Americans eat a lot of sugar – 15 percent of daily calories are from added sugar alone. Sugar’s high caloric price as well as its rising market cost are moving consumers and food makers to replace sugar with ever rising amounts of low-calorie sweeteners such as Equal, NutraSweet, Splenda, Sweet'N Low, Stevia and many others. Replacing sugar with no-calorie sugar substitutes potentially saves many calories, but also raises concerns about what happens when you dissociate sweetness from energy: how does non-caloric sweetness affect appetite, eating habits and weight?
And since the sugar-substitute experiment is long underway, it’s a good idea to stop and see how the trial is faring: are low caloric sweeteners helping in the obesity fight?
Food and nutrition experts met in the spring of 2011 in Washington DC to do just that in a workshop called: “Low-Calorie Sweeteners, Appetite and Weight Control: What the Science Tells Us”. The presentations of this workshop are summarized in a upcoming supplement of the Journal of Nutrition and make for some interesting reading.
Does sweetness promote overeating?
Tasting something sweet activates pleasure centers in the brain. Do you know what else activates these neural reward pathways? Addictive drugs such as alcohol and opiates work on the same brain mechanisms. That of course doesn’t mean that drug addiction and our affection for sweet food are the same thing – but it does help explain how strong and well conserved our sweet preference is. Loving sweet is innate and present even before birth. It probably served our species well, leading babies to crave mother’s milk and all other aged humans to seek ripe fruit.
A few interesting findings from the article about sweetness and food preference:
- Sweet taste makes pain go away: a Cochrane review showed that sweet tasting solutions reduced the reaction to pain in babies. Sweetness continues to act as an analgesic in childhood.
- We sense sweet taste through taste receptors in the mouth, but receptors are present also in our intestine and our pancreas. Stimulating these receptors leads to a cascade of physiologic reactions, including insulin and other hormone secretion, stomach emptying, appetite control and gut motility. These receptors can’t tell caloric sweeteners and non-caloric sweeteners apart -- they react to both, to a degree that isn’t completely understood.
- Young kids prefer super sweet -- the sweeter the better. They’ll always gravitate to sweet rather than plain. Kids can also discriminate between sweet-tasting foods differing in energy content, preferring those that are more energy dense.
- Preferring sweetness is natural, but also learned: babies and young kids exposed to sweet foods and drinks prefer sweet foods, and eat more of them. Through their experience with food kids ‘learn’ what should and shouldn’t taste sweet. Repeated exposure to sweet drinks leads to preference of sweet drinks.
- The ready availability of sweet, highly rewarding foods, can promote overeating and weight gain. Adding sweetness (caloric or non-caloric) to foods that are not naturally sweet -- think cereal, water, yogurt or milk -- creates dietary habits of overconsumption. It’s just human nature.
The science of non-caloric sweeteners
Thanks for hanging in there up until now. I bet you’re curious to know the bottom line verdict of this workshop. Two years ago, the new Dietary Guidelines for Americans concluded that:
“The replacement of sugar-sweetened foods and beverages with sugar-free products should theoretically reduce body weight. Yet many questions remain, as epidemiologic studies show a positive link with use of nonnutritive sweeteners and BMI. Additionally, whether use of low calorie sweeteners is linked to higher intake of other calories in the diet remains a debated question.”
I’m afraid not much has changed.
The workshop concluded that the bulk of epidemiologic, observational studies, but not all of them, reported that use of low-caloric sweeteners is associated with obesity and weight gain. However, association doesn’t prove causality. Real evidence, the experts say, can only come from well-performed randomized controlled clinical trails, in which people will be assigned randomly to consume either non-caloric sweeteners for long periods of time, or serve as controls.
Until then, the large-scale non-randomized population experiment is ongoing, we’re all part of it, and I don’t think it’s going too well. I choose to be in the control group.
Full disclosure: I’m vice president of product development for Herbal Water, where we make organic herb-infused waters that have zero calories and no sugar or artificial ingredients. I’m also a pediatrician and have been promoting good nutrition and healthy lifestyle for many years.