Popular Sweetener Has Major Problems

This article originally appeared on The Epoch Times and was republished with permission.

Guest post by Flora Zhao

Stevia, known for its zero calories and potential benefits, such as lowering blood pressure and blood sugar, is often considered an excellent substitute for sugar. However, is this sweetener—used by Paraguayans for over a thousand years and by the Japanese for several decades—truly free from side effects?

Stevia Is Excreted, but Liver Problems May Pose Issue

Generally, stevia is thought to be metabolized and excreted without accumulating in the body.

Stevia’s sweetness comes from steviol glycosides. Steviol glycosides are a group of substances, among which stevioside and rebaudioside A are the two most common in commercial products.

Our stomachs and upper small intestines cannot break down or absorb steviol glycosides. Therefore, ingested steviol glycosides enter the lower gastrointestinal tract intact. In the colon, gut bacteria break down steviol glycosides into steviol, a process completed within 24 hours. Subsequently, most of the steviol is rapidly absorbed into the bloodstream through the intestinal wall, while any unabsorbed steviol is excreted in feces. The steviol entering the bloodstream is further metabolized into steviol glucuronide in the liver and ultimately excreted in the urine. This is why human experiments have shown no detectable levels of steviol in the blood after consuming steviol glycosides, while steviol glucuronide is detected in urine, and steviol is found in the feces.

“Factors like diet, medication use, or individual differences could potentially impact the metabolism of stevia and its metabolites,” said Lisa Young, an adjunct professor of nutrition in the Department of Nutrition and Food Studies at New York University and a registered dietitian nutritionist, in an email interview with The Epoch Times. She noted that while rare, some individuals may experience adverse reactions or intolerance to steviol, which “could cause gastrointestinal symptoms, allergic reactions, or other health concerns.”

Additionally, she emphasized the crucial role of the liver in the metabolism of stevia, indicating that liver diseases or impaired liver function may impact this process. “Individuals with liver diseases or those taking medications that affect liver function may need to exercise caution regarding the consumption of stevia.”

Potential Impact of Stevia on Gut Microbiome

Some in vitro and animal experiments have found that stevia or steviol may potentially impact the gut microbiome.

An animal study published in Nutrients in 2019 revealed that, compared to those only drinking water, rebaudioside A consumption altered the gut microbiome composition in mice. However, Ms. Young noted that while the hindgut microbiome of mice and humans share some similarities, many bacteria present in the mouse gut are absent in humans. Therefore, there are certain limitations to animal studies.

A study conducted by Israeli scientists in 2020 revealed that stevia and steviol do not possess bactericidal properties. However, they may potentially interrupt communication among Gram-negative bacteria in the gut, leading to gut microbial imbalance. Additionally, steviol may also exhibit inhibitory effects on the competition among gut bacteria.

Lactobacillus reuteri is often incorporated into food as a probiotic. In an earlier study, stevioside and rebaudioside A were found to inhibit the growth of six strains of Lactobacillus reuteri, with the inhibitory effects varying depending on the specific strain.

An in vitro experiment published in the journal Genes in 2019 suggested that in a simulated human intestinal environment, steviol decreased the population of Bifidobacteria (healthy bacteria), hindered the degradation of bacterial food, and concurrently led to an increase in colonic pH.

Another in vitro experiment, published in the Journal of Agricultural and Food Chemistry in 2019, demonstrated that sweetener products containing steviol glycosides and erythritol altered the structure and diversity of the human gut microbiome to some extent. However, the study concluded that, overall, there was no negative impact on the gut microbial community due to the consumption of stevia.

A review published in Microbiology in 2022 indicated that current knowledge about stevia’s impact on the gut microbiome has primarily come from in vitro and animal studies. Due to a lack of randomized clinical trials conducted in human populations, there is no definitive evidence to elucidate how stevia influences the gut microbiome, and further research is needed.

Ms. Young noted that the impact stevia has on the gut microbiome remains an active area of research, and conclusions may vary. However, she emphasized that “most studies face limitations in terms of biological relevance because it is challenging to directly apply tested concentrations to human exposure levels.”

Gastrointestinal Discomfort Caused by Stevia-Based Products

The adverse effects of stevia-based products often do not stem from steviol glycosides.

