Artificial sweeteners – and their most popular protégé, diet soda – haven’t exactly been the nutritional godsends they were supposed to be. In the last 30 years, their consumption has risen considerably, but so have obesity and other chronic diseases. Of course, there are other unhealthy habits that can explain our poor health in the U.S. But – amid rather mixed evidence – there’s been some suspicion that artificial sweeteners are linked to some serious health risks: Overweight and obesity, high blood pressure, metabolic syndrome, diabetes, kidney dysfunction, heart attack, and hemorrhagic stroke. A new study finds what may be the “missing link” between artificial sweeteners and at least some of these problems: Belly fat.
Belly fat is known to be, medically speaking, the ugliest form of fat. Also known as visceral fat, as it ensheathes the visceral organs, belly fat is itself a known risk factor for heart disease, cancer, diabetes, and metabolic syndrome, among others. The new study, from the University of Texas Health Science Center at San Antonio, set out to determine whether there was any connection between diet soda consumption and this particular form of fat. If there is, the authors reasoned, it may partially explain the connection between artificial sweeteners and the chronic diseases that some researchers believe exists.
The researchers followed 750 European-American and Mexican-American people over the age of 65 for almost 10 years. The researchers had them answer questions about their diets, exercise routines, and other lifestyle habits. They also took measurements of their height, weight, and waist circumference at several intervals throughout the study period.
It turned out that people who drank the most diet soda (at least one drink per day) had a much steeper rise in waist circumference over the years than those who didn’t drink the stuff at all. After adjusting for other variables like smoking status, age, activity level, the results were still striking: Waist circumference increased 0.8 inches for “non-users” (that is, non-diet-soda-drinkers), 1.83 in for occasional users, and 3.16 inches for daily users.
The researchers did not adjust for calorie intake, and it’s certainly possible that this or other variables were responsible for the connection.
Belly fat may explain, at least partially, the many other health risks that are linked to artificial sweeteners. But why would artificial sweetener lead to a rise in belly fat in the first place?
There are a few explanations. One that’s gotten some recent attention is that artificial sweeteners may shift the assortment of friendly bacteria in the gut. A study last fall found altered ratios of gut bacteria (along with glucose intolerance) in both mice and men after drinking artificially sweetened drinks for a week. Gut bacteria are well known to affect how we digest and metabolize food, and if their ideal ratios are altered in any way, this may pave the way for overweight and obesity.
The drinks are also highly acidic, says study author Sharon Fowler, which could play a role in the bacteria of the gut. “The gut microbiome is like our personal inner rainforest,” she says. “If our intestines are like an ecosystem, then could drinking highly acidic drinks like sodas day after day be comparable to acid rain in a real rainforest? To borrow from Austin Powers, it’s not a ‘consequence-free environment.’”
Fowler also points out that diet sodas are “hyper-sweet,” which might trick our bodies into behaving differently. “We have sweetness receptors not just on our tongues but also in our intestines and pancreas,” says Fowler. “If these sweets receptors are getting hyper-activated, they may be triggering the release of insulin when the body doesn’t really need it — or by failing to trigger it when it does.” And this could, over time, lead to metabolic dysfunction.
Or it could be purely psychological, the rationale being that since we’re saving so many calories with diet drinks we think we’re entitled to them elsewhere. Food expert Marion Nestle, who’s written about the artificial sweetener debate, is a little skeptical about studies like this new one. “Belly fat is about genetics plus calorie balance,” says Nestle, the author of Food Politics. “That’s the easiest explanation. There’s not much evidence that diet sodas help people lose weight (except in clinical trials) so it’s not hard to guess that people compensate for them by eating more.”
The artificial sweetener debate is not likely to be settled soon. Even the website Upworthy just took down and apologized for a post touting the safety of artificial sweeteners, after realizing that the article may not have been totally balanced.
In the meantime, if you can avoid or cut down on artificial sweeteners by opting for naturally sweetened or unsweetened drinks, it’s probably the way to go. “The further away we get from eating real foods, the more we get into trouble,” says Fowler. “I’d urge people to consider giving up hyper-sweet beverages that we can’t even predict the consequences of at this point. If you need to the caffeine boost, switch to tea or coffee – the antioxidants have opposite effect from what’s happening with diet soda. Or if you’re craving sweets, move to actual fruit or to mineral water with a little splash of fruit juice. It doesn’t take a lot of sweetness to feel satisfied.”
And she says, remember there are other compounds in soda besides the sweetener. Last month a highly publicized study suggested the caramel color in some sodas, 4-methylimidazole, was found in amounts sufficient to increase our cancer risk, prompting the authors to call for federal regulation. “Being calorie-free doesn’t mean being consequence-free,” says Fowler. “There are many more dimensions to diet soda than calories – it makes no sense to pour hyper-sweet, acidic beverages into our bodies. We’re just not set up for that.”
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