Natural Health Products

Canadian Diabetes Association Clinical Practice Guidelines Expert Committee

Richard Nahas MD, CCFP Jeannette Goguen MD, MEd, FRCPC

  • Key Messages
  • Recommendations
  • Figures
  • Full Text
  • References

Key Messages

  • Seventy-eight percent of patients with diabetes reported taking a natural health product (NHP) for various indications.
  • Some NHPs have shown a lowering of A1C by ≥0.5% in trials lasting ≥3 months in adults with type 2 diabetes, but most are single small trials so it would be premature to recommend their widespread use.
  • Healthcare providers should always ask about the use of NHPs since some may result in side effects or drug interactions.


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.


These guidelines include NHPs because they are widely used by patients, but the evidence of their efficacy and safety is unknown to most prescribing physicians. In a recent Canadian study of 502 patients with diabetes, 78% reported taking an NHP, with similar frequency in people with type 1 and type 2 diabetes (1). While it is important to be aware of potential harms, side effects and drug interactions, some NHPs may be potentially important new therapeutic agents. Interestingly, metformin is derived from French lilac, a remedy used to treat diabetes since the Middle Ages, and identification of the active agent guanidine led to the synthesis of biguanides (2).

In general, 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. At the present time, concerns remain about standardization and purity of available compounds, including their contamination with regular medications and, in some cases, toxic substances (3).

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%.

The following NHPs lowered A1C by ≥0.5% in trials lasting at least 3 months in adults with type 2 diabetes:

  • Coccinia cordifolia (4)
  • Ganoderma lucidum (5)
  • Salacia reticulata (6)
  • Soybean-derived pinitol extract (7)
  • Touchi soybean extract (8)
  • Pterocarpus marsulium (vijayasar) (9)
  • Gynostemma pentaphyllum (10)
  • Marine collagen peptides (11)
  • Silymarin (12,13)
  • Citrullus colocynthis (14)
  • Trigonellafoenum-graecum (fenugreek) (15)

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.

The following NHPs failed to lower A1C by ≥0.5% in trials lasting at least 3 months in adults with type 2 diabetes:

  • Tinospora crispa (16)
  • French maritime pine bark (17)
  • Soy phytoestrogens (18)
  • Agaricus blazei (19)
  • Antioxidants (fruit/vegetable extract) (20) , (pomegranate extract) (21)
  • Camellia sinensis (22)
  • Cinnamomum spp (cinnamon) (23–27)
  • Momordica charantia (bitter melon or bitter gourd) (28)
  • Flaxseed oil (29)
  • Ginseng (30)
  • Coenzyme Q10 (31)
  • Vitamin C (32)
  • Vitamin D (33–35)
  • Vitamin E (36–38)

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

The following NHPs have demonstrated conflicting effects on A1C in trials lasting at least 3 months in adults with type 2 diabetes:

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.


It is important to consider potential harm from the use of NHPs. In 1 trial of Tinospora crispa , hepatotoxicity was seen in 2 patients (16). Large doses of Citrullus colocynthis can induce diarrhea, but no side effects were reported in the lower doses used in 1 trial (14). Momordica charantia , an NHP commonly used for glycemic control, is an abortifacient (62). 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 (63).

Clinicians should ask all patients with diabetes about their use of NHPs. Potential concerns should be addressed using a patient-centred approach that ensures patient safety while respecting their views to maintain a positive therapeutic relationship. For more detailed information about specific NHPs, practitioners should consult previously published reviews (64).


  1. 1.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].
  2. 2.Healthcare providers should ask about the use of natural health products [Grade D, Consensus].


