Supplements to Improve Insulin Sensitivity: Sorting Them by the Evidence
No supplement can replace physical activity, sleep and a fibre-rich diet when it comes to improving insulin sensitivity. Some products do have interesting data behind them, while others have much less than people think. In its clinical practice guidelines, Diabetes Canada considers the evidence insufficient to recommend any specific natural health product. Here is an honest look at the most common options, what Health Canada allows them to claim, and the precautions to take, especially if you are already on treatment.
Insulin sensitivity: what are we actually talking about?
Insulin is the hormone that allows glucose to move from the blood into cells, mainly those of the muscles, liver and fat tissue. When these cells respond less well, the pancreas has to produce more insulin to get the same effect: this is called insulin resistance. Good insulin sensitivity is the opposite.
In studies, insulin sensitivity is often measured with an index called HOMA-IR, calculated from fasting blood glucose and insulin. Glycated hemoglobin (HbA1c) reflects average blood glucose over the past two to three months instead. The two don't always move together, and that matters for what follows: a supplement can improve one without changing the other.
Before any supplement: move, eat, sleep
Before talking about supplements, let's recall what does most of the work:
- Move regularly, ideally combining walking, cycling or swimming with strength training. Muscle is the main user of glucose.
- Focus on fibre, legumes, whole grains, vegetables and whole fruit rather than juice.
- Get enough sleep, since chronic lack of sleep disrupts blood sugar regulation.
- Get your situation assessed if you have a family history of diabetes, a large waist size or borderline blood test results. Prediabetes is diagnosed with a blood test, not with a supplement.
For fibre in particular, our article Dietary fibre and its benefits offers practical ways to add more to your day.
Magnesium, especially when intake is low
Magnesium plays a role in insulin action inside cells. A meta-analysis published in 2016 pooled clinical trials on the subject, in people with and without diabetes. It found a significant improvement in the HOMA-IR index, but no change in HbA1c or fasting blood glucose across the studies as a whole. The effects were clearer when supplementation lasted four months or more.
Diabetes Canada describes the results on blood glucose as conflicting, and notes that one trial showed no effect in people with normal magnesium levels. In other words, magnesium makes the most sense for correcting a low intake, which is far from rare: our article Magnesium, a common deficiency in Canada explains why.
Chromium: two meta-analyses, two conclusions
Chromium is probably the mineral most associated with blood sugar. Health Canada's multivitamin and mineral monograph allows it to claim that it "provides support for healthy glucose metabolism" and "helps to maintain normal blood glucose levels."
The studies, however, disagree:
- A 2014 meta-analysis (25 randomized trials in people with diabetes) found an average HbA1c drop of 0.55%, mainly with chromium picolinate and above 200 µg per day.
- A 2015 meta-analysis (14 trials, 875 participants) found no effect on HbA1c, whatever the form of chromium.
Diabetes Canada points to the high heterogeneity of these studies and possible publication bias. On the safety side, a licensed chromium picolinate product reviewed is contraindicated during pregnancy and breastfeeding, and asks users to consult a health care practitioner if they have diabetes or a kidney disorder.
Cinnamon: not all varieties are equal
Here is a nuance few sites mention. Health Canada has published two separate monographs:
- Chinese cinnamon (Cinnamomum aromaticum, also called cassia) can carry the claim "helps to support healthy blood glucose levels," at 3 to 6 g of dried bark per day, with no more than 4 g per dose. It is contraindicated during pregnancy, and you should consult a practitioner if you are breastfeeding or have diabetes.
- Ceylon cinnamon (Cinnamomum verum) does not have this claim in its monograph. It is recognized there as a source of antioxidants and for traditional digestive uses.
Even for cassia, Diabetes Canada reports conflicting results from one trial to the next. Sprinkling cinnamon on your oatmeal is still a tasty habit, but it is not a treatment.
Alpha-lipoic acid, a regulated antioxidant
Alpha-lipoic acid is an antioxidant the body makes naturally. Its Health Canada monograph allows the claim "helps in glucose metabolism" at 600 mg per day of DL-alpha-lipoic acid, or 300 mg per day of the R form.
The monograph requires two warnings that say a lot about how it works:
- Consult a health care practitioner before use if you have diabetes, or if you are pregnant or breastfeeding.
