Sunday, February 16, 2014

Do Flesh-Free Diets Damage Mental Health?

Dr. Emily Dean writes as if to make people wonder whether this observational study suggests that a meat-free diet adversely affects mental and physical health, despite reducing body mass index.

This study reported that vegetarians in their selected Austrian population have a higher incidence of cancer and chronic health conditions, more anxiety disorder and/or depression, and get more medical treatment than carnivores.  Whoa....looks like a goldmine for carnists!

However, the authors of this study have clearly stated:
"Potential limitations of our results are due to the fact that the survey was based on cross-sectional data. Therefore, no statements can be made whether the poorer health in vegetarians in our study is caused by their dietary habit or if they consume this form of diet due to their poorer health status."
It seems that people who promote animal-based diets or believe in the nutritional necessity of animal flesh (i.e. carnists) have either an ignorance of or a great resistance to recognizing the importance of the phenomena of reverse causation and regression dilution bias.  Also, when it suits them, they prefer to make a lot of ruckus about some observational studies, to support their biases and distract attention from observation or intervention studies that contradict their belief in the importance of dietary animal flesh.  The question:  Does the idea that flesh-free diets damage mental health have a broad range of support from studies lacking significant bias?

Reverse Causation Explained

Due to evidence that consumption of animal products promotes chronic diseases, people who develop chronic diseases often adopt plant-based diets as a way to manage their conditions.  As a result, in random populations selected from Westernized populations, poor health increasingly correlates with eating a plant-based diet.  In such populations, chronic disease causes people to adopt plant-based diets; but failure to account for this can lead one to erroneously conclude that plant-based diets cause people to develop chronic diseases.

This issue now clouds the waters with regards to consumption of saturated fats.  As a consequence of the evidence that consumption of saturated fat promotes cardiovascular disease, physicians have recommended diets low in saturated fats to their patients who have cardiovascular disease or risk factors for it.  Consequently, in any random sample of people in Western populations, an increasing proportion of the people who eat diets restricted in animal fats consists of people who have already shown signs of cardiovascular disease.  As a result, in any analysis of a random sample of the population, the association between saturated fat consumption and cardiovascular disease has been diluted by this phenomenon.  

The Adventist Health Study provides a way around this problem.  Although many Adventists adopt a plant-based diet only after developing a chronic disease, a large proportion of this population has adopted plant-based diets for cultural rather than medical reasons.  Consequently, this population has less dilution of associations between plant- vs. animal- based diets and disease. Perhaps this partially explains why carnivores tend to discount data from Adventist studies.

People who have chronic diseases visit doctors more often, and also suffer more anxiety and depression and social isolation than people who do not have chronic diseases.  If these people also eat a plant-based diet, consumption of a plant-based diet will associate with more anxiety, depression, and social isolation.  Again, reverse causation that will generate regression dilution bias.

Observational data contaminated by reverse causation and regression dilution biases does not support suggestions that eating a plant-based diet causes people to lose their minds, nor does it support  Dr. Dean's suggestion that there exists a "general trend that vegetarians aren't quite as mentally healthy as omnivores."

Wait just a minute.  According to a 2011 CDC report:
  • "From 1988–1994 through 2005–2008, the rate of antidepressant use in the United States among all ages increased nearly 400%."
  • "Eleven percent of Americans aged 12 years and over take antidepressant medication."
Does this data support Dr. Dean's suggestion that there exists a general trend that meat-eaters have better mental health than vegetarians?

During the time that antidepressant use increased four-fold, total meat consumption in the U.S. has been consistently on the rise.  If meat is the happy meal sin qua non, why did the 2011 CDC report state that antidepressants are "the third most common prescription drug taken by Americans of all ages in 2005–2008 and the most frequently used by persons aged 18–44 years"?  

Do proponents of eating animals believe that pharmaceutical corporations invested in antidepressants because they knew they would recoup their investment by selling those drugs to the large population of depressed vegans visiting physician's offices every day? 

