Dear Mark: Vegetarianism Causes Cancer?; Glucosamine Useless?; Decision Fatigue Debunked?

DM--Vegetarianism and cancerFor today’s edition of Dear Mark, I’m answer three questions. First, does long-term vegetarianism cause cancer or alter our genetic code? Some media coverage of the latest vegetarianism study seemed to suggest as much. Next, is glucosamine just totally useless if you’re not going to fork out a ton of money for pharmaceutical grade stuff? Maybe not, but let’s find out. And finally, I’ve written about decision fatigue a couple times before. What’s my take on the new research seeming to debunk one of the central concepts supporting it—ego depletion/finite willpower?

Let’s go:

Hi Mark,

Did you hear the news about vegetarian diets changing the DNA of people who are on them for a long time and even causing cancer? Lines up pretty well with what you’ve been saying all these years.


Okay, I should probably explain this study a little more. It’s really interesting but some folks are getting it wrong. They’re getting it wrong because the headlines are misleading and, sometimes, blatantly false.

No, long-term vegetarianism doesn’t alter your DNA. Long-term vegetarianism has altered the DNA of a population. Here’s how it works.

Long term vegetarianism in traditionally-vegetarian populations like South Asians has selected for certain traits. Because they eat very little animal foods, they get very little to no pre-formed long-chain PUFAs, which are found almost exclusively in animals. They have to rely on their own endogenous synthesis of these fats. In a long-term vegetarian population, traits which increase the ability to synthesize long-chain PUFAs from shorter ones will be selected for and provide benefits to reproduction and overall fitness. They are essential fatty acids, after all, especially important for building baby brains and ensuring proper development. If you can’t eat DHA, you’d better make it.

Traditionally vegetarian populations may very well benefit from their traditional vegetarian diet. My hunch is that a lack of availability of animal foods and other sources of pre-formed long-chain PUFAs (fatty fish, etc) selected for vegetarianism and made it fitness-enhancing. The people without the “vegetarian gene” wouldn’t fare as well in a vegetarian world; those with it would. It probably still enhances health given the proper context—an ancestral vegetarian diet. What does the fatty acid composition of an ancestral vegetarian diet look like for South Asians?

Well, ghee, mustard oil, and to a lesser extent coconut oil were the most common cooking fats before industrialization.

Ghee is mostly saturated fat, with the balance coming from monounsaturated fat (MUFA) and a small amount of CLA and omega-3s in the form of ALA (if grass-fed, which it likely was).

Mustard oil is about 60% MUFA, 20% PUFA (from linoleic acid), 12% SFA.

Coconut oil is almost entirely saturated fat.

So while they didn’t exactly eat high-fat diets, the fat they did eat was more SFA and MUFA than PUFA. And since they weren’t eating many animals, they needed an enhanced capacity to manufacture their own long-chain PUFAs from the modest amount of short-chain ones (linoleic and alpha-linolenic acids) they did eat. It worked well. Fewer precursors to long-chain PUFAs, more efficient conversion.

Things change, though, and what works well in one environment isn’t guaranteed to work well in another.

In modern India, a lot of the ghee and mustard oil have been replaced by vegetable ghee (basically trans-fat) and various cheaper vegetable and seed oils. What once was SFA/MUFA-rich and PUFA-moderate is now PUFA-rich with a side of industrial trans-fat. That’s a lot of precursors. And conversion from the precursors into long-chain PUFAs is poorly regulated by the body. If linoleic acid is lying around, the body is gonna try to convert it all into arachidonic acid. Someone with the “vegetarian gene” that makes them really, really good at converting linoleic acid into arachidonic is in trouble on a modern vegetarian diet. Excessive amounts of arachidonic acid (from unchecked conversion) crowd out the ALA-EPA/DHA conversion pathway, increase systemic inflammation, and are linked to heart disease and cancer. Bad stuff all around.

This is exactly why it’s important to heed your recent ancestry.

