Research We’re Reading

NRI scientists are reading latest findings in the field of nutrigenomics to share new information with you.




Artificial Sweeteners: New Findings Suggest Negative Health Implications

From the desk of: Karen D. Corbin, Ph.D., R.D. 

As a registered dietitian, I am often asked: “What do you think about artificial sweeteners?” My answer is always the same: “Since they are artificial and not enough research has been conducted to know for certain if they can be harmful, I suggest using them in moderation, learning to drink beverages that are naturally sugar-free, or using regular sugar instead but in moderation.” New research published in the journal Nature indicates a negative impact of artificial sweeteners on the helpful bacteria that live in our intestines. The findings were intriguing and provide one important piece of the puzzle to help better understand the role of these food additives on health.

sugarsubstitutes_612THE STUDY
Artificial sweeteners have been shown to have beneficial effects on weight and metabolism, while other studies have shown the opposite. Despite this controversy, the Food and Drug Administration has approved six different artificial sweeteners for use in the United States. Most artificial sweeteners pass through the intestinal tract without being digested, making them available for processing by the bacteria that reside normally in the gut. These bacteria are very important for processing nutrients and can affect our metabolism and health.

A group of scientists at the Weizmann Institute of Science in Israel wanted to find out if artificial sweeteners affect the types of bacteria in the gut and, if so, what the impact is on metabolism. In mice, the scientists found that artificial sweeteners lead to insulin resistance and an imbalance of bacteria in the gut (dysbiosis), compared to water alone or water with natural sugars like glucose or sucrose. When gut bacteria from mice fed artificial sweeteners were transferred to mice that had no bacteria in their gut, the same harmful metabolic effects occurred.

This strongly suggested that the harmful metabolic effects of artificial sweeteners were due to their effects on the gut bacteria. In non-diabetic humans, the scientists also found that long-term consumers of artificial sweeteners had many traits characteristic of metabolic syndrome and fatty liver. Importantly, when they fed healthy volunteers who did not normally consume artificial sweeteners an acceptable daily amount of artificial sweeteners for six days, their metabolisms worsened and their gut bacteria changed.

The study was well done, but focused most of its efforts on one specific artificial sweetener, so the findings may not apply equally to all of them. The part of the study where people were asked to consume artificial sweeteners was very small, and some of the people did not have the same response as others.

Although this study does not provide conclusive evidence that all artificial sweeteners are harmful for all people, it does suggest one way that these food additives could have negative health consequences. Moderation still stands as a reasonable course of action.

Reference: Artificial sweeteners induce glucose intolerance by altering the gut microbiota Nature. 2014 Sep 17. doi: 10.1038/nature13793. PMID: 25231862

Gut Microbes Can Determine Your Weight

From the desk of: Steve Zeisel, M.D., Ph.D.

Gut microbes have been making a lot of news lately. As the name implies, these bacteria reside in the intestine and fulfill a variety of functions essential to our health, specifically ensuring that we digest foods properly. But that’s only the beginning. A recent study shows that gut microbes can also determine your weight.

134248288THE STUDY
Gut microbes were harvested from 4 pairs of women who were twins. One twin was thin and the other twin in each pair was obese. The microbes were transplanted in mice. The mice getting the microbes from the obese twin became fatter while the mice getting microbes from the paired lean twin did not get fatter.

Until recently we did not realize that the microbes that we house in our guts have an important role in nutrition and metabolism. This study demonstrates that obese people have different microbes in their guts than do lean people and these microbes can change our body weights. How do they do this? We do not yet know but perhaps these microbes make calories more available from hard to digest foods, or perhaps they make signals that disturb how we respond to hormones like insulin.

Our gut microbes are influenced by what we eat. Vegetarians have different microbes than do meat eaters. Some foods, like yogurt, contain bacteria and may help change our microbes. Antibiotics used to treat infections, also can make big changes in our bacteria. Babies delivered vaginally are populated with very different bacteria than babies delivered by C-section.


ReferenceGut microbiota from twins discordant for obesity modulate metabolism in mice. Science. 2013 Sept 6;341(6150):1241214. doi: 10.1126/science.1241214. PMID: 24009397.