Diet soda is probably making you fat and giving you diabetes, study says

A series of experiments conducted by researchers in Israel suggests that artificial sweeteners are a causative factor in metabolic disorders like glucose intolerance, a forerunner to diabetes.

According to New Scientist, chemical sweeteners have caused glucose intolerance in mice because they alter the bacterial balance in the gut, and early testing shows they do the same in some human subjects.

"The most shocking result is that the use of sweeteners aimed at preventing diabetes might actually be contributing to and possibly driving the epidemic that it aims to prevent," said study co-author Eran Elinav of the Weizmann Institute of Science in Rehovot, Israel to New Scientist.

The study's abstract -- published in the journal Nature -- said, "Non-caloric artificial sweeteners (NAS) are among the most widely used food additives worldwide, regularly consumed by lean and obese individuals alike. NAS consumption is considered safe and beneficial owing to their low caloric content, yet supporting scientific data remain sparse and controversial."

Elinav and co-author Eran Segal said, "Collectively, our results link NAS consumption, dysbiosis and metabolic abnormalities, thereby calling for a reassessment of massive NAS usage."

Companies that make and use artificial sweeteners like saccharine, aspartame, Sucralose, Sorbitol, neotame and others insist that the chemicals are safe. The substances are cheap to manufacture and taste up to 20,000 times sweeter than sugar.

Gavin Partington of the British Soft Drinks Association said, "Decades of clinical research shows that low-calorie sweeteners have been found to aid weight-control when part of an overall healthy diet, and assist with diabetes management."

The U.S. Food and Drug Administration told New Scientist that "all approved high-intensity sweeteners have been thoroughly studied and have a reasonable certainty of no harm to consumers under their approved conditions of use."

Elinav and Segal, however, noted that some testing of the super sweeteners showed a link between diabetes and weight gain. In order to establish a causal link, they carried out a series of experiments on lab mice.

First,  they added one of the three most commonly used sweeteners -- saccharine, Sucralose or aspartame -- to the drinking water of healthy young mice. The dosage to the animal was equivalent to the maximum daily intake recommended for humans by the FDA. Two separate control groups were established, mice drinking only water and mice drinking water sweetened with glucose, the main chemical in sugar.

After 11 weeks, all of the mice were given a high glucose liquid to drink and their responses were monitored by blood tests to see how the body was processing the sugar.

Under normal circumstances, the body takes in sugar and releases insulin, a hormone that directs cells to use the glucose for energy or store it as fat.

"Glucose intolerance occurs when this process becomes inefficient, and is strongly associated with type 2 diabetes," wroteNew Scientist's Helen Thompson.

In the mice who had been consuming artificial sweeteners, blood glucose spiked at a significantly higher level than in the control mice and took longer to return to norma.

"They showed significant glucose intolerance," Segal said, "at levels comparable to a metabolic disease."

The sweeteners were significantly altering the composition of the mice's gut biome, the teeming ecosystem of bacteria that lives in our alimentary tract. Scientists have established a link between changes in the gut biome and weight gain and have been using bacteria from healthy people to treat diseases and infections in people whose balance of bacteria has been disrupted.

Segal and Elinav studied health data on 381 people and found a relationship between artificial sweetener use and glucose intolerance, but, Elinav cautioned, "(Y)ou could argue that maybe these people first gained weight and started getting aspects of metabolic disease, such as glucose intolerance, and then started consuming the artificial sweeteners to counteract that."

The team attempted to duplicate their findings with mice in a small sample of human subjects. Seven human volunteers consumed the maximum recommended daily dose of saccharine, the equivalent of about three to four table packets.

Of the seven, three saw no change in overall glucose intolerance or in the composition of the digestive flora over the course of five days. The other four volunteers, however, saw a dramatic change in their gut biome.

Pre-testing sequencing showed that the non-responders had a different type of gut organism before consuming the sweeteners than the systems of those who did respond, indicating that certain people's gut biome makes them more vulnerable to the sweeteners' effects.

Artificial sweeteners are among the most widely-used food additives, spanning the spectrum of processed foods from soft drinks to chewing gum to hundreds of ice creams, breakfast cereals, candies and other items.

Segal noted to New Scientist that the widespread consumption of these chemicals corresponds with the mushrooming obesity and Type II diabetes epidemic around the world. He believes that this isn't a coincidence, that artificial sweeteners are contributing directly to the epidemic that they were created to fight.

Industry group the International Sweeteners Association strongly disputes this theory, saying in a statement, "There is a broad body of scientific evidence which clearly demonstrates that low-calorie sweeteners are not associated with an increased risk of obesity and diabetes as they do not have an effect on appetite, blood glucose levels or weight gain. As shown by numerous peer reviewed studies, by providing sweetness without the calories, low-calorie sweeteners can help with weight management and can be enjoyed by people with diabetes."

Perdue University's Susan Swithers said that while it's early to extrapolate this laboratory data from mice to humans, "This is a really important paper."

Swithers particularly admired one aspect of the study, in which Segal and Elinav transferred bacteria from the guts of human subjects into lab mice. They found that only mice who received gut flora from people who responded to artificial sweeteners became glucose intolerant.

"It's always a concern to make a direct extrapolation to humans," she said, "but they provide a small amount of evidence that the same effect happens in humans, and then put the results back into animals -- that was clever."