Do Stevia and Other Sweeteners Break a Fast?

Short answer: Pure stevia doesn't break a fast for most goals. A few drops have essentially no calories, and the FDA says sweeteners like it generally don't raise blood sugar [1]. The catch is the packet: many stevia and sucralose packets are mostly dextrose, maltodextrin or erythritol, even when the label says 0 calories [2][3][4][5].

In PingDiet terms, a few drops of pure stevia in black coffee is about as close to zero as a sweet taste gets. A packet with dextrose in it is a small Ping.

Who should skip fasting: Johns Hopkins Medicine says intermittent fasting isn't for children and teens under 18, people who are pregnant or breastfeeding, people with type 1 diabetes who take insulin, or anyone with a history of eating disorders, and that everyone should check with a doctor before starting [15]. This page is general information, not medical advice.

Does stevia break a fast?

It depends on two things: what's actually in your stevia, and what kind of fast you're doing.

The sweet part of stevia is a group of compounds called steviol glycosides. The FDA says they're 200 to 400 times sweeter than sugar and aren't absorbed in the upper digestive tract [1]. You need so little that the amount in a few drops has almost no calories.

What you buy in the store is usually not just stevia, though. The FDA only allows high-purity steviol glycosides (at least 95% pure) as a sweetener. Whole stevia leaves and crude stevia extracts aren't approved for use in food [1]. Because the pure extract is so strong, companies blend it with a bulking ingredient so a packet looks and pours like sugar.

What's actually in a stevia packet?

We checked label data in USDA's FoodData Central for common tabletop sweeteners. The first ingredient is often not the sweetener on the front of the box.

Source: USDA FoodData Central, Branded Foods label data [2][3][4][5][6][7]. Recipes change, so check the box in your hand.

All of these can say "0 calories." FDA label rules let any serving with less than 5 calories be listed as zero [8]. A gram of dextrose or maltodextrin has about 4 calories, and it's a carbohydrate your body absorbs as sugar. One packet is a tiny amount. Four or five packets across a morning of coffee is not.

The cleanest choice is a liquid stevia or monk fruit whose ingredient list is just water, the extract and maybe a preservative. Compare liquid stevia drops on Amazon and read the ingredient panel on the listing before you buy.

Does stevia spike insulin?

The short version: on its own, not in a way studies have been able to show. Most of the research tested stevia alongside food, so it can't tell you exactly what happens in the middle of a fast.

• In a 2010 study of 31 adults, stevia-sweetened snacks before meals led to lower insulin after eating than snacks sweetened with aspartame or sugar [9].
• In a 2017 study of 30 healthy men, drinks sweetened with stevia, monk fruit or aspartame produced no difference in total glucose or insulin over 3 hours compared with a sugar drink. The sugar drink caused a big spike first, and the others caused a bigger rise after lunch [11].

People worry about a "cephalic phase" insulin response, a small release of insulin triggered by tasting something sweet. We didn't find a study that measured it with stevia during a fast. If you find that sweet coffee makes you hungrier, that's a good enough reason to skip it.

Do other sweeteners break a fast?

The FDA has approved six high-intensity sweeteners as food additives. It treats purified stevia, monk fruit extract and thaumatin as generally recognized as safe [1]. Here's how the common ones compare for fasting.

Sucralose. One small study is worth knowing about. In 17 adults with obesity who didn't normally use sweeteners, drinking sucralose 10 minutes before a glucose drink led to a 20% bigger insulin response than water [10]. That was with sugar on board, not during a fast, but it's the main reason some people avoid Splenda while fasting.

Erythritol. In a study of 20 adults, a large 75-gram dose of erythritol didn't raise blood glucose or insulin [12]. The FDA says sugar alcohols don't cause a sudden rise in blood glucose. In 2023 it reviewed a paper linking erythritol to heart problems and found that the observational studies it cited didn't establish that erythritol caused them [1].

Aspartame. Unlike most of the others, it has calories, but it's so sweet that you use far less of it than sugar [1]. People with the genetic disorder phenylketonuria (PKU) have to avoid it.

Does stevia break a fast for autophagy or ketosis?

