Stevia - Natural Sweetener With Anti-Diabetes + Anti-Obesity Effects? Research Update: GLP-1, Insulin, Glucose Transport and Uptake, Inflammation, Bitterness & Safety
|Stevia is certainly one of the best choices to use as a sweetening agent. It is yet important to point out that this has nothing to do with the fact that it is "natural" - as "natural" as the white stevioside powder ism anyway.|
The results Ripken et al. presented about 3 weeks ago are yet only the tip of a whole heap of studies of which Nabilatul Hani Mohd-Radzman and colleagues believe that it is sufficient to postulate that the Stevia rebaudiana Bertoni plant "could benefit the community medicinally through several different pathways, all eventually leading to its antihyperglycemic qualities." (Mohd-Radzman. 2014)
But is there really convincing evidence that the beneficial effects of the consumption / use of stevia and its main sweetening agent stevioside go beyond the mere reduction in sugar consumption? Yes, there is; and here is a brief overview of what we've learned so far:
- Anti-inflammatory effects -- Some scientists believe that Stevia’s utility in diabetes protection is due to its antioxidant properties; a hypothesis that is supported by analysis of the phenols that may be extracted from the plant.
Stevia has a large overall proportion of phenols, up to 91 mg/g; it is proposed that these constituents extracted from the leaves are the major agents contributing towards the anti- hyperglycemic activities exerted by the plant (Shivanna. 2013). This is further supported by the fact that the leaves have a greater ability to scavenge free radicals and prevent lipid peroxidation than controls such as butylated hydroxytoluene, butylated hydroxyanisole, and tertiary butyl hydroxyquinone.
Figure 1: Effect of Stevia on lipid peroxidation in liver in STZ treated rats (n = 8; Shivanna. 2013).
The same goes for the levels of the pro-inflammatory cytokine NF-kappaB and TNF-alpha of which researchers from the Shanghai Institute of Endocrine and Metabolic Diseases report that it was significantly downregulated in a study on a C57BL6J mouse model of insulin-resistance, when the rodents received stevioside supplemented chow (Wang. 2012).
- Direct beneficial effects on blood glucose levels -- Whether the beneficial effects of stevia on blood glucose management are mediated solely via its anti-inflammatory effects is not yet certain. The initially mentioned effects on GLP-1, for example, could (and probably will) also contribute to the significant decrease in blood-glucose levels Susuki et al. observed in a study from 1977 that was published in the Japanese science journal Nippon Nogei Kagaku Kaishi (Susuki. 1977). The Japanese researchers fed rats a stevia enriched high carbohydrate + high fat diet and observed "a significant reduction in glycemia" after four weeks on the otherwise highly prodiabetic rodent equivalent of the Western diet.
You cannot stand the bitter taste of stevia? Unlucky you! You've simply got the wrong genes. As scientists from the Laboratory of Molecular Anthropology and Centre for Genome Biology at the University of Bologna observed in a very recent study, men and women with the TAS2R4 gene polymorphism rs2234001 and /or the TAS2R14 (TAS = taste receptor) gene polymorphism rs3741843 will never understand how the rest of us can ignore the obnoxious bitterness of steviosides - I know, that's bitter ;-)
- That these benefits are not rodent specific and don't arise in response to an interaction with certain components in the rodent chow was demonstrated 27 years later by Gregersen, et al. (2004). In their paper in the January issue of Metabolism, the scientists report that they observed a similar, highly significant reduction (an average of 18%) in postprandial glucose levels in Type II diabetic patients given test meals supplemented with stevioside..
A 2010 study by Anton et al. confirmed this (Anton. 2010) this; postprandial glucose levels were significantly lowered in patients supplemented with Stevia, compared to those
given aspartame (a type of synthetic sweetener) or sucrose (normal table sugar). In that, the slightly increased insulin levels in the stevia vs. aspartame group provides further support for the involvement of GLP-1, which is likewise involved in health insulin function (Kjems. 2003)
Figure 2: Total energy intake of type II diabetics in kcal/day on days with aspartame, setvia or sucrose sweetened foods (left); corresponding plasma insulin levels (Anton. 2010)
- Possible interactions with the gut & its microbiome -- The research on the interactions of stevia with the microbes in our gut is still in its infancy.
Table 1: Effects of non-nutritive sweeteners on gut hormones and glucose absorption:in vivo effects on animals (Brown. 2014)
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- Gregersen, Søren, et al. "Antihyperglycemic effects of stevioside in type 2 diabetic subjects." Metabolism 53.1 (2004): 73-76.
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- Ripken, Dina, et al. "Stevia Glycoside Rebaudioside A Induces GLP-1 and PYY Release in a Porcine Ex Vivo Intestinal Model." Journal of agricultural and food chemistry (2014).
- Shivanna, Naveen, et al. "Antioxidant, anti-diabetic and renal protective properties of Stevia rebaudiana." Journal of Diabetes and its Complications 27.2 (2013): 103-113.
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