Metformin & Sweet Potatoes - What Do They Have in Common? Both Reduce Blood Glucose & Increase Insulin Response, Decrease Total Cholesterol & Increase HDL

Image 1: Leaves of wild sweet
patatoes from the Phillipines
(photo by Obsidian Soul)

"Nature knows best!" Who would have thought that this motto of mine applies to the #1 paleo-pasta-replacement, the sweet potato, as well? While the tuberous roots do of course contain many of those nasty carbohydrates, which, in reminiscence of the fat-phobia of the closing 20th century, could be called the "bad fats of the early 21st century", the whole plant also comes with a whopping dose of a Metformin-esque anti-diabetes drug that would undo potential damage secondary to carbohydrate overload., uf... yes if we consumed its heart-shaped or palmately lobed leaves (they are edible and non-toxic!)

In the VNU Journal of Science, Natural Sciences and Technology, Do Ngoc Lien and his Vietnamese colleagues published some very interesting data on the effects an ethyl acetate extract from the leaves Ipomoea batatas (L) Lam (sweet potato). had on glucose, insulin and lipid levels in a streptozotocin treated mouse-model of human diabetes type II (Lien. 2011):

When obese-diabetic mice [were] administrated orally daily by ethyl acetate fraction of 1000mg lyophilized powder/kg for 21 days, we showed that maximum hypoglycaemic (36.77%) and hypolipidemic effects, such as TC (35.18%), TG (29.17%), and LDLc (51.97%) were proven in treated mice compared to the control (untreated mice)

The results become particularly interesting, if we have a closer look at the effect size compared to what the current gold-standard in pharmacological diabetes management, Metformin (cf. figure 1):

Figure 1: Relative effect of 21 days on n-hexant (EtOH), chloroform (Chlf) and ethylacetate concentrates of sweet potato leave extract or Metformin on blood glucose and insulin levels compared to untreated control
(calculated based on Lien. 2011)

If we now calculate the ratio of glucose / insulin and take that as an (unreliable) measure of insulin sensitivity (cf. figure 2), we see that 1g/kg (human equivalent 81mg/kg) of an ethylacetate extract from the leaves sweet potato was ~90% as effective as the current diabetes drug of choice, Metformin, in restoring insulin sensitivity and thusly reducing blood glucose to acceptable levels.

Figure 2: Effect of 21 days on n-hexant (EtOH), chloroform (Chlf) and ethylacetate concentrates of sweet potato leave extract or Metformin on "insulin sensitivity", approx. by glucose/insulin ratio (calculated based on Lien. 2011)

The underlying mechanism, the scientists believe, is a compensation of the existing imbalance between hexokinase and glucose-6-phosphatase activity in the liver of the diabetic mice. I am not sure, though, whether this restorative effect on the formation and breakdown of glucose fully explains all the beneficial effects of the sweet potato leave extract, which also include a -29.17% reduction in the nasty triglycerides, of which many scientists think that they are rather causative of, than corollary to the insulin resistance that is at the heart of type II diabetes, and a reduction of the total cholesterol/ratio from 19.02 to 8.14 (MDs still want their patients in the <4.0 regions, today). In view of the "pharmacological" (I need these "" in order not to get sued by the FDA ;-) potency of the leaves of a root vegetable, probably no-one would know of, if it had not been heavily promoted by Robb Wolf (whom I regard very highly) and the rest of the Paleo Crowd (some of whom have unfortunately turned into fanatics),  I guess you will probably understand why I foresee an increasing demand for the formerly worthless foliage of Ipomoea batatas.