In the midst of the Ebola crisis it may seem counterintuitive to write this article telling you that not only are micro-organisms important but they could be a secret weapon for success.
The human gut contains approximately 100 trillion bacteria, ten times more than there are human cells. Don’t be alarmed: Although microbes can be the most deadly things on the planet, they also shape your density, have many roles in health and disease, and bad gut bacteria has even been shown to be a cause of depression. They are the gatekeepers for your digestion. So feed them well, and you’ll be well looked after
Are you getting smarter, or do you feel like you are losing your mind? Well maybe you are. You lose 10,000 brain neurons every day but these are replaced with the creation of new ones thanks to signalling molecules. for example, BDNF (Brain derived neurotrophic factor) causes neurogenesis (the formation of new neurons) that protects against our brain degenerating. You need to make new neural pathways to learn and work effectively, therefore increase in factors such as BNDF has been shown to improve cognitive performance. The bacterial microbiota in the gut helps normal brain development. Bifidobacterium breve, commonly found in probiotics, has been shown (only in animal models so far) to increase BNDF in the brain.
Some gut bacteria can even alter neurotransmitter levels directly by converting glutamate – an excitatory transmitter – into GABA – an inhibitory brain chemical, the brain’s natural chill pill.
Gut microbes can not only talk to each other, via various receptors and proteins, but also with neighbouring intestinal cells, and communicate with a branch of the nervous system known as the enteric nervous system (ENS) whose neurons surround the entire gastrointestinal tract. Essentially it’s your second brain.
A simple change in diet can shift your brain up a gear
Researchers at UCLA have neatly shown that probiotics can also affect resting brain activity in human subjects. They used yoghurt that contained 4 different species of bacterium including bifidobacterium and lactobacillus. This study involved 36 women divided into three groups: one group ate a specific yogurt containing a mix of several probiotics twice a day for four weeks; another group consumed a dairy product that looked and tasted like the yogurt but contained no probiotics; and a third group ate no product at all. Their brain state was accessed using Functional magnetic resonance imaging (fMRI) scans that were conducted both before and after the four-week study period looked at the women's brains.
Certain bacteria is also correlated with lower intellect. H.Pylori can not only lead to stomach ulceration, but its confirmed presence has been shown to correlate with poorer cognition in a study of over 400,000 people, in the US.
You can positively alter your own microbiome with your diet. Fermented foods, such as yoghurt, kimchi, sauerkraut and pickled vegetables are fantastic for this reason. Kimchi in particular contains Lactobacillus pentosus that has been shown in mice to protect against memory deficits, by increasing BDNF.
Many traditional fermented foods (think honey, sake, miso, and soy sauce) contain isomalto-oligosaccharides and have been shown in animals and human beings to have a beneficial effect in promoting the growth of Bifidobacteria and Lactobacilli, the good bacteria.
Your unconscious manipulators contributing to obesity
Do you ever wonder why you crave certain food? Some foods, particularly those ladened with sugar, produce a dopamine rush, but it could be due to your gut bacteria that are manipulating your desires. Bacteria release signals that are carried along the vagus nerve that runs from the digestive system to the brain. These signals affect our mood, appetite and entice us to eat what the bacteria crave. Our diet has a great impact on the microbial populations in the gut, and in return they influence what we eat, which is why giving up certain foods can be so difficult. So the more you eat cakes and sweets, the more sugar craving bacteria grow that perpetuate the problem.
A highly caloric diet, might provide food for microbial growth, permitting certain species to bloom, overriding other organisms and the immune system. Therefore this may result in low diversity, leading to a vicious cycle of increased manipulation and chronic energy excess. Such a positive feedback mechanism could drive long-term changes in satiety, and could lead to obesity.
The good the bad and the putrifying
The good news however is that because microbiota are easily manipulated by prebiotics, probiotics, antibiotics and dietary changes, altering our microbiota offers a surprisingly effective option to altering much from the way we think about obesity.
While much research points towards the importance of gut bacteria, research is still far behind with most studies still only looking at mice models, with diets and brain function far removed from our own. It’s an exciting and growing area of research, that comes a long way from the over simplified molecular nature of treating disease. There is definitely growing evidence to show that your microbiota has more impact on you than you would have thought.
In a society where high-sugar foods is the norm, these foods are a mismatch to our evolutionary past and not only are they undermining our optimal nutritional status, they have untold effects on the microbiome and ultimately the brain.
What’s your gut feeling?
References (studies and reviews)
- Alcock et al (2014) Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and potential mechanisms. Bioessays. 2014 Oct;36(10):940-9
- Barrett, E., et al. (2012). "gamma-Aminobutyric acid production by culturable bacteria from the human intestine." J Appl Microbiol 113(2): 411-417.
- Bested, A. C., et al. (2013). "Intestinal microbiota, probiotics and mental health: from Metchnikoff to modern advances: Part II - contemporary contextual research." Gut Pathog 5(1): 3.
- Beydoun, M. A., et al. (2013). "Helicobacter pylori seropositivity and cognitive performance among US adults: evidence from a large national survey." Psychosom Med 75(5): 486-496.
- Bercik, P. et al. The intestinal microbiota affect central levels of brain-derived neurotropic factor and behavior in mice. Gastroenterology 141, 599–609.e3 (2011). A key study showing the utility of microbiota transplantation in mice to examine the microbiota–gut–brain axis.
- Claesson, M. J., et al. (2012). "Gut microbiota composition correlates with diet and health in the elderly." Nature 488(7410): 178-184.
- Cryan, J. F. and T. G. Dinan (2012). "Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour." Nat Rev Neurosci 13(10): 701-712. Great review compling many studies that show how microbiota influence brain behaviour
- Dinan, T. G. and J. F. Cryan (2013). "Melancholic microbes: a link between gut microbiota and depression?" Neurogastroenterol Motil 25(9): 713-719.
- Hsiao, E. Y., et al. (2013). "Microbiota modulate behavioral and physiological abnormalities associated with neurodevelopmental disorders." Cell 155(7): 1451-1463.
- Jung, I. H., et al. (2012). "Lactobacillus pentosus var. plantarum C29 protects scopolamine-induced memory deficit in mice." J Appl Microbiol 113(6): 1498-1506.
- Krajmalnik-Brown, R., et al. (2012). "Effects of gut microbes on nutrient absorption and energy regulation." Nutr Clin Pract 27(2): 201-214.
- Savignac, H. M., et al. (2013). "Prebiotic feeding elevates central brain derived neurotrophic factor, N-methyl-D-aspartate receptor subunits and D-serine." Neurochem Int 63(8): 756-764.
- Tillisch, K. et al. Modulation of the brain–gut axis after 4-week intervention with a probiotic fermented dairy product. Gastroenterology 142, S-115 (2012)
- Tillisch, K., et al. (2013). "Consumption of fermented milk product with probiotic modulates brain activity." Gastroenterology 144(7): 1394-1401, 1401 e1391-1394. Key study, in humans, showing how yoghurt, with particular bacterium, affect cognition
- Diet affects mix of intestinal bacteria and risk of inflammatory disease