Is this an effective medicine or a condiment?

Is this an effective medicine or a condiment?

We don’t yet have a cure for diabetes, but we have insulin; it controls the disease and allows Type 1 diabetics to lead a relatively normal life instead of suffering and quickly dying as they all did in the pre-insulin era. We know to counsel Type 2 diabetics about weight loss, diet, and exercise; and when those measures are not enough, we have prescription medications that work very well to control symptoms and help prevent complications.

For some people, that’s not good enough. They want to find “natural” remedies to supplement or replace conventional treatments. In a recent article on SBM, Scott Gavura quoted a pharmacy customer who said “I don’t want to take any drugs. Do you have something natural I can use to cut my blood sugar?” Scott went on to cover the questionable evidence for cinnamon in that article. Many other “natural” remedies have been proposed. Here’s an alphabetical list: acetyl L-carnitine, aloe, alpha-lipoic acid, banaba leaf (not banana!), basil, berberine, bilberry, biotin, bitter melon, cinnamon, chromium, coQ10, crepe myrtle, fenugreek, fish oil, fructo-oligosaccharides, green tea, ginseng, glucomannan, gymnema, hibiscus, Indian kino tree extract, magnesium, mistletoe, olive leaf, onion, psyllium, purslane, resveratrol, starch blockers, thiamine, vanadium, and vitamins. I compiled that list from just three websites; I’m sure there are many more natural remedies that I missed. These natural remedies have been recommended on the basis of rather shaky preliminary evidence that they lower blood sugar, usually by only a small amount. Even the CAM-friendly National Center for Complementary and Integrative Health (NCCIH) concluded:

There is not enough scientific evidence to suggest that any dietary supplements can help prevent or manage type 2 diabetes.

They also warn that “Some dietary supplements may have side effects, including interacting with your diabetes treatment or increasing your risk of kidney problems.”


Marketers are eager to sell these natural remedies to diabetics, and they often mix several ingredients together; but they never bother to test whether the product itself is effective. The latest candidate was advertised in my local newspaper (a reliable source of unreliable health claims). It’s called Plavinol.

From their website:

Plavinol is a breakthrough formula that works with your body to fight the effects of unhealthy blood sugar. With it’s [sic] active ingredient ‘Morus Alba’ along with 4 supporting nutrients, Plavinol is effective in promoting healthy insulin response and weight loss including:

  • Post meal blood sugar
  • Healthy weight
  • Improved A1C levels
  • Supports metabolism

The ingredients and daily doses are:

  • Mulberry leaf extract (1% deoxynojirimycin) 500 mg
  • Gymnema sylvestre leaf extract 400 mg
  • Ashgawandha root and leaf extract 250 mg
  • Banaba leaf extract (1% corosilic acid) 48 mg
  • Vanadium 100 mcg

A month’s supply costs $78.85.

Active ingredient: Morus alba (white mulberry)

There are a number of positive mouse studies of Morus alba alone or in combination with other herbal remedies. But mice are not people.

There has been little research on humans. One study used mulberry leaf extract with enriched 1-deoxynojirimycin (DNJ) content (approximately 1.5%, half again as much as in Plavinol). It was a two-part study. The first part was a double blind crossover trial in 12 subjects. It found that a single dose decreased the rise of blood sugar after a glucose challenge; but insulin levels did not change. The second part was a 12-week randomized controlled trial (RCT) of 76 subjects. 1,5‐anhydroglucitol levels increased gradually and were higher than controls at the 8 and 12 week points, but not earlier. There were no significant differences in fasting plasma glucose, insulin, hemoglobin A1C, or glycated albumin.

An uncontrolled human study from Romania in 1989 found that a mixture of Morus alba with two other herbs (not the ones in Plavinol) lowered blood sugar levels in 74 out of 82 patients.

The Natural Medicines Comprehensive Database (NMCD) which I consider the most reliable source of information about natural medicines, rated it as only “possibly safe” and “possibly effective” and noted that the studies failed to show a decrease in HbA1C, which is the most reliable measure of the effect on diabetes over a period of time.

The 4 “supporting nutrients”

The other ingredients in Plavinol are said to be “supporting nutrients,” but there is no evidence that they improve the effects of mulberry. And there is no explanation of the rationale by which they were chosen. The evidence for them is scanty.

Gymnema silvestre leaf extract: NMCD effectiveness rating: “Insufficient reliable evidence to rate.” Safety rating: “Possibly” safe.

Ashgawandha root and leaf extract: NMCD effectiveness rating: “Insufficient reliable evidence to rate.” Safety rating: “Possibly” safe.

Banaba leaf extract: NMCD effectiveness rating: “Insufficient reliable evidence to rate.” Safety rating: “Possibly” safe.

Vanadium: NMCD effectiveness rating: “Insufficient reliable evidence to rate.” Safety rating: “Likely safe.”

Studies of vanadium for diabetes typically used doses of 30-150 mg daily, orders of magnitude greater than the amount in Plavinol. Even at those higher doses, the evidence was unconvincing. A 2008 review concluded “There is no rigorous evidence that oral vanadium supplementation improves glycemic control in type 2 diabetes. The routine use of vanadium for this purpose cannot be recommended. A large-scale randomized controlled trial is needed to address this clinical question.” A 2016 review concluded “vanadium administration for the treatment of human diabetes is misplaced.”

Conclusion: Condimentary medicine?

As a Healthline article warns: “Supplements should not replace standard diabetes treatment…Some supplements have shown promise in animal studies. However, there is currently only limited evidence that they have the above mentioned benefits in humans.”

Richard Rawlins, an orthopedic surgeon in the UK, coined the term “condimentary medicine.” It “adds spice and flavor but has no actual effect on the course of treatment.” Until they have been properly tested against a placebo, we can’t really know whether products like Plavinol are mere condiments, or whether they are safe and effective additions to the therapeutic armamentarium for diabetes.


Posted by Harriet Hall

Harriet Hall, MD also known as The SkepDoc, is a retired family physician who writes about pseudoscience and questionable medical practices. She received her BA and MD from the University of Washington, did her internship in the Air Force (the second female ever to do so),  and was the first female graduate of the Air Force family practice residency at Eglin Air Force Base. During a long career as an Air Force physician, she held various positions from flight surgeon to DBMS (Director of Base Medical Services) and did everything from delivering babies to taking the controls of a B-52. She retired with the rank of Colonel.  In 2008 she published her memoirs, Women Aren't Supposed to Fly.