nonvegetarians compared with 4.6% for vegetarians.

“Absolute rates” means no adjustment for age or anything else.  And yet the meat-eaters, who fall into the 55-64 age group on average, had a heart-disease rate of 6.8%, while the vegetarians, who fall into the 45-54 age group on average, had a heart-disease rate of 4.6%.

Hmmm … the CDC chart shows heart-disease deaths more than doubling as we move from one age bracket to the next (an increase of 131%), yet our older meat-eaters were just 32% more likely to have heart disease than their younger vegetarian counterparts, according to the study.  Something doesn’t feel right here.  Given the difference in average age, the difference in death rates in the non-adjusted data ought to be more dramatic.

Oh, but wait … if you read the study, the researchers weren’t comparing death rates.  They were comparing a diagnosis of heart disease – a combination of deaths chalked up to heart disease and heart-related problems such as angina.  In fact, of their 1,235 medical data points, just 169 were actual heart-disease deaths.  Which leads me to our next question:

Q: Is there any important data that seems to be missing?

A: Oh, you betcha.  The researchers had medical records for diagnoses of heart-related problems, they had medical records for heart-disease deaths, they knew who was and wasn’t a vegetarian, and they dutifully reported the differences in all heart-related problems combined for meat-eaters versus vegetarians … and yet stunningly, they didn’t report the difference in death rates – not for heart-disease deaths, and not for deaths from any cause.

Never fear.  This isn’t the first time these researchers dug into the data they collected for the purpose of publishing a paper.  Here’s the conclusion from another study using the same dataset titled Mortality Among British Vegetarians:

The mortality of both the vegetarians and the nonvegetarians in this study is low compared with national rates. Within the study, mortality from circulatory diseases and all causes is not significantly different between vegetarians and meat eaters, but the study is not large enough to exclude small or moderate differences for specific causes of death, and more research on this topic is required.

In other words, We’d like more funding so we can keep torturing the data until it tells us that eating meat will kill you.

Go enjoy your steak.

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41 Responses to “The Latest “Meat Kills!” Study”
  1. Glen Nagy says:

    Great breakdown of the study Tom. Can you post a link to the study, I haven’t been able to find it.

    The abstract is available online:

    http://ajcn.nutrition.org/content/early/2013/01/30/ajcn.112.044073.abstract

    I received the full study from someone in academia.

  2. Kristin says:

    Well heck. Seems like I’ve become a fangirl if I’m the first to post a comment to this article. I think one of the takeaways I have from this article is how easy it is to blind yourself with your own bias (well, unless it was deliberate and I’m not going there.) This is a great analysis. I’ve read some studies and I’m also a computer programmer (and therefore can do math better than teenage Barbie) and I get my knickers in a twist at the language.

    So I have a lot of respect for you digging through the data to present a coherent analysis for those of us who didn’t take all that time. As a programmer with a day job and know how much work that is I just have to ask: has your work with Fathead, this blog and all your speaking engagements allowed you to retire from cutting code for a living or are you just that driven?

    Nope, still coding for a living. I wrote the post at the office after work, then drove home after 9:00. Chareva was just finished cooking up a steak when I got home. There goes my 54-year-old heart.

  3. Darren Doyle says:

    Thanks for the analysis! This is what popped into my head as I was reading… It’s likely that this is some spurious math, and the numbers are not really direct comparisons (hospitalizations/deaths from IHB vs overall deaths) … I welcome corrections…

    GIVEN:
    Meaties: 55-64 age bracket = 6.8% probability of IHD
    Veggies: 45-54 age bracket = 4.6% probability of IHD

    General Populace: 45-54 age bracket = 85.4 deaths per thousand
    General Populace: 55-64 age bracket = 198.0 deaths per thousand

    85.4 –> 198.0 = 232% increase
    198.0 –> 85.4 = 57% decrease

    SO…
    4.6% increased 232% = 10.672% for veggies compared to 6.8% for meaties
    OR
    6.8% decreased 57% = 2.924% for meaties compared to 4.6% for veggies

    BOTTOM LINE:
    When you age adjust, the veggies have a 57% higher cumulative probability of IHD.

    Yup, something doesn’t pass the smell test here.

