Is Stevia Safe?

steviaWell we’ve hit the major artificial sweeteners in previous posts in this series. Today we look at a natural sweetener, stevia.

Stevia (stevia rebaudiana) is a sweetener that many people have been using for hundreds of years. It is native to Central America and South America. The leaves are around 40 times sweeter than sugar and the extract is about 300 times sweeter. It dissolves very quickly in and can have somewhat of a bitter aftertaste.

So we can’t call stevia an artificially sweet seduction since it is natural. But is it another sweet seduction or is it a winner to make things oh so wonderfully sweet?

Study Time!

In a study of rats, 0.5mg/kg of stevia lowered blood glucose levels in diabetic rats and glucose tolerance testing in normal rats. It also reduced insulin sensitivity in the diabetic rats and enhanced insulin secretion and insulin utilization.1

So even though insulin increased, sensitivity and utilization of the insulin was better. That is important to remember. If insulin merely goes up and isn’t used because of sensitivity, that is bad. If insulin goes up and is used, like in healthy individuals that’s ok. That’s the way it’s supposed to be.

In another study of diabetic induced rats, stevia was used to compare blood glucose levels with normal and diabetic controls. Subjects were fed 150mg/kg, 200mg/kg and 250mg/kg of stevia per day. Significant decreases in blood glucose were measured as well as non-significant decreases in body weight. Glimepiride (a diabetic drug which increases insulin secretion) was also used as a comparator. Glimepiride lowered blood glucose significantly more than stevia at all doses.2

In yet another rat trial, rats were made diabetic and given stevia, methi seeds, stevia with methi seeds, or glimepiride. They were followed for 60 days. Blood glucose decreased the greatest with glimepiride, next with methi and stevia combo, then methi alone, then with stevia alone. Stevia did create a significant effect on blood glucose by itself. 3

Another study shows that rats fed lots of fructose were able to decrease insulin resistance with a good ol dose of … guessed it, stevia.4

In an actual human study, subjects were given preloads of stevia, aspartame or sucrose before being fed a meal. 20 min after the meal blood was drawn and glucose and insulin measured. Compared to sucrose, aspartame and stevia produced less postprandial glucose levels. Stevia produced significantly lower insulin levels compared to aspartame and sucrose.

In another human study in subjects undergoing glucose tolerance tests, 5 grams of steavia leaves were given at 6 hour intervals for 3 days. The groups were separated into stevia and an aqueous arabinose solution. Stevia increased glucose tolerance and decreased glucose levels during the study.6

Other effects

Stevia appears to have some fertility effects, at least in rats. In one study a water decoction (a way of extraction by boiling chemicals from herbs or plants) was given to rats that were fertile. The infertility continued for 50-60 days after intake stopped. To the researchers no other effects were noticed. This was in females.7

In male rats in chronic (60 days according to the paper) administration produced,

“produced a decrease in final weight of testis, seminal vesicle and cauda epididymidis. In addition, the fructose content of the accessory sex glands and the epididymal sperm concentration are decreased. Stevia treatment tended to decrease the plasma testosterone level” 8

So these poor buggers not only had smaller testes but also less sperm and decreased testosterone. Not exactly a thrilling side effect.

Gut Flora

Stevia doesn’t appear to alter gut flora which is a good thing. The bacteria are able to alter it to steviol however that was the end of it. The tests were done with samples from human donors in vitro.9, 10  How’s about that for donating to science!? We can suppose that this would translate over to a real life human intestine but you never know in these types of studies. This information is promising though.

Blood Pressure

In a study in China, participants were given 500mg of stevia 3 times per day for two years vs placebo and blood pressure was measured. A significant decrease was noted after 1 week. The change was from 150 [7.3] to 140 [6.8] mm Hg; DBP, from 95 [4.2] to 89 [3.2] mm Hg. That’s not too bad. A side note from this study is that more people on placebo had a thickening of the left ventricle than people on stevia (34% vs 11.5% respectively) Quality of life scores were better with stevia. There was no difference in adverse effects between groups.11

Another study found no difference in blood pressure using 3 different doses of stevia, up to 15mg/kg/day.12 This for me would be the 500mg three times daily. The difference in this study is that it was dosed twice daily rather than three times daily. Is this enough to make a difference? I don’t know. I could develop all kinds of protocols for a study to look at these questions but the real question is does this harm you? In both of these studies no adverse effects were seen compared to placebo.

Some have claimed that stevia will raise epinephrine and cortisol. I can’t find any evidence to support this. If anyone has anything I’d love to see it. If that is true it would be a big ding against stevia but again I can’t find evidence to support it.

Stevia may also have oxalates in them which can be problematic for people with kidney stones made from the same substance. I can totally buy that the leaves have them, but I haven’t been able to confirm the extract.

