A Limited (And Complex) Role For Artificial Sweeteners

by Stephanie Linakis, MPH

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Replacing sugar sweetened beverages with artificially sweetened, zero and reduced calorie substitutes would seem to be one foolproof strategy for weight loss, right? Well, maybe – the story could be more complicated. Our body’s myriad biological and psychological pathways challenge what would logically appear to be a simple choice. The body can easily recognize and process a natural, calorie free substance such as water. Drinks – and yogurt and other products – that are artificially sweetened (with aspartame, saccharin, or sucralose, for example), however, can confuse our systems and may lead to unintended consequences. 

Like with so many things, the evidence is mixed. (We nutrition researchers sure have our work cut out for us!) Some studies suggest that artificial, or nonnutritive, sweeteners facilitate weight loss especially when used as a substitute for sugary drinks. In a 2012 study by Ruyter et al., normal-weight children who were told to drink a cup of artificially sweetened drink at school each day gained less fat and weight than those instructed to drink one cup of a sugary drink. The study lasted for 18 months, and during the follow-up, those drinking artificially sweetened drinks gained 1 kg less (2.2 lbs) than those drinking the sugary drinks.

On the other hand, new data suggests that artificial sweeteners may not be without their problems. In 2012, Brazilian researchers conducted an experiment with rats and those fed artificial sweeteners gained more weight than those fed table sugar. A very recent study in Nature, which has reopened this debate with new vigor, claims that artificial sweeteners can in fact raise blood sugar levels by altering the balance of gut microbes in mice.

Behaviorally, these mechanisms are complicated, too. Take a Diet Coke. If you are congratulating yourself, consciously or not, for choosing a zero-calorie alternative over the “real thing,” you might reward yourself or feel justified in eating a caloric snack at another point in the day. Our research group conducted focus groups among college students and asked them whether they considered calorie content when choosing what to drink and eat. Most of the students we spoke to tended to consider calories when choosing food, but beverages carried different currency it turns out, and calories rarely crossed their mind when choosing what to drink. We mortals can do funny calculus where self-discipline is concerned (industry marketing may play a role here too, of course).

In my last post, I wrote about policy proposals to tax sugar-sweetened beverages. My opinion has not changed in the last month. Excess sugar consumption can result in abnormal cholesterol, insulin resistance, and other metabolic problems and I would certainly like to see fewer people consuming fewer sugar-sweetened drinks. The science to support an association between artificial sweetener consumption and weight gain is equivocal; that between higher sugary drink intake and weight gain is not. Whether the results from the study in Nature (conducted with mice) extend to humans is uncertain, and more research is called for before conclusions can be drawn. Until then, I can see a limited role for artificially sweetened drinks as an alternative to sugar-sweetened ones. Best yet, opt for water. Your body digs it.