Can Mulberry Leaf Extract Used for Weight Loss

I don’t normally read the freebie newspapers in Toronto as their content is the journalistic equivalent of the lead in the Toronto water supply: both slowly sap your intellect away.

But I ride public transit and those papers are littered everywhere, rolling around the TTC. So against my better judgment I picked up the paper on May 20,  skipped past the article from the “holistic nutritionist” (a topic for another day) and stumbled across this advertisement:

“The Man Who Made the Whole Town Lose Weight”

Impressive headline.  Reading further it turns out that “Johnny Petterson”, a local health food store owner in Alesund, Norway, had started selling mulberry leaf extract leaf tablets to his customers, and they lost weight – after only 10 days.  According to the advertising copy, Johnny has helped over 1500 customers lose weight. Apparently this product is for sale at major pharmacies in Canada. So it’s time to do a bit of digging into this scientific breakthrough unearthed by a health food store owner.

Here’s excerpts from the ad (here is a similar PDF) – and my comments.

“When blood sugar is stable, sugar cravings disappear” – This statement is contradicted by the American Heart Association, which summarizes the evidence as, “We don’t really know enough about all the factors that cause specific food cravings.”

“I studied the effects of mulberries on blood sugar, insulin and fat burning” – There is one very small trial that evaluated mulberry leaf extract on blood sugar levels and observed that it reduced the initial increase in blood sugar after eating sugar. There is one unblinded evaluation of an ingredient extracted from mulberry leaves (1-deoxynojirimycin)  that suggests it may slow the rise in blood sugar after a meal. But there is no data to demonstrate that mulberry has any influence on “fat burning” or, most importantly, weight. The Natural Medicines Comprehensive Database, the most credible and evidence-based summary of information on “natural” products, has almost no information on this item – because no evidence has been published that meets its strict quality requirements.

“Mulberry leaves lead to lower insulin secretion, which makes you able to burn stored fat better and also reduce fat storage from excess calories” –  The very preliminary evidence that exists does suggest that mulberry leaves may have some sort of biological effect. The active ingredient may be the chemical 1-deoxynojirimycin, which appears to be an alphi (α)-glucosidase inhibitor. It may act to blunt the spike in blood sugar after a meal, by interfering with carbohydrate absorption.  The prescription diabetes drug acarbose (Prandase/Glucobay) is also an α-glucosidase inhibitor, so this ingredient from mulberry may have a similar effect.

The terms “burn stored fat better” is clinically meaningless. There is no evidence that mulberry reduces fat storage.

“Taking mulberry leaves, my customers changed to a healthier diet without even noticing it” – Wait, didn’t he just say that the mulberry affects insulin secretion? How did diet come into the picture? If it’s affecting insulin levels, why is the diet changing? Based on the very preliminary research with mulberry leaves, all we can propose is that mulberry leaves might affect how quickly sugars are absorbed. There is no evidence that this will have any impact on dietary choices. Further, this has not been observed with prescription drugs with the same action.

“We now know from clinical studies how mulberry leaf extract regulate blood sugar levels.” Ummm, no we don’t. Where’s the randomized clinical trials in human subjects that demonstrate this product is safe and effective?

The website makes even more questionable claims:

“You will experience that you ar no longer as tempted by foods and especially sugar. You will more easily stay on a healthy diet. Gradually you will lose weight (especially abdominal) and any retained water.” Again, there is absolutely no published evidence that the product will do this. No references are provided.

“Mulberry leaves contain phytosterols, which are cholesterol-lowering agents. While most studies have been done on mulberry’s effect on blood sugar, the studies found that serum cholesterol levels  also dropped by about 12% on average.” Yet again, there is no persuasive evidence to demonstrate this is the case.  Another unsubstantiated, unreferenced claim.

“Mulberry is safe and natural. But do not use mulberry during pregnancy or when breastfeeding” There is zero published evidence that demonstrates short-term or long-term mulberry leaf consumption is safe. No research has been conducted to determine what its side effects are. Based on the very preliminary evidence noted above, mulberry could potentially be dangerous if consumed by diabetics. Most importantly, studies have been done with mulberry leaves, or isolated ingredients. There is no published information or research with Mulberry zuccarin to demonstrate that it has the same effects.

Bottom Line

This is an interesting product. Mulberry leaves do seem to have some sort of biological activity and may contain chemicals that could be useful in the treatment of diabetes. But to claim that this product is a diabetes treatment is premature. Not enough information is known about the risk, benefits, or even what an appropriate dose might be. Moreover, if it actually works, this supplement could put diabetics at risk of low blood sugar (hypoglycemia).  So instead, the product is marketed as a weight loss support supplement – a completely unsubstantiated claim. There is no published to demonstrate that mulberry will help with short-term or long-term weight loss.

If mulberry leaf extract was considered a drug product, there is zero likelihood it would be currently permitted for sale in Canada, the US, or any other jurisdiction.  Why? Because with drugs, conclusive evidence of efficacy and safety is required before sale is allowed.  But call it a natural health product, and all the barrier to sale disappear. It seems any manufacturer can take a unevaluated product, make unsubstantiated health claims, provide no  direct evidence of safety or efficacy, and yet secure shelf space in pharmacies.  As for Canadians,  Heath Canada’s Natural Health Products Directorate is missing in action (again) – failing to regulate health products, and failing to protect the health and safety of Canadians.