International Health News

Diabetes - Tree Bark a Sweet Solution?

by Maurice McKeown, BDS, PhD
(our New Zealand correspondent)

Many of us believe that nature has as much, if not more, to offer than the pharmaceutical companies. Herbal medicine is the basis of most traditional healing systems. The judicious use of plants has eased human ills in the past and continues to do so. Many of our most important medicines have come from plants; yet we don't usually think of trees as important sources of medicinal products. They aren't particularly edible after all.

Some of our most important natural drugs come from trees. Aspirin originally came from the bark of the willow tree. The development of the anti-malarial drug quinine from the bark of the Cinchona tree - a native of South America, had a profound influence on human development. Today the best known tree bark medicine is tamoxifen, which comes from the Pacific Yew tree. It was originally used to treat ovarian cancer but now is the main weapon in the prevention of the recurrence of breast cancer.

There are lesser know medications which derive from tree bark. An extract of Pau D'Arco bark is used for its antibacterial, antifungal and immuno-stimulant properties. The bark of the Neem tree is used in Indian traditional medicine for its curative properties. Pygeum - a substance used primarily to combat prostate problems comes from the bark of the African tree Pygeum africanum. Yohimbe tree bark is believed to have beneficial effects in relieving anxiety disorders.

Other tree bark derivatives are now under scrutiny. One from a Samoan tree, used in their traditional medicine, is under investigation by the US National Cancer Institute. It may prove valuable in combating HIV. The South American Graviola tree is being investigated as its bark contains a group of phyto chemicals called annonaceous acetogenins. Some of these substances have now been patented, as they are believed to have anti-tumor and pesticidal properties.

Today the best know tree bark extract that adorns the shelves of health food stores is known by its modern commercial name of pycnogenol. This pine bark extract was developed by the French researcher Jack Masquelier who has pioneered the use of the extract and grape seed extract which contains even higher concentrations of similar phyto active compounds. The main value of these substances is known to lie in their rich content of oligomeric proanthocyanidins (OPC's - sometimes referred to as PA's or PCO's). They have many potentially valuable health applications - notably enhanced cardiovascular health.

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It seems likely that many more beneficial tree components await discovery. It may not however be necessary to hack your way up the Amazon for additional medical help. Benefits could be as close as your pantry. The tree bark extract there may be more valuable than we all realise. It is, of course, cinnamon which comes from the inner bark of the young shoots of the cinnamon tree - Cinnamomum zeylanicum (or its close relative Cinnamomum cassia).

Only last year new research suggested that cinnamon powder may be of great value to sufferers of type 2 diabetes and those with blood sugar problems.(1) There are also indications that the oil fraction of cinnamon which contains a substance - cinnamaldehyde has related health values. It is known to inhibit aggregation of platelets and thus may reduce the tendency of blood to clot.

OPC's are present in small amounts in fruit, nuts and some beans. The best endowed fruit are berries and some pip fruit. It has been calculated that the best source in the regular US diet is apples, closely followed by chocolate (the cacao bean contains large amounts) and grapes. Daily consumption is calculated to be approximately 70 mg. (2)

Fruit is universally accepted as a healthy and valuable food. It could be that its OPC content is a major health-promoting factor. OPC's are believed to have valuable properties as potent antioxidants with specific beneficial effects on the cardiovascular system. A new database on the OPC content of common foods, just published by the USDA (US Department of Agriculture), puts cinnamon at the top of the list; far above grape seed extract.(3)

A 1999 study at the University of Munster in Germany concluded that pine bark extract, which contains similar OPC's, was much more effective at low doses than aspirin, in inhibiting platelet aggregation in smokers. It was also noted that a single 200 mg dose of pine bark extract was effective over a 6-day period. Interestingly the researchers found that aspirin significantly increased bleeding time, while the pine bark (pycnogenol) did not. It was concluded that OPC's act by inhibiting the formation of thromboxane A-2, a platelet aggregating compound.(4)

Another study published in 2001 found that pycnogenol was able to reduce blood pressure in mildly hypertensive patients.(5) There was a concomitant fall in blood thromboxane levels. The authors discussed the various effects of elevated thromboxane levels and also pointed out that pycnogenol also increases production of nitric oxide (NO) by endothelial cells. NO is of course a vasodilator.