  4. Beowulf says:

    I’m so glad you jumped on this one. When I read the news article today, I put on my Science for Smart People hat (the one that has padding in the forehead region) and did some thinking, but I didn’t get quite all of the issues you pointed out. It’ll be a nice link to send anyone who brings up the study. Thanks!

    Thanks for reading.

  5. Marilyn says:

    A headline like “Vegetarians Cut Heart Disease Risk” could just as well mean that vegetarians reduced heart disease risk among their own group.

  6. Anne Robertson says:

    Another confounder could be that many people call themselves vegetarians while still eating fish.

  7. Jan C says:

    Just a couple of other points to add to the pot here. I’m actually taking part in that EPIC study. I joined it at the start because the researchers were advertising for vegetarians in the Vegetarian magazine here in the UK. I was very interested in vegetarianism at the time and followed a largely vegetarian diet (but with fish) for many years. For some years we ate no meat at all.

    I can’t remember what was filled in for the first questionnaire, but there have been two subsequently, I think. They require you to fill in a food diary for one week, which I faithfully did each day, so it was certainly more accurate than not. Having said that, both times I filled in the diary they weren’t ‘typical’ weeks, for one reason or another, so I had to make a note in the comments section.

    I remember when the researchers were looking for people to take part, they were particuarly interested in getting more vegetarians. Those people who are interested enough to buy the Vegetarian magazine (published by the Vegetarian Society), and who would have responded because of that, would be very health-conscious, eating lots of fresh vegetables and aiming for low-fat meals and being more inclined to cook from scratch – I certainly have never bought ready-made meals. Other vegetarians might just elminate meat and eat soya-based and other ‘fake’ vegetarian foods in its place, but they may not have been the ones taking part. So this could also be an important aspect of the research. The vegetarians taking part may not necessarily be representative of all vegetarians.

    Incidentally, I’ve recently increased my meat consumption dramatically.

    Considering that the vegetarians they recruited tend to be more motivated and health-conscious, the fact that they don’t have a lower overall mortality rate speaks volumes.

  8. JasonG says:

    I believe we Average Joes are smart enough to use logical reasoning to navigate BS articles and science. Your always entertaining analysis exactly guides us how to spot creative facts. Thank you, Tom.

    My new English 102 teacher frightens me because he teaches with the mantra, “Respect me because my PhD grants me expertise.” For a research paper, we are required to find only “scholarly” sources which are peer-reviewed, published by academic institutions, and written by highly-credentialed authors.
    We are told that our thesis and paper cannot have an opposing viewpoint, since “there is only one-side to a fact.” Doesn’t he realize that those institutions can use the peer review system to silence opposing views? Is it impossible for those authors to be biased? Doesn’t sound logic trump perceived authority?

    Unfortunately in schools, many teachers don’t want students to think. The goal is to train an obedient populous. This is particularly interesting since my class focuses on gay, lesbian, bisexual, and transgender studies. The class encourages tolerance. What happened in recent history when these same academic institutions usually held an anti-gay sentiment? Back then, searching for scholarly sources would have given a completely different opinion. Only because the status quo was challenged, did the schools change their standing.

    Bottom line is we can think for ourselves. People need to think critically and trust their own judgement instead of having unquestioning faith in popular experts.

    “the refusal to think–not blindness, but the refusal to see” –Ayn Rand.

    There’s only one side on these issues? That’s one scary teacher.

  9. Taysha says:

    One thing that really gets to me is the Diabetes angle here. I’m T1. ALL I hear from my doctors is how I’m doomed to all these horrible outcomes because the research tells them so and I should just get on all these drugs to prevent them.
    Except that I’m actually pretty healthy (very overweight, but there was this one thing about having kids and having to push insulin by the vial for 9 months so they’d be healthy….yeah).
    What they don’t tell you, is the research usually doesn’t look much at compliant diabetics (who have few complications and don’t fit clinical trials) but looks at non-compliant diabetics, or undertreated diabetics (the ones who get told “you’ll be fine if your blood sugar averages 180″), who are the majority. So, of course, even if they adjust for conditions like diabetes, they usually tend to make the crucial mistake of not discriminating between compliant and non-compliant. And the difference is huge.
    So they could just as easily be seeing an effect of compliance with diabetes treatment as the effect of a steak. Takes a heck of a lot more discipline to be a healthy diabetic than a vegetarian.

