This colony of bacteria that we host from birth, which scientist call our ‘gut microbiota’, outnumber human cells 10 to 1. This means that for every human cell there are 10 bacterial cells living in us. In light of this microbial dominance, it would be rather naïve of us to credit all our food craving decision-making to our minds rather than our matter. This raises the humbling question: is our gut microbiota our true mastermind?
Does the evidence stack up?
Recent studies have shown our gut microbiota not only affect our mood and satiety by creating happiness (serotonin and dopamine) and appetite (leptin and ghrelin-like) hormones but can manipulate our taste buds to make us crave different foods. This discovery has taken the scientific world by storm, uncovering direct pathways through which our gut microbiota communicate with our brain. It’s a phenomenon termed the ‘gut-brain axis’. Researchers from Switzerland have proposed this gut-brain axis may explain why some of us are “chocoholics” and others less bothered, with suggestions the two behaviour types host different gut microbial profiles(1). Animal studies have also shown that manipulation of the gut microbiota can predispose animals to a preference towards sweet or fatty food (1) (2). These findings are just another piece of the pie linking the gut microbiota and obesity (pun intended...).
Is our gut bacteria making us fat?
According to the latest research from the US, our gut bacteria may bias us toward obesity, with a study in twins demonstrating distinct differences in the gut bacterial profiles between obese and lean twins (3). Further to this, transferring the fecal-gut bacteria from an obese twin to germ-free mice resulted in transmission of obesity compared to the mice who received the lean co-twin’s sample (4). This landmark finding suggests that obesity may, in fact, be contagious, explaining why cohabitating partners host more similar gut profiles compared to those living apart (5). This finding provides new insight into the obesity epidemic spreading across the globe.
Feeding the inner universe
Just like the gut microbiota can manipulate some of our food choices, research has revealed that we, in turn, can manipulate them. Choosing plenty of high fibre foods is thought to be key in selectively promoting the growth of a healthy gut profile. In particular, including unrefined whole-grains, fresh fruits and plenty of vegetables, including legumes, is associated with an optimal gut profile and healthy body weight.
Some simple tips to up your fibre intake include substituting some of the meat in dishes for legumes, such as chickpeas or lentils, and moving away from traditional white rice and pasta to more of the ancient whole-grains, such as quinoa and buckwheat. If you’ve recently been on a course of antibiotics, have suffered from infective diarrhoea or have just been run down and not eating well a probiotic supplement may help re-balance your gut microbiota.
With this new research in mind, next time you feel a craving coming on, instead of negotiating with your conscience, perhaps you may want to check-in with the health of your gut microbiota?
Rezzi, S, Ramadan, Z, Martin, FP, Fay, LB, van Bladeren, P, Lindon, JC, Nicholson, JK, Kochhar, S: Human metabolic phenotypes link directly to specific dietary preferences in healthy individuals. J Proteome Res, 6: 4469-4477, 2007.
Duca, FA, Swartz, TD, Sakar, Y, Covasa, M: Increased oral detection, but decreased intestinal signaling for fats in mice lacking gut microbiota. PLoS One, 7: e39748, 2012.
Turnbaugh, PJ, Hamady, M, Yatsunenko, T, Cantarel, BL, Duncan, A, Ley, RE, Sogin, ML, Jones, WJ, Roe, BA, Affourtit, JP, Egholm, M, Henrissat, B, Heath, AC, Knight, R, Gordon, JI: A core gut microbiome in obese and lean twins. Nature, 457: 480-484, 2009.
Ridaura, VK, Faith, JJ, Rey, FE, Cheng, J, Duncan, AE, Kau, AL, Griffin, NW, Lombard, V, Henrissat, B, Bain, JR, Muehlbauer, MJ, Ilkayeva, O, Semenkovich, CF, Funai, K, Hayashi, DK, Lyle, BJ, Martini, MC, Ursell, LK, Clemente, JC, Van Treuren, W, Walters, WA, Knight, R, Newgard, CB, Heath, AC, Gordon, JI: Gut microbiota from twins discordant for obesity modulate metabolism in mice. Science, 341: 1241214, 2013.
Song, SJ, Lauber, C, Costello, EK, Lozupone, CA, Humphrey, G, Berg-Lyons, D, Caporaso, JG, Knights, D, Clemente, JC, Nakielny, S, Gordon, JI, Fierer, N, Knight, R: Cohabiting family members share microbiota with one another and with their dogs. eLife, 2: e00458, 2013.