by Nancy Clark MS RD CSSD - Today’s runners are confronted with a plethora of foods and beverages containing low- or no-calorie sweeteners (LNCS): Diet Pepsi, Halo-Top ice cream, Gatorade Zero, Nuun. Questions arise: 

Are these products a better option than their sugar-containing versions? 

Will they help you lose weight? 

Are they safe? 

Should runners eat them or avoid them?                                                                                                                                                                                                                                                                                                                                                                                                                                           The goal of this article is not to recommend for or against LNCS sweeteners such as Equal (aspartame), Sweet ‘n Low (saccharine), and Truvia (stevia), but rather to offerscience-based information to help you decide whether or not they are safe to include in your sports diet.

Background info

     The 2020-2025 US Dietary Guidelines for Americans state that we should limit added sugars to less than 10% of our daily calories. The average (i.e., unfit, over-fat) American consumes about 270 calories (17 teaspoons, 13% of total calories) of added sugars a day. Soft drinks, other sweetened beverages, cookies, candy, and desserts are common culprits. For a sedentary person who may require 1,800 calories a day, 10% of calories equates to 180 calories (45 g) of added sugars a day that displace wholesome foods. Given that exercise enhances our ability to metabolize sugar, runners and other active people are less likely to end up with health issues (prediabetes, type 2 diabetes) related to sugar consumption. For them, added sugars can be a useful source of muscle fuel. Ideally, the sugar comes surrounded with nutrients, such as a post-exercise recovery chug of chocolate milk or flavored Greek yogurt.

    Today’s serious runners often select their foods more wisely than the average American. Their hope is to not only enhance performance but also reduce their risk of injury and invest in their longevity. For a runner eating more than 3,000 calories a day, the guideline of less than 10% of total calories from added sugars equates to 300 calories (75 g) of added sugars a day. That leaves plenty of space for some sugary sports foods and treats, if desired. 

   Runners’ bodies tend to readily use sugars (they appear in the blood as glucose) to replenish depleted muscle glycogen stores. During long, hard workouts, sugar-filled gels and sports drinks can enhance performance. So why would a runner want to choose a Gatorade-Zero, Nuun, or Propel with NLCS? Well, if weight-conscious, LNCS can help runners save a few calories (though doing so while exercising can hurt performance). With meals and snacks, swapping a can of sugar-sweetened soda for a diet soda ideally allows the runners to enjoy 150 more calories of nutrient-dense foods, such as fruits or veggies. (We know what often happens, however.The saved calories go towards cookies. Ha!)

    Are foods sweetened with LNCS a way for runners to have their cake and eat it too? The media has certainly painted a halo of horror on LNCS, leading many to believe they are mysterious chemicals, contribute to obesity, and bolster one’s sweet-tooth. Are they really bad for you? Let’s take a look at what science says. 

Aren’t they nothing but (scary) chemicals?
All foods are made of chemicals: carbon, oxygen, nitrogen. Aspartame (brand names are NutraSweet and Equal) is made of two amino acids that taste 200 times sweeter than table sugar. You need very little of it. The powder in the blue packet is mostly a harmless filler that keeps the few molecules of sweetener from getting lost in the packaging.

Are they safe to consume?
Sugar substitutes are among the most highly studied ingredients out there. The FDA, WHO and other global health organizations have confirmed the safety of these products in doses well above the amounts commonly consumed by humans. Studies which reported a link to cancer were done with animals given absurd amounts of no- or low-cal sweeteners and are not relevant to humans in real-life.

That said, the FDA has established Acceptable Daily Intakes (ADI) for these sweeteners. ADI is the amount of a LNCS a human can consume every day during their life —with a built in 100-fold safety factor below which no adverse effects have been seen. For aspartame, the ADI equates to 107 of those little blue packets a day (19 cans of diet soda every day of your life). So yes, some runners could overshoot the ADI—but it’s highly unlikely!

Do low- and no-calorie sweeteners lead to weight loss?
LNCS are one tool in a dieter’s toolbox. They can help dieting rowers lose weight IF they displace calories the dieter does not replace. For example, one athlete told me he lost 30 pounds in a year just by trading in his lunch- and dinner-time can of Pepsi for Diet Pepsi. That one simple change shaved off 300 calories a day that he did not replace. That said, research indicates people can easily compensate for the calories by eating more of other foods… 

Do low- and no-calorie sweeteners lead to weight gain?
No. People who drink diet soda are more likely to be over-weight, but diet soda did not cause the weight gain. Rather, people who live in large bodies are more likely to use LNCS to save some calories.