Basic Science and Interventions

In Powered By Plants I have a section discussing the effects of dietary arachidonic acid (AA), present almost exclusively in animal flesh, on brain health.  According to Farooqui et al,  high levels of AA in the brain promote neuroinflammation and brain damage, and chronic neuroinflammation is associated with slow progressive neurodegenerative diseases such as Alzheimer’s, Parkinson’s, Down syndrome, Huntington disease, and multiple sclerosis.  High body levels of AA can only result from eating animal tissues; multiple studies have shown that consuming linoleic acid from plants does not increase tissue levels of AA

In PBP I discuss at some length intervention studies that have explored the effects of reducing meat intake or increasing plant food intake on mental health.  The following are some of the studies I discussed.

Kjeldsen-Kragh et al. reported that patients who adopted a vegetarian diet for treatment of rheumatoid arthritis showed an unexpected decrease in psychological distress in comparison to patients who continued to consume animal flesh.  This study is particularly interesting because the authors report having an expectation that patients assigned to eat the vegetarian diet would experience increased distress compared to those allowed to continue eating flesh.  In other words, they reported a result contrary to their expectation/bias.

Schweiger et al. reported that healthy young women assigned to a vegetarian weight loss diet had significantly better global mood than those assigned to a mixed diet group; they found a significant correlation between relative carbohydrate intake and global mood.

Weidner et al. studied the effect of 5 years of dietary cholesterol reduction on negative emotions including depression and aggressive hostility.  They reported that people who followed a low-fat, high complex carbohydrate diet (more plants, less animal flesh) at the end of the study had significantly greater improvements in depression and a reduction of aggressive hostility, concomitant with a reduction in blood cholesterol levels, compared to those who ate a high-fat “American diet.”

Beezhold et al. compared the mood states of vegetarian and omnivorous Seventh Day Adventist adults. They found that omnivorous SDAs reported significantly higher levels of anger-hostility, tension-anxiety, depression-dejection, and confusion than vegetarians.  Further analysis revealed that individuals with low intakes of EPA, DHA, and AA, fatty acids found only in animal flesh, reported having the better moods. 

Following up on this research, Beezhold and Johnston randomly assigned 39 omnivores to consume either an omnivorous diet, a diet restricting flesh to fish only, or a lactovegetarian diet free of meat, fish, and poultry.  They reported that the individuals assigned to the vegetarian group experienced a significant improvement in mood scores on standardized tests.  In their words:
“These data suggest that consuming a diet high in meat, fish, and poultry may negatively impact mental state. Beyond differences in the ratio of long-chain fatty acids, vegetarian diets are typically rich in antioxidants, potentially conveying mood protection for the VEG group via reduction of oxidative stress.”
Based on my review of the research, I doubt very much that people who eat animals (carnivores) have better mental health and more happiness than people who eat B12-supplemented plant-based diets.  On the contrary, the trend seems in the opposite direction.

Why Eat Animals For X Nutrient?

In my view, except for sociopaths who lack empathy, most people who eat animals or their secretions have enough empathy to feel at least a bit uncomfortable with their choice to support the imprisoning, injury, and slaughter of animals so that they can have flesh, eggs, or milk on their plate.  This is why so-called "humane" animal husbandry exists – people want grass-fed, free-range animal products in part because they care about animal welfare (although perhaps not enough) and want "feel-good meat."

Due to their discomfort and cognitive dissonance, empathic people struggle to find justifications for eating animals in claims of "necessity."

In this case, the carnivores want to believe that their happiness biologically depends on the animal foods they eat.  Its not just that they like to enjoy eating flesh at another sentient being's unnecessary expense, its that they NEED to eat flesh to get the NUTRIENTS necessary to feel HAPPY.  If they can identify a perceived NEED for X nutrient (choline, B12, K2, whatever is the nutrient du jour) they hope they can justify their eating flesh, eggs, and milk and all the enslavement, injury, suffering, and killing of innocent young animals involved.

I don't believe we presently have evidence that people eating well-planned whole foods, strictly plant-based diets need to take supplements of choline, zinc, iron, creatine, carnitine, iodine, or any other nutrient except B12 and possibly, in certain circumstances, vitamin D, for any purpose, including promotion of mental health.  Nevertheless, if at any point in time, we do obtain such evidence, you can obtain all of these nutrients in supplemental form.  Any nutrient you believe you need to maintain happiness can be obtained from a non-animal source.

