Tuesday, October 21, 2014

Is Meat Unhealthy? Part I


At Dr. McDougall's Advanced Study Weekend, I had the opportunity to hear a number of researchers and advocates make the case for a "plant-based diet", which is a diet containing little or no animal foods.  Many of them voiced the opinion that animal foods contribute substantially to the primary killers in the US, such as heart disease and cancer.  Some of the evidence they presented was provocative and compelling, so it stimulated me to take a deeper look and come to my own conclusions.

No matter what the health implications of meat eating turn out to be, I respect vegetarians and vegans.  Most of them are conscientious, responsible people who make daily personal sacrifices to try to make the world a better place for all of us.

My Experience with Vegetarian and Vegan Diets

I've always been somewhat conscious of the food and drink I put into my mouth.  When I was in college, I had a few interactions with vegetarian and vegan advocacy groups, which graphically described the inhumane horrors and environmental devastation of meat production.  I didn't find those people particularly credible, so I brushed them off, but I did file their words in the back of my mind for future reference.

Graduate school was the first time I was really able to take full control of my diet, so I decided to begin thinking a bit harder about its ethical and environmental implications.  I read John Robbins' book Diet for a New America, and did some additional research on my own.  I quickly figured out that the vegetarian and vegan groups actually had somewhat of a point about the ethical and environmental implications of meat production.  To arrive at the truth, I had to sort fact from fiction, hyperbole, and emotional appeals, but I did end up being convinced that some aspects of typical meat production are indeed inhumane and environmentally damaging.  I was not convinced by the argument that meat is universally unhealthy, however.

I was mortified by the ethical and environmental implications of meat production, so I became a vegetarian, and not long thereafter, a vegan.  I cooked nearly everything myself, focusing on a variety of fresh, whole foods.  I was the pain in the ass who goes over to friends' and relatives' houses and refuses to eat anything that contains animal products, which I regret to this day.  I remained vegan for about six months, until I became convinced that 1) not all animal foods are unethical, and 2) I had access to ethical eggs and dairy at the farmer's market.  I remained vegetarian for about two years, until I decided I could also source ethical meats.

I felt just fine as a vegetarian and I didn't notice any change in my health one way or another.  However, old friends who came to visit during that period did repeatedly ask me if I was sick, because of the amount of weight I had lost-- largely muscle.  I had grown paler as well.

Today, I'm a happy omnivore, but I still think the ethical and environmental consequences of meat consumption are important.  I don't write about them much here, because it's not my area of expertise, but they continue to impact my personal choices.  If it were simply a matter of taste, I'd eat meat all day.  I would love to get half my calories from meat, but I don't.  I actually eat less meat than most people in the US, frequently replacing it with beans or lentils.

The reality is that meat is a resource-intensive food, when compared to most other staple calorie sources like potatoes, grains, and beans.  That's why it's more expensive, per unit calorie, and almost always has been since the dawn of agriculture.  That said, not all meat is equally environmentally costly.  Poultry and certain types of fish are relatively efficient meats, while conventionally raised beef is remarkably inefficient.  Traditional mixed farms can produce a modest amount of meat from food waste and agricultural waste-- actually increasing environmental efficiency.  Simon Fairlie makes that point in his book Meat: A Benign Extravagance.  But that's not how most of our meat is produced today.

In the end, we all make environmental compromises.  We own houses, heat our houses, drive cars, take planes, own cats and dogs, have children, etc.  Like it or not, in these situations we are sacrificing the environment for our own personal gain.  The idea, however, is to make smart decisions that maximize our gain while minimizing environmental costs.

Vegetables are a good example of this.  On a per-calorie basis, vegetables are environmentally costly.  That's because they contain few calories, require a lot of water and nutrients, and generally require rapid transportation and refrigeration to remain fresh.  Our environmental footprint would be smaller if we avoided vegetables and ate nothing but calorie-dense grains, beans, potatoes, and sweet potatoes.  Yet we eat vegetables because we like the nutrition, variety, and pleasure they provide.  The same is true of meat: it's not as environmentally efficient as beans, but it plays an important role in our diet.

