854. Do artificial sweeteners help—or hurt—efforts to manage weight? Fresh research offers some surprising new answers.
854. Do artificial sweeteners help—or hurt—efforts to manage weight? Fresh research offers some surprising new answers.
References:
The role of sweeteners in weight loss | Nature Reviews Endocrinology
Transcript:
If you’ve ever wondered whether using artificial sweeteners is helping you, hurting you, or just confusing the issue—you’re not alone. The science around sugar substitutes has shifted more than once over the years. And recently, a large, long-term study added an important new chapter to the story—one that challenges some long-held concerns about the microbiome and weight maintenance.
Hello and welcome to the Nutrition Diva podcast, a show where we take a closer look at nutrition news, research, and trends and help you make more informed decisions about what you eat. I’m your host Monica Reinagel, and over the 17 or so years that I’ve been doing this podcast, artificial sweeteners or sugar substitutes have been a topic that we have talked about many times.
Our mothers and grandmothers used saccharine (Sweet-n-Low) to sweeten their tea and coffee. But saccharine fell out of favor in the 80s, in large part due to fears about cancer risks that were later debunked. But by then, my own Generation X had moved on to Splenda and Equal, which we thought tasted better than saccharine. By the time the millennials were looking for ways to cut calories, more natural sweeteners like erythritol, stevia and monkfruit were on the scene.
Although the color of little packets kept changing, the underlying premise was largely the same. By replacing sugar with one of these sugar substitutes, we could reduce the amount of calories and sugar we consumed. But even as the sweeteners continued to evolve, questions remained about whether these ingredients were really helping.
After all, epidemiological studies clearly showed that the people who used these sweeteners were more likely to gain weight or become obese. Then again, that could have been a case of reverse causality. They were using these sweeteners because they were struggling with weight gain.
There were also suspicions that, even though they did not contain any sugar or calories, the sweet taste might still trick the brain somehow, leading to increased hunger, or sugar cravings, or even fat storage. These concerns have also mostly been debunked, but by then a new fear had arisen: Sugar substitutes might drive weight gain by messing with your microbiome.
Some short-term studies showed changes in the gut population after heavy consumption of these sweeteners and in the absence of further research, it seemed prudent to exercise some caution–particularly around heavy use.
If you comb through the Nutrition Diva archives, you’ll find episodes exploring every little twist and turn of this saga–including the possibility that they might cause unhelpful changes in our gut bacteria. But some research published late last year adds some important new information to that aspect of the story. This was a large and (more importantly) longer-term trial that looked at how replacing sugar-containing foods with artificially-sweetened equivalents affected body weight and the microbiome. The results may surprise you.
This year-long trial involved about 300 adults with overweight or obesity. Everyone in the study started with a two-month weight-loss phase, during which they followed a calorie-restricted diet designed to help them lose at least five percent of their body weight. But the goal of study was to look at what happened next.
After the initial two-month weight loss phase, participants were randomly assigned to one of two groups. Both groups followed dietitian-designed meal plans that represented a generally healthy pattern of eating–so, fruits, vegetables, whole grains, lean protein, and so on. Both groups were encouraged to limit added sugars to less than ten percent of total calories. The key difference was how they went about doing that.
In the control group, participants were asked to limit their sugar intake without resorting to sugar substitutes. The other group was encouraged to swap out sugar-containing foods and beverages with versions sweetened with low or no-calorie sweeteners. Acceptable sweeteners included saccharine, sucralose (Splenda), aspartame (Equal) as well stevia, erythritol, and a few others. Basically, the whole gamut.
So what happened?
Both groups regained some of the weight they had lost. The group that didn’t use any sugar substitutes regained about half of their lost weight. The group using the sugar substitutes only regained about a third. So it appears that incorporating these artificially sweetened foods was helpful in this regard.
But here’s an interesting thing: the group using the sugar substitutes did not appear to have consumed any fewer calories than the control group. And yet they regained less weight. Which brings us to perhaps the most surprising outcome: the results of the microbiome analysis.
