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After last week’s article many of you asked about a natural alternative to sugar and artificial sweeteners: stevia. It is widely used in the low carb community to satisfy sugar cravings or simply add a touch of sweetness to a hot beverage or dessert, but should it be? What is stevia? Is it safe? What is its effect on insulin, if any, and does it have a place in a Primal Blueprint eating strategy? Let’s investigate.
Stevia is an herbaceous family of plants, 240 species strong, that grows in sub-tropical and tropical America (mostly South and Central, but some North). Stevia the sweetener refers to stevia rebaudiana, the plant and its leaves, which you can grow and use as or with tea (it was traditionally paired with yerba mate in South America) or, dried and powdered, as a sugar substitute that you sprinkle on. It’s apparently quite easy to grow (according to the stevia seller who tries to get me to buy a plant or two whenever I’m at the Santa Monica farmers’ market), and the raw leaf is very sweet.
Most stevia you’ll come across isn’t in its raw, unprocessed form, but in powdered or liquid extract form. The “sweet” lies in the steviol glycosides — stevioside and rebaudioside — which are isolated in these extracts. Some products use just one, while others use both stevioside and rebaudioside. Stevioside is the most prevalent glycoside in stevia, and some say it provides the bitter aftertaste that people sometimes complain about; rebaudioside is said to be the better tasting steviol glycoside, with far less bitterness. Most of the “raw or natural” stevia products use the full range of glycosides, but the more processed brands will most likely isolate one or more of the steviol glycosides. The popular Truvia brand of stevia products uses only rebaudioside, as do both PureVia and Enliten. Different brands provide different conversion rates, but compared to sucrose, stevioside is generally about 250–300 times as sweet and rebaudioside is about 350–450 times as sweet.
Does Stevia Affect Insulin?
There is one in vitro study that showed stevioside acts directly on pancreatic beta cells to stimulate insulin secretion and another which shows similarly insulinotropic effects of rebaudioside, which may give you pause. Insulin secretion sounds like an insulin spike, no? And since we tend to be wary of unneeded insulin spikes, maybe we should avoid stevia. It’s not so simple, of course. For one, this was an in vitro study, performed in a super-controlled laboratory petri dish type setting; this was not an in vivo study of animals or people eating stevia in a natural, organic way. The results of in vitro studies are notorious for not panning out when you try to replicate them in vivo. Secondly, insulin secretion isn’t necessarily a bad thing. I mean, we need it to shuttle nutrients into cells, and we’d die without it. As I mentioned in the dairy post a few weeks back, insulin is millions upon millions of years old. It’s been preserved throughout history because it’s an essential hormone. It’s not always the bad guy, especially if you’re insulin sensitive.
In fact, the evidence is mounting that stevia actually is an insulin sensitizer that can aid in glucose tolerance and clearance after a meal. The Japanese have been using stevia for decades in the treatment of type-2 diabetics. Let’s look at a few recent studies. In fructose-fed rats, a single instance of oral stevioside increased insulin sensitivity and reduced postprandial blood glucose in a dose-dependent manner. The same study also found that diabetic rats given stevioside required less exogenous insulin for the same effect. Taken together, these results suggest that stevia may not just be a good sugar substitute for diabetics, but an effective supplement for treatment of their insulin resistance.
Another study looked at the postprandial effects of stevia, sucrose, and aspartame in human subjects. Compared to sucrose eaters, stevia eaters showed lower postprandial blood sugar levels. Compared to both sucrose and aspartame eaters, stevia eaters had far lower postprandial insulin levels. Furthermore, eating stevia did not induce increased appetite throughout the day, indicating stable blood sugar and satiety levels. Another strike in stevia’s favor.