The humane implications of meat consumption continue to guide my decisions as well.  I don't buy conventional pork because it seems to be one of the least humane meats.  This is both because living conditions can be inhumane, and pigs are intelligent creatures (roughly equivalent to dogs).  I worry less about the living conditions of fish and poultry, although I do generally buy humane-certified products.  For environmental and humane reasons, I eat more poultry and fish than other types of meat.  I periodically eat grass-fed beef and lamb as well.

I don't claim to live an ethically spotless life.  I could live in a lean-to without electricity, grow all my own food, and not have children.  I could sell my car and stop flying on airplanes.  I could turn my thermostat down another five degrees and brave the wrath of my fiancée.  But I'm not going to, because I make compromises.  Eating a modest amount of (relatively humane and environmentally efficient) meat is one of those compromises, and I'm comfortable with it.

I'm not going to discuss the ethical implications of meat consumption further in this series-- the rest will focus on health.  I just wanted to take a moment to acknowledge that these issues are important.


What is Meat?

For the purposes of this series, meat is the flesh of an animal.  That includes the flesh of mammals, birds, fish, shellfish, and insects.  It also includes tissues other than muscle, such as liver.

It doesn't include eggs or dairy, although since those are nutritionally similar to meat in some respects, I'll discuss them a bit along the way.

Vegetarian vs. Vegan

In this series, I'll attempt to parse out the health impacts of eating meat.  This will invoke research that focuses on omnivores, vegetarians, and vegans.  These three groups differ from one another physically and physiologically in a number of ways, however vegans appear to be the most distinct.

This is probably because vegetarians eat eggs and dairy, which provide many of the same nutrients found in meat.  The vegan diet is the most nutritionally distinct of the three diets.

Since the discussion will center in part around evaluating the influence of animal-derived nutrients on health, it will include vegans in comparisons when possible, rather than only comparing omnivores to vegetarians.

In the next post, I'll examine our evolutionary history with meat.


Unknown said...

Good post, Stephan. This is something I often try to consider in my buying decisions as well. In addition to Simon Fairlie's book, are there other resources you could recommend on the topic? Thanks!

Gretchen said...

A very reasoned discussion of the ethics. Nice to see something on this topic that isn't a rant.

I always thought potatoes and beans were vegetables, albeit starchy vegetables. How do you classify them?

Anonymous said...

In my experience the author's or reporter's answer to the question posed by headlines that end with a question mark is usually (95%+): no.

Regardless, I await part two with interest.

m said...

Thank you for this post. It is painful to see so little introspection in the paleo-type crowd about the environmental implications of their diet choices. I would encourage you to do a little more research into the environmental implications. I studied evolutionary biology but now work on climate change, and so try and balance the imperative of global impacts with personal health.

Here are some links to get you started.

















Unknown said...

I'm really looking forward to this series - I actually started my blog purely as a way for me to explain my own stance on eating meat - I didn't get past part one in my series but I know yours will be amazing! (if you're interested - my part one is the evolution argument! http://www.catfoodisgoodforyou.com/2013/08/do-i-need-meat/)

Unknown said...

Calorie for calorie and nutrient for nutrient, beef is not all that bad from an environmental perspective. I would highly recommend the book Meat: A benign extravagance. Even convention raised beef spend the vast majority of their lives on pasture, utilizing land unsuited for agriculture- in many cases they are replacing previously displaced ruminants like bison thus enhancing biodiversity and carbon sequestration. Most feedlot use the manure for local ranches or hay production and many even tap it for methane.

Stephan Guyenet said...

Hi Unknown,

Honestly, there are other people who would be better qualified to answer that question. Fairlie's book would certainly be a good start, although it's tough to read at times.

Hi Gretchen,

Definitions of the word vegetable differ, but when I say it I usually mean a low-calorie plant food that's not a fruit. I classify potatoes as a starchy staple. It's not a botanical classification; I classify them by the role they play in the diet.

Hi brec,

Haha, good thought. This is Whole Health Source though, so I promise to give you a more complicated answer than yes or no (although I'd be happy to provide a simple answer if I believed it).

Hi m,

Thanks, I'll have a look. I don't claim to be knowledgeable about the environmental or ethical implications of meat production-- but I do think it's an important consideration.

Hi Cat,


Hi Elizabeth,

Thanks for the thoughts.

Running Eimear said...

