How Your Gut is Manipulating You, and How Probiotics Can Help You Take Back Control of Your Diet
Don’t Trust Your Gut
A paper published in BioEssaysrecently gave an overview of the ways in which our food cravings and diet are affected by the nutritional needs of the microbiome (i.e. the mix of bacteria unique to each of us at any given time). These bacteria are thought to transmit signals via the vagus nerve up to the brain to affect how we respond to food and the likelihood that we'll eat certain things. The bacteria cause us to crave foods that favour their survival but which can kill off the competition. Unfortunately, what favours any given bacterium may not be helpful for our own health and wellness.
The authors of this paper cite examples such as the Bifidobacteria family which thrives on fibre and is largely responsible for the health of the large intestine (Alcock et al., 2014). Less helpful bacteria, such as Bacteroides, are much more abundant in the guts of people who eat a lot of meat and dairy. Craving that steak may, therefore, not be so much a personal choice as a subliminal message coming from your gut.
Gut Bacteria and Allergies
The risk of B. fragilis infection is significantly decreased in those who regularly take beneficial bacteria in the form of probiotic supplements. In fact, in one study looking at the development of Japanese Cedar Pollinosis (a common allergy in Japan), levels of B. fragilis were seen to be higher in those suffering from allergy symptoms, while those taking Bifidobacteriumlongum had significantly lower levels of B. fragilis and significant relief from allergic symptoms (Odamaki et al., 2008).
How Bacteria Influence Our Emotions
The complex interplay between these bacteria and our nervous system happens because there are millions of neurons in the enteric nervous system, i.e. the nervous system in the gut. The bacteria in our gut act on these nerves and are transmitted to the medulla at the base of the brain via the vagus nerve, which acts as a communication axis.
The enteric nerves can be manipulated both directly by the bacteria themselves and indirectly by bacterial metabolites. Microbes also influence hormone secretion, especially serotonin and dopamine, which then affect levels of hunger, happiness, behaviour and cravings for specific foods. Stimulation of the vagus nerve may even alter our perception of taste by altering the activity of flavour receptors. Bacterial toxins can make us feel unwell, while some bacterial activity can lead to an influx of happy hormones that lead us to associate certain foods with feeling good.
Improving Brain Function and Reducing Anxiety with Probiotics
The idea of the gut-brain connection has been explored before. Indeed, an interventional study using functional magnetic resonance imaging (i.e. MRI scans while people performed certain tasks) reported reduced levels of anxiety and perceived stress, improved coping mechanisms, and enhanced sensory processing in women taking a probiotic containing B. longum, L. bulgaricus, Streptococcus thermophiles (Tillisch et al., 2013). Another study even found that B. longum had a protective effect over the health of brain cells commonly damaged after a heart attack (Girard et al., 2009).
Probiotics clearly have a role to play in digestive and immune system health, and the evidence is mounting to suggest that they can significantly affect our psychological well-being. So, next time you have a craving for bacon, refined carbohydrates or other unhealthy foods you might not want to go with your gut feeling.
For more about the benefits of probiotics check out our 5 Top Tips for How to Choose a Quality Probiotic Supplement
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