  10. eddie watts says:

    VEGETARIANS CUT HEART DISEASE RISK!

    by eating meat…

  11. Adam says:

    Good work. The biggest issue I have with any comparitive analysis such as this is that there is no control on what either group eats other than the fact that they eat meat (or not). One person’s diet might be preformed soy infused chicken nuggets washed down with a supersized Coke-Cola three times a week while the other might be a nice slab of grass fed prime rib with ice water and mixed greens. No doubt the study was junk science at its best.

    Good work Tom I enjoy your posts!

    They reported on intakes of fruits, vegetables and whole grains, but there was nothing about sugar. Since sugar could well be the most damaging food we put in our bodies, that’s a huge oversight.

  12. Jason says:

    Great job Tom! I’m a huge fan here in Australia. My wife lost 20 kilos since watching FATHEAD and ditching the carbs. We’ve never felt better.

    The female newsreader I heard sounded so smug as she reported this study – as if it were fact – not some pointless observational study.

    Now we’re the ones who feel smug when people tell us we should be eating those “heart-healthy” whole grains and not all that “artery-clogging” saturated fat!

    I feel sorry for the herd who believe the mainstream media.

    Keep up the good work.

    Most media health reporters lack either the ability or the motivation to analyze studies and see if they’re actually meaningful.

  13. Phyllis Mueller says:

    Thanks for this timely analysis. I also found it interesting that the authors are cancer researchers, but I didn’t see anything in their analysis about cancer deaths in the two groups. Did the full study mention this?

    Was the term “vegetarian” defined? (Many people who call themselves “vegetarians” are frequent fish eaters, for example.)

    The age-group analysis is the most telling. If nothing else kills you first, heart problems will eventually. That’s an inconvenient truth that gets ignored, particularly by “wear red” campaigns for raise heart disease “awareness,” the American Heart Association, and research studies such as this one.

    They defined “vegetarian” as someone who claims to have avoided meat and fish for at least five years. They didn’t cover cancer in this report, but did in another one. In that study, vegetarians had slightly lower rates of cancer overall (again, probably less sugar in the diet) but actually had higher rates of colon cancer. So much for “meat causes colon cancer.”

  14. Firebird says:

    Davey Jones, I’d like to have a word with you on this article. You’re a vegetarian, what are your thoughts on heart disease and heart attacks…wait a minute…

    To quote another dead singer, “Don’t be cruel …”

    Funny, though.

  15. darMA says:

    I’m so glad you’ve been addressing vegetarian/vegan studies and issues recently because it ties in with what I was watching last night – a very scary but informative video about B12 deficiency, ie, signs, symptoms, red flags, related health problems and the disastrous results if gone untreated. It includes interviews with doctors, researchers and victims, including a pediatrician who was near death until he was finally diagnosed and a vegetarian family’s beautiful little boy who is permanently brain damaged. It’s about 53 minutes long but is riveting and important for (I think) everyone to see because everyone is at risk of it being overlooked or misdiagnosed.

    http://www.youtube.com/watch?v=BvEizypoyO0&feature=youtu.be

  16. Stephanie says:

    I always love your study breakdowns!

    On another note, I know I’m a bit late, but I’m just finishing Lierre Keith’s “The Vegetarian Myth.” Excellent book. I almost feel like giving a copy to all my vegetarian friends, but I know they wouldn’t read it and they would look at me like I’m a crazy person. Everybody knows that a vegetarian diet is the healthiest/most ethical/doubleplusbest way to to eat. Right, right !?!?

    I’d wager that would be a “you can lead a horse to water …” situation.

  17. Lori says:

    Maybe the adjusted heart disease rates for vegetarians was higher because they generally eat less protein than meat eaters. With insufficient protein, the body digests its own muscle.

  18. Eric says:

    As an aside, I’m sporting my new Wheat Is Murder shirt in the office today :-)

    I’ll bet that draws a few looks.

  19. TonyNZ says:

    Are you getting smarter or are these studies getting dumber?

    And in regard to JasonG’s post, this sounds like eugenics of the academic literature.

    Sadly, I don’t think it’s a case of me getting smarter.

  20. Brian Edwards says:

    I am curious about including the Southeast Asians who eat a vegetarian diet in America. It is well know they have high rates of metabolic syndrome and subsequent cardiovascular disease. Interesting analysis Tom.