So I am wasting my money on my Glucosamine supplement (well, maybe the Chondroitin and MSM have been doing something lol) and I need a prescription manufactured by an Italian company. I sent them an email to see if it is available in the states. The type I’ve been using is the Hydrochloride shellfish free form. I did read this which seems to contradict the study that asserts only the pCGS form has therapeutic properties:

“Studies have shown glucosamine HCL, when combined with chondroitin sulphate, could help alleviate pain caused by degenerative joint disease. The results of a 16-week trial on 34 males who suffered chronic pain of the knee showed significant improvement in the relief of symptoms caused by osteoarthritis. The inclusion of sulphur in chondroitin sulphate is also thought to improve the effectiveness of cartilage development.”

Who knows for sure? Always learn something and / or get another perspective from Mark’s Sunday links.

No, I don’t think you’re necessarily wasting your money. I’ve gone back and forth on glucosamine. The “science-based medicine” crowd claims it’s totally useless, but I’m not so sure. A team of researchers in one study branded glucosamine sulfate powder with an identifying brand so that they could track where it went in the body after ingestion. When the subjects swallowed it, the glucosamine appeared in their synovial fluid. Synovial fluid sits inside the joint, providing lubrication and cartilage precursors like glucosamine to build and repair damaged cartilage, so this could be meaningful. A later study found that glucosamine sulfate was more effective than glucosamine hydrochloride at showing up in synovial fluid after oral dosing. You may want to try glucosamine sulfate, which when combined with chondroitin may improve moderate-to-severe knee pain and even reduce the rate of cartilage degradation.

While I agree with the concerns about such things as multi-tasking — our brains simply aren’t wired to cope with numerous tasks at once — I wouldn’t get too hung up on worrying about decision fatigue. Much of that notion arises out of research on “ego-depletion,” which may soon become infamous as one of the most oversold ideas in the history of psychology. A recent intensive effort to replicate one of the most basic findings has failed miserably, calling the whole field of research into question.

Wow, yeah. That’s pretty big. Here’s an article about the paper in question.

The funny thing is that ego depletion/decision fatigue exists for people who believe in it. That’s exactly what the research shows. So if you’ve benefited from thinking about your willpower as a finite resource, don’t read the article! Keep doing what you’re doing cause it’s working for you.

I still think the “decision fatigue” concept and post I wrote have merit, if only because too many decisions reduce quality of life. Making choices is just another thing to worry about. It takes time. It takes mental “energy,” even if we can’t quantify that energy or measure its depletion. And worst of all is when we don’t make the decision. When we sit there at the crossroads, agonizing over which single origin bean to select for our morning pour-over. Because until we make the decision, we can’t progress to the next one and get on with our day. Once or twice? No problem. But if every moment of your day features a decision to make and you can’t make it, you’re wasting your most valuable resource: time.

That’s it for today, everyone. What’s your take on the three subjects?

Thanks for reading!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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33 thoughts on “Dear Mark: Vegetarianism Causes Cancer?; Glucosamine Useless?; Decision Fatigue Debunked?”

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  1. Man, just when you think linoleic acid can’t get any worse it does. Crazy to think a modern day vegan diet isn’t any better at preventing disease than the SAD diet. Guys like Neal Bernard, Dean Ornish, John McDougall ought to be ashamed of there selves for leading thousands of people down the wrong path.

    1. You can see how badly McDougall has aged. Even his followers have noted that. You just have to check the comment section of some of his most recent webinars.

    2. You don’t think they are all doing their best to help people? Regardless of their efficacy, it seems pretty harsh to suggest that of someone trying to do good hah. Plus, their protocols are likely to be the best approaches for a portion of the global society.

      1. Lets see, they disregard new research, they’re funded by the grain lobby in Washington, plus they recommend a low fat high carb diet filled with large amounts of whole grains. Can’t say even their protocols help even a portion of the population. Veganism is a religion, hence the “ism”. The fact it don’t help cancer, heart disease or diabetes any better than a McDonalds diet suggests it’s a pretty inferior diet. I suppose a vegan diet devoid of grains and is higher in fat would be less bad, but no one is advocating a diet like this. All the vegan diets are high starch.