  1. 1 E.A. Ryan M.E. Pick C. Marceau Use of alternative medicines in diabetes mellitus Diabet Med 18 2001 242 245
  2. 2 A.Y. Oubre T.J. Carlson S.R. King G.M. Reaven From plant to patient: an ethnomedical approach to the identification of new drugs for the treatment of NIDDM Diabetologia 40 1997 614 617
  3. 3 R.B. Saper S.N. Kales J. Paquin Heavy metal content of ayurvedic herbal medicine products JAMA 292 2004 2868 2873
  4. 4 R. Kuriyan R. Rajendran G. Bantwal A.V. Kurpad Effect of supplementation of Coccinia cordifolia extract on newly detected diabetic patients Diabetes Care 31 2008 216 220
  5. 5 Y.H. Gao J. Lan X.H. Dai A phase I/II study of Ling Zhi mushroom Ganoderma lucidum ( W.Curt.:Fr.) Lloyd (Aphyllophoromycetidae) extract in patients with type 2 diabetes Int J Med Mushr 6 2004 33 39
  6. 6 M.H. Jayawardena N.M. de Alwis V. Hettigoda A double blind randomised placebo controlled cross over study of a herbal preparation containing Salacia reticulata in the treatment of type 2 diabetes J Ethnopharmacol 97 2005 215 218
  7. 7 M.J. Kang J.I. Kim S.Y. Yoon J.C. Kim I.J. Cha Pinitol from soybeans reduces postprandial blood glucose in patients with type 2 diabetes mellitus J Med Food 9 2006 182 186
  8. 8 H. Fujita T. Yamagami K. Ohshima Long-term ingestion of a fermented soybean-derived Touchi extract with alpha-glucosidase inhibitory activity is safe and effective in humans with borderline and mild type-2 diabetes J Nutr 131 2001 2105 2108
  9. 9 R.S. Hariharan S. Venkataraman P. Sunitha Efficacy of vijayasar ( Pterocarpus marsupium ) in the treatment of newly diagnosed patients with type 2 diabetes mellitus: a flexible dose double-blind multicenter randomized controlled trial Diabetol Croat 34 2005 13 20
  10. 10 V.T.T. Huyen D.V. Phan P. Thang Antidiabetic effect of gynostemma pentaphyllum tea in randomly assigned type 2 diabetic patients Horm Metab Res 42 2010 353 357
  11. 11 C.F. Zhu G.Z. Li H.B. Peng Treatment with marine collagen peptides modulates glucose and lipid metabolism in Chinese patients with type 2 diabetes mellitus Appl Physiol Nutr Metab 35 2010 797 804
  12. 12 S.A. Hussain Silymarin as an adjunct to glibenclamide therapy improves long-term and postprandial glycemic control and body mass index in type 2 diabetes J Med Food 10 2007 543 547
  13. 13 H.F. Huseini B. Larijani R. Heshmat The efficacy of Silybum marianum (L.) Gaertn. (silymarin) in the treatment of type II diabetes: a randomized, double-blind, placebo-controlled, clinical trial Phytother Res 20 2006 1036 1039
  14. 14 H.F. Huseini F. Darvishzadeh R. Heshmat The clinical investigation of Citrullus colocynthis schrad (L.) fruit in treatment of type II diabetic patients: a randomized, double blind, placebo-controlled clinical trial Phytother Res 23 2009 1186 1189
  15. 15 F.R. Lu L. Shen Y. Qin Clinical observation on trigonellafoenum-graecum L. total saponins in combination with sulfonylureas in the treatment of type 2 diabetes mellitus Chin J Integr Med 14 2008 56 60
  16. 16 C. Sangsuwan S. Udompanthurak S. Vannasaeng Randomized controlled trial of Tinospora crispa for additional therapy in patients with type 2 diabetes mellitus J Med Assoc Thai 87 2004 543 546
  17. 17 X. Liu J. Wei F. Tan Antidiabetic effect of Pycnogenol French maritime pine bark extract in patients with diabetes type II Life Sci 75 2004 2505 2513
  18. 18 V. Jayagopal P. Albertazzi E.S. Kilpatrick Beneficial effects of soy phytoestrogen intake in postmenopausal women with type 2 diabetes Diabetes Care 25 2002 1709 1714
  19. 19 C.-H. Hsu Y.-L. Liao S.-C. Lin K.-C. Hwang P. Chou The mushroom Agaricus blazei Murill in combination with metformin and gliclazide improves insulin resistance in type 2 diabetes: a randomized, double-blinded, and placebo-controlled clinical trial J Altern Complement Med 13 2007 97 102
  20. 20 E. Rytter B. Vessby A.R. Asg Supplementation with a combination of antioxidants does not affect glycaemic control, oxidative stress or inflammation in type 2 diabetes subjects Free Radic Res 44 2010 1445 1453
  21. 21 A.K. Fenercioglu T. Saler E. Genc The effects of polyphenol-containing antioxidants on oxidative stress and lipid peroxidation in Type 2 diabetes mellitus without complications J Endocrinol Invest 33 2010 118 124