  21. What jumped out at me is that the vegans weigh less.
    That is a confounding co-variable.
    They matched the two groups for age but not for weight?
    They claim cholesterol is less in Vegans. To not specifically talk about comparing LDL-P or apo B, they show they don’t understand the lipid profile.
    Read Understanding the Entire Lipid profile Thomas Dayspring MD, FACP at https://docs.google.com/document/d/1OLlPcLWorU7cSq8fJh8CXuzYVR_85w_SoHgoRdl6kKk/edit

    They claimed they adjusted for BMI.

  22. Larry says:

    I usually sent your blog to my Kindle to read. The Kindle is B/W only. It would be helpful if you would indent quoted text.

  23. Ulfric M Douglas says:

    I’d just like to point something out :
    FISH = MEAT

    Now, are there any studies which actually study vegetarians?

  24. labrat says:

    I always like to reverse the numbers in these studies. Truth is regardless of what you eat after 11 years 99% of you will still be alive! A little perspective is always a good thing.

    I also like to point out that nearly 100% of the people who died in the past 10 years ate carrots and broccoli at some point in their lives.

  25. Archie Robertson says:

    I’m afraid there is a little misspelling in the name of the famous Greek researcher: it’s not Dr. John Ionnidis but Dr. John Ioannidis (or Dr John P. A. Ioannidis, to give his full handle!).
    Sorry to nit-pick, but “Google oblige”!

    Nit-pick away. I’d rather get the man’s name right, thanks.

  26. Graybull says:

    Great Job……once again. My question is this……….

    As an analysis of a longer larger study about Cancer and Nutrition…….why the headlines about heart disease? Could it be that their own cancer – nutrition for vegetarians versus meat eaters may have not come out the way they desired….so better to massage data and make headlines with something else?

    Can you tell that I am a tad cynical?

    If you’re not cynical, you’re not paying attention.

  27. Dave Mayo says:

    Great breakdown, I’m going to post this to my facebook group.

  28. Marilyn says:

    I sometimes find all these heart disease scare tactics to be a little hollow. As I look back at my relatives who have died, in most cases, those who died of heart problems got the better deal.

    I hope to live to a ripe old age, but when the time comes, I’d rather die of a sudden heart attack than fade slowly from cancer or Alzheimer’s.

  29. Galina L. says:

    There is a new trend about vegans. They offer you to watch long and annoying videos. Some of vegan-wackos made insane amount of videos which are impossible to watch and especially to listen, fortunately, there is a written text, which is still super-annoying to read.
    http://www.plantpositive.com/
    I realized, it is necessary to stop being polite when it comes to vegan propaganda. Why not to declare, sorry, but my mind is closed to certain things , period.

    I don’t watch their videos or read their articles anymore either. It’s always the same old cherry-picked, observational nonsense.

  30. gollum says:

    I’ve basically given up on these “studies”, but you need to give them a break:

    Weight is not external, it’s related to something they have been trying to measure. That’s what I’d call Anti-controlling.
    Weight is not independent of age, so you would control for the same influence twice.
    Anti-controlling is even worse than noncontrolling, because you can actually reverse the causality. It works like this:
    You “control” for basically what you are trying to measure and the remainder are dreck effects.

    Case in point, you “study” LC and anticontrol for weight and blood sugar (and if that doesn’t suffice, for a lot of other parameters too). You will negate all the benificial effects of LC and the remainder will be the freak cases where you have something like kidneys at 5 % or familial young-artery-clogging which are made worse by LC.
    Same thing, indirectly, if you make people sign up for study and throw them out if they have diabetes, which could be helped by LC.
    This is not fantasy, I think I have seen this in at least one “study”, I think it was vegetarians too (nurses?) and they threw out diabetes cases at the start – but I don’t remember well.

    It’s pretty surprising that the non-vegetarian diabetes rate is so high. That either means selection bias on overdrive or meat causes diabetes. (I think total mortality was low enough not to eliminate heart-disease-in-the-making.)
    Apart from total mortality I’d really like to see figures for those who refused dairy and eggs, too.

  31. Great, Tom!
    One more thing about true vegetarians, they eat a lot of carbohydrate poor vegetables (usually less than 5 % carbohydrates) and amino acid deficient proteins together with a lot of oils (aioli, mayonnaise) which means they are eating LCLPHO (Low Carb, Low Protein, High Oil) diet.