Final thoughts….for now

It looks as though stevia is probably OK for use. If a person is having problems with infertility it may be best avoided. Some forms are sold with other fillers like maltodextrin so they may not truly be zero calories, although if you’re using 1 packet of the stuff it will be less than 4 calories. But if you’re using bulk you’ll have to take care like you would with sucralose, which you’ll never find in my house. Nasty stuff that is!

If you’re diabetic or worried about blood sugar then it appears stevia is beneficial, at least to some degree. Like I always say, try it out and see what happens to you because you and I are not the same people, and neither of us are rats.

You probably won’t find me using 500mg caps of stevia for blood pressure reduction either since I feel that a good diet and some movement will likely take care of that, but it won’t raise it either (unless you’re eating it with junk). From time to time you might see me sweeten something with it, but not regularly and certainly not in bulk. I like my testes the way they are thanks.


1.Chen, Tso-Hsiao, et al. “Mechanism of the hypoglycemic effect of stevioside, a glycoside of Stevia rebaudiana.” Planta medica 71.02 (2005): 108-113.

2.Sumon, M. H., et al. “Comparative efficacy of powdered form of stevia (Stevia rebaudiana Bertoni) leaves and glimepiride in induced diabetic rats.” Bangladesh Journal of Veterinary Medicine 6.2 (2008): 211-215

3.Rafiq, Kazi, et al. “Comparative efficacy of stevia leaf (stevia rebaudiana bertoni), methi seeds (trigonella foenum-graecum) and glimepiride in streptozotocin induced rats.” International Journal 2229 (2011): 7472.

4.Chang, J-C., et al. “Increase of insulin sensitivity by stevioside in fructose-rich chow-fed rats.” Hormone and metabolic research 37.10 (2005): 610-616.

5.Anton, Stephen D., et al. “Effects of stevia, aspartame, and sucrose on food intake, satiety, and postprandial glucose and insulin levels.” Appetite 55.1 (2010): 37-43.

6.Curi, R., et al. “Effect of Stevia rebaudiana on glucose tolerance in normal adult humans.” Brazilian journal of medical and biological research= Revista brasileira de pesquisas médicas e biológicas/Sociedade Brasileira de Biofísica…[et al.] 19.6 (1986): 771.

7.Planas, G. M., and J. Kucacute. “Contraceptive Properties of Stevia rebaudiana.” Science (New York, NY) 162.3857 (1968): 1007.

8.Melis, M. S. “Effects of chronic administration of< i> Stevia rebaudiana</i> on fertility in rats.” Journal of ethnopharmacology 67.2 (1999): 157-161.

9.Gardana, Claudio, et al. “Metabolism of stevioside and rebaudioside A from Stevia rebaudiana extracts by human microflora.” Journal of agricultural and food chemistry 51.22 (2003): 6618-6622.

10.Koyama, E., et al. “In vitro metabolism of the glycosidic sweeteners, stevia mixture and enzymatically modified stevia in human intestinal microflora.” Food and Chemical Toxicology 41.3 (2003): 359-374.

11.Hsieh, Ming-Hsiung, et al. “Efficacy and tolerability of oral stevioside in patients with mild essential hypertension: a two-year, randomized, placebo-controlled study.” Clinical therapeutics 25.11 (2003): 2797-2808

12.Ferri, Letícia AF, et al. “Investigation of the antihypertensive effect of oral crude stevioside in patients with mild essential hypertension.” Phytotherapy Research 20.9 (2006): 732-736.


Foods with Sugar

Here is a quick video discussing some foods with sugar in them and how much sugar is there. This isn’t anything novel but I thought it’d be fun to just show a few things and their sugar content. By the way, I know I say tomato soup in the video and a can of tomato paste shows up but both can have added sugar so just enjoy!


Does Acesulfame Potassium Spike Insulin?

sugar lipsWe’ve now looked at sucralose, saccharin and aspartame. Next up is acesulfame potassium. It too is commonly found in soft drinks, tooth paste, medications and I frequently see it in protein powders to sweeten up a post workout shake. But what effect does acesulfame potassium (ace-k) have on insulin or anything else. Well you guessed it, we’re going to find out.

I’ve largely ignored rat studies up till now, but the evidence with this one isn’t as abundant as others so we gotta go with what we have. So lets get dirty.

Rats were given an infusion of ace-k and blood levels were drawn at intervals after the administration of the dose. A dose of 150mg/kg of bodyweight were infused. Lets stop right there. I weigh about 106kg. For me that would be the equivalent of almost 16gm of ace-k. That’s an insane amount of an artificial sweetener and if you ate that much a day I’m sure you wouldn’t be feeling very well. I’ve read that Coke Zero has about 50mg of ace-k per can so to get the equivalent the rats were getting that’s like me drinking 320 cans at one time. If the taste of the Coke didn’t kill me then I’m sure hyponatremia probably would. I know there is probably a conversion that one would need to use to actually figure out what that dose would be in a human and it would be less, but still a lot . Anyway, these rats received a very large amount of ace-k and their insulin levels went up by around double. No increase in blood glucose was seen. 1 So this study supports the notion that if you consume unholy amounts of ace-k your insulin is likely to go up.