Interesting introduction to the series. I have been vegetarian and vegan twice, which caused me to realise meat was definitely important for health. However, like you, I don't eat a lot of meat now, and my husband is mostly vegetarian (eats some fish). I wonder how much (or, more correctly, how little) a person needs to eat to gain the benefits to their health from eat meat/eggs/dairy. Of course the answer will be highly varied, based on a wide range of factors. I'm looking forward to the rest of the series.

Puddleg said...

I'm glad you mentioned the high cost of non-starchy vegetables.
It's also relevant that ruminants can be raised on minimally developed pasture land, which would not support plant crops without extensive landscaping, irrigation, and chemical input; this kills off the wildlife that shares pasture land with ruminants and uses up fossil fuels.
A landscape of beans is a pretty depressing prospect, compared to rolling hills spotted with sheep or cows, goats or deer.

LPaForLife said...

Great topic! I have been thinking about this for a long time. This is not easy to answer because cooking meat well done and or processing it probably makes it into something bad. Many studies don't separate out these effects. The real question should be, is unprocessed meat that is properly prepared bad and How much is good or bad?

I really look forward to your series.

Anonymous said...

Great! Whenever you post something new that ends with "Part X" I know it'll be compelling.

Billy Oblivion said...

I could live in a lean-to without electricity, grow all my own food, and not have children. I could sell my car and stop flying on airplanes. I could turn my thermostat down another five degrees and brave the wrath of my fiancée.

From an "enviromentalist" perspective the only one of those--once you "do the math" that reduces pollution is turning your thermostat down.

If you lived in a lean-to anywhere outside of Southern California--you'd need some source of external heat from one third to most of the year, and you'd still need to *cook*, especially if your diet was beans and tubers. This would mean cooking with wood, charcoal or dung. Now, if just *you* were doing it, it wouldn't reduce your pollution footprint much (focusing on carbon alone is ignoring the longer lasting and more damaging problems), and there's the whole "what to do with all that waste" problem.

One of the things that Vegans and some vegetarians ignore in their harangues against meat production (and I'll agree that factory farms are ethically questionable) is that (a) land is not fungible and (2) done a certain way raising animals for meat production can help restore damaged lands, increase biodiversity, and provide good, high quality sources of protein.

There are ranches in Nevada and Arizona that produce meat and milk from land that *cannot* be farmed, and have had some sort of ruminants grazing them for thousands of years.

Tam said...

I'm looking forward to hearing what you have to say on this topic. I was a vegetarian in high school with no trouble or ill effects, but as an adult I find it too difficult.

J said...

Great, as always thankyou for opening out the debate in a calm manner.
Re cost of fresh vegetables and environmental impact of commercially raised and store bough produce - I'm going to state the obvious.
Buy local (farmers markets), grow your own, with family and friends is much more fun and productive. Forage for wild greens, some of the most nutrient dense foods on the planet. Take a wild plant walk with an experienced local forager.
Thank you for the conversation.

Benden Bizden said...

Very interesting point of views, thanks for sharing! Being 6 months pregnant, I am looking forward to the discussions to come.

raphi said...

The problem is mono-crop agriculture.

There is nothing 'environmentally costly' that is inherent to either a bean, a potato, kale, pork, fish or shellfish. But, in a mono-crop agriculture system where beans, grains & starches are grown to the expense of a variety of other plants (& animals), they become devastating products, sadly.

I also do not consume conventional pork or poultry due to their treatment, taste, nutritional profile & because I'd be supporting factory farming.

Opting for beans instead is unlikely to be a better alternative.

A better alternative is probably consuming local meats/fished fish (!) with a diligent focus on OFFAL. Eating more animals along with all their bits will do a few things

1) less waste
2) higher nutritional density
3) discourage factory farming
4) encourage alternative (non-batshit crazy) farming methods
5) cut thru the myth that plants = always good / meat = always bad

Now, personally, I'm up for trying insects but I sense that isn't in the wheelhouse of most people. If we're still disgusted by liver, we've got a long way to go.

Galina L. said...