    So they get too little of essential amino acids, too much of cancer causing omega-6 containing oils. And on top of that, they get too little minerals and vitamins as the veggies have 1-1 000 times less minerals and vitamins than meat and animal fat.
    Cows are having grass for 20 h/day to get enough nutrients. We just have to use a couple of hours per day to prepare our meat that contains all the nutrients the cow so carefully collected for us in exactly the right proportions. We must be thankful to the cow that is doing all the work for us so we can enjoy a lot of leisure time.

    I’ve had vegan zealots inform me that gorillas are big and strong and only eat plants. I replied that gorillas spend most of their non-sleeping time foraging and chewing. I’ve got better things to do with my time.

  32. sapphirepaw says:

    I saw someone “reporting” on this study :(

    It went something like “Study finds MEAT KILLS. This should make people vegetarian! There’s a huge opportunity for faux meat vendors, a market worth X billion pounds annually in the UK. Lots of people buy faux meat! Once again, veggies are healthy, skip the real meat.”

    I might not have noticed except I’ve read your whole blog, including the part about spotting bias. So, double thanks.

    Thanks for reading.

  33. Christopher says:

    Fun Fact: Morningstar Farms Vegeterian “Chick’n” nuggets have 59 ingredients. Chicken McNuggets have like 20-25 ingredients.

  34. Bret says:

    I feel like I should begin a catalog of bogus studies like this and include the names of both the participating researchers and the journalists who delivered the articles/TV segments in the media. After 20 or 30 years, when the public has finally managed to wake up on these issues (I hate to be pessimistic, but I think it will take at least that long), we can all point and laugh and bestow on those people their due disgrace for promulgating so much flagrant misinformation for so many years.

    I enjoy mocking “studies” like this one, but I get pissed off simultaneously, because I know that they are only reinforcing incorrect information in the majority of people who read them. Most people don’t know what we know, and they don’t have a clue about how science works–so they stand no chance of penetrating the poor science and sloppy reporting and discovering just how rampant the b.s. runs. Now it’s gotten to the point where most people think the issues are already understood and the answers already known–but only because this nonsense has been shoved in their faces time and again, not because anyone’s made a compelling case.

    A friend of mine over Christmas thought he would show off his sharp intelligence on this issue by ripping off the British PSA, saying “I don’t like to put anything in my body that is solid at room temperature, because it will sit that way in my arteries.” I decided to have a little fun and paraphrased your line from your science speeches on YouTube, saying “Okay, but your arteries are about 25 degrees warmer than room temperature, aren’t they?” He gave me a look of slight confusion for about 0.75 seconds and then continued babbling, as if he had never heard me in the first place.

    I thought about pursuing the point further, but I know what the result would have been. He would have changed the subject, while internally thinking “What kind of extremist fools is Bret listening to? Everybody knows animal fat is unhealthy…”

    This friend has gained quite a few pounds since high school, and he thinks it’s because he is less active now than he used to be with no matching decrease in calorie consumption. It’s frustrating, because he’s remarked on how much thinner I am than before, and I have mentioned how I got here, but it’s like it doesn’t even register in his brain. He’s already got his mind made up. And there are so many other people who are exactly the same way. Sometimes I feel inclined to force the issue, but I know that would bring me down to the same level as the vegan evangelists you mentioned last post. I’ll respect his right to choose his own way over trying to set him straight. But still, I hate to watch him (and so many others) continue to get fatter and less healthy without knowing why.

  35. I think that there is an issue here that might make things simpler and for which all the points above apply.

    Relative risk by itself doesn’t mean anything. You have to know the absolute risk. My favorite example is still that I can give you a strategy that will improve your chances of winning a game of chance by 50 %. Would that change your likelihood of playing. (The game is the lottery: strategy: buy two tickets instead of one). I had actually brought this out in the last “meat kills” study http://wp.me/p16vK0-cM which was most telling because Harvard actually came out and admitted that their report of relative risk was too scary.

    This is in popular statistics books: you need to see absolute reduction in risk, or another better indicator, number needed to treat. This paper says “Vegetarians had a 32% lower risk …of IHD than did non-vegetarians.” But, you have to ask what was the risk to begin with? Well, you can actually calculate a rough number because they tell you how many people developed IHD and most of us would just divide the cases by the number in each group. If you do that, risk for vegetarians is about 2 % and for non-vegetarians is bout 3 %.