  22. 22 T. MacKenzie L. Leary W.B. Brooks The effect of an extract of green and black tea on glucose control in adults with type 2 diabetes mellitus: double-blind randomized study Metab Clin Exp 56 2007 1340 1344
  23. 23 B. Mang M. Wolters B. Schmitt Effects of a cinnamon extract on plasma glucose, HbA, and serum lipids in diabetes mellitus type 2 Eur J Clin Invest 36 2006 340 344
  24. 24 S.M. Blevins M.J. Leyva J. Brown Effect of cinnamon on glucose and lipid levels in noninsulin-dependent type 2 diabetes Diabetes Care 30 2007 2236 2237
  25. 25 P. Crawford Effectiveness of cinnamon for lowering hemoglobin A1C in patients with type 2 diabetes: a randomized, controlled trial J Am Board Fam Med 22 2009 507 512
  26. 26 R. Akilen A. Tsiami D. Devendra N. Robinson Glycated haemoglobin and blood pressure-lowering effect of cinnamon in multi-ethnic Type 2 diabetic patients in the UK: a randomized, placebo-controlled, double-blind clinical trial Diabet Med 27 2010 1159 1167
  27. 27 S. Suppapitiporn N. Kanpaksi S. Suppapitiporn The effect of cinnamon cassia powder in type 2 diabetes mellitus J Med Assoc Thail 89 suppl 3 2006 S200 S205
  28. 28 A.M. Dans M.V. Villarruz C.A. Jimeno The effect of Momordica charantia capsule preparation on glycemic control in type 2 diabetes mellitus needs further studies J Clin Epidemiol 60 2007 554 559
  29. 29 D.E. Barre K.A. Mizier-Barre O. Griscti K. Hafez High dose flaxseed oil supplementation may affect fasting blood serum glucose management in human type 2 diabetics J Oleo Science 57 2008 269 273
  30. 30 V. Vuksan M.K. Sung J.L. Sievenpiper Korean red ginseng ( Panax ginseng ) improves glucose and insulin regulation in well-controlled, type 2 diabetes: results of a randomized, double-blind, placebo-controlled study of efficacy and safety Nutr Metab Cardiovasc Dis 18 2008 46 56
  31. 31 J.G. Eriksson T.J. Forsén S.A. Mortensen The effect of coenzyme Q10 administration on metabolic control in patients with type 2 diabetes mellitus Biofactors 9 1999 315 318
  32. 32 H. Chen R.J. Karne G. Hall High-dose oral vitamin C partially replenishes vitamin C levels in patients with type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistance Am J Physiol Heart Circ Physiol 290 2006 H137 H145
  33. 33 P. Patel L. Poretsky E. Liao Lack of effect of subtherapeutic vitamin D treatment on glycemic and lipid parameters in Type 2 diabetes: a pilot prospective randomized trial J Diabetes 2 2010 36 40
  34. 34 R. Jorde Y. Figenschau Supplementation with cholecalciferol does not improve glycaemic control in diabetic subjects with normal serum 25-hydroxyvitamin D levels Eur J Nutr 48 2009 349 354
  35. 35 M.D. Witham F.J. Dove M. Dryburgh The effect of different doses of vitamin D(3) on markers of vascular health in patients with type 2 diabetes: a randomised controlled trial Diabetologia 53 2010 2112 2119
  36. 36 E. Lonn S. Yusuf B. Hoogwerf Effects of vitamin E on cardiovascular and microvascular outcomes in high-risk patients with diabetes: results of the HOPE study and MICRO-HOPE substudy Diabetes Care 25 2002 1919 1927
  37. 37 M. Boshtam M. Rafiei I.D. Golshadi Long term effects of oral vitamin E supplement in type II diabetic patients Int J Vitam Nutr Res 75 2005 341 346
  38. 38 N. Suksomboon N. Poolsup S. Sinprasert Effects of vitamin e supplementation on glycaemic control in type 2 diabetes: systematic review of randomized controlled trials J Clin Pharm Ther 36 2011 53 63
  39. 39 B. Ludvik B. Neuffer G. Pacini Efficacy of Ipomoea batatas (Caiapo) on diabetes control in type 2 diabetic subjects treated with diet Diabetes Care 27 2004 436 440
  40. 40 B. Ludvik M. Hanefeld G. Pacini Improved metabolic control by Ipomoea batatas (Caiapo) is associated with increased adiponectin and decreased fibrinogen levels in type 2 diabetic subjects Diabetes Obesity Metab 10 2008 586 592
  41. 41 M.D. Althuis N.E. Jordan E.A. Ludington Glucose and insulin responses to dietary chromium supplements: a meta-analysis Am J Clin Nutr 76 2002 148 155
  42. 42 J. Martin Z.Q. Wang X.H. Zhang Chromium picolinate supplementation attenuates body weight gain and increases insulin sensitivity in subjects with type 2 diabetes Diabetes Care 29 2006 1826 1832
  43. 43 N. Kleefstra S.T. Houweling F.G. Jansman Chromium treatment has no effect in patients with poorly controlled, insulin-treated type 2 diabetes in an obese Western population: a randomized, double-blind, placebo-controlled trial Diabetes Care 29 2006 521 525
