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."
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.