    But, they do a more sophisticated analysis because there is a time factor. But, as Tom points out, they actually tell you the absolute risk:

    “On the basis of the absolute rates of hospitalization or death from IHD, the cumulative probability of IHD between ages 50 and 70 y was 6.8% for non-vegetarians compared with 4.6% for vegetarians.”

    What? Absolute difference of 2.2 % Would anybody give up kielbasa for those odds? Once you have odds like that, all the points raised above kick in.

    Number needed to treat = 1/absolute risk ~ 50. So, fifty people would have to become vegetarians to keep one person from having IHD. Given all the other crap that flesh is heir to could this possibly mean anything?

    It’s very meaningful. It means the researchers desperately want to convict meat for crimes it didn’t commit.

  36. Nowhereman says:

    Thank heavens we have Dave Evans Healthy Diets and Science blogsite:

    http://healthydietsandscience.blogspot.com/

    If you ever need to counter anyone who says anything about meat and fat being unhealthy, just direct them here.

    Yup, that’s why he’s listed on the blogroll.

  37. John James says:

    If your calculations and assumptions are correct then, based on your figures, that would mean that the vegetarians in the study had double the measured heart disease risk of the meateaters. This would be gold to the meat industry, contradicting all prior studies, and would be used for their marketing. Have you spoken to them?

    The only query is your central assumption, upon which all your conclusions depend, that the 32% lower heart disease risk for the vegetarians has not been age adjusted. The researchers unambiguously state that it has been adjusted. See:
    http://www.bdlive.co.za/life/health/2013/02/03/vegetarians-may-have-lower-risk-of-heart-disease

    Could you be wrong?

    In his critiques of observational studies, Dr. John Ioannidis has pointed out many cases of statistical manipulation, no doubt many by researchers who made unambiguous statements about their adjustments.

    The slight difference I quoted — 4.6% of vegetarians having some kind of heart-related diagnosis vs. 6.8% of the meat-eaters — was for the raw, unadjusted data. Given that heart-disease deaths more than double as people move into the age bracket that the average meat-eater was in, adjusting that small difference for age shouldn’t leave much of anything.

  38. Martin Lopez says:

    Hi Tom

    Fantastic article. Now this is science, with measurements, stats and suchlike. And look how easy it is to manipulate the truth. So how much easier it is to manipulate the truth in economics and politics. No wonder Obama got elected for a second term.

    In classical Greece and Europe in the middle ages, the study of rethoric and logic were considered a vital part of education, so that the educated person could not be decieved so easily. Perhaps if Greece and the rest of Europe still had such an education they would not be in the mess they are in today. Is there a message here somewhere?

    Martin

    Education helps, but there’s a difference in how people think. For some, it works like this: if it’s true, I’ll believe it. For others, it’s case of: if I believe it, it’s true. I posted a 21-part debate with my leftist pal Paul on my other blog. Despite me showing him the clear, simple, undeniable math of the situation, he still believes we can keep spending at our current level without going belly-up if we just raises taxes on “rich people” — whatever that means. He wants to believe it, so it must be true.

  39. John James says:

    So you cannot see any possibility then, from your distant viewing and assumptions about the data, that you could be simply wrong?

    As a remote possibility? Sure. But considering that the same researchers have reported in other studies of the same dataset that vegetarians and meat-eaters have the same mortality rate, that seems unlikely, wouldn’t you say? If the meat-eaters truly have significantly higher rates of heart disease — the number one killer in modern societies — then their mortality rate ought to be significantly higher as well. If not, then something else is killing the vegetarians at a similar age.

  40. Dan says:

    I’m still struggling how to use my “Science for Smart People.” I’m just not good at reading these studies, I’m trying to find good primers on how, but I still feel like I’m confused or don’t understand a lot.

    Perhaps some books would help?

    http://www.amazon.com/Bad-Science-Quacks-Pharma-Flacks/dp/0865479186/ref=pd_sim_b_5

    http://www.amazon.com/How-Lie-Statistics-Darrell-Huff/dp/0393310728/ref=sr_1_1?s=books&ie=UTF8&qid=1360172078&sr=1-1&keywords=lie+with+statistics

    http://www.amazon.com/Cartoon-Guide-Statistics-Larry-Gonick/dp/0062731025/ref=pd_sim_b_2

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