Dr. Jeannette Goguen's article (displayed below).  She works out of the University of Toronto and has kindly allowed me to reproduce her note on this web site.

Health Canada's Canadian Adverse Reaction Newsletter.  This is a professional publication, but the issue (entitled "Adverse reactions to natural health products") of October, 2002 is excellent reading for both lay and physician audiences and I would heartily recommend having a look at it.

Health Canada's Natural Health Products Directorate.  In particular check out their Warnings/Advisories page.

Aloe vera

Coccinia indica (ivy gourd)

Garlic

Ginseng

Gymnema sylvestre

Oolong tea

Vanadium

Beta Carotene - A very important medical study ("The Heart Protection Study") looked at beta carotene and found no benefit from this.

Cinnamon - A study published in December, 2003 suggested that cinnamon could help improve blood glucose levels.  i had really hoped this would be the case; imagine having a safe, effective and tasty therapy!  Alas, a more definitive study published in 2007 has determined that cinnamon is, in fact, not effective in the treatment of diabetes.  It is however, really scrumptious when sprinkled over apple sauce!

Vinegar - Can this be true?  An article published in January, 2004 suggests that drinking 20 grams of apple cider vinegar with your meal can reduce insulin resistance and lead to significantly improved blood glucose levels.  Stay tuned...

Vitamin E - Tons of people take Vitamin E.  In fact I was told a few years ago by a professor at the University of Toronto that annual North American sales totalled THREE HUNDRED MILLION DOLLARS!  Wow!  Now that would be okay if taking extra Vitamin E actually provided some health benefit.  But it probably doesn't.  Two landmark (i.e., really important and well done studies) have looked at this issue, but neither the HOPE Study nor the Heart Protection Study showed any benefit on one's health (in particular the heart) from taking supplemental Vitamin E.

Multivitamin/Mineral Supplements - I commonly get asked if it is necessary to take vitamin and/or mineral supplements.  My feeling has been that if one eats a well-balanced diet and follows the current nutrition guidelines (such as provided by the ADA and CDA), that vitamin supplements generally do little except give you expensive urine.  An editorial in the British Medical Journal, though not specifically talking about diabetes, expresses a similar sentiment (though without, ahem, the allusion to the urine).  Note that this advice regarding vitamins does NOT apply to pregnancy (see my pregnancy web page for discussion re folic acid supplements) nor to lactating women, the elderly, strict vegetarians and other select groups.  Having said all this I was struck by the results of a study done in 2003 (published in the Annals of Internal Medicine) which looked at the potential use of a multivitamin/mineral supplement at reducing the risk of infections; the study found that people with diabetes taking the supplement had an absolutely astounding lowering of their risk (whereas 93 percent of people taking a placebo developed an infection over the span of a year, only 17 percent of people taking the supplement developed an infection.  Even more amazing was the fact that people with diabetes taking a placebo had an 89 percent likelihood of missing a day from work, but 0 percent [yup, zero, that wasn't a typo] of people with diabetes taking the supplement missed work.  Unbelievable!!  Of course, that's not necessarily all good news if you were looking for an excuse to play hooky from work now and then).  Now, on the other hand, the study was made up of only a very, very small number of participants so it could be that the study results were simply a fluke.  Anyhow, I think we can conclude two things from all this: 1) we have to remain open-minded; it could be that taking a multivitamin/mineral supplement may be a very good thing to do and 2) we have to remain open-minded; it could be that taking a multivitamin/mineral supplement is a complete waste of money.  We await more definitive studies...