And as more people are persuaded that a vegetarian diet is a healthy diet, it is essential that they are made aware of the possible adverse effects of such a diet.
In 2008, a study was published which showed that adopting a vegetarian lifestyle could lead to a significant amount of brain shrinkage, and that the more extreme the diet (vegan) caused the most extreme brain loss. I reported this at Vegetarians have smaller brains
Now, a 2012 study links vegetarianism with other mental conditions. The mental conditions studied include:
- Unipolar Depressive Disorders
- Anxiety Disorders
- Somatoform Disorders and Syndromes
- Eating Disorders
A small but increasing number of people - now a considerable minority of populations in Western - countries are choosing to restrict meat in their diets or cut it out altogether for various reasons.
During the past decades, increasing knowledge has emerged about the effects of vegetarian diet on nutritional status and physical health. Taken as a whole, studies have shown that vegetarians are in good physical health compared with national averages and as healthy as non-vegetarians with a comparable background and lifestyle.
Many different processes could, in principle, produce differences between vegetarians and meat eaters in rates of mental disorders. On a biological level, nutrition status resulting differences in nutrient intakes from a vegetarian diet may affect neuronal function and synaptic plasticity, which in turn influences brain processes relevant for onset and maintenance of mental disorders [3,4]. For example, there is strong evidence that long-chain n-3 fatty acids causally affect risk for major depressive disorders [5,6]. Also low vitamin B12 levels appear to be causally linked, not only to brain shrinkage, but also to major depressive disorders. Studies have reported that vegetarians show lower tissue concentrations of long-chain n-3 fatty acids [7,8] and vitamin B12 [9,10] which may elevate the risk for major depressive disorder.
Besides differences in nutrition status, vegetarians and non-vegetarians differ in a number of psychological and socio-demographic characteristics that may influence their risk for mental disorders. Vegetarians are predominantly female , are more likely to live in urban areas and to be single . All these factors are correlates of the presence of mental disorders . Moreover, vegetarians tend to be more aware of the factors influencing their dietary intake and of the importance of a healthy lifestyle in general, they tend to define themselves negatively by emphasizing what they do not do; they tend to stress their dissimilarity from others and thereby accentuate their differences from the general society . Thus, some psychological and socio-demographic characteristics of vegetarians, such as negative self-definition and dysfunctional eating attitudes, could have detrimental effects on mental health.
To be fair, any associations that may be found between vegetarian diet and mental disorders could be attributable to several possible causal mechanisms:. For example:
- the biological effects of diet have an influence on brain processes that increases the chance for the onset of mental disorders, in which case it could be expected that adopting a vegetarian diet would precede the onset of mental disorders;
- relatively stable psychological characteristics influence the probability of choosing a vegetarian diet pattern, and developing a mental disorder occurs independently, in which case the adoption of the diet and the onset of a mental disorder would be unrelated;
- developing a mental disorder increases the likelihood of choosing a vegetarian diet, in which case the onset of the mental disorder would precede the vegetarian diet.
Rates of mental disorders in vegetarians
Shown in the figures below are the 1-month, 12-month and lifetime prevalence rates of mental disorders in participants who were completely vegetarian, predominantly vegetarian, and in non-vegetarian matched samples. As you will see, the 12-month and lifetime prevalence rates of depressive disorders were nearly 15 % higher in the completely vegetarian group compared to the non-vegetarians. As could be expected, prevalence rates of individuals with a predominantly vegetarian diet were somewhere in between the other two.
Kinds of food eaten by participants with and without mental disorders
Consumption of food products by individuals with and without mental disorders showed a very consistent pattern: individuals suffering from a depressive, anxiety, or eating disorder as well as from a somatoform disorder and syndrome consumed less meat. This pattern emerged for 1-month, 12-month as well as lifetime prevalence rates. Analysis in a subsample of non-vegetarians also consistently showed that people suffering from a mental disorder also ate less meat than people without a mental disorder.
On the whole, the results of this study strongly corroborate the past findings in smaller samples of adolescents and young adults, which have demonstrated that in contrast to physical health, a vegetarian diet is not associated with better mental health. Whether compared with a control group of non-vegetarians matched for important socio-demographic characteristics, or with non-vegetarians in general, vegetarians show elevated prevalence rates of diverse mental disorders.
The authors say that: "Importantly, we found no evidence for a causal role of vegetarian diet in the etiology of mental disorders. Rather, our results are more consistent with the view that the experience of a mental disorder increases the probability of choosing a vegetarian diet, or that psychological factors influence both the probability of choosing a vegetarian diet and the probability of developing a mental disorder."
Either way, studies like this and many others demonstrate clearly that vegetarianism may have some serious consequenses affecting the brain.
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