As steviol glycosides are several hundred times sweeter than sucrose, most stevia-based products on the market are not 100 percent pure steviol glycosides. Instead, they often consist of a blend of steviol glycosides and some sugar alcohols. For example, you might find a combination of 1 percent steviol glycosides and 99 percent erythritol. These products are commonly found in supermarkets, usually as white crystalline powders, their appearance resembling that of granulated or powdered sugar.

Ms. Young stated that erythritol, present in stevia-based products, is recognized by the U.S. Food and Drug Administration (FDA) as generally recognized as safe (GRAS). However, excessive consumption can result in side effects such as bloating, cramps, flatulence, or diarrhea. Additionally, the inclusion of other substances like sugar alcohol in stevia products may also cause adverse effects, especially for individuals sensitive to these additives.

There are eight types of sugar alcohols approved by relevant regulatory authorities for use as sweeteners in food, including erythritol, hydrogenated starch hydrolysates, lactitol, isomalt, mannitol, maltitol, sorbitol, and xylitol. Some individuals may experience various gastrointestinal discomforts after consuming these substances.

Specifically, sugar alcohol substances may increase gas production after fermentation by bacteria in the gut, contributing to bloating in the gastrointestinal tract. Additionally, these substances can lead to the retention of water in the small intestine, causing abdominal discomfort. Sugar alcohols also impose a greater osmotic load on the gut, leading to increased water concentration in the colon and resulting in loose stools. Moreover, the fermentation of sugar alcohols in the gut may impact the intestinal environment by altering the gut microbiome and its metabolism, influencing the intestinal immune barrier, and potentially increasing the risk of a so-called “leaky gut.”

However, it is important to note that there is a significant variation in symptoms among those who consume sugar-alcohol substances. Factors such as the type of sugar alcohol, the amount ingested, the consumption of food alongside the substance, and the intestinal ability to reabsorb water can all lead to different outcomes. Moreover, people with lower gastrointestinal tolerance or those with intestinal diseases tend to experience more symptoms than healthy people.

The substances present in stevia-based products may also impact cardiovascular health.

A review published in Nature Medicine in 2023 highlighted a link between erythritol consumption and an increased risk of adverse cardiovascular events (including death or nonfatal heart attacks or strokes) and the formation of thrombosis. The researchers stated that further research on the long-term safety of erythritol is warranted. However, it is important to note that some controversy surrounds this study.

Potential Impact of Stevia on the Brain and Nervous System

Scientists have also assessed the potential impact of stevia and its metabolites on the brain and nervous system. However, due to medical ethical considerations, these studies are primarily conducted through animal experiments.

The previously mentioned 2019 animal study suggested that the consumption of stevia may impact the dopamine reward system in the brain.

In 2020, two clinical doctors jointly published a case report, suggesting for the first time a potential association between the symptoms of restless legs syndrome (RLS) and the consumption of stevia. A patient developed symptoms of RLS while using stevia, and these symptoms resolved after discontinuation. Several months later, upon a trial reintroduction of stevia, the RLS symptoms reappeared within two days. The doctors proposed that stevia might selectively reduce dopamine levels in specific regions of the brain, or the intake of stevia could affect iron absorption. Both factors are considered significant contributors to RLS.

In addition to potentially affecting the dopamine system, animal experiments have shown that stevia may also influence memory.

Researchers at the University of Southern California published a study in 2022 where they provided juvenile rats with either artificial sweeteners or water with added stevia for a month and then tested their memory. The results revealed that both artificial sweeteners and stevia impaired the rats’ memory compared to those only drinking water. These rats were less likely to remember objects or navigate through mazes successfully. A study conducted by Filipino researchers in 2015 revealed that mice consuming stevia or two other artificial sweeteners (aspartame and sucralose) showed no significant difference in their learning ability in a water maze compared to mice drinking only water. However, mice consuming stevia exhibited higher levels of cell death in the hippocampus. Another study also conducted in the Philippines in 2014 found that mice with a higher intake of stevia, compared to those only drinking water, exhibited a longer duration of reaction when subjected to heat, suggesting that stevia might inhibit the sensitivity of the mice’s nervous system.

Stevia May Disrupt Endocrine Function and Affect Immunity

In the body, steviol glycosides are first metabolized into steviol, which possesses a steroid-like structure. Therefore, researchers suspect that stevia may act as an endocrine disruptor.

For instance, a cell experiment demonstrated that a certain concentration of steviol could disrupt the endocrine function of human sperm cells and also impact cell viability.

Read the full story at the Epoch Times.