  2. Re: glucosamine and MSM. My husband & I both have mild arthritis. We had been taking a glucosamine/MSM supplement that worked. After reading that glucosamine has little or no benefit we tried MSM by itself. It works just as well as the combined form & is cheaper. Of course, there is always the placebo effect – I’m not ruling it out completely. 🙂

  3. I laughed aloud at the concept of vegetarian diets “altering your DNA.” It’s amazing how some folks won’t dig through the innards of a research paper but would rather just take headlines at face value. Interesting article linked regarding Glucosamine. Yet another thing for me to learn more about. To the internet! (Oh wait, I’m already here.)

    1. Ditto, thanks Mark. I can buy the Chondroitin sulfate and MSM as separate supplements.

  4. On the decision fatigue point, I keep my clothing options down to a few key outfits that I enjoy. I put them on rotation, so I barely have to put any thought into what I wear every day. The same thing goes for my meals. I have a few tried and true recipes that I put on rotation. Keeping my decisions fewer keeps my brain freed up for other things. And that’s how I like it. It just feels less overwhelming. 🙂

    1. I also have a few recipes that I put on rotation–these happen to be the ones that don’t raise our blood sugar much (less than 10 pts.) after a meal.

      As for clothing options, I have Hubby’s wardrobe on a rotation because he dresses in the dark–I bought an over-the-door coat rack with 7 hooks on it, and pair up pants with shirt, and hang each pair on a hook for him to grab and put on. He knows a week in advance what he’s wearing, and I make wardrobe adjustments according to the weather forecast. His shirts are of colors that will go with all his pants, so it really doesn’t matter if there’s a last-minute replacement due to a bad zipper or a popped button. I like to think of it as Garanimals for Adults.

  5. I tend to get decision fatigue, or maybe it’s choice overload, in regular grocery stores. It’s gotten worse as I’ve gotten older because I have to wear reading glasses. But for the reading glasses to be effective enough to read labels, they end up rendering the overall view of the shelves quite blurry. If a quarter of the shelf is full of several varieties of all the same stuff, well, I can’t tell you how many times I’ve either bought the wrong thing or just given up and left without the thing at all because the effort involved in making a decision is just too great.

    1. Related to that is what we commonly call buyers remorse. Most people can confidently choose from two or three options and feel good about it. But over three, each choice not chosen is perceived as a loss. So if you have ten choices, you also have nine potential regrets that eat away at your pleasure and confidence at your first choice no matter had good it was. In study after study, too many choices reduces our happiness and sometimes prevents us from even making a choice.

      I have four surfboards. They are all identical models. Exact duplicates. Most of my friends have at least seven different boards. Some have over ten.

      Guess who’s complaining about choosing the wrong board for the conditions every day? Not me. By eliminating all options but one, I can focus on my surfing and not wonder about how good that last wave would had been if I had just picked my 5’2″ twin with the squash tail, instead of the 5″4″ quad with the rounded pin.

      That is not an exaggeration. I hear this every day. Mo’ boards, mo’ problems.

  6. I have been taking a glucosamine, chondroitin, and MSM complex for years. I can’t say which of those components individually is or is not effective, but the complex overall is absolutely effective at reducing joint pain in my case.

  7. Mark, I need you to address stress-junkies. I think I’ve realized that I am one. Not that I’m stressing out about it but I do seem to almost manufacture points for me to stress out about. It’s as if unless I’m engaged stressfully in interactions, I cannot be engaged at all.

    This is kind of related to the multi-tasking thing in case you were wondering where the heck that came from.

  8. Actually the selective pressure didn’t maximize the fitness or long term health and efficiency, but it’s rather a struggle for survival. We can’t thrive on a vegetarian diet because it goes beyond the boundaries of our species. Aside from DHA we should be able to syntetize B12, taurine, B6, be more efficient for creatine and carnitine, absorb non eme iron and zinc from plants, break down antinutrients and process plant proteins. In other words, we should go back to a fermentative guts, but what does it mean? Lose our brain and getting back to a chimp state. There’s no way that a Sapiens could actually thrive on a vegetarian diet and there’s no vegetarian hunter gatherer society on planted ever documented. We are not chimps. Have you actually seen how asians look like? Almost everyone has got curved limbs clear sign of lack of childhood nourishment toward the extremity of ricket. They are weak and sarcopenic but no six pack there. They are weak and short. Height is just increasing in Japan for example since western food and meat has been introduced. At one side this is bad because they imported bad food that makes us really sick, but on the other side it enlighted the importance of meat in human diet. Meat and fish, there’s far more than DHA, Aiello, Cordain and others docet.
    Someone may not agree at 100% with Cordain on some controversial point, but the evidence for meat need is unquestionable.

