Common Digestive Issues and Additives
One of the most frequently reported problems with stevia is gastrointestinal distress. While pure stevia extract is generally well-tolerated, many commercial stevia products are not 100% pure. They are often blended with other ingredients to add bulk and counteract stevia's intense sweetness. The primary culprits behind digestive problems are typically sugar alcohols like erythritol or fillers such as dextrose and maltodextrin.
The Role of Sugar Alcohols
Sugar alcohols are a common additive because they provide a similar texture to sugar and don't raise blood glucose significantly. However, they are not fully absorbed by the body. Instead, they travel to the large intestine where they are fermented by gut bacteria, which can lead to uncomfortable side effects.
- Bloating and Gas: The fermentation process creates gas, causing bloating and abdominal discomfort.
- Diarrhea: For some, consuming larger amounts of sugar alcohols can have a laxative effect, leading to diarrhea.
- Upset Stomach: Nausea and indigestion are also common complaints among sensitive individuals.
How Fillers Affect Blood Sugar
Additives like maltodextrin, derived from starches like corn, can unexpectedly raise blood sugar levels in some people. This is particularly concerning for individuals with diabetes who are using stevia to control their glucose intake. It is essential to read the ingredient list carefully to avoid products that contain these fillers.
Unpleasant Aftertaste and Taste Perception
While the goal of using stevia is to replicate the sweetness of sugar without the calories, many users report a distinct and unpleasant aftertaste. This issue is primarily associated with the presence of certain steviol glycosides, such as stevioside, which has a natural bitterness in addition to its sweetness.
- Metallic or Licorice-like Taste: The aftertaste is often described as metallic, licorice-like, or even slightly soapy.
- Interaction with Bitter Receptors: Scientific studies suggest that the compound rebaudioside A (Reb A) activates both sweet and bitter taste receptors on the tongue, creating this polarizing flavor profile.
- Varies by Product and Person: The intensity of the bitter aftertaste can vary significantly depending on the stevia product's purity and the individual's unique taste perception. Highly purified Reb A products aim to minimize this effect, but it remains a common complaint.
Potential Endocrine and Hormonal Concerns
Though research is still developing and often conflicting, some studies suggest that stevia may have the potential to act as an endocrine disruptor. Endocrine disruptors are chemicals that can interfere with the body's hormonal systems. The concern arises from the fact that steviol glycosides have a similar molecular structure to steroid hormones.
Initial animal studies in the 1960s and 1970s hinted at contraceptive properties, though these were based on extremely high doses that are not relevant to typical human consumption. More recent in vitro (cell-based) research found that steviol could affect progesterone production and progesterone receptor activity. However, other studies have shown no reproductive effects at normal intake levels, and some reviews have found no evidence of endocrine disruption in humans. People with hormonal imbalances or fertility concerns may still want to exercise caution and consult a healthcare provider.
Risk of Allergic Reactions
For individuals with allergies to certain plants, stevia could pose a minor risk of a cross-reactive allergic reaction. Stevia belongs to the Asteraceae/Compositae family, which also includes common allergens like ragweed, chrysanthemums, and daisies.
In theory, if you are sensitive to ragweed, your immune system could mistake similar proteins in the stevia plant for the ragweed proteins and trigger an allergic response. Symptoms can range from mild (itching, tingling in the mouth) to more severe (hives, breathing difficulties), though severe reactions are rare. The risk is much lower with highly purified stevia extracts, as the processing removes most allergenic compounds.
Drug Interactions and Effects on Blood Pressure
Stevia has been found to have a diuretic effect, which means it increases urination. It is also known to lower blood pressure in some cases. For this reason, it is crucial to consult a doctor before using stevia if you take certain medications. Stevia can interact with:
- Antidiabetic drugs: Stevia can lower blood sugar, and combining it with diabetes medication could cause blood sugar to drop too low (hypoglycemia).
- Antihypertensive drugs: Similarly, its blood pressure-lowering effects could amplify medications for high blood pressure, causing it to drop to unsafe levels.
- Lithium: The diuretic action could affect how the body removes lithium, potentially causing harmful accumulation.
Comparison of Stevia and Sugar
| Aspect | Purified Stevia Extract | Standard Sugar (Sucrose) |
|---|---|---|
| Calories | Zero | High |
| Blood Sugar Impact | Negligible (Pure) / Potential for spikes (Blends) | High, causing rapid spikes |
| Taste Profile | Intensely sweet with potential bitter aftertaste | Sweet, well-understood flavor |
| Dental Health | Non-cariogenic (doesn't cause cavities) | Promotes tooth decay and cavities |
| Common Additives | Often blended with sugar alcohols or fillers | None |
| Digestive Effects | Can cause bloating/gas (due to additives) | None, though high intake can cause issues |
| Drug Interactions | Potential interactions with diabetes, BP meds, lithium | No known drug interactions |
| Aftertaste | Common, described as licorice-like or metallic | None |
The Problem with Crude Stevia and Purity
One of the biggest issues with stevia revolves around its form. While highly purified steviol glycoside extracts (often called Reb A) are approved by regulatory bodies like the FDA for use in food and beverages, crude stevia extracts and whole-leaf stevia are not. The FDA has stated that there is insufficient safety information regarding the use of these less-refined forms. Concerns include potential impacts on the reproductive system, kidneys, and cardiovascular system. This means that the product's safety largely depends on its level of refinement, and consumers should be wary of unpurified versions marketed as supplements.
Conclusion
While stevia offers a zero-calorie alternative to sugar with potential benefits for blood sugar management and weight control, it is not without its downsides. The most significant issues often arise from the additives found in many commercial products, which can cause digestive problems and unexpected blood sugar fluctuations. Additionally, some individuals may experience an unpleasant aftertaste, and there are potential risks related to drug interactions and hormonal function, though research is ongoing and conflicting on these points. Consumers should choose highly purified stevia products, read ingredient labels carefully, and consult a healthcare provider if they have pre-existing conditions or are taking medication. Ultimately, moderation and awareness of the product's composition are key to navigating the bad side of stevia successfully.
For more in-depth scientific reviews on the effects of low-calorie sweeteners, see this comprehensive meta-analysis from PubMed: Effect of stevia on blood glucose and HbA1C: A meta-analysis.
