Zero-calorie sweeteners can help some people with weight loss. However, their effect on metabolism is less clear. A new article takes a look at the evidence. Several studies have found higher rates of metabolic syndrome in people who consume artificially sweetened drinks. Metabolic syndrome is a group of harmful health factors that tend to occur together. The factors include high blood sugar, high blood pressure, high triglycerides (a blood fat), a large waist and low HDL (“good cholesterol”). Metabolic syndrome increases the risk of heart disease. In other studies, people who started out with similar weights tended to gain more weight if they drank zero-calorie sweetened sodas than if they drank water. The study authors say that the artificial sweeteners may confuse the body’s response to sweets. When diet soda drinkers consume real sugar, the body may not react properly. The journal Trends in Endocrinology and Metabolism published the article. CNN.com reported on it July 19.
By Mary Pickett, M.D.
Harvard Medical School
What Is the Doctor’s Reaction?
Diet drinks and zero-calorie sweeteners ought to promote weight loss and improve health. After all, 6% of all American calories come from drinks sweetened with sugar or corn syrup. So people who have only “diet” drinks are getting fewer calories.
But the jury is out on whether artificial sweeteners can truly help us with weight loss. An article released online last week summarized what we know about sweeteners and health. Zero-calorie sweeteners include:
- Aspartame (NutraSweet, Equal)
- Saccharin (SugarTwin, Sweet’N Low)
- Acesulfame potassium (Ace-K, Sunette)
- Sucralose (Splenda)
Small amounts of these sweeteners have seemed safe in short-term studies. They don’t seem to trigger insulin release or other effects on metabolism that we see from real sugars. Metabolism is the rate at which our bodies store fat and sugar, use energy and burn calories.
But in long-term studies, it is much harder to see an advantage. People who often consume sugar substitutes seem to have the same problems with weight gain, type 2 diabetes, heart disease and high blood pressure as those who use real sugar. These problems are parts of an overall decline in health known as the metabolic syndrome.
Fans say that zero-calorie sweeteners can’t be blamed for these connections. They point out that our long-term studies are “observational.” They come from watching people who are leading real lives and making their own choices. Wouldn’t people who are overweight be more likely to choose diet drinks? Wouldn’t this explain the link?
Unfortunately, this thinking has, perhaps, begun to fall apart. Observational studies have compared people who had similar weights at the start of the studies. Those who regularly had artificially sweetened drinks tended to gain more weight than those who avoided all sweetened drinks.
In one study, children were randomly assigned to drink zero-calorie sweetened drinks or only water. After 6 months, fasting blood sugar levels were up for the children who had the artificially sweetened drinks, even though the drinks did not contain sugar.
These studies make it hard to feel certain that artificial sweeteners help with weight control or good health.
Experts are not sure how artificial sweeteners might disrupt our normal metabolism. If it truly exists, this metabolic shift might occur during digestion. But it also could be triggered by taste. Nature shows that our bodies have evolved to respond when we are eating sweets.
We are mammals, after all. A large part of our genetic code is shared with mammals in the wild. For example, bears have to hibernate. They have to store up fat for the winter. In late summer, berries and other foods in the wild tend toward their sweetest. Sweet taste might in some way tell our bodies that it’s time to store fat. This may be key to survival of the fittest. For bears, eating sweet berries may shift their metabolism so that they can build a layer of bear fat.
In pioneer days, Americans also had sugar only on special occasions. But our sweet diet is no longer a short, seasonal event. It is year-round. We need less of this “store fat” message in our bodies.
What Changes Can I Make Now?
Americans take in way too much sugar, and we seem addicted to sweetness. The harm of “real” sugar goes beyond the calories. Digestion of sugar also affects our metabolism. There are early signs that artificial sweeteners might act in a similar way.
Sugar contributes to obesity, diabetes risk, blood pressure and unhealthy cholesterol levels. It also has been linked to fatty liver and having a large waist. In 2009, the American Heart Association recommended that Americans sharply limit “added sugars.” These include corn syrup, cane sugar, brown sugar and honey. They are added to foods and drinks during processing or at the table.
So far, no expert group has advised against the use of zero-calorie sweeteners. But I advise my patients to avoid both sugar and sugar substitutes. It is better for us if we do not crave sweets.
The most effective way to reduce sugar in your diet is to avoid sweetened drinks. Americans get 33% of their added sugar from soft drinks. These include sodas, punch, sweetened tea, lemonade and sports drinks. Experts estimate that a daily 12-ounce serving of a sugar-sweetened drink can add about 15 pounds to your weight in a year.
I recommend that you wean yourself away from sweet drinks. If water is not interesting enough for you, choose bubbly water, add a sprig of mint or other herb, or drink it with a wedge of lemon or lime.
What Can I Expect Looking to the Future?
We need more research about the long-term effects of artificial sweeteners. These sweeteners might have effects on our metabolism. In the end, they may not be such a sweet substitute.