For many years stevia has been considered to be a safe sugar substitute, but recently there has been some controversy over this natural sweetener. In fact, some healthcare professionals now recommend for their patients to avoid stevia. Some of my thyroid and autoimmune thyroid patients have also questioned whether or not it’s safe to consume stevia, and so I figured I’d dive into the research and put together a blog post on this topic.
Before discussing the health benefits and potential risks of stevia I’d like to cover a few basics. First of all, stevia is a plant that has been used as a sweetener for hundreds of years. However, it’s only been recent that many products have included it as a sugar substitute. Some of the products that include stevia include soft drinks, ice cream and other desserts, protein powders, and many other products.
Whole plant stevia is also known as Stevia rebaudiana Bertoni. Stevia extract refers to a preparation that is made by steeping the leaves of the stevia plant, which in turn extracts the compounds responsible for the plant’s sweet taste. These compounds are called steviol glycosides. There are 11 major steviol glycosides, and rebaudioside A and stevioside are the most abundant (1). High-purity stevia extracts consisting of 95% or greater steviol glycosides are required to meet US and European regulatory approvals and safety standards for foods and beverage use.
Health Benefits of Stevia
The truth is that many people don’t use stevia for any specific health benefits. For example, many people add stevia to coffee or tea as a substitute for white sugar and/or artificial sweeteners. But there is research demonstrating specific health benefits of stevia, which I’ll discuss below:
Diabetes Mellitus. One rat study looked at the effects of stevia leaves and its extracted polyphenols on diabetes (2). The results of the study showed a reduction of blood glucose, the liver enzymes (ALT and AST) and insulin, and suggested that stevia leaves not only have a hypoglycemic effect, but can also alleviate liver and kidney damage. Another study showed that aqueous extract of stevia has anti-diabetic effects in albino rats (3).
Hypertension. A few animal studies show evidence that stevia may help to reduce blood pressure. One study showed that stevioside given intravenously to hypertensive rats was effective in blood pressure reduction (4), while another study on hypertensive dogs showed that stevioside is an effective antihypertensive natural product (5). A human study investigated the long-term efficacy and tolerability of stevioside in patients with mild essential hypertension (6). The study showed that after 2 years, the stevioside group had significant decreases in systolic and diastolic blood pressure.
Cancer. Although a few in vitro studies demonstrated that Stevia rebaudiana extracts have antiproliferative and proapoptotic properties on cancer cells (7) (8), including pancreatic cancer cell lines (9) (10), another study showed no impact of stevia on the pancreatic cancer (11).
Inflammation. A few studies show that stevioside possesses anti-inflammatory and immunomodulatory properties by decreasing the synthesis of proinflammatory cytokines (12) (13). And since an increase in proinflammatory cytokines is associated with autoimmune conditions, perhaps stevia can benefit people with Graves’ disease and Hashimoto’s.
Obesity. There is evidence that by lowering energy intake, stevia may lead to the reduction and prevention of obesity (14).
Lyme disease. One study looked at the effectiveness of whole leaf Stevia extract against Borrelia burgdorferi species, which are associated with Lyme disease (15). The results of the study demonstrated that Stevia had significant effect in eliminating Borrelia burgdorferi spirochetes and persisters, and therefore might be an effective agent in helping people with Lyme disease.
Tooth decay. Stevia is non-cariogenic, and when used over table sugar it can be a way of preventing dental caries (16). In addition, some of the stevia extracts exhibits antimicrobial properties against the bacteria that play a role in tooth decay (17).
What Are The Risks of Stevia Consumption?
Over the last few years there has been some controversy related to stevia. Here are a few of the controversies associated with stevia:
1. Stevia and fertility. There is an animal study that showed that chronic administration of a stevia extract may decrease the fertility of male rats (18). There are a few problems with this study. First of all, it was a single study that hasn’t been reproduced. Second, it was conducted on rats, and animal studies don’t always translate to humans. And third, the abstract didn’t specify how much stevia was given to the rats over the 60 day period. The truth is that more research is needed, but if someone is having fertility problems and consumes stevia regularly then it probably is best to stop consuming it, just to play it safe.
