Do we really need zero calorie sweeteners and are they safe

Artificial sweeteners, known more recently as non-nutritive or low-calorie sweeteners, have been a source of great hope. What could be better than enjoying sweetness in foods but without the calories? Sucralose, xylitol, stevia, saccharin, aspartame, there are a lot of them out there. You may add them to food yourself, you may consume them in beverages, and if not, there’s a good chance they’ll show up in foods that you buy. But, do they work and are they safe? Few know this area like Dr. Richard Mattes, distinguished Professor of Nutrition Science at Purdue University. 

Interview Summary

So Rick, thanks so much for joining us. You’ve done pioneering work on this area and there are a few people better positioned to discuss this topic, so I appreciate you joining us today. So let’s start off with why do we need these sweeteners at all?

Well, I think the primary driver here is concern about the consumption of nutritive sweeteners – sugars. It is the case that often sugars are consumed in foods that provide limited other nutritional value. So they add calories without nutrients. And then given an environment where there’s concern about weight gain and obesity, there is a reasonable assumption that we can reduce sugar intake without compromising nutritional status. So, it’s a good target for interventions to manage body weight. Low-calorie sweeteners, as you pointed out, are one approach that can be taken to reduce sugar intake without compromising the sensory qualities of foods. I think it’s very well accepted that the sensory qualities of foods are really the primary driver of food choice. We as nutritionists would like to believe people make food choices based on nutrition. We recognize the importance of cost and convenience. But the reality is if a product does not have the right sensory properties, people just won’t consume it. We have to pay attention to the sensory properties of foods. Added sugars are presently contributing about 13% of daily energy intake – so that’s a very high percent without contributing a lot of nutrients. To give you a little more perspective, at the 75th percentile in the US population, that translates to about 400 kilocalories a day for males, about 300 kilocalories a day for females. If we use a 2,000 kilocalorie diet as sort of the standard, which is what’s used on food packaging labels, that represents 20% for males and 15% of energy on a daily basis. It’s very, very high. Now, the Dietary Guidelines Advisory Committee from 2020 reviewed sweeteners and their relationship to body weight. In their modeling analyses they concluded that people can really only take in something on the order of 5 to 6% or so of energy from added sugars without going into positive energy balance. That is taking in more energy than we need and as a result, putting ourselves at risk for weight gain. That is based on what it would take to obtain all the necessary nutrients in the diet if we make smart food choices. There’s very little discretionary room for added sugars. As a result, low-calorie sweeteners are a way to reduce total sugar intake, again, without compromising sensory quality.

That makes good sense and those numbers are really quite striking. Can you give us a little bit of a sense of how much these low-calorie sweeteners are consumed and how they show up in the food supply?

Well, the primary source is through sweetened beverages, but there is increasing use in solid foods as well. They are ubiquitous in the food supply, I think that’s safe to say, but low calorie sweetened beverages are the primary source.

There’s been concern that these low-calorie sweeteners can disrupt carbohydrate metabolism and result in greater hunger and food intake. What do you think about that?

Yes, this has been very extensively studied and my interpretation of the literature is that they do not disrupt carbohydrate metabolism. We know that when people consume nutritive sweeteners sugars, that they are absorbed, the blood sugar rises. That elicits the release of insulin as a way to get the sugar out of the blood and into our cells. When blood sugar levels drop and insulin levels are relatively high, that’s viewed as a sort of metabolic signal that we should be hungry and be interested in eating again. However, my reading of the literature shows that low-calorie sweeteners do not elicit a rise in insulin, do not lead to a drop in blood sugar and as a result don’t generate a hunger signal. But even if they did that, the question is, does a rise in blood sugar or a drop in blood sugar or a rise in insulin after a typical meal really serve as the driver, or the primary mechanism for generation of hunger signals? There’s an experimental approach called euglycaemic clamp. We don’t need to go into all of the details, but suffice it to say it’s an approach that allows one to independently manipulate the level of glucose in the blood or the level of insulin in the blood. When those studies have been done, they demonstrate unequivocally that independent changes in glucose do not alter appetitive sensations, hunger, nor do independent manipulations of insulin. They undoubtedly change following a meal, but they are not the cause of the generation of hunger signals.

So this gets right at the heart of a key question. Some people are saying that, when you consume these artificial sweeteners, they rev up the body in a way that makes you want to eat. You’ll then consume as many calories as you might have if you’d been consuming sugar or maybe even overdo it. But you’re saying there’s not a biological basis for that in science.

That’s correct. I think where there is credibility to that scenario lies more in cognitive or psychological dimension. When people use a product or a food that is reduced in energy, and we require products that we purchase to label their energy content and often claims are made about them being low energy when they are, people are overly optimistic about the energy that they save when they consume these products. So they may then may be more inclined to indulge subsequent to that and overestimating the amount of energy they saved, they can indeed offset the benefit of substituting a low-calorie sweetener for a nutritive sweetener and result in higher energy intake. But that is not a biologically-driven phenomenon. It therefore requires more education in terms of how to use low-calorie sweeteners to better effect, rather than it being a biological basis that is kind of out of people’s control.

If people are consuming diet beverages for example, and they’re getting accustomed to a high level of sweetness because they’re consuming these throughout the day, does that generalize to other parts of their diet? Might they then like other things sweeter than they might have otherwise or have sort of a drive for these things?

I think where there is credibility to that scenario lies more in cognitive or psychological dimension. When people use a product or a food that is reduced in energy – and we require products that we purchase to label their energy content and often claims are made about them being low energy when they are – people are overly optimistic about the energy that they save when they consume these products. So, they may be more inclined to indulge subsequent to that and overestimating the amount of energy they saved, they can indeed offset the benefit of substituting a low-calorie sweetener for a nutritive sweetener and result in higher energy intake. But that is not a biologically-driven phenomenon. It therefore requires more education in terms of how to use low-calorie sweeteners to better effect, rather than it being a biological basis that is kind of out of people’s control.

That seems like a really important question to nail down, doesn’t it? Because what you say about salt and fat and the dairy products and things makes all the sense in the world. I know I’ve experienced myself with low fat dairy products compared to when I was a kid and people were drinking high-fat versions of milk and things. So if that’s true and it does apply to sweetness, then you’d think the artificial sweeteners would be counterproductive because they keep people consuming sweet and not getting used to less of it over time. Does that make sense?

That’s a most interesting question and highly relevant right now. So there is a reasonable body of science on the effects of exposure to sensory qualities and the preferred level of that quality in foods for salt and for fat. If one consumes high salt levels, foods with high levels of salt and saltiness, they generally come to like and actually prefer foods that are high in salt. If you’ve gone on a diet that limits sensory exposure, it’s not the amount of sodium actually consumed, it’s the sensory exposure that determines this. If you limit sensory exposure to salt, you can actually come to prefer low salt foods. The same is true for fat. Probably many people have exposed themselves to low fat dairy products, for example, and over time actually come to prefer them to the higher fat versions. But the story for sweeteners is still very much unknown. There is a small amount of evidence based on short-term studies with small sample sizes that would suggest that scenario holds, at least in kids, but the largest and probably best-controlled study to date fails to find an effect of exposure to sweetness on the preference for sweetness of foods. In contrast, they find that it alters the sensory perception (that is the intensity of sweetness) but not the preference or the liking of sweetness. So the jury is still out on that scenario.

Let me ask one of the bottom line question:  Are low-calorie sweeteners associated with lower or higher body weight?

Yes, that’s the logical conclusion. The question is whe