In an in vitro study on rat pancreases, islet cells (the ones responsible for insulin release) were bathed in solutions of ace-k. Insulin concentrations were measured at different times after introduction into the ace-k media. Insulin went up. 2 It’s important to remember though that this setting was in vitro, not a real life situation. So these results may or may not translate over to the real clinical realm.

What about humans?

In a human study, diet soda (sucralose and ace-k sweetened) or soda water was given to 22 healthy subjects 10 min before an oral glucose test. Researchers looked at glucose, insulin and GLP-1. Remember that GLP-1 is a hormone that can increase insulin release. Measurements were taken at 30 min intervals for 3 hours after the glucose test. As expected all three rose, the only difference was the GLP-1 rose signifcantly more in those who had the diet soda than those who had soda water.3 In this particular study the GLP-1 didn’t seem to affect insulin. Could this increase in GLP-1 cause problems over time for people? For some people it most certainly could and for others it probably wouldn’t make any difference. The real answer is we just don’t know, and a person can only truly know by testing how it affects themself.

In a feeding study participants who were mild diabetic or borderline diabetic were given meals sweetened either with sugar or aspartame and ace-k. Blood glucose, insulin, triglycerides, FFA, and C-peptides were measured after ingestion of the meals. Blood glucose rose significantly more in the group that had sugar than aspartame and ace-k. Insulin also rose more in the sugar group. 4 This was done over four meals on different days. Again this study shows that, at least in combo with aspartame, ace-k doesn’t seem to affect insulin or blood sugar. Now again this is in a very short term study and doesn’t tell us much about chronic ingestion of ace-k.

From some anecdotal articles I’ve read about people trying to lose weight it has caused problems in some and not in others. One claims that it only hampers the weight loss of “normal people” and very lean athletes. 5


As with the other artificial sweeteners one of the common complaints associated with ace-k is headache. I can say that I do see a lot of migraine medications go out of the pharmacy fairly regularly. I of course can’t claim that it is due to artificial sweeteners like ace-k but I often wonder if people got artficial sweeteners out of their diet if headaches wouldn’t subside at the same time.

In one study of rat feces, researchers noted that anaerobic bacteria were prevented from fermenting glucose with ace-k, cyclamate and saccharin. 6 This doesn’t show conclusively a change in gut bacteria, but it could lead to a change over time which could lead to other problems. What I’m trying to say is that it hasn’t been well studied (at least to my knowledge) and so we can only speculate as to what’s really going on in the gut. Again if you feel like crap after eating something crappy like an artificial sweetener, then stop. Every once in a while, if it causes no problems, then in my opinion it’s like having a nice ice cream (without artificial crap). Ice cream isn’t exactly health food is it? But it sure is tasty and if you give up ice cream forever because it’s not good for you that’s your choice not mine. But I don’t have ice cream every night.

I think if I was ingesting ace-k on a regular basis and was having problems like weight loss or if I was diabetic and having sugar control issues, then I would stop ingesting it for a while and see what would happened. Ultimately the only person responsible for your health is you and if this article has convinced you that ingesting ace-k is ok and won’t cause any problems, then I invite you to reread the article.

I’d love to hear any experiences you’ve had with ace-k or any other  artificial sweeteners.


1.Liang, Yin, et al. “The Effect of Artificial Sweetener on Insulin Secretion 1. The Effect of Acesulfame K on Insulin Secretion in the Rat (Studies In Vivo).” Hormone and metabolic research 19.06 (1987): 233-238.

2.Liang, Yin, et al. “The effect of artificial sweetener on insulin secretionII. Stimulation of insulin release from isolated rat islets by Acesulfame K (in vitro experiments).” Hormone and metabolic research 19.07 (1987): 285-289.

3.Brown, Rebecca J., Mary Walter, and Kristina I. Rother. “Ingestion of diet soda before a glucose load augments glucagon-like peptide-1 secretion.” Diabetes Care 32.12 (2009): 2184-2186.

4.Fukuda, Masahiro, et al. “Aspartame-Acesulfame K-containing Low-Energy Erythritol Sweetener Markedly Suppresses Postprandial Hyperglycemia in Mild and Borderline Diabetics.” Food science and technology research 16.5 (2010): 457-466.


6.Pfeffer, M., S. C. Ziesenitz, and G. Siebert. “Acesulfame K, cyclamate and saccharin inhibit the anaerobic fermentation of glucose by intestinal bacteria.” Zeitschrift für Ernährungswissenschaft 24.4 (1985): 231-235.