My mother used to joke about my "drinking problem." But before you think I have a problem with alcohol, know that my issue had nothing to do with wine. It was the 2-liter bottle of diet soda that I went through almost daily that she saw as an issue.
I kicked my diet soda addiction several years ago after I started paying attention to what I was putting in my body. I stopped buying anything with artificial sweeteners in it. Although I didn’t know at the time that artificial sweeteners aren’t particularly effective in achieving weight loss or can increase your chances of getting diabetes, I knew I didn’t want so many artificial foods in my family’s diet. I initially went with my gut on that decision, and now my gut has a reason to thank me.
A 2018 study suggests artificial sweeteners disrupt the production of gut bacteria. Researchers exposed a certain strain of E. coli to six different types of sweeteners — aspartame, sucralose, saccharine, neotame, advantame, and acesulfame potassium-k. This E. coli is the type that lives in the mucus of our intestines and keeps our digestive tract healthy. They discovered that the E. coli became stressed after being exposed to artificial sweeteners, which affects the growth and reproduction of gut microbes.
"This is further evidence that consumption of artificial sweeteners adversely affects gut microbial activity which can cause a wide range of health issues," wrote professor Ariel Kushmaro.
This study isn't the first to examine artificial sweeteners' effects on the gut.
A 2014 scientific study also suggested that the reason artificial sweeteners may be a factor in diabetes, even though they don't contain sugar, is because they mess with gut bacteria. Rodale News reported that scientists found that when mice drank water that contained the artificial sugar substitutes saccharin, aspartame and sucralose, the mice developed glucose intolerance — something that can be linked to type 2 diabetes and other metabolic diseases. Mice fed plain water or water with regular sugar didn’t develop the glucose intolerance.
When scientists manipulated the gut bacteria in the mice’s stomachs and killed most of it off, they found that the glucose intolerance disappeared.
Based on what they found in mice, scientists conducted a small trial on humans that measured the gut bacteria of healthy people who consumed artificial sweeteners. They found that after just one week, participants started showing glucose intolerance and their gut bacteria composition had changed.
Do artificial sweeteners make us fat?
No sugar and fewer calories make artificial sweeteners an attractive choice for those looking to keep the sweet taste but lose the pounds. A study presented at ENDO 2017, the Endocrine Society's annual conference in April, demonstrated that some sweeteners encourage the accumulation of fat, particularly among the already obese.
Researchers first took the common low-calorie sweetener sucralose — you know it as Splenda — and placed roughly the amount of sucralose from four cans of diet soda on stem cells from human fat tissue. The cells were placed in a petri dish for 12 days, and the results weren't all that great for sucralose consumers. There was an increased expression of genes that mark fat production and inflammation and an increase in the accumulation of fat droplets in cells.
Based on these results, a second experiment was conducted, this time using biopsy samples of abdominal fat from those who consumed primarily sucralose. Four of the people were obese and four were a healthy weight. The first group demonstrated a higher increase in sugar (glucose) transport into cells and an overexpression of fat-producing genes compared to those at a healthy weight. Additionally, the first group's sweet taste receptions were 2.5-fold higher than those who didn't consume sweetners. The abundance of such receptions may play a part in allow glucose to center the cells.
"Many health-conscious individuals like to consume low-calorie sweeteners as an alternative to sugar. However, there is increasing scientific evidence that these sweeteners promote metabolic dysfunction," said Dr. Sabyasachi Sen, an associate professor of medicine and endocrinology at George Washington University in Washington, D.C., and the study's principal investigator, said in a statement.
The study was, as Sen noted, very small, and needs to be replicated on a much larger scale to confirm the findings. "However, from our study," Sen said, "we believe that low-calorie sweeteners promote additional fat formation by allowing more glucose to enter the cells, and promotes inflammation, which may be more detrimental in obese individuals."
A more recent review of the scientific evidence on artificial sweeteners concluded that there is no clear evidence that they help people manage their weight.
"We were really interested in the everyday person who is consuming these products not to lose weight, but because they think it's the healthier choice, for many years on end," Meghan Azad, lead author of the review and a research scientist at the University of Manitoba, told NPR. The review was published in the Canadian Medical Association Journal.
A 2018 study further expanded on the theory that artificial sweeteners can lead to diabetes and obesity.
This study was also conducted on mice — half were given a diet of sucrose and fructose (types of sugar) and the other half aspartame or acesulfame potassium (types of artificial sweeteners). Both groups experienced different levels of biochemicals, fats and amino acids.
Researchers believe "based on their findings" that consuming too much artificial sweetener can affect how our bodies metabolize fat and stores energy — which in turn can lead to an increased risk of diabetes and obesity.
"We observed that in moderation, your body has the machinery to handle sugar; it is when the system is overloaded over a long period of time that this machinery breaks down," lead researcher Brian Hoffmann said. "We also observed that replacing these sugars with non-caloric artificial sweeteners leads to negative changes in fat and energy metabolism."
Diet sodas and stroke and dementia
An April 2017 study found a link between diet sodas and a higher risk of stroke and dementia. The research didn't show a direct cause-and-effect relationship, only causation, and the researchers point out that the study had many limitations. Yet, because people who drank diet soda every day were almost three times as likely to develop stroke and dementia, researchers suggest that they may not be the healthiest alternative. The study was published in the American Heart Association's journal Stroke.
“Our study shows a need to put more research into this area given how often people drink artificially-sweetened beverages,” Matthew Pase, Ph.D., a senior fellow in the department of neurology at Boston University School of Medicine and lead author of the study, said in a statement.
And don't swap your diet soda for a regular soda or other sugary drink, the researchers caution.
“Although we did not find an association between stroke or dementia and the consumption of sugary drinks, this certainly does not mean they are a healthy option," Pase said. "We recommend that people drink water on a regular basis instead of sugary or artificially sweetened beverages.”
It’s important to remember that artificial sweeteners aren’t only found in diet sodas. They can also be found in other low-calorie treats like yogurt, ice cream, bakery products and candy.
Editor's note: This story has been updated since it was published in September 2014.