The awareness of how our eating behaviour affects our bodies and mental health is on the rise as research within the field is expanding as well as increased efforts to inform the general population about eating habits, nutrition and its effects on the body and mind. Our own school of psychology at Bangor University has even designed their own program, called Food Dudes, to encourage schoolchildren to eat more fruit and vegetables to promote a healthier lifestyle.
Commonly known is that what you eat can cause heart disease, diabetes, obesity and other physical problems. What’s not often considered and what research now has begun to look deeper into is the importance of our diet on our mental health and the factors involved for different psychological conditions, such as depression (Cabrera et al. 2007; Mattar et al. 2011). This blog will evaluate and criticize different types of protein sources and how it affects your brain and emotions.
There are many ways in which what you eat affects you, but on a fundamental level – what you eat affects your neurotransmitters and thereby hormones which in turn affects your mood, energy levels and motivation (Canetti et al. 2002). The nutrient most of us are aware of is protein and that it is necessary for muscle maintenance and weight control as it controls the hunger effect (Batterham et al. 2002). What we don’t know is that protein is crucial in the uptake of Tyrosine and Tryptophan, which is responsible for the production of Dopamine, Norepinephrine and Serotonin in the brain (Choi et al. 1997; Schaechter & Wurtman RJ, 1990).
Protein can be found in most animal products however nutrients from plants such as beans and soy may be equally sufficient as a source of protein. Friedman and Brandon (2001) reviews for the benefits of soy-products being lowered fat gain, lower serum cholesterol and glucose levels in diabetic rats. This suggests that soy products can be used as a means to treat obesity as it’s a good source of protein with low fat rate which makes it beneficial during energy-restricted diets. Criticism to their studies is that their research was mainly done on rats; however they acknowledge this and assess the necessity of further research on humans. Opposing factors to the use of soy is the risk of prostate or breast cancer and hormonal imbalance; though these are mostly animal studies and point out that we don’t know how consumption will affect humans (Setchell et al. 2011). There are some cases where men consuming heavy amounts of soy can experience gynecomastia reduced sexual desire and impotence due to the female plants sex hormone phytoestrogen (Thornton, 2009). However, this may only have been one contributing factor as there is low evidence for plant hormones affecting either males or females (Kurzer, 2002; Weber et al. 2001).
In their study, Choi et al. (1997) found that all sources of protein tested (milk, soy and gluten) raised dopamine and norepinephrine levels as expected. Interestingly they discovered that lactalbumin (found in milk) increased the serotonin levels when zein (wheat) and casein (eggs, cheese), did not. It seems that soy itself does not raise serotonin levels as it does not contain lactalbumin; however it does contain complex carbohydrates that will increase levels of tryptophan which cares for this effect (Schaechter & Wurtman RJ, 1990).
Different types of protein seem to be affecting the body differently because of its molecular compounds, the way these affect our mood can be one underlying factor to depression as your diet may be limiting you uptake of necessary nutrients required to feel good. Studies carried out on elderly and anorexia nervosa patients shows that malnutrition is one contributing factor to depression (Cabrera et al.2007; Smoliner et al. 2009; Wade et al. 2000). Because of proteins properties of increasing levels of “feel good” hormones we can conclude that whenever we are feelings down and have cravings for unhealthy food – what our body really is telling us is to eat protein to restore the hormonal balance. Our body knows what it needs and signals it to our brain, our body is best at taking care of itself, we must simply learn to listen to it in order to increase well-being.
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