Stevia is the hot new kid on the block when it comes to natural ‘sugar free’ sweeteners. It has been hailed as the natural sweetener that does not raise blood sugar levels and is good for your teeth, but is it really the guilt free sweetener of your dreams? In this post we discuss stevia properties and effects, including any potential stevia dangers.
What is Stevia?
The stevia plant is a small perennial, which belongs to the same botanical family (Compositae/Asteraceae family) as sunflowers, Jerusalem artichokes and chrysanthemums. This herb has little green leaves that produce extremely sweet compounds known as glycosides, with the variety Stevia rebaudiana being the sweetest. It is native to South America where it has been used traditionally as a sweetener and as a medicine.
The two major sweet-tasting steviol glycosides found in S. rebaudiana are stevioside and rebaudioside A, but rebaudiosides C, D, E and F, rubusoside and duldoside are also found. These glycosides are up to 250 times sweeter than sucrose.
The natural stevia (S. rebaudiana) leaf contains around 80-85% water and also other nutrients and antioxidants such as ascorbic acid, beta-carotene, chromium, magnesium, iron, potassium and quercetin.
Stevia is Natural?
Stevia is being used more and more as a ‘non-caloric’ sweetener and is touted as the healthy alternative to sugar, but I think there is one very important thing that needs to be pointed out here:
A stevia extract that is a white powder or liquid of stevioside or rebaudioside A is very different to the traditionally used whole leaf. This is a very defining point.
Many years ago when I was doing my degree in Nutritional Medicine, stevia was something know only to ‘us hippies’ and you could only get it as the whole leaf, dried or as a tincture. Or even better – you grew and dried your own leaves! In these forms, stevia is known to have many health containing properties such as being high in antioxidants. The issue with this natural dried leaf was however, that when consumed in large quantities, it leaves a bitter aftertaste and therefore was not appealing to the masses.
This is where the extracted compounds enter the market – which were isolated to try to give maximum sweetness without the bitter aftertaste (although this apparently is still a common complaint of various brands). These powdered white extracts, liquids or even extracts mixed with other sweeteners or sugars are all you seem to be able to find in the shops now. Either way – in this form not very ‘natural’, as we see it, it is not in its whole form…it is an extracted compound.
The issue is the amount being consumed and that it is showing up in everything. Reports such as that from South East Farm Press note that “The United States is the largest single market for high purity stevia extracts at approximately 300 metric tons of finished products annually. This represented roughly 65 percent of the global market for high purity stevia extracts in 2011. (www.southwestfarmpress.com, July 16, 2014). The market is booming as the world keeps trying to deal with an obesity epidemic and everyone is scrambling to get a hold of this no-calorie sweetener.
Is Stevia Safe?
If you want a quick, non-geeky summary, skip down to the end. Otherwise read on!
There have always been mixed opinions about this and below is the response to the question from the American Food and Drug Administration.
“Is Stevia an ‘FDA approved’ sweetener?
FDA has not permitted the use of whole-leaf Stevia or crude Stevia extracts because these substances have not been approved for use as a food additive. FDA does not consider their use in food to be GRAS (generally recognised as safe) in light of reports in the literature that raise concerns about the use of these substances. Among these concerns are control of blood sugar and effects on the reproductive, cardiovascular, and renal systems. Food additives and GRAS affirmation petition or pre-petition submissions for the use of such substances that FDA has received in the past have not contained the data and information necessary to establish the safe use of these substances as ingredients in food.”
In December 2008, the FDA granted rebaudioside A (reb-A) GRAS – shortly after which Coca-Cola and PepsiCo announced their intended use of reb-A in zero-calorie beverages.
Summary of 2010 evidenced-based systemic review of stevia by Ulbricht et al:
- ‘Likely safe’ when taken at recommended dosing.
- ‘Possibly unsafe’ when taken by children or pregnant or lactating women or for periods longer than 2 years due to insufficient evidence.
- ‘Likely unsafe’ when used in people with a known allergy or sensitivity to the daisy family (Compositae/Asteraceae family).
- S. rebaudiana has been used traditionally used by Paraguay’s rural and indigenoius populations for the control of fertility (as a contraceptive), although they are not sure about its effectiveness.
- Data from an 8-week animal trial suggested S. rebaudiana does not adversely affect male body and testicular weights or impact sperm, however a study of chronic administration (60 days) indicated that it decreases male fertility.