People eating animal-based 'paleo' and low-carbohydrate diets are not generally opposed to taking various supplements to correct for deficiencies caused by modern lifestyles, such as vitamin D deficiency due to insufficient sun exposure, or EPA/DHA/fish oils due to an incorrect perception that these are required and deficient in the food supply.  Atkins himself recommended a boat-load of supplements.  The Atkins website even has a page entitled "Don't Forget to Take Your Supplements." They apparently don't believe that the Atkins diet is nutritionally sound without those supplements. 

On what basis then can they object to people taking a few supplements to achieve their goals with a plant-based diet, in order to bring an eventual end to eating animals?  If taking fish oil supplements is OK for carnivores, what's wrong with vegans taking B12?  If its OK for a paleo- or primal- dieter to take vitamin D to remedy the effects of insufficient sun exposure, what's wrong with the same person taking supplemental choline to make up for a (perceived) lack of choline in your food, with a goal of reducing animal suffering?

Why is it 'wrong' to take supplements if it helps us reduce harm done to non-human species, but not to remedy the weaknesses of an animal-based diet?

Again, I haven't seen any evidence that eating animal products protects against choline deficiency (less than 10% of the general population reaches recommended intakes, despite eating animal products – beware that the article just linked was "made possible with an unrestricted education grant from the Egg Nutrition Center").  Nor have I seen any evidence that whole foods plant-based diets supply insufficient choline (people eating plant-based diets rich in betaine, lower in methionine and higher in cysteine may have a lower choline requirement than carnivores).  Nevertheless, hypothetically, if you found you needed more choline than you could obtain from a whole foods plant-based animal-free diet, why would you choose to kill animals in order to eat eggs or meat rather than take a inexpensive choline supplement ($9.00 for a month's supply, or 30 cents a day)?  You have a clear choice:  meet your needs with or without exploiting or slaughtering animals.

Similarly, if you really believe in low-carbohydrate dieting, know that you can do it without eating anything from animals.  I'm not recommending them here, but we have plenty of plant-based protein powders, mock meats, etc., etc.. including gluten- and soy-free varieties for those of you who need (or, in most cases, think you need) to avoid those foods.  Jenkins et al have shown that a plant-based low-carbohydrate diet (rich in gluten, by the way) works better than an animal-based diet for reducing risk factors for cardiovascular disease.  You can make your diet as high in protein or fat as you want, without killing animals.

Since most 'paleo' and 'low-carb' dieters use a computer, they must not be opposed to using technology to improve the lives of sentient beings.  Perhaps they need to think – or, better, feel – about this issue for a while.


Travis HL said...

Great post, and excellent explanation of reverse causality!

In regards to reverse causality, a recent study in the Netherlands, researchers found that 75% of the vegetarian participants with cancer adopted a vegetarian diet after diagnosis, consistent with previous research which found that cancer survivors are highly motivated to adopt a more plant-based diet with the intention of improving poor health.

Another cross-sectional study which found the benefits of a plant-based diet on cognitive performance:

Some trials addressing the negative effects of low-carb diets on mood and cognitive function:

The list could go on.

Rex said...

Don, I gotta say I am astounded by the fact that you still apparently place so much faith in nutrition science when it's a field still in its infancy. You've been trained in Chinese Medicine! Why would you study anything else? The other flawed assumption you make is that population-based studies are valid when they are almost worthless because different people have different constitutions...that's Chinese medicine 101. Ayurveda is the same. You can't hope to study a population of people, look at their meat intake, health outcomes and then give a yes or no answer to meat's benefits...totally ridiculous! Certain kinds of meat have benefits for certain people. I am sure you have read about Ayurveda...What is the point of going on a continual tirade about the evils of eating animals when some people clearly need them according to older forms of medicine?

Don said...


LOL. Why would I study anything else? Because other things have value. Some say that Chinese medicine says that rhino horn is a remedy for impotence. That is complete bullshit, and exemplifies that Chinese medicine while having much of value is contaminated with fairy tales as well. Ayurveda? Don't get me started on that impractical 'medicine' for elites.