I want to join George in his acknowledgement of your point about the high environmental cost of eating not-starchy vegetables. Fresh produce is not only a poor source of nutrients, but on the top of it doesn't stay fresh long and it creates more opportunities for a food waste. It could be also a great drain for an individual budget if a person decides to eat a lot of organic produce.
I don't think humanity uses resources wisely. Observing massive amount of wasted food in a modern society is upsetting for me. I think animals could be a great way to utilize most of what is going into dumpsters today.Many standards of modern life are bad for the environment - perfect lawns are a source of a water pollution and only picture perfect fruits are sold in stores. May be goats on a front lawn and chicken on a backyard would be better use of our resources. I hope in a future animal waste will be used for growing insects for chicken and farmed fish food, or even for a dogs and cats food.

TheGiantess said...

Interesting. I am guessing that because you eat beans and lentils (and if I recall from a past post, peanuts) that you disagree with the stance of other bloggers, namely Paul Jaminet, who maintains that legumes are toxic. Is that the case, or do you just accept the toxic nature of beans in exchange for reducing the environmental impact?

I have found since my introduction into being an aware eater, which has been for some 10-15 years that the more I know, the more a grocery store trip can become crippling. I have so much information in my head that it becomes difficult to decide what is the least evil thing to put on my dinner plate. While I can see how poultry is a pretty benign in terms of environmental destruction, I think that lumping fish into that category can be dangerous. So much of our ocean is overfished… so unless you're buying from a source that really tries to harvest ethically (i.e. Whole Foods) it seems to me that a lot of damage is being done.

Anyway, excited to read the rest of the series.

JWO said...

Here is an interesting excerpt from Robin Hanson on a way to address the ethics of livestock:

"But would it really take radical new technologies to produce happy livestock? I suspect that some of these enthusiasts have been distracted by a shiny Far sci-fi solution of genetic engineering, to the point of missing the presence of a powerful, long-used mundane agricultural version: animal breeding."

Stephan Guyenet said...

Hi Giantess,

I don't think beans are toxic. The supposed dire consequences of bean consumption don't seem to materialize in cultures that consume them daily for a lifetime, and the scientific literature overall suggests they're healthy to eat. The only significant exception I'm aware of is that some people are sensitive to the fermentable fiber they contain, which can cause flatulence and exacerbate IBS.

If you poke around enough in the literature, you can make an argument that just about any food is unhealthy. See Melissa McEwen's article "Just Kale Me". That's why I like to ground myself by considering 1) what healthy traditional cultures eat, and 2) what the WEIGHT of the scientific evidence says. Mechanism is interesting but it only serves to explain or support a demonstrated biological effect-- it is not sufficient by itself to demonstrate that an effect exists or is biologically significant. That's where a lot of diet-health folks get tripped up trying to make arguments from biochemistry etc. It sounds impressive but it's not empirically grounded.

ICG said...

I look forward to this discussion. Right now I'm eating mostly vegan, but still eat some meat/dairy with my family and other social occasions. So far I've lost weight, feel better and have more energy, for whatever my N=1 experiment is worth.

I'd be interested to see some discussion of the so-called blue zones. These are regions with the longest lifespans. While their diets differ a bit, they all eat largely plant-based meals with small doses of animal products and oils. Longevity in these regions may also be associated with lifestyles, exercise, social/community ties, etc., which are beyond the scope of this.

Simon Whyatt said...

I also await the upcoming posts, having followed a very similar nutritional journey.

Having done my own research, I came to the conclusion that eating grass fed beef and lamb was actually a better choice for the environment and animals, in the UK at least...

I think the latter is key however. The most sustainable food is that which can be produced locally, with the minimal input of energy or disruption to the local ecosystem.

Industrial meat production is bad, there's no question about that. Can everyone eat grass fed beef? Probably not, but then eating bananas in the UK isn't sustainable either. I'd wager the typical veggie/vegan diet has a far greater impact on the planet then mine.

With regards to assessing the health aspects, I think the cofounder will be that as groups, vegans and veggies are much more homogenous than "meat eaters" I.e. a typical meat eater most likely eats SAD, probably a very different diet to that eaten by those reading this blog.

So Stefan, your work is cut out for you, good luck!

psychic24 said...

Hi Stephan,

I was wondering if you had any suggestions in regards to someone who would like to ground themselves in a more vegetarian diet (that's not too low in fat), but has rather significant GI issues (precluding them from consuming any fodmap containing foods).

Unknown said...

The suspense!!!!

I assuming it wont be to negative because it does not sound like you are going to give up meat anytime soon.

Kevin said...

