Are We What We Eat?

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September 24, 2014

Every morning I enjoy a cup of dark roast coffee with cream and Sweet N’ Low (saccharin). A recent article in the journal Nature, “Artificial Sweeteners Induce Glucose Intolerance by Altering Gut Microbiota” may cause me to change this habit.

Saccharin was discovered by a Hopkins chemist Constantin Fahlberg. Its safety was long questioned due to concerns that it caused bladder cancer in rodents. In 2001 the USDA reversed its position and deemed it safe after it was found that rodent physiology was unique to rodents, and doesn’t apply to humans. Theodore Roosevelt is quoted as saying “Anybody who says saccharin is injurious to health is an idiot.” Based on the article in Nature he might change his position.

Dr. Elinav, et. al. at Weizmann Institute in Israel looked at the effects of saccharin, sucralose and aspartame (artificial sweeteners – AS) on gut bacteria (microbiome) in mice and humans. They found that although AS are not absorbed, they impact our microbiome and it is this change that is associated with glucose intolerance, a condition linked to diabetes and metabolic syndrome.

In the first part of the study, mice were fed AS for 11 weeks. They then did a glucose tolerance test on them to see how they processed sugar. Mice given the AS had higher levels of glucose in their blood than those that were fed sugar or just water (controls). Then the mice given the AS were given antibiotics to kill all of their gut bacteria. This resulted in normalization of their glucose levels. The researchers also transplanted gut bacteria (fecal material) from the mice fed the AS into mice who did not have gut bacteria (germ free mice) and this resulted in those mice developing the same abnormal glucose levels. Somehow the AS changed the bacteria in such a way as to interfere with proper processing of sugar. Genetic analysis of the mice’s microbes showed changes in specific metabolic pathways that were felt to be linked to diabetes/metabolic syndrome.

That’s the rodent part of the story. The researchers then took 7 (OK – not exactly a huge number) healthy lean human volunteers and gave them 5 days of the “recommended dose” of saccharin. Sixty percent of them developed abnormal elevations of blood sugar. Transferring their stool into mice again resulted in abnormal blood sugar levels in those mice.

So what is a poor soul like me supposed to do with this information? What does this imply about the use of fecal transplant for patients with C. difficile, an infection that develops after all the other gut bacteria are wiped out by antibiotics? Do those of us who have frequent exposure to antibiotics have less risk of diabetes? Would having daily yogurt or a probiotic change one’s risk of diabetes if you regularly consumed AS? This area of study is fascinating and murky! However, my best advice to myself, despite the small human study size, will be to try to wean off the saccharin, skip the sugar and enjoy the natural flavors of coffee, cream and now perhaps cinnamon.


J. Suez et al. “Artificial sweeteners induce glucose intolerance by altering gut microbiota.” Nature (2014) doi:10:1038/nature13793