Healthy Sugar Substitutes or Hidden Hormone Disruptors? What Research Says About Stevia, Monk Fruit & More

Healthy sugar substitutes are everywhere this time of year, from sugar-free pumpkin lattes and protein bars to “better-for-you” Halloween candy sweetened with stevia, monk fruit, erythritol, or sucralose, to name a few. Many of us reach for these non-nutritive or zero-calorie sweeteners hoping for a healthier alternative to sugar itself. 

While they may not spike blood sugar the way traditional sugar does, the question remains: are they truly harmless? Let’s unpack what current science says about these sugar substitutes so you can navigate the holidays with sweetness that actually supports your hormones and energy levels.

Meet Today’s Most Popular Sugar Alternatives 

• Stevia: Derived from the Stevia rebaudiana plant, stevia is considered a natural zero-calorie sweetener and is 200-300 times sweeter than sugar. 
• Monk Fruit (Luo Han Guo): Monk fruit sweetener comes from the extract of a small green melon native to Asia. It’s estimated to be about 100-250 times sweeter than sugar, although it is often combined with other sugar substitutes like erythritol in many products.
• Erythritol: Erythritol is a sugar alcohol naturally found in small amounts in fruits, and is about 70% as sweet as sugar. Xylitol is another member of the sugar alcohol family, commonly found in chewing gum and toothpaste for its anti-cavity benefits.
• Sucralose: Sucralose (aka Splenda) is an artificial sweetener made by modifying sugar molecules, making it 600 times sweeter than sugar. Sucralose is very prevalent in low-calorie and sugar-free products, even health foods like protein powder.
• Allulose: Allulose has gained more popularity lately as a newer “rare sugar” found naturally in small amounts in figs and raisins. While it is naturally found in some foods, commercial allulose is produced from modifying fructose using an enzyme reaction.

Understand How Sweeteners Affect Metabolism, Hormones, and More 

Impacts on Metabolic Health

Non-nutritive sweeteners don’t contain energy, or calories, but let’s explore how they may still impact the blood sugar balance and metabolic health. 

Across the research, stevia has been shown to have mild blood sugar lowering effects, but did not influence insulin levels or hemoglobin A1c (a 3-month estimate of blood sugar balance). Monk fruit has been shown to decrease post-meal blood sugar rises by 10-18%, and decrease insulin responses by 12-22%, however long-term effects on metabolism and insulin regulation have yet to be studied. 

Erythritol has not been shown to significantly influence glucose or insulin levels. Interestingly, there is evidence that it may stimulate the release of gut hormones like GLP-1 and cholecystokinin (CCK), both of which play beneficial roles in supporting feelings of fullness, slowing digestion, and promoting better appetite control.

These are the same hormones targeted by many popular weight loss medications. However, these effects were noticed with dosages around 50 grams of erythritol, which is equivalent to about 35 grams of table sugar. To put this into perspective, this is about the amount of sugar in a can of soda, which is much more erythritol than we would recommend consuming regularly!

One study showed similar GLP-1 and CCK-boosting effects after consumption of 25 grams of allulose. Recall that this can help with appetite regulation and fullness queues. Despite these effects, allulose did not impact levels of the hunger hormone ghrelin. When chronically elevated, ghrelin can negatively affect metabolism and even downregulate hormones like GLP-1 and CCK.

Research on sucralose is mixed but compelling. While some studies suggest no significant effect of sucralose on blood sugar and insulin levels, several studies conclude that both short and long-term sucralose consumption effectively decreases insulin sensitivity, which leads to higher insulin levels and blood sugar dysregulation. Over time, this impaired insulin response can contribute to fatigue, inflammation, weight gain, and a higher risk of chronic conditions like insulin resistance, type 2 diabetes, and PCOS.

Concerns about Heart Health

You may have heard recent concerns about the safety of erythritol as it pertains to heart health. A variety of observational studies have seen an association between higher blood erythritol levels (which occurs from consistent erythritol consumption) and cardiovascular disease, in addition to major cardiovascular events such as stroke. 

The study that really brought this to light was released in Nature Medicine in 2023. In it they state that when erythritol was administered to blood cells in a lab at levels similar to what would be found in our bloodstream after erythritol consumption, these cells became stickier and more prone to blood clots. 

This was followed up with animal research confirming erythritol consumption increases the speed of blood clot formation. Finally, a follow-up human study showed that consuming erythritol does, in fact, increase blood levels of erythritol similar to the increases studied in this preliminary research.

These studies provide insight into correlation, not causation, so more research is needed to fully understand the impact of erythritol on heart health and to determine long-term safety.

Good or Bad for Gut Health?

The gut microbiome has profound influence over all aspects of our health, including metabolism, inflammation signaling, thyroid function, and estrogen balance. Unfortunately, several sweeteners can disrupt it.