"....some people clearly need them according to older forms of medicine" Right. I once had a Chinese physician tell me that I needed to eat dog meat. Yeah, dog meat is really medicinal. So you think I should have taken him seriously? LOL.

Chinese medicine is not stagnant in time, it is evolving like every other discipline...for thousands of years it has incorporated useful information from outside (non-Chinese) sources. Why should modern Chinese medicine practitioners live in a bubble, when ancient physicians did not? Chinese medicine will evolve with current knowledge, and dispense with myth-information, or die.

From Chinese medicine, I take what is useful and I and leave the rest. Eating animals is not useful, no matter how many "older medicines" claim so. I wonder why you think all things claimed by ancient Chinese sources are flawless, unless you are unaware of the fact that, as in Western medicine evolution, it dragged along a lot of crap installed by sub-par physicians who had all kinds of crazy beliefs.

As for the different constitutions claim, this is bogus. Humans are a single species. Would you find "different constitutions" among cattle, some needing a Vata dosha diet, and others needing a Kapha dosha diet? How about chimps? Why would humans be different?

Also, you forget that a lot of Chinese medicine recommendations came into existence as "treatments" for people who were impoverished and undernourished. In such circumstances, I am sure it looked like meat was beneficial. I don't ever see any starving people in my practice. I see people suffering primarily from nutritional excesses, not deficiencies.

There were eminent Chinese physicians who due to their Taoist and Buddhist sensibilities recommended avoiding the use of animals whenever possible. Today it is completely possible for anyone in a modern wealthy nation to avoid eating animals and be very well nourished. I am not presenting anything incompatible with Chinese medicine.

Rex said...

I disagree big time with most of what you said, and I think your ideas on Chinese medicine, while valid, distort reality. You cherry pick rhino horn, dog meat, and other absurdities to validate your claim that Chinese medicine and Ayurveda do not have the right idea when it comes to meat consumption. That's like me saying western surgical techniques are worthless because people used to practice blood-letting. You are right that they are ever-evolving, dynamic fields and that there is plurality in them. Not trying to be a dick here, and I am by no means an expert...But unless you were trained for many years by pre-cultural revolution Chinese physicians, you don't know enough about this field to pick and choose what parts are valid. Personal experience from empirical observation and extensive training from knowledgeable teachers in a master-apprentice relationship is the only way to properly learn Chinese medicine. That's the way it's been for thousands of years. That's why lineage holders were so revered. They are pretty rare nowadays, and many that remain are quacks.

First off, it is 100% indisputable that people have different constitutions. Yes we are all members of Homo sapiens, but does that mean we all have the same innate metabolic rates, height, weight, build, circulation, strength, appetites, tolerances to heat/cold, dryness/humidity, etc.? Come on...if what you are saying were true, everyone would respond in the exact same way to the same external stimuli...Ayurveda and Chinese Medicine may have their flaws, but they are a lot more realistic in their approach to treating disease because they take into account the whole person and they recognize individual differences in constitution.

I can guarantee you that since it is an indisputable fact that people have different constitutions, it is also an indisputable fact that this phenomenon exists in all other species as well. Cattle all eat grass, but do they all have the exact same weight, build, diseases, metabolic rates, etc? obviously not. Maybe some grasses have different properties than others, and cows will pick and choose which to eat based on their individual needs. Same for chimps, gorillas, etc.

I understand you are against meat consumption, but you are unfortunately mistaken in your belief that meat is not useful. I wish you were right, but it is not possible for all human beings on this planet to achieve balanced health without meat consumption. Some people require meat. Unless you are a highly advanced spiritual practitioner who spends most of the day in quiet meditation, long term, you will likely also need to eat some meat as well. See Dr. Klaper's work on vegan "failure to thrive" in his Vegan Health Study. Your theory just does not hold water I'm afraid. I wish veganism were a viable option for everyone...but it's not.

Rex said...

