Can we affect bacterial communication?

Artificial Sweeteners

Artificial Sweeteners

Are they truly zero-calorie, healthier alternatives to sugar?

With the human gut microbiome entering the spotlight of health research, any “zero-calorie” food item might need to be re-examined. The foods we eat influence the diversity in our gut. Any diet high in fibre, or in simple carbohydrates, or one that decreases transit time through the small intestine, can potentially alter the bacterial species present. A fibreless, sugar rich diet is particularly notorious for causing an overgrowth of unbeneficial bacteria in the colon and even in the small intestine. These strains owe their success to a much higher metabolism, one dependent to a constant influx of undigested sugar.

Since gut bacteria are known to communicate with us, the host, via chemical messengers, and to influence our behaviour, it should come as no surprise that an unbalance inside the gut is one of the proposed causes of overfeeding and even sedentary behaviour.

If the artificial sweeteners can be digested by bacteria, then they provide a huge burst of energy to the colon, compared to the usual amount of fibre.

Furthermore, some sugar alcohols are known for their anti-microbial effects. Does this mean the sweeteners can kill certain beneficial strains and allow harmful ones to spread?

To test this, we used two analogs of common gut bacteria: B.megaterium and E.coli. They were grown on LB media containing glucose, sorbitol, mannitol, or a commercial sweetener (sucralose-erytritol). The aim is to compare growth with the glucose medium and see whether they can be called “zero-calorie” or not.

There is also a negative control, containing only LB. Comparing to the growth in such a low calorie medium will show if the sweeteners have a toxic effect.

The 2% refers to the concentration of glucose in the control medium: 2g/100ml. Visually, the slope is consistent in all media. Only the commercial sweetener has shown different initial growth which is likely due to a much higher osmotic pressure stressing the bacteria.

In this image it is clearly seen that E.coli can grow on all chosen media. The toxicity of sweeteners, if there is any, is not significant in the short-term proliferation. Since they are poorly absorbed in the small intestine, the consumption of sweeteners is comparable to a regular flow of partially digested / absorbed food in terms of energy availability

Unfortunately, the two species of bacteria are not enough to make any proper conclusion but, since the growth curves were strikingly similar in all media, there is clearly a potential for artificial sweeteners to perturb the microbiome. Future research should test a much wider range of bacterial species found in the human colon, and not merely analogues, to see if the pattern is the same. Long term incubation should also be tested, especially on pathological strains know to infect the small intestine, to see if the sweeteners can sustain an overgrowth long term. Finally, the sweeteners should be compared to a truly zero-calorie medium, controlled for osmotic pressure, to see if there is any long term toxic effect. The sample should be tested for any possible metabolites or ‘waste products’ that might be antimicrobial or irritating to the intestine lining.

If you wish to know more, there are the references used:

Walker, A.W., Ince, J., Duncan, S.H., Webster, L.M., Holtrop, G., Ze, X., Brown, D., Stares, M.D., Scott, P.,

Bergerat, A., Louis, P., McIntosh, F., Johnstone, A.M., Lobley, G.E., Parkhill, J. and Flint, H.J., 2011.

Dominant and diet-responsive groups of bacteria within the human colonic microbiota. The ISME

Journal, [online] 5(2), pp.220–230. Available at:

[Accessed 16 Mar.

2017]

Tapiainen, T., Kontiokari, T., Sammalkivi, L., Ikäheimo, I., Koskela, M. and Uhari, M., 2001. Effect of

Xylitol on Growth of Streptococcus pneumoniae in the Presence of Fructose and Sorbitol.

Antimicrobial Agents and Chemotherapy, [online] 45(1), pp.166–169. Available at:

[Accessed 16 Mar. 2017]

Swithers, S.E., 2013. Artificial sweeteners produce the counterintuitive effect of inducing metabolic

derangements. Trends in Endocrinology & Metabolism, [online] 24(9), pp.431–441. Available at:

[Accessed 5 Mar.

2017]

Payne, A.N., Chassard, C. and Lacroix, C., 2012. Gut microbial adaptation to dietary consumption of

fructose, artificial sweeteners and sugar alcohols: implications for host–microbe interactions

contributing to obesity. Obesity Reviews, [online] 13(9), pp.799–809. Available at:

[Accessed 5

Mar. 2017]