Autophagy. Nobody knows for sure. We found no human study that measured autophagy after stevia. In a 2019 reader Q&A in the journal Autophagy, Dutch biochemist Alfred Meijer said the small amount of leucine in one stevia product wasn't enough to interfere with autophagy. He also said autophagy speeds up most after 24 to 48 hours of fasting [13]. That's one expert's opinion about one product, not proof. If autophagy is your reason for fasting, plain water, black coffee and plain tea are the safe choices.

Ketosis. Pure stevia has essentially no carbs, so a few drops won't move you out of ketosis. Packets are a different story because of the dextrose or maltodextrin. A single packet is a small amount, but several add up.

Can I put stevia in my coffee while fasting?

Yes, for most people doing 16:8 or a similar fast. A few drops of pure stevia in black coffee keeps the cup close to zero calories. The cream is usually the bigger problem, not the sweetener. Our guide to what you can add to coffee while fasting covers milk, cream, butter and collagen.

A few ways to keep the cup clean:

• Use liquid drops over packets.
• Check the ingredient list for dextrose, maltodextrin or "sugar."
• Watch flavored syrups labeled sugar-free. They can contain sugar alcohols and other add-ins.
• If sweet coffee makes you hungrier, try it black for a week and see.

Going for something warm without coffee? Lemon water is another option, and our bone broth guide explains where broth fits.

Are sweeteners good for weight loss?

That's a different question from whether they break a fast. In 2023, the World Health Organization recommended against using non-sugar sweeteners to control weight. Its review found no long-term benefit for reducing body fat in adults or children [14]. The WHO called it a conditional recommendation, and it doesn't apply to people who already have diabetes.

In the 2017 study above, people who had a sweetened zero-calorie drink ate more at lunch, which made up for the calories they had saved [11]. So treat stevia as a way to make black coffee easier to drink during your fasting window, not as a weight-loss tool.

When should you skip sweeteners entirely?

• Before a fasting blood test. MedlinePlus says to drink only plain water. Juice, coffee, soda and flavored waters with sugar or sweeteners can affect your results [16].
• During a strict water fast or autophagy-focused fast, if you want zero doubt.
• If you have diabetes or take glucose-lowering medicine. Talk with your doctor about fasting at all before you start, sweetener or not [15].

More on what breaks a fast

If you take vitamins or capsules in the morning, see do supplements break a fast. For salt and electrolyte drinks, read our electrolytes guide. The full What Breaks a Fast section covers more drinks and add-ins.

Photo: Towfiqu barbhuiya, Pexels

Sources

1. U.S. Food and Drug Administration. Aspartame and Other Sweeteners in Food
2. USDA FoodData Central. Truvia Calorie-Free Sweetener (FDC 2617324), Branded Foods
3. USDA FoodData Central. Best Choice Stevia Sweetener (FDC 2545534), Branded Foods
4. USDA FoodData Central. Essential Everyday Stevia Sweetener (FDC 2673300), Branded Foods
5. USDA FoodData Central. Equal Sucralose Packets (FDC 2013134), Branded Foods
6. USDA FoodData Central. Splenda Granulated (FDC 946384), Branded Foods
7. USDA FoodData Central. Skinnygirl Monk Fruit Liquid Sweetener (FDC 1920665), Branded Foods
8. Legal Information Institute. 21 CFR 101.9(c)(1), Nutrition labeling of food
9. Anton SD, et al. Effects of stevia, aspartame, and sucrose on food intake, satiety, and postprandial glucose and insulin levels. Appetite. 2010;55(1):37-43
10. Pepino MY, et al. Sucralose affects glycemic and hormonal responses to an oral glucose load. Diabetes Care. 2013;36(9):2530-2535
11. Tey SL, et al. Effects of aspartame-, monk fruit-, stevia- and sucrose-sweetened beverages on postprandial glucose, insulin and energy intake. Int J Obes. 2017;41(3):450-457
12. Wölnerhanssen BK, et al. Gut hormone secretion, gastric emptying, and glycemic responses to erythritol and xylitol in lean and obese subjects. Am J Physiol Endocrinol Metab. 2016;310(11):E1053-E1061
13. Meijer AJ. Autophagy in practice: stevia and leucine. Autophagy. 2019;15(12):2043
14. World Health Organization. WHO advises not to use non-sugar sweeteners for weight control in newly released guideline (May 15, 2023)
15. Johns Hopkins Medicine. Intermittent Fasting: What Is It, and How Does It Work?
16. MedlinePlus, National Library of Medicine. Fasting for a Blood Test