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Over the course of the year, the group using sugar substitutes showed distinct changes in their gut microbiota—but not the kind that had raised red flags in earlier, shorter-term studies. In fact, several of the shifts were in a direction that many researchers consider favorable.
Specifically, the sweetener group showed an increase in the type of gut bacteria associated with the production of short-chain fatty acids, or SCFAs. These compounds—things like acetate, propionate, and butyrate—have been linked in other research to healthier body weights and improved metabolic health.
Short-chain fatty acids can stimulate the release of hormones that help regulate appetite and glucose metabolism, and they may also modestly increase energy expenditure. So one hypothesis is that these microbial changes could have contributed to better weight-loss maintenance even without a significant difference in calorie intake.
I think it’s especially noteworthy that these microbiome changes weren’t just the result of reducing the amount of sugar in the diet. Because remember: both groups reduced their added sugar intake. The additional shifts in the group that used the sugar substitutes appear to be linked to the inclusion of those compounds. That certainly runs counter to the story that artificial sweeteners harm the microbiome. Instead, they seem to have nudged it in a direction that supports weight maintenance.
Now, there are still a couple of unanswered questions. The intervention group didn’t consume just one type of sweetener. They used a mix of artificial sweeteners like saccharin, sucralose, and aspartame, along with sugar alcohols and plant-derived options like stevia. So, the results reflect the combined effects of several sweeteners, not just one.
On the one hand, that’s probably closer to the way these sweeteners would actually be used in the real world. However, it also means we can’t say whether certain sweeteners were responsible for specific microbial changes. Different compounds may well have different effects, and this study can’t distinguish that.
Even so, the long-term use of sugar substitutes in the context of a healthy diet did not appear to harm the gut microbiome. And the microbial changes that were observed offer a plausible explanation for why the sweetener group maintained a bit more weight of their loss.
So, what (if anything) are we to take away from this?
Those of you who have been following me for a while know that my position has generally been that sugar substitutes should generally be consumed with the same degree of moderation that you would use with actual sugar. If you wouldn’t drink 2 or 3 sugar-sweetened sodas every day, perhaps it’s not a good idea to have 2 or 3 artificially sweetened sodas either.
To be completely transparent, one of my reasons for this advice was that it was not clear whether heavy use of these sweeteners might have unintended consequences for the microbiome. This recent study suggests that this may not be as much of a concern.
But another reason for that advice is that, while they may reduce the amount of sugar and calories you’re taking in, artificially-sweetened beverages and desserts usually aren’t adding anything positive to the diet. Plus, they don’t really fill you up. So, rather than have you eat tub after tub of calorie-free jello, I’d prefer that get in the habit of having a piece of fresh fruit when you are in the mood for a little something sweet. And I think that the way the sweeteners were used in this study follows that general paradigm.
Everyone was following a generally healthy diet. The sweeteners weren’t being used as a way to replace meals with calorie-free foods. They were a way to reduce the sugar in foods people were already eating—sweetened yogurt, spreads, coffee, tea—without giving those foods up altogether. So this was less about cutting calories (which, in fact, it didn’t) and more about reducing sugar while keeping the overall eating pattern intact.
Now let me be clear: I don’t think this means you should add artificial sweeteners to your diet in an attempt to hack your microbiome. But it does suggest that their impact on the microbiome appears to be less of a concern than we had thought. If anything, the effects on the gut flora were somewhat positive, at least when used in the context of a healthy diet. And that’s really the key. Because even when they are sugar-free, sweetened foods will never be the foundation of a healthy diet. But as this study demonstrates, when used thoughtfully, they may sometimes be a useful tool.
I’d love to hear from you on this one. Have you found sugar substitutes to be helpful or counterproductive? If you’ve been avoiding them, will this new research cause you to rethink your position? Let me know by emailing me at nutrition@quickanddirtytips.com–or, if you’re listening on Spotify right now, look for the poll in your player and log your vote.
And if you’re interested in having me present at your next virtual or in person conference, find out more at wellnessworkshere.com
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