    1. I have to say I agree with doctor Cordain on most of his work an theories. Even his stance on dairy, which is scrutinized by some in the primal blueprint community. To be fair though to Cordain’s outlook on dairy, his studies and interviews seem to always focus on milk. Here at the primal blueprint Mark and all the commenters seem to focus on dairy fat like butter maybe some cream but mostly butter. Cordain’s argument is still correct in my opinion, what causes the problem is the bovine insulin and lactose (bovine sugar) in the milk. When you consume just the fat these compound aren’t present. Now he mentions no dairy at all because there’s people who strictly want to follow a strict Paleolithic diet with no Neolithic foods. People who say Cordain is wrong or outdated need to get their facts straight.

  9. I have to say that as much as I love eating Primal, I know that it’s not for everyone. There are some people who thrive on vegetarian or even, huh?, vegan diets.
    I’m just not one of them.
    But what I love about Mark is that he isn’t a hater!

    1. I’m with Christina! I have friends that are thriving on vegetarian, near-vegan diets. I was a vegetarian for over thirty years but have found I actually feel even better cutting out the grains and adding some ethically raised meat. And still tons of veggies!

      1. Yes, I’m with Christina and Elizabeth. I feel best with some meat, but I would like to begin limiting my meat to ethically raised. So I might begin experimenting with some easier to digest beans and rice. I can’t eat yogurt or too many eggs, so reducing my meat consumption will be challenging. It’s worth a try, though. Mark’s Daily Apple rocks because, as you said, Christina, Mark is not a hater. And Mark, thank you for explaining the vegetarian/cancer link so well. I saw this bit of research in Science Daily last week. I figured it would cause quite a stir.

  10. Adding on to the idea that lessening decisions adds to quality of life: you are far more likely to make the “immediate gratification” decision if you opt to make a decision every time rather than just once. Decide to go to the gym Monday, Wednesday, and Friday versus picking every day if you want to go and you are much more likely to make it to the gym 3 times a week (or whatever habit you want to implement). Decide to not eat cake at all versus deciding every time it’s offered to you. Most people are far more likely to stick to their long term goals if they make the decision once versus every time.

    1. I completely agree, Becky. This is what works for me – I eat within a framework (primal) and then I don’t have to keep making decisions all the time.

      1. Agree, same here: for me I set routines (habits) , with no fuss if I have to break them

  11. I have a tendency to vacillate on supplements like glucosamine. I’ve given it to my senior dog in conjunction with fish oil off and on for years. It seemed to help, but since switching him to a primal diet based on raw meat, offal, bone, etc, his mobility has improved, not to mention his overall energy since nixing that dreadful, pro-inflammatory, grain-based commercial dog food from his diet.

  12. I feel like I’ve experienced some “decision fatigue,” and I have now done quite a few things to simplify my life.

    I’m a stay-at-home, homeschooling mother, and planning has especially helped me to reduce the fatigue that comes from the constant choices that must be made throughout the day. For example, If I take the time to plan dinners ahead of time, then I use my brain power at once, and I don’t have to make some kind of split-second dinner decision at 5:30 PM.

    Thanks for the informative blog post!

  13. So unless you have an evolutionary line of being a Vegan, its not going to work for you, and by following the diet, you will pretty much removing yourself from the gene pool – the inability to manufacture critical body fats is evident in a lot of Vegans who almost go into a psychotic rage – evident of a brain dysfunction of some sort due to malnutrition.

    It seems like a vicious cycle – the more they stay on a totally Vegan diet, the more their brain function deteriorates, and the less chance they will accept what they are doing is killing them (as rational thinking goes out the window).