  44. 44 D. Ghosh B. Bhattacharya B. Mukherjee Role of chromium supplementation in Indians with type 2 diabetes mellitus J Nutr Biochem 13 2002 690 697
  45. 45 R.A. Anderson A.M. Roussel N. Zouari Potential antioxidant effects of zinc and chromium supplementation in people with type 2 diabetes mellitus J Am Coll Nutr 20 2001 212 218
  46. 46 R.A. Anderson N. Cheng N.A. Bryden Elevated intakes of supplemental chromium improve glucose and insulin variables in individuals with type 2 diabetes Diabetes 46 1997 1786 1791
  47. 47 N. Kleefstra S.T. Houweling S.J. Bakker Chromium treatment has no effect in patients with type 2 diabetes in a Western population: a randomized, double-blind, placebo-controlled trial Diabetes Care 30 2007 1092 1096
  48. 48 E.M. Balk A. Tatsioni A.H. Lichtenstein Effect of chromium supplementation on glucose metabolism and lipids: a systematic review of randomized controlled trials Diabetes Care 30 2007 2154 2163
  49. 49 C.A. Albarracin B.C. Fuqua J.L. Evans I.D. Goldfine Chromium picolinate and biotin combination improves glucose metabolism in treated, uncontrolled overweight to obese patients with type 2 diabetes Diabetes Metab Res Rev 24 2008 41 51
  50. 50 C. Albarracin B. Fuqua J. Geohas Combination of chromium and biotin improves coronary risk factors in hypercholesterolemic type 2 diabetes mellitus: a placebo-controlled, double-blind randomized clinical trial J Cardiometab Syndr 2 2007 91 97
  51. 51 M.-H. Lai Antioxidant effects and insulin resistance improvement of chromium combined with vitamin C and E supplementation for type 2 diabetes mellitus J Clin Biochem Nutr 43 2008 191 198
  52. 52 J. Racek L. Trefil D. Rajdl Influence of chromium-enriched yeast on blood glucose and insulin variables, blood lipids, and markers of oxidative stress in subjects with type 2 diabetes mellitus Biol Trace Element Res 109 2006 215 230
  53. 53 M. Rodríguez-Morán F. Guerrero-Romero Oral magnesium supplementation improves insulin sensitivity and metabolic control in type 2 diabetic subjects: a randomized double-blind controlled trial Diabetes Care 26 2003 1147 1152
  54. 54 H.W. deValk R. Verkaaik H.J. van Rijn Oral magnesium supplementation in insulin-requiring type 2 diabetic patients Diabet Med 15 1998 503 507
  55. 55 N.L. Eibl H.P. Kopp H.R. Nowak Hypomagnesemia in type II diabetes: effect of a 3-month replacement therapy Diabetes Care 18 1995 188 192
  56. 56 J. Eriksson A. Kohvakka Magnesium and ascorbic acid supplementation in diabetes mellitus Ann Nutr Metab 39 1995 217 223
  57. 57 Y. Song K. He E.B. Levitan Effects of oral magnesium supplementation on glycaemic control in Type 2 diabetes: a meta-analysis of randomized double-blind controlled trials Diabet Med 23 2006 1050 1056
  58. 58 G. Derosa A.F. Cicero A. Gaddi The effect of L-carnitine on plasma lipoprotein(a) levels in hypercholesterolemic patients with type 2 diabetes mellitus Clin Ther 25 2003 1429 1439
  59. 59 A.R. Rahbar R. Shakerhosseini N. Saadat Effect of L-carnitine on plasma glycemic and lipidemic profile in patients with type II diabetes mellitus Eur J Clin Nutr 59 2005 592 596
  60. 60 G. Derosa P. Maffioli I. Ferrari Orlistat and L-carnitine compared to orlistat alone on insulin resistance in obese diabetic patients Endocr J 57 9 2010 777 786
  61. 61 G. Derosa P. Maffioli S.A.T. Salvadeo Sibutramine and L-carnitine compared to sibutramine alone on insulin resistance in diabetic patients Intern Med 49 2010 1717 1725
  62. 62 M.B. Krawinkel G.B. Keding Bitter gourd ( Momordica charantia ): a dietary approach to hyperglycemia Nutr Rev 64 2006 331 337
  63. 63 R.R. Simon V. Marks A.R. Leeds J.W. Anderson A comprehensive review of oral glucosamine use and effects on glucose metabolism in normal and diabetic individuals Diabetes Metab Res Rev 27 2011 14 27
  64. 64 G.Y. Yeh D.M. Eisenberg T.J. Kaptchuk Systematic review of herbs and dietary supplements for glycemic control in diabetes Diabetes Care 26 2003 1277 1294
Reproduced with permission from Canadian Journal of Diabetes © 2013 Canadian Diabetes Association. To cite this article, please refer to For citation.

*The Canadian Diabetes Association is the registered owner of the name Diabetes Canada. All content on, CPG Apps and in our online store remains exactly the same. For questions, contact