Stevia is broken down by microbes in the gut, namely Bacteroides species, but there is mixed research on whether its impact on the gut microbiome is significant. One small study showed that consuming 180mg of stevia per day (about 75% of the Acceptable Daily Intake (ADI)) influenced gut microbes by increasing certain species and decreasing others. As of now, there hasn’t been conclusive evidence to show that stevia has a significant impact on human gut microbiome composition or diversity at concentrations typically consumed. 

Monk fruit contains compounds that can be broken down by our gut bacteria that actually serve as prebiotics, or food sources for these microbes. In preliminary lab studies, this has been shown to increase bacterial production of anti-inflammatory short-chain fatty acids (SCFAs) like acetate, propionate, and butyrate. Animal studies on allulose also show beneficial effects on the gut microbiome. However, data in humans is limited and more research is needed to confirm these promising benefits. 

Erythritol is believed to have a neutral effect on the gut microbiome, although many individuals report digestive upset, bloating, gas, or diarrhea with moderate to large amounts of erythritol or other sugar alcohols. 

Sucralose, however, consistently is shown to alter the gut microbiome by reducing microbial diversity, proliferating overgrowth species, and decreasing beneficial species like Lactobacillus. These effects were seen after consuming 102 mg of sucralose per day for 2 weeks, which is the equivalent of consuming 1 diet soda every day for 2 weeks.

Effects on Reproductive Hormones

How these sweeteners may impact reproductive function is not often discussed, especially because human research on this subject is limited. However, you may have heard concerns related to stevia’s effects on reproductive hormones and fertility. 

Historically in native Paraguayan folk medicine, high-dose stevia teas or decoctions were used among women for oral contraception. That being said, the impacts on fertility occur only at extremely high doses that are well beyond normal dietary consumption. 

Animal research that showed stevia influenced fertility and lowered testosterone in males was conducted using chronically high doses of stevia. In female animal models, stevia consumption was shown to disrupt fertility and reduce pregnancy rates by disrupting hormone cycles. Another animal study showed very high dose stevia consumption for 28 days caused changes within the ovaries and to reproductive hormone production. However, it’s really important to note that this was with continuous ongoing stevia exposure at levels that are well above and beyond normal dietary levels for humans. 

That being said, there is no clinical evidence showing that stevia suppresses reproductive hormones. Of course, it’s advised to limit consumption of any of these sweeteners, and to certainly not exceed the set ADIs.

Sucralose has also been shown in animal studies to disrupt reproductive hormone balance. While we don’t know the significance in humans, we know that sucralose can impair insulin sensitivity in humans, which in turn can impact hormone signaling, especially in conditions like PCOS. 

Interestingly, new animal research showed other mechanisms by which sucralose impaired fertility, by increasing oxidative stress and disrupting autophagy, or processes that help cells regulate their own function. While human research is needed to confirm these effects in humans, this research was conducted to reflect sucralose doses equivalent to the current ADI.

In regard to other sugar substitutes, no evidence suggests that erythritol, monk fruit, or allulose alter estrogen or other reproductive hormones to influence fertility outcomes.

Strategizing Smarter Sweets for the Holidays

Of course, anything in excess can come with its downsides, and that includes sugar substitutes. There’s no perfect sweetener, but if we had to choose, we recommend opting for single-ingredient organic stevia, monk fruit, or allulose. Keep in mind that these are much sweeter than sugar, and the sweet taste alone activates dopamine reward pathways in the brain. This “sweetness without calories” loop can keep cravings alive and make it harder to retrain your palate before the holidays.

Our top 3 functional tips for a sweeter, more balanced holiday season:

• Gradually cut back on sweeteners now. Your taste buds can adapt to less sweetness in as little as two weeks!
• Stay hydrated and replenish your minerals. Cravings can signal a need for more essential minerals like sodium, potassium, or magnesium.
• Read labels carefully. Many “healthy” products use not-so-great sugar substitutes like sucralose, and many sugar substitute products are not pure extracts, but rather sweetener blends (i.e. monk fruit with erythritol).

Want to Squash Your Sugar Cravings Before the Holidays?!

You don’t have to fear sweeteners, but by better understanding them you can make the best choices for you and your family this holiday season! 

If you’re looking to lock in for 4 weeks before being in full swing with the holidays, join us in our upcoming live group program – Functional Thyroid Foundations! This is your functional nutrition roadmap to more energy, less inflammation, and better thyroid and hormone health. 

If you experience brain fog, fatigue, hair loss, thin or brittle hair or nails, feeling depleted from physical activity, bloating, or puffiness, this program is for you. You deserve to feel like yourself again, especially going into the holidays! Join us in our next live program, beginning soon!

Written by Romana Brennan, MS, RDN