    Every single Vegan I have met seems to be verging on a mental disorder.

    Having said that, I believe the average population eats way more meat than they need – you need enough healthy fat to thrive, which isn’t a lot, and no more.

    1. How many vegans have you met? Probably not enough to draw overarching conclusions about their propensity for psychotic rage. I’m not a vegan or vegetarian, but I know many, including a few physicists, a mathematician, a triathlete and a financial executive. I also know some who are unstable or unpleasant or unwell, just like I know carnivores who are unstable and unpleasant and unwell. There are of course pros and cons to all diets, and they are interesting to contemplate on an individual level, but I think big conclusions are best left to scientific investigations, rather than personal perceptions based on a few encounters. Finally being vegan does not remove anyone from the gene pool. It doesn’t work like that.

      1. It’s not about hating, it’s about species appropriate food. Even chimps are not totally vegan and must rely though in small percentage in insect and small mammals. Our digestive tract and physiology say that there’s no way that a sapiens can thrive on a vegetarian diet, there are people who develop problems before, others later in life. Nature doesn’t care about ethics or politically fair.
        If chimps didn’t start to eat meat, we would still be hanging ob trees.

  14. We don’t have 4 stomachs, we have a residual cecum, our gut is a midway between a chimp and a cat, we have quite the same inefficiency of cats in taurine methabolism, etc… if people want to become chimps again, you can eat vegetarian and I completely respect every choice, but please don’t sell vegetarian diets as healthy, present them as your choice

  15. I need your help people. Anybody here know any good paper on our primal instinct & aesthetic perception? I was assigned to review a paper on anything aesthetic, came across this video ( I’m totally sold with his idea, but I don’t know where to find an actual paper on this topic.

    Thank you soooooo much! 🙂

  16. I also want to give a shout out to MSM. Oddly enough it did nothing for my joint pains but MSM cured my chronic fatigue so more than happy with that result. I find Boron is what keeps my knees, wrists, back and neck strong & pain free. Whenever I forget to take my daily Boron, they start acting up on me again.

    1. Please tell me more about your “daily boron”. How much do you take, and how often? I’m a massage therapist and need all the support I can get for my wrists, neck, and back.

  17. Researchers have been chipping away at ego-depletion for years. The idea that ego strength can be infinite, originated from the creator of mindset, Carol Dweck. Roy has spent the last decade or so defending his research by publishing review articles and replications of his original study.

    The issue is that current Psychological studies on ego-depletion are not dynamic, which is good if you want to isolate a particular element, but bad for real world application of a theory. Roy and Carol can both be right. If you are doing something that you have mastered it is easy to believe that your ego strength is infinite, but it is much harder to adopt this belief if you are working on something that you struggle with. As a real-world example, someone working at their dream job would be able to endorse infinite ego-strength, someone working a job they hate would struggle to endorse infinite ego-strength.

    The most overlooked aspect of this theory, is that it has been replicated and tested since 1980 by Health Psychologists. It is a little known phenomenon known as “stress”, feel free to Google this if you haven’t seen this obscure term before. The tasks that Roy and others have designed utilized “emotion/thought suppression” to sap ego and then had participants complete cognitive tasks to determine deficits. See the works of James Gross for a prolific review of how suppression generates a stress response. Roy, being a social psychologists, has performed literary acrobatics to avoid using health psychology terminology in his ego-depletion publications. He designed his study to be low stress and therefore somehow different than the previous 30 years of stress research.

    So yes, STRESS can cause cognitive deficits. It is ALSO true that if you believe stress is a good thing or a worthy challenge, it can promote improved health and resilience.

  18. The diet of my most recent ancestors was near starvation…poor, dirt farmers, who endured racism and religious persecution…came to America and faired some what better but kept their diets limited…potted meats and potatos/tubers and greens when they could get them.

    So what am I supposed to do continue to starve, eat at a subsistence level?

    Which BTW, I’m the guy who can go for hours, days with little food while those around me are dropping like flies…

    Perfect diets are like the golden fleece…