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Canadian Pharmacists Association
Canadian Pharmacists Association
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Chapter 21: Natural Health Products

Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada

Introduction
  • Natural Health Products (NHPs) include herbal medicines, vitamins, minerals and other essential nutrients, probiotics and many other naturally occurring substances.
  • Since 2004, they have been regulated in Canada by the Natural Health Products Directorate of Health Canada.
Management
  • Natural health products are not recommended for glycemic control for individuals with diabetes as there is insufficient evidence, at this time, regarding efficacy and safety [Grade D, Consensus].
  • The current level of evidence for the efficacy and safety of NHPs in people with type 2 diabetes is lower than that for pharmaceutical drug treatments. Trials tend to be of shorter duration and involve smaller sample sizes.
  • Presently concerns remain about standardization and purity of available compounds, including their contamination with regular medications and in some cases, toxic substances.
  • While a number of NHPs have been studied to evaluate their impact on cardiovascular and other outcomes in patients with type 2 diabetes, this guideline is limited to NHPs for improving glycemic control. Trials were considered for review if they were randomized, controlled, and reported changes in glycated hemoglobin (A1C) over at least 12 weeks of treatment. Positive trials were those that demonstrated a reduction in the placebo-subtracted A1C of at least 0.5%.
Complications
  • It is important to consider potential harm from the use of NHPs. Most clinical trials have evaluated small sample sizes over relatively short periods of time and, thus, may not identify side effects or risks.
  • Drug-herb interactions may also occur. The most well described is Hypericum perforatum (St. John's wort), which can affect the metabolism of many drugs, including statins, by inducing CYP3A4.
  • Some studies have reported poorer glycemic control in patients using glucosamine sulfate for osteoarthritis, but a systematic review concluded that the evidence does not support this concern.
  • Healthcare providers should ask about the use of natural health products [Grade D, Consensus]. Potential concerns should be addressed using a patient-centred approach that ensures patient safety while respecting their views to maintain a positive therapeutic relationship.
Table 1: Various NHPs and their effects on A1C values.
Lowered A1C by ≥0.5% in trials * Failed to lower A1C by ≥0.5% Conflicting effects on A1C in trials
  • Coccinia cordifolia
  • Ganoderma lucidum
  • Salacia reticulata
  • Soybean-derived pinitol extract
  • Touchi soybean extract
  • Pterocarpus marsulium (vijayasar)
  • Gynostemma pentaphyllum
  • Marine collagen peptides
  • Silymarin
  • Citrullus colocynthis
  • Trigonellafoenum-graecum (fenugreek)
  • Tinospora crispa
  • French maritime pine bark
  • Soy phytoestrogens
  • Agaricus blazei
  • Antioxidants (fruit/vegetable extract), (pomegranate extract)
  • Camellia sinensis
  • Cinnamomum spp (cinnamon)
  • Momordica charantia (bitter melon or bitter gourd)
  • Flaxseed oil
  • Ginseng
  • Coenzyme Q10
  • Vitamin C
  • Vitamin D
  • Vitamin E
  • Ipomoea batatas (caiapo)
  • Chromium
  • Magnesium
  • L-carnitine
All trials lasted at least 3 months in duration; results are for adults with type 2 diabetes. Natural health product (NHP); Glycated hemoglobin (A1C).

* These products are promising and merit consideration and further research, but, as they are mostly single, small trials, it is premature to recommend their widespread use.

† It should be noted that in many cases, small sample sizes made the trials insufficiently powered to establish a significant benefit from NHP interventions.

‡ It should be noted that vanadium, a trace element that is commonly used to treat type 2 diabetes, has not been studied in trials evaluating glycemic control over a period of 3 months or longer.

For definitions of the levels of evidence cited in this chapter, please refer to the Guideline Recommendations: Levels of Evidence.

If you would like more details on this topic, please visit the Canadian Diabetes Association Clinical Practice Guidelines: Chapter 21.