09 Jul Artificial Sweeteners Harm the Microbiome
A paper published in Nature provides evidence in support of an emerging idea that artificial sweeteners are not directly bad for people (humans cannot even digest most of them). Rather, they may be bad for the zillions of microbes that live in people’s guts—and this, in turn, may be bad for their human hosts.
Between three and ten times as many bacteria live on or in the typical human as there are cells in that person’s body. Researchers have only recently begun to appreciate the importance of these fellow travellers, known collectively as the “microbiome”. Gut bacteria, in particular, seem able to affect all kinds of bodily functions. Their actions and secretions have been implicated in everything from depression and arthritis to the regulation of the immune system.
Several previous studies have suggested that artificial sweeteners might affect intestinal bacteria. But the Nature paper, is the most robust yet. The initial work was done in mice. Three groups of rodents were given water containing aspartame, sucralose or saccharin, three common commercial sugar substitutes. Three control groups were given plain water or water laced with glucose or sucrose—sugars from which the body can extract energy.
After a week, Dr Elinav and Dr Segal gave their animals a hefty dose of glucose and measured how well they processed it (inability to do so properly is a risk factor for obesity, and is characteristic of diabetes). The mice drinking the artificial sweeteners had higher levels of glucose in their blood than did their confrères who had been sipping water or ordinary sugar.
To check whether the sweeteners were affecting the murine microbiome, the researchers dosed their mice with broad-spectrum antibiotics. Sure enough, killing off the gut bacteria reversed the metabolic changes. To make doubly sure, they transplanted faeces from mice that had been drinking artificial sweeteners into others that had been raised in sterile conditions, and which, therefore, had no gut bacteria of their own. Once the transplanted bacteria had colonised their new hosts, these too began showing signs of glucose intolerance.
Gene sequencing confirmed that mice fed artificial sweeteners had a notably different set of bacteria living in their guts from those fed on the natural kind. Intriguingly, the microbiomes of the sweetener-fed mice looked a lot like those found, by other studies, in obese individuals.
Resources:
Artificial sweeteners induce glucose intolerance by altering the gut microbiota Jotham Suez et al, Nature 514,181–186 (09 October 2014) doi:10.1038/nature13793