Experiments on Mice
Scientists fed 10-week-old mice drinks containing either:
• saccharin (the sweetener in the pink packets of Sweet’N Low),
• sucralose (the yellow packets of Splenda),
• aspartame (the blue packets of Equal),
• sugar, or
• plain water.
The amount given to the mice was equivalent to four diet sodas per day for a human. After one week, the mice fed diet drinks had higher than normal blood sugar levels in response to eating sugar, while those that drank sugared water or plain water did not. Saccharin, aspartame and sucralose are chemically very different from each other, but they all caused the same abnormal rise in blood sugar. A high rise in blood sugar after eating sugar is called “glucose intolerance”, which is a marker for diabetes and increased risk for heart attacks.
The scientists then gave antibiotics (ciprofloxacin/metronidazole or vancomycin) to the mice who had been given artificial sweeteners and found that this prevented the high rises in blood sugar. This implied that changes in the intestinal bacteria had caused the rise in blood sugar because killing the changed bacteria (with the antibiotics) returned the mice to normal.
Then they injected intestinal bacteria from saccharin-drinking mice into mice who had never had saccharin and the mice developed very high blood sugar levels after eating sugar. DNA tests showed that the transplanted bacteria now lived in their intestines and were causing the same high rise in blood sugar that occurred in the artificial-sweetener-fed mice.
Experiments on Humans
The researchers then studied 381 non-diabetic people and found that those who use artificial sweeteners regularly had a high incidence of high blood sugar levels after being fed sugar, and that the bacteria in their intestines were also different from people who did not use artificial sweeteners.
Then for six days they fed saccharin to seven people who previously avoided artificial sweeteners, and four of them developed high blood sugar levels. Next they injected bacteria from humans fed saccharin into mice intestines and the mice developed high blood sugar levels after being fed sugar. They showed that the intestines of the artificial-sweetener-fed mice had increased amounts of short-chain-fatty acids that are readily absorbed into the bloodstream. This is the first study to show that intestinal bacteria are changed by artificial sweeteners.
How Intestinal Bacteria Can Raise Blood Sugar
Artificial sweeteners and many other carbohydrates in the food that you eat are not absorbed directly from your intestines. However, this study suggests that artificial sweeteners change your gut bacteria and the new bacteria are able to break down non-absorbable chains of sugars and starches into short-chain fatty acids. Short-chain fatty acids are readily absorbed from your colon to provide extra calories from a wide variety of foods that you eat. As you absorb more calories from carbohydrates than you normally do, your blood sugar will rise higher, you are likely to gain weight and increase your risk for diabetes.
Trillions of bacteria live in your intestines. You have more bacteria in your intestines than you have cells in your body. Research on gut bacteria is probably the hottest area of medical research today, under the umbrella of the huge Human Microbiome Project funded by the U.S. National Institutes of Health (NIH). This new study will undoubtedly be followed by hundreds of more detailed experiments to clarify the effects of artificial sweeteners on intestinal bacteria and whether they increase risk for diabetes and obesity.
More research is needed, but I believe that this will prove to be the ground-breaking study that completely changes our thinking about artificial sweeteners. I would not wait for future studies; the evidence from this study is so strong that I now recommend avoiding regular use of artificial sweeteners. Drink only water or unsweetened beverages and severely limit sugar-sweetened foods, except during prolonged exercise.