It seems that OPC's have great potential in improving the health of the cardiovascular system. The cinnamon study on human subjects identified an average 20% drop in blood sugar levels in weeks. More surprising was the finding that triglyceride, LDL cholesterol and total cholesterol levels all fell substantially. There doesn't appear to be any immediate explanation of the mechanisms involved in blood fat reduction. It is thought that a substance present in the water soluble fraction of cinnamon MCHP (methyl hydroxychalcone) acts as an insulin mimic activating cell surface receptors. Type 2 diabetics produce enough insulin. It is the ability of that insulin to activate target cells that is at fault. It is likely that the MCHP normalises blood sugar by enhancing insulin receptor sensitivity.

The good news is that the human cinnamon study found that modest daily amounts were just as valuable as higher doses. There were suggestions that smaller doses were more valuable in reducing blood fats than larger doses of three and six times as much. The study also noted that the 'cinnamon effect' persisted for at least 20 days after cessation of treatment. It may therefore not be necessary to consume cinnamon every day. It concluded that half a teaspoonful of cinnamon powder daily was sufficient to provide the desired reductions in blood sugar and fat levels. Cinnamon may have the potential to reduce the amount of insulin needed by diabetics. It might even eliminate the need for it in some individuals. Some authorities now believe that currently accepted limits for blood sugar levels are too high. The authors believe that cinnamon may have a place in blood sugar control in non-diabetic individuals.

We can't conclude too much from one human study. Laboratory work is, however, providing some corroboration (6,7). Clearly further clinical studies must be done. As modest doses of cinnamon and pine bark or grape seed extracts have no known deleterious effects, it may be useful for those with type 2 diabetes to add some cinnamon to their diet. The anti-clotting properties of OPC's suggest that substances containing them will also be valuable in reducing the risk of blood clots as a result of air travel or after surgical procedures. Commercial preparations are now coming on the market containing OPC's to combat deep vein thrombosis.


  1. Khan A, Safdar M, Khan MMA, Khattak KN, Anderson RA. Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes Care 2003 Dec: 26(12): 3215-8
  2. Gu L, Kelm MA, Hammerstone JF, Beecher G, Holden J, Haytowitz D, Gebhart S and Prior RL Concentrations of Proanthocyanidins in common foods and estimations of normal consumption. Journal of Nutrition 2004 Mar 134: 613-617
  3. The USDA Database for the Proanthocyanidin Content of Selected Foods Aug 2004
  4. Putter M, Grotemeyer KHM, Wurthwein G, Araghi-Niknam M, Watson RR, Hosseini S and Rohdewald P. Inhibition of smoking-induced platelet aggregation by aspirin and pycnogenol. Thrombosis Research 1999 Aug 95:4 155-161
  5. Hosseine S, Lee J, Sepulveda RT, Rohdewald P and Watson RR. A randomized double blind, placebo controlled, prospective 16-week crossover study to determine the role of Pycnogenol in modifying blood pressure in mildly hypertensive patients. Nutrition Research 2001 Sept 21:9 1251-1260
  6. Broadhurst CL, Polansky MM, Anderson RA. Insulin-like biological activity of culinary and medicinal plants aqueous extracts in vitro. Journal of Food Chemistry 2000 Mar 48:3 849-52
  7. Qin B, Nagasaki M, Ren M, Bajotto G, Oshida Y and Sato Y. Cinnamon extract (traditional herb) potentiates in vivo insulin signalling in rats. Diabetes Research in Clinical Practice 2003; 62: 139-48.


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