Last time I talked about probiotics and their somewhat dubious efficacy claims. Now it’s time to mention prebiotics. For those who were not taking notes or slept through the previous lecture, probiotics supposedly contain “good” bacteria that will help to maintain gut health. Prebiotics, on the other hand, contain no bacteria but various non-digestible carbohydrates, such as lactulose and inulin, that are meant to promote gut health by lowering intestinal pH and selectively stimulating the growth of beneficial bacteria. Many pathogenic bacteria prefer a neutral pH and studies have shown that ingesting lactulose can reduce or eliminate Salmonella from rats and humans (Crittendon 1999). Unfortunately a diet laced with lactulose failed to stop Salmonella shedding in two python species (Holz and Middleton 2005). However, consuming it for six weeks did result in increased faecal bifidobacteria and lactobacilli (“good” bacteria) in humans (Bouhnik et al 2004).
Despite the variable results reported above prebiotics are not necessarily species specific the way probiotics need to be. I suspect the beneficial effects of yoghurt are not because of the bacteria they contain but because they produce an acidic environment more conducive to “good” bacterial growth. The good news is that many of the foods we eat contain prebiotics. High levels can be found in chicory root, dandelion greens, Jerusalem artichokes, garlic, onions and leeks (Moshfegh et al 1999). As usual a balanced and varied diet will provide your body with everything it needs, without resorting to expensive supplements.
Dr. F. Bunny
Bouhnik, Y., A. Attar, F.A. Joly, M. Riottot, F. Dyard, and B. Flourie. 2004. Lactulose ingestion increases faecal bifidobacterial counts: a randomised double-blind study in healthy humans. European Journal of Clinical Nutrition 58: (3) 462-466.
Crittendon, R.G. 1999. Prebiotics. In: Tannock, G.W. (ed.): Probiotics: A Critical Review. Horizon Scientific Press, Wymondham, Norfolk, UK. Pp. 141-156.
Holz, P.H., and D.R. Middleton. 2005. The effect of feeding a prebiotic on Salmonella excretion in carpet pythons, Morelia spilota, and scrub pythons, Morelia amethystina. Journal of Herpetological Medicine and Surgery 15: (1) 4-6.
Moshfegh, A.J., J.E. Friday, J.P. Goldman, and J.K. Chug Ahuja. 1999. Presence of inulin and oligofructose in the diets of Americans. Journal of Nutrition 129: 1407S-1411S.