Brain-Gut Communication and Metabolic Power

Today I'm going to discuss a study that challenges what scientists (and consumers) believe about the human metabolism. This study doesn't directly discuss effects of gut bacteria, but instead hormones secreted in the gut (which are regulated by gut bacteria). Nevertheless, I found this study extremely interesting and believe it highlights an important concept; the power of the mind and its communication with the gut.
It's widely accepted that the nutritional facts of our food item of choice, whether it be a slice of pizza or a bowl of salad, will effect our bodies in  predictable ways as labeled on the side of the box or bag. Metabolic science asserts that the degree in which you metabolite food is directly related to the amount of calories being consumed. Grhelin (regulated by Helicobacter pylori) is a hormone secreted in the gut that tells your brain you are hungry and slows your metabolism. If you chose to eat a low-calorie meal (such as a  salad), grhelin levels only drop a little and as a result, the metabolism only increases marginally. On the other hand, if you chose to indulge in a high- calorie meal (like a whole box of meat-lover's pizza), grhelin levels drop more and metabolic activity is increased significantly. 

A study investigating the power of food labels over human physiology discovered that metabolism may be influenced by the brain. Could food labels act as placebo pills and alter the rate of metabolism in the human body? Could reading the icecream's nutrition facts actually effect your waistline? 

In this particular study, 2 groups of people were given  the same milkshake which contained about 300 calories. The catch? Each group received differently labeled milkshakes. One group received a milkshake that was labeled "Low-Calorie, Sensishake, 0% Fat, No Added Sugar, Only 140 Calories". The second group received the same milkshake, only labeled as "Indulgence, 620 Calories". It was discovered that grhelin levels dropped about three times more when the participant believed he/she was indulging in a high-calorie shake in comparison to the "Sensishake" group (Crum et al, 2011). This means that despite both groups drinking the exact same milkshake, one group had a different metabolic response. 

This is an astounding study, as it suggests that our beliefs about our food matter in the metabolism of it.

Reference: 

Crum, A. J., Corbin, W. R., Brownell, K. D., & Salovey, P. (2011). Mind over milkshakes: Mindsets, not just nutrients, determine ghrelin response.. Health Psychology, 30(4), 424-429.

An Inflamed Brain is an Unhappy Brain

Last week I discussed the effects gut bacteria have on the central nervous system and as well as their influence on behaviors observed in mice. These findings suggest that perhaps gut flora manipulation would prove to be an effective treatment of psychological disorders. To elaborate on this idea, I found a study that measured psychological changes under the treatment of probiotics. This study investigated the effects of probiotics on depression, hostility, and anxiety-yielding promising results for potential future treatment methods. A probiotic formulation of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 was given to a general population. Using the Hopkins symptoms checklist-90, the researchers found that people who received the probiotics significantly improved over a 30 day period with a decrease in anxiety and depression,  as well as sub-areas such as obsessive compulsion and paranoid-ideation (Messaoudi  et al., 2011). One possible explanation for these findings is that probiotics reduce brain inflammation. The probiotics used in this research decrease the amount of inflammatory-inducing cytokines (proteins that signal other cells) found in the gut (Messaoudi  et al., 2011). It's speculated that the signals from the cytokines travel via the vagus nerve to the brain (although there are other hypothesis about how these signals travel as well). Brain inflammation has been linked to depression and anxiety; thus priobiotics' ability to reduce inflammation signaling may be linked to the study's findings. However, researchers concluded that not only can probiotics assist in behavioral abnormalities, but in general well being. Moreover, it is believed that chronic stress could disrupt the delicate balance of gut bacteria and thus potentially lead to diseases. However, the researchers speculate that taking probiotics could keep the gut in good health and prevent such unbalance in the future if/when stress arises (Messaoudi  et al., 2011).


Reference:
Messaoudi, M., Violle, N., Bisson, J., Desor, D., Javelot, H., & Rougeot, C. (2011). Beneficial psychological effects of a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in healthy human volunteers. Gut Microbes, 2(4), 256-261.

Gut Flora and the Brain

This week I'll begin discussing how microbiota of the gut can effect your brain! Believe it or not, the bacteria you host in your gut may play an important role in brain chemistry and behavior.

One study I found particularly interesting investigated whether or not anxiety could be linked to gut flora. Researchers took 'fearless' mice and 'anxious' mice and swapped their gut bacteria; so the fearless mouse now had the anxious mouse's microbiota (and vice versa). By altering the microbes of the gut, the anxious mice became bold while the fearless mice became timid. Additionally, the researches investigated the effects of diet, probiotics, and antibiotics on a group of aggressive mice. Due to various alterations of microbes, the aggressive mice appeared to become more docile (Collins, et al., 2013).
You might be asking yourself, 'how could this be possible?!' Well, by measuring the brain chemistry of mice with altered gut microbiota, researchers discovered chemical changes in areas of the brain dealing with emotion/mood as well as an increase in a chemical known as brain-derived neurtrophic factor. Moreover, brain-derived neurtrophic was found to be increased in the hippocampus region of the brain, and is believed to influence both learning and memory (Bercik, et al., 2011). 

Because this is a relatively new area of study, there are still many unknowns. However, researchers are hopeful that eventually alteration of gut flora could become an effective treatment for various disorders of the central nervous  system, including  psychiatric disorders (Collins, et al., 2013).



I found this short video really informative (and fun). It explains gut flora across the human body and discusses why gut microbiota are so important. Although it does not discuss the effects of microbiota on the brain, I still thought it might help some of you grasp the idea of the human microbiome. Enjoy!

(Gudenkauf, 2013). 

References:

 Bercik, P., Verdu, E. F., Denou, E., Collins, S. M., Mccoy, K. D., Macri, J., et al. (2011). The Intestinal Microbiota Affect Central Levels of Brain-Derived Neurotropic Factor and Behavior in Mice.Gastroenterology, 141(2), 599-609.e3.

Collins, S. M., Kassam, Z., & Bercik, P. (2013). The adoptive transfer of behavioral phenotype via the intestinal microbiota: experimental evidence and clinical implications. Current Opinion in Microbiology, 16(3), 240-245.

Gudenkauf, A. (Producer). (2013). The Invisible Universe of the Human Microbiome. United States: NPR.