Another environmental impact of beef and lamb production is the killing of predators (coyotes, mountain lions, wolves, foxes, eagles, crows, bears ...) by ranchers and the federal government.

Unknown said...

Hello Dr. Guyenet. I understand why you don't eat Pork, since you don't feel comfortable eating an animal of that level of intelligence. But the rest of your reasoning is flawed; since your individual eating habits, or any other individual comforts, have no impact on the environment as a whole, nor on how many cows are slaughtered... In fact, you could do 100% of what you feel like, or even a 1000 times that, and not move the needle one blip with regards to the big picture. Therefore, why are you punishing yourself in this manner? This is actually a question I have of most people who restrain themselves thusly. Yes, I understand that if everyone did what they wanted this could have an impact; however, your individual choices, or any other individuals' individual choices, don't change the collectives behavior. So why shouldn't I, or anyone else just do what they like and enjoy?

Chris Wilson said...

Stephan wrote, "Mechanism is interesting but it only serves to explain or support a demonstrated biological effect-- it is not sufficient by itself to demonstrate that an effect exists or is biologically significant. That's where a lot of diet-health folks get tripped up trying to make arguments from biochemistry etc. It sounds impressive but it's not empirically grounded."
Yes to this! Excellent explanation. It reminds me how in applied work with statistical tests/models "statistically significant" is often conflated with *biologically significant*. So the corollary is that any number of effects can be demonstrated to exist, but only a few are biologically significant.

The problem is to analyze where the weight of evidence is when meaningful effects at a population level can be rather small, say 10% reduction in relative risk on average for some dietary pattern or another. In noisy systems, you either need tons of data or strong priors to estimate those effects properly.

I used to buy the simplistic argument that since correlation != causation, we can pretty safely ignore all the epidemiological models and rely on our favorite lines of mechanistic/evolutionary reasoning + RCTs when favorable. But now, having done lots of applied regression models and seen lots of alternative diet ideas turn out flat, I'm not so sure. I think we DO need observational and cohort work to understand real-world effects better...

I'm looking forward to your continued explorations and how you currently are thinking about reconciling these different kinds of evidence.


Stephan Guyenet said...

Hi Biryon,

I disagree. My actions have a small impact on billions of people.

Hi Chris,

Good thoughts. I remain quite skeptical of most observational studies on diet, in large part because the typical assessment methods are remarkably inaccurate and thus leave open the possibility that the researchers are actually measuring something other than their variable of interest (e.g., wishful thinking). The relationship between BMI and self-reported energy intake is a perfect example of a misreporting bias that led to incorrect conclusions. But I agree that observational studies are part of the scientific picture. We can't just ignore them.

Also, RCTs have their own substantial limitations, particularly when they're studying diseases that may take decades to develop. Different methods complement one another and we have to consider the totality of the evidence, while remembering the limitations of each method.

glib said...

I dislike a premise of this post, which is that meat from insects is similar to meat from beef. It is not. You can raise, given appropriate facilities, 500 kcal of insects daily, out of your own excrement. They would have superior zinc, calcium, iron, B12, and I am guessing, K2, compared to "regular" meat, and of course provide proteins. They would even provide compost.

Also, for warm blooded animals, the most efficient meat is rabbit. I have a friend who raises them solely out of acorns raked from the woods, hay from under the fruit trees, and table scraps. It is amazing to see so much meat (150 plus rabbits a year) raised out of zero feed. And rabbit is superior meat when it comes to the above minerals and vitamins (not a surprise since rabbits, too, are coprophagous). Other meats are currently sustainable, including lion fish, asian carp, and feral hog.

Nate D said...

I very much enjoyed your article -- looking forward to the next part in the series!

Like you, I would eat nothing but meat (and chocolate!) all day if there were no consequences. I came to almost the exact same conclusions that you did, and my family started to eat a vegetarian diet for a few months as well. I even wrote a blog post detailing my experience being vegetarian and lifting weights. Anecdotally, I found that being a vegetarian no effect on my strength or stamina, but I didn't stay on that diet too long before I was back to eating meat.

My wife would have no problem keeping this diet indefinitely, as she doesn't really like meat that much, but both my son and I love the taste of meat. So we decided to eat it again, just less often. Maybe once or twice a week.

