Artificial sweeteners like Splenda and Equal were once touted as a calorie counter’s best friends: You can drink all the sweet tea, lemonade, and soda you like, without ingesting a single calorie or gram of sugar. You can even eat pudding, ice cream, yogurt, baked goods, and other desserts sweetened with sugar-free substitutes. And yet, the proliferation of sugar-free foods and beverages doesn’t seem to have made a dent in the obesity epidemic.
I tackled this paradox in one of the very first Nutrition Diva episodes back in 2008. Back then, we still weren’t sure whether there was something about artificial sweeteners that directly promoted weight gain. Scientists wondered, for example, whether artificial sweeteners might backfire by causing cravings for other sweets or an increased appetite that would lead you to consume more calories. Early studies in rats seemed to support this theory, but results in human trials have been mixed.
This much is crystal clear: Artificial sweeteners do not automatically lead to weight loss or prevent weight gain.
Alternatively, it could have been more of a behavioral phenomenon. For example, it could be that using artificial sweeteners gives people a false sense of security that leads them to over-consume other foods. (The old “I’m having Diet Coke so super-size the fries” effect.)
This much is crystal clear: Artificial sweeteners do not automatically lead to weight loss or prevent weight gain. Among people who use artificial sweeteners, the only ones who seem to consistently lose or maintain their weight are the ones who also strictly monitor and restrict their intake of other foods.
How do artificial sweeteners affect blood sugar?
Another supposed advantage of artificial sweeteners is that they do not cause an increase in blood sugar the way sugar does. This would seem to have obvious benefits for those with diabetes or pre-diabetes. But a growing body of research suggests exactly the opposite.
Although the artificial sweeteners themselves don’t cause your blood sugar to rise, they appear to have a negative impact on your blood sugar response to other foods.
One large study found that consumption of aspartame (Equal) is associated with an impaired ability to manage glucose in those who are overweight.
Another study found that overweight subjects who did not typically use artificial sweeteners experienced higher blood sugar and insulin spikes from meals eaten after they ingested sucralose (Splenda).
Even though both have zero sugar and calories, your blood sugar is likely to be higher after the meal with the diet soda.
These findings were confirmed in a more recent study, which found that consuming sucralose all by itself didn’t affect the body’s ability to metabolize sugar. But consuming sucralose together with foods containing carbohydrates did. In fact, the effect was especially pronounced in adolescents—so much so that the teenagers participating in the trial were removed early due to ethical concerns. In other words, having a diet soda with your meal is not the same as having water with your meal. Even though both have zero sugar and calories, your blood sugar is likely to be higher after the meal with the diet soda. Over time, those higher blood sugar and insulin spikes can increase your risk of developing Type 2 diabetes, as well as lead to weight gain.
And “reduced sugar” products or recipes that use a combination of sugar and artificial sweeteners in order to reduce calories without sacrificing all of the flavor and texture that sugar provides may actually do more harm than good.
The artificial sweetener industry pushes back
Manufacturers of artificial sweeteners and products have pushed back against these conclusions. The Calorie Control Council (an industry group for artificial sweeteners) tried to make a big deal of a 2018 study that found that daily intake of aspartame (found in Equal) for 12 weeks had no effect on blood sugar response, appetite, or body weight.
One interesting thing I noticed about this study is that some of the aspartame was delivered in a capsule form. So, if taste receptors do play a role in the body’s hormonal or metabolic response to artificial sweeteners, this effect would have been muted in the study.
The study also involved only normal-weight subjects. And other studies have suggested that, ironically, artificial sweeteners may have more deleterious effects in overweight people than they do in normal-weight people.
The gut connection
The explanation for this mystery may reside (along with the answer to so many of life’s unanswerable questions) in the gut. When it comes to digestion, blood sugar, insulin, appetite, and fat storage, the bacteria that live in your intestines are calling a lot of the shots. As I described in a previous episode, both Equal and Splenda—which are the two most commonly used zero-calorie sweeteners—promote the growth of specific strains of intestinal bacteria that are associated with obesity.
The case against artificial sweeteners seems to be getting stronger and stronger as time goes on.
The case against artificial sweeteners seems to be getting stronger and stronger as time goes on. But what if, despite all that, you just don’t feel that you can give up zero-calorie sweeteners? Is there any way to use them safely? Here’s my best advice:
How to use sugar-free sweeteners safely
1. Use them in moderation. Stop thinking of non-caloric sweeteners as “free” foods that you can consume in unlimited quantities. Use the same degree of moderation as you would use with real sugar. The recommended limit for added sugar is 25 grams per day. That translates to no more than one 12-ounce can of diet soda or 3 packets of artificial sweetener per day. Here are equivalent measures for other types of non-caloric sweeteners.
2. Try the more natural ones. In terms of their effects on gut bacteria, newer sugar-free sweeteners, such as stevia and monk fruit, and sugar alcohols, like xylitol and erythritol, appear to be a better choice than more synthetic sweeteners like sucralose (Splenda) and aspartame (Equal.) They are also getting easier to find, as there is an increasing number of available beverages, snack bars, desserts, and baking mixes made with stevia, monk fruit, and sugar alcohols. You’ll even find little packets of them at coffee bars. However, the same guidelines for moderation still apply.
3. Make sure you’re feeding the good bacteria, too. A diet rich in prebiotic and probiotic foods promotes more desirable strains of intestinal bacteria, which can help keep the balance tipped in your favor. That means lots of legumes, whole grains, and fermented and cultured foods.
RELATED: What are Prebiotics?