- Stevioside (250mg) capsules given 3 x daily may decrease blood pressure.
- Caution is advised with people with impaired kidney function as “animal studies have shown that higher doses of stevia affect renal activity and perfusion, sodium excretion and urinary flow.” (Ulbricht et al, 2010)
- Stevioside may act as a calcium antagonist, so there is potential for calcium channel blocker drug interaction.
- The hyperglycaemic benefits of stevia have only been studied in Chinese populations in only two studies and there is debate as to if this benefit would be seen in different population groups.
- Stevioside has been shown to not be mutagenic, however there is conflicting results from studies on steviol (which is a compound which can be degraded by gut flora from stevioside). Steviol produced dose-related positive responses in some mutagenicity tests. This has not been shown in situ in the human body.
Stevia – Safe Sweetener or Hidden Nasty? Find out why the answer is still unclear.
In 1999, the European Commission Scientific Committee on Food produced a paper titled ‘Opinion on Stevioside as Sweetener’ in which they concluded:
“In the safety assessment of the specific stevioside preparation for which approval is sought, several questions of concern were raised by the Committee regarding the specifications of the extracts that had been tested, questionable chronic toxicity and carcinogenicity studies, and possible effects on the male reproductive system that could affect fertility. Furthermore, steviol, one metabolite of stevioside, that is produced by the human microflora is genotoxic and induces developmental toxicity. The Committee is not satisfied with the submitted documentation and has concern about possible toxicity. Areas that need further studies are stated in the above opinion. The Committee reiterates its earlier opinion that the substance is not acceptable as a sweetener on the presently available data”
Since this article was published, subsequent studies have shown that neither steviol or steviol glycosides are absorbed by humans. The glycosides may be hydrolyzed by intestinal microflora to steviol, but no detectable levels of the glycosides or steviols were detected in the blood or urine in human subjects. (Pawar et al, 2013)
Now this very well may be the case…but my mind begins to ask questions about compromised gut integrity, leaky gut or inflammation in the gut that may cause increased intestinal permeability – could this lead to steviols being able to pass though the gut and into the blood? Something to think about…
So is stevia safe?
The overwhelming sense I get from all the literature is best summed up by Goyal et al – “Despite centuries of use, there is still lack of comprehensive clinical studies on stevia as a supplement” (Goyal et al, 2010)
I would further add to this that the impact of a highly processed extract, when consumed in large doses, has not been sufficiently studied and that is the real issue.
So our take home points on the use of stevia as a sweetener are:
- We would recommend minimal usage and certainly not use daily.
- We would not recommend use for children, pregnant or lactating women.
- If you are going to use stevia, try to look out for the powdered whole leaf or tincture.
- Grow your own stevia plant
- Even though the stevia is ‘non-caloric’ we would prefer to recommend whole, natural sources of sweeteners such as raw honey or maple syrup – just use less of them and slowly reduce your palate from needing so much sweetness
If you have any questions about stevia, please leave a comment. We’ll be keeping an eye on the latest research into stevia so we can keep our guides and investigative posts as updated as possible.
Boileau A, Fry, JC, Murray, R, A new calorie-free sugar substitute from the leaf of the stevia plant arrives in the UK, Nutrition Bulletin, Article first published online: 10 FEB 2012,DOI: 10.1111/j.1467-3010.2011.01945
Ulbricht C, Isaac R, Milkin T, Poole EA, Rusie E, Grimes Serrano JM, Weissner W, Windsor RC, Woods J, An evidence-based systematic review of stevia by the Natural Standard Research Collaboration, Cardiovasc Hematol Agents Med Chem, 2010 Apr;8(2):113-27
Pawar RS, Krynitsky AJ, Rader JI, Sweeteners from plants–with emphasis on Stevia rebaudiana (Bertoni) and Siraitia grosvenorii (Swingle), Anal Bioanal Chem. 2013 May;405(13):4397-407. doi: 10.1007/s00216-012-6693-0. Epub 2013 Jan 23
Scientific Committee on Food, Opinion of Stevioside as a Sweetener, 1999, UROPEAN COMMISSION DIRECTORATE-GENERAL XXIV, CONSUMER POLICY AND CONSUMER HEALTH PROTECTION