Don’t these sweeteners trick the body into thinking it’s getting sugar—and trigger a spike in blood glucose, followed by a crash, and hunger? Well controlled, randomized studies indicate the answer is no. Nor do LNCS make people feel hungrier. Some animal studies have shown that LNCS might increase appetite, but those studies were conducted with large amounts of LNCS that we would never consume. This has not been replicated in humans.

Do low- or no-cal sweeteners have a negative impact on the microbiome?
Questionable research with mice who consumed very large amounts of saccharin suggests it might impact the microbiome of rodents. But no conclusive evidence to date indicates LNCS negatively impact the human gut microbiome. Stay tuned.

The bottom line
We are all born with an innate desire for sweet tastes, starting with breast milk. We have many options for satisfying that sweet tooth in good health. Take your choice!

Sports Nutritionist Nancy Clark, MS, RD counsels both casual and competitive athletes in the Boston-area (Newton; 617-795-1875). The 6th edition of her Sports Nutrition Guidebook (2020) can help you figure out how to eat to perform well and be healthy. Visit NancyClarkRD.com. 

For more information:
Joan Salge Blake RD PhD with Hope Warshaw RD, Certified Diabetes Educator 


Laviada-Molina H, Molina-Segui F, Pe ́rez-Gaxiola G, et al. Effects of nonnutritive sweeteners on body weight and BMI in diverse clinical contexts: systematic review and meta-analysis. Obes Rev 2020; 21:e13020 

Position of the Academy of Nutrition and Dietetics: Use of Nutritive and Nonnutritive Sweeteners https://www.andeal.org/vault/2440/web/JADA_NNS.pdf   

Read more of Nancy Clark’s articles on  www.runohio.com  

Teaming Up with Good Nutrition -  http://runohio.com/index.php/news-features/news/143-the-athlete-s-kitchen-teaming-up-with-good-nutrition-by-nancy-clark-ms-rd-cssd  

The ABC's of Sports Nutrition  http://runohio.com/index.php/news-features/news/140-the-athlete-s-kitchen-the-abc-s-of-sports-nutrition    

Elite vs. Recreational Athletes -  http://runohio.com/index.php/news-features/features/89-sports-nutrition-elite-vs-recreational-athletes   

Food, Runners & Joyful Eating http://runohio.com/index.php/news-features/features/77-the-athlete-s-kitchen-food-runners-joyful-eating  

Midlife Weight Gain -  http://runohio.com/index.php/news-features/features/123-the-athlete-s-kitchen-by-nancy-clark-ms-rd-cssd-midlife-weight-gain    

Sports Nutrition:  Fads, Facts and Fallacies -  http://www.runohio.com/index.php/news-features/features/106-athlete-s-kitchen-sports-nutrition-fads-facts-and-fallacies-by-nancy-clark-ms-rd-cssd     

Microbes, Bones & Heat   http://runohio.com/index.php/news-features/features/171-sports-nutrition-update-microbes-bones-heat  

Eating Clean: Unintended Consequences - http://runohio.com/index.php/news-features/features/56-the-athlete-s-kitchen-eating-clean-unintended-consequence      

Winning the War against Snack Attacks -  http://runohio.com/index.php/news-features/features/42-the-athlete-s-kitchen-winning-the-war-against-snack-attacks-by-nancy-clark-ms-rd-cssd    

Sports Nutrition Updates -  http://runohio.com/index.php/news-features/features/38-athlete-kitchen-by-nancy-clark-sports-nutrition-updates     

Your Sports Diet: Quality Calories for Weight Management?  http://runohio.com/index.php/news-features/features/27-your-sports-diet-quality-calories-for-weight-management      

Sports Nutrition Resources: Books, Blogs, Websites and Podcasts   http://runohio.com/index.php/news-features/features/18-the-athlete-s-kitchen-sports-nutrition-resources-books-blogs-websites-and-podcasts       

 Intestinal Distress: Gutting It Out - http://www.runohio.com/index.php/news-features/features/109-the-athlete-s-kitchen-intestinal-distress-gutting-it-out-by-nancy-clark-ms-rd-cssd-july-2020     

Hot Weather Hydration Tips -  http://www.runohio.com/index.php/news-features/features/113-athlete-s-kitchen-hot-weather-hydration-tips-by-nancy-clark-ms-rd-cssd