2. Stevia and gut bacteria. One study evaluated the influence of stevia glycosides on the growth of Lactobacillus reuteri strains (19). According to the study, two stevia glycosides impaired the growth of the analyzed strains. This doesn’t mean that consuming stevia will affect all of the strains of Lactbacillus retueri, let alone other strains of bacteria. Once again, more research is needed, and even the study concluded that it’s necessariy to evaluate the influence of stevia glycosides on other groups of micro-organisms.
3. Stevia and Cytochrome P450 enzymes. I came across a study which showed that steviol caused a weak inhibition of CYP3A4 and CYP2C9 (20). These enzymes play a role in the metabolism of certain drugs. As a result, food-drug interactions can be a concern when taking stevia.
4. Stevia and ragweed allergies. Although I haven’t come across any research that has showed an association between stevia and ragweed allergies, I’ve read some blog post comments suggesting that people were unable to tolerate stevia for this reason. Stevia is part of the Asteraceae/Compositae plant family, which includes ragweed, chrysanthemums, marigolds, daisies, and other plants (21). In theory, people who have allergies to ragweed and other plants in the same family may also react to stevia.
Other Natural Sugars and Sweeteners To Consider
For those who choose not to consume stevia, you might wonder which other natural sweeteners are safe to consume. I’ll refer you to a blog post I wrote in the past entitled “Natural Sugars, Sweeteners, and Thyroid Health”, as I discuss the different natural sweeteners. I even discussed stevia, although this current blog post goes into much greater detail. Even though I recommend reading the blog post I wrote on natural sweeteners, here are four natural sugars and sweeteners to consider using:
- Maple syrup
- Luo han (monk fruit)
Beware of “Hybrid” Stevia Products
If you choose to consume stevia, ideally it should be 100% whole leaf stevia without added ingredients. Some products will include stevia, but will also include other sweeteners such as sugar alcohols or agave, both of which I discuss in the blog post I’ve written in the past on natural sugars and sweeteners. Dextrose is another ingredient added to some stevia products, and this is commonly derived from genetically engineered corn. Not only do you need to be aware of other ingredients included, but some of these are highly processed using numerous chemicals to extract the steviol glycosides from the leaf.
Should You Avoid Stevia?
I personally have reduced my consumption of stevia recently, although I don’t completely avoid it. I used to add stevia regularly to my green tea and herbal teas, but over the years I have learned to enjoy these without stevia…or any other sweeteners. So I don’t add honey to my tea, or any other sweeteners. I do I use an electrolyte powder that has stevia (after my sauna therapy sessions).
The truth is that more research is needed, but probably the same is true for many other herbs. After all, while herbs such as ashwagandha, rhodiola, milk thistle, etc., are overall considered to be safe, there are some people who don’t tolerate these and other herbs. As for whether stevia can affect fertility, more research is definitely needed, but my guess is that there have been many people who were able to conceive while consuming stevia. That being said, if someone is having a difficult time conceiving then it might be wise to take a break from stevia.
My biggest concern with stevia is the evidence showing that a few stevia glycosides inhibited Lactobacillus reuteri strains. And I mentioned earlier that one of the benefits of stevia is in preventing tooth decay by inhibiting certain bacteria, which includes Streptococcus mutans and Lactobacillus acidophilus. Keep in mind that this doesn’t confirm that consuming small amounts of stevia will cause gut dysbiosis, and we need to keep in mind that there are other herbs that also possess antimicrobial properties, including oregano and berberine.
Overall I think 100% whole leaf stevia is a safe option for many people when taken in small amounts. This doesn’t mean that everyone will tolerate it well, but the same is true when taking herbs, as many people do fine when taking certain herbs, while some people have a negative reaction. And so you need to listen to your body. As I mentioned earlier, if someone is trying to conceive it might be best to take a break from stevia, although if anyone reading this has conceived while consuming stevia regularly please feel free to share this in the comments section below.
In summary, many people use stevia as a natural sweetener. Stevia can potentially benefit those with diabetes mellitus, high blood pressure, cancer, inflammation, obesity, Lyme disease, and even tooth decay. There is some evidence that stevia can decrease fertility and have a negative effect on some of the good bacteria. However, more research is needed in these areas. My opinion is that stevia is similar to other herbs in that it offers some good benefits when taken in small amounts, but there are also potential risks. And just as is the case with other herbs, some people may have an allergy to stevia. If you choose to consume stevia it’s best to use 100% whole leaf stevia.
Please feel free to share your thoughts about stevia in the comments section below!