I'm not so much worried about the ethics of eating meat, but there is no denying that a large part of climate change and environmental pollution is due to raising livestock for meat. I'm all about sustainability and efficiency, and your conclusion is spot on: Most meat is a horrible choice for caloric intake due to it being very inefficient to raise and unsustainable in the long term.

Can't wait to read the real meat of this series (pun intended)!

tomR said...

Refering to muscle issues on non-meat diets:
what do you think about the reccomendation of the vegetarian powerlifter Jason Blaha to use supplemental essential amino acids? These powders are claimed to be for vegetarians (not vegan).


The recommended essential amino acids 15g serving contains:

Leucine 5g
Valine 2.2g
Lysine 2.2g
Phenylalanine 1.8g
Threonine 1.5g
Isoleucine 0.9g
Histidine 0.7g
Methionine 0.5g
Tryptophan 0.2g

tomR said...

In modern times we shouldn't use abstract thinking as a solution to environmentaly-friendly purchases. Abstractions hide information, so the are faulty.

Eg. you can make any plant environmentaly-unfriendly by sprying gobs of pesticides on it. If this particular plant you buy is in a good-species category (statistically environment-friendly) but individually it was oversprayed, then you end up buying the wrong plant from the wrong producer based on abstract thinking.

Right now we have enough spying and big-data technologies to trace each individual carrot from planting to the purchase. Why not utulize it and process information per-item, rather than per-category?

Jason Voegele said...

Hi Stephan, I look forward to the remainder of this series! I was wondering if you might consider a future post or series on "Is Wheat Unhealthy"? I'd be very interested to read your assessment of what the literature has to say about this topic.

Linda Watson said...

For Galina L. - an organic diet with more fruits and vegetables than most Americans currenty eat is possible on a food-stamp budget. The Cook for Good project explores this, at first for vegetarian and now for vegan diets.

Stephan, I'm looking forward to next posts in this series. I hope you address the effects of soy and pesticides. The recent research that usually received headlines such as "Vegetarians And Vegans Have Lower Sperm Counts Than Meat Eaters, Research Finds" actually put the blame on soy, pesticides, and B12 deficiency, not an absence of food from animals.

Our individual choices do matter. What is any ocean but a multitude of drops?

ICG said...

"I'm not going to discuss the ethical implications of meat consumption further in this series-- the rest will focus on health. I just wanted to take a moment to acknowledge that these issues are important."

Kudos for this. One thing I don't like about many vegan/vegetarians is how they go back and forth with nutritional, ethical and environmental arguments. Those are three separate issues. I prefer reading McDougal, Fuhrman, et. al. on plant-based diets. They stick to their area of expertise.

CJ said...

Hi Stephen, I just read both parts of the blog. And I am commenting on this one because I am a vegetarian both by choice and because my religion insists so. Most people I have seen around me those from my religion who also practice vegetarianism are a mix of healthy and unhealthy. However most of the older generation have had a pretty long life. Upto 100 years even. I think the subgroup of people following the religion have adapted well to the meatless diets and are thriving well. And I think there may have been some genetic adaptations as well which a proper scientific study might reveal.

truthseeker said...

I highly recommend reading "All Flesh is Grass: Pleasures and Promises of Pasture Farming" by Gene Logsdon. And "The Vegetarian Myth" by Lierre Keith. I was a vegetarian for 20+ years and almost ruined my digestive system. Been eating basically Paleo style for 4 years and at 61 years of age feel healthier, stronger and younger than I have since I was 40.

JMo said...


Are you familiar with the work of Gary L. Francione? He is an "abolitionist" vegan who believes that an animal's sentience (consciousness, capacity to feel pain) is sufficient to proscribe the use of that animal as a resource in any way whatsoever. Under analysis, an animal's relative intelligence to humans or other animals (as with pigs) is wholly irrelevant to the moral calculus; all that matters is the capacity for pain and suffering. I am curious to know what your position is on this issue (the sufficiency of sentience vs. the relevance of intelligence) -- I think a commitment to the former would significantly alter your analysis.

Walkitout said...

Beans are not only healthy but they are great nitrogen fixers for the soil
I No longer believe that grass fed beef is a real solution to any long term enviormnetnal strategy . it seems like an unrealistic pipe dream and I'm sure the promotors of this even know these things.