I have lived in China, speak Chinese fluently, have spoken with many Chinese medicine physicians both here and in China. I don't know what you were taught, or who taught you, but never have I encountered a single tidbit of information from any Chinese physician or TCM textbook that suggests veganism is an appropriate diet for everyone. Absolutely preposterous. They all say that veganism may be very useful and effective in the short term for many people but in the long term serious deficiencies will likely result for many people no matter how whole-foods-plant-based the diet. And by the way, the diversity of fruits, vegetables, herbs, grains, and traditionally processed foods is much, much lower in our day and age than it used to be in the past. This is the result of the revolution in agriculture and the disappearance of family farms. People commonly used to eat all parts of an animal and still do in China. There are thousands of different foods in the Materia Medica, and yet if you walk into Whole Foods or even a farmer's market, you can find only a few varieties of each kind of vegetable. Veganism is more than just a diet, it's a lifestyle. You have to change your entire way of life if you want to sustain it long term. The only way I know to reduce caloric requirements (and also increase lifespan by the same token) is through meditation. Some monks take only one meal a day between 11 and 1 PM. I don't know about you, but if I ate only one meal a day, for a week, I would look like a stick figure at the end of it...eventually I would probably be hospitalized if I kept it up. That said, vegetarianism (including dairy and/or eggs) may be suitable for much larger numbers of people, but still may be inadequate for some.

Rex said...

One more point...

"Also, you forget that a lot of Chinese medicine recommendations came into existence as "treatments" for people who were impoverished and undernourished. In such circumstances, I am sure it looked like meat was beneficial. I don't ever see any starving people in my practice. I see people suffering primarily from nutritional excesses, not deficiencies."

I believe you. Americans suffer from nutritional excess AND nutrional deficiency. There is also going to be a possible selection bias for people you treat. But that is hardly proof that meat is never useful let alone that a whole foods plant based vegan diet is appropriate for everyone.

"There were eminent Chinese physicians who due to their Taoist and Buddhist sensibilities recommended avoiding the use of animals whenever possible."

This is true. But the key words are "whenever possible" and it's not always possible. Especially for lay people. Monks are a different story...

"Today it is completely possible for anyone in a modern wealthy nation to avoid eating animals and be very well nourished. I am not presenting anything incompatible with Chinese medicine."

Oh but you are. Even going back to the Neijing, animal foods are seen to be "beneficial." This is not in reference to medicine but to the components of a balanced diet.

Anonymous said...

This interventional study found that feeding mice ground beef reduced anxiety, improved learning and memory and decreased food seeking behavior. This was associated with an improved diversity of the gut microbiome.

Physiol Behav. 2009 Mar 23;96(4-5):557-67. doi: 10.1016/j.physbeh.2008.12.004. Epub 2008 Dec 24.

Memory and learning behavior in mice is temporally associated with diet-induced alterations in gut bacteria.

Li W1, Dowd SE, Scurlock B, Acosta-Martinez V, Lyte M.

Author information


The ability of dietary manipulation to influence learning and behavior is well recognized and almost exclusively interpreted as direct effects of dietary constituents on the central nervous system. The role of dietary modification on gut bacterial populations and the possibility of such microbial population shifts related to learning and behavior is poorly understood. The purpose of this study was to examine whether shifts in bacterial diversity due to dietary manipulation could be correlated with changes in memory and learning. Five week old male CF1 mice were randomly assigned to receive standard rodent chow (PP diet) or chow containing 50% lean ground beef (BD diet) for 3 months. As a measure of memory and learning, both groups were trained and tested on a hole-board open field apparatus. Following behavioral testing, all mice were sacrificed and colonic stool samples collected and analyzed by automated rRNA intergenic spacer analysis (ARISA) and bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP) approach for microbial diversity. Results demonstrated significantly higher bacterial diversity in the beef supplemented diet group according to ARISA and bTEFAP. Compared to the PP diet, the BD diet fed mice displayed improved working (P=0.0008) and reference memory (P<0.0001). The BD diet fed animals also displayed slower speed (P<0.0001) in seeking food as well as reduced anxiety level in the first day of testing (P=0.0004). In conclusion, we observed a correlation between dietary induced shifts in bacteria diversity and animal behavior that may indicate a role for gut bacterial diversity in memory and learning.