- Stop use and consult a practitioner if you experience sweating, paleness, chills, headache, dizziness or confusion, which may be symptoms of low blood sugar.
Psyllium, a fibre that works at the table
Psyllium is a soluble fibre that forms a gel in the gut. A 2015 meta-analysis of 35 randomized trials showed improved fasting blood glucose and HbA1c in people being treated for type 2 diabetes, when psyllium was taken before meals. The effect was modest in prediabetes and absent in people with normal blood glucose: the higher the starting blood glucose, the greater the benefit.
In Canada, the psyllium monograph only covers its use as a bulk-forming laxative, with no blood glucose claim. It asks users to drink enough fluids and to take it a few hours before or after other medications and natural health products, since it can interfere with their absorption. It also contraindicates its use in diabetes where blood sugar is difficult to regulate.
Vitamin D: a role in prevention, not control
Diabetes Canada's guidelines state that trials have not shown improved blood glucose in people who already have diabetes. The picture is somewhat different for prevention: a review published in 2020 reports that, in three large trials in people with prediabetes, vitamin D reduced the risk of developing diabetes by 10% to 13% compared with placebo.
If you have been diagnosed with prediabetes, vitamin D is therefore worth discussing with your doctor, ideally backed by a blood test.
What about berberine?
Berberine is probably the most studied supplement for blood sugar in recent years, and Diabetes Canada lists it among products that lowered HbA1c by at least 0.5% in trials lasting at least three months. However, it interacts with many medications and is contraindicated during pregnancy. Its case deserves a full analysis with a health professional, rather than an improvised trial.
Comparison table of the options
| Supplement | What Health Canada allows it to claim | What the studies say | Key precaution |
|---|---|---|---|
| Magnesium | Prevention of magnesium deficiency, among others, with no blood glucose claim | Improved HOMA-IR, little effect on HbA1c | Most useful when intake is low |
| Chromium | Healthy glucose metabolism, normal blood glucose levels | Conflicting meta-analyses | Picolinate contraindicated during pregnancy and breastfeeding |
| Chinese cinnamon | Healthy blood glucose levels (3 to 6 g per day) | Conflicting results | Contraindicated during pregnancy |
| Alpha-lipoic acid | Helps in glucose metabolism | Claim based on older trials | Consult if you have diabetes |
| Psyllium | Bulk-forming laxative use only | Benefit proportional to starting blood glucose | Contraindicated if diabetes is difficult to regulate, space from medications |
| Vitamin D | No blood glucose claim | No effect in diabetes, modest preventive effect in prediabetes | Blood test recommended |
The risk of hypoglycemia when you're already on treatment
This is the most important point in this article. If you take a diabetes medication, adding a product that lowers blood sugar can add to its effects and cause hypoglycemia. That is precisely why the alpha-lipoic acid and Chinese cinnamon monographs ask people with diabetes to consult a practitioner.
Diabetes Canada also recommends that health professionals routinely ask their patients which natural health products they take, and favour products with an NPN, since some unlicensed products have been found contaminated with medications. So bring the full list of your supplements to your doctor or pharmacist, and never change a prescribed treatment on your own.
Frequently asked questions about insulin and supplements
What is the best supplement for insulin resistance?
There is no clear winner. Magnesium has the most consistent data on the insulin resistance index, especially when intake is low, and psyllium helps more when blood glucose is already high. The right choice depends on your diet, your blood test results and your medications.
Can these supplements be combined?
Several formulas do. If you have diabetes or take a medication that lowers blood sugar, each addition increases the risk of hypoglycemia: have the combination reviewed by a professional before starting, and introduce one product at a time.
How long before judging a blood sugar supplement?
In the magnesium meta-analysis, the effects were clearer after four months or more. Since HbA1c reflects blood glucose over the past two to three months, you need to wait at least that long to assess a change with a blood test.
Can supplements prevent type 2 diabetes?
No supplement has been shown to replace lifestyle changes. Vitamin D has shown a modest reduction in risk in people with prediabetes, but physical activity, diet and medical follow-up remain the foundation.
Where to start, in practice
To improve insulin sensitivity, lifestyle habits do most of the work. Among supplements, magnesium and psyllium have the strongest arguments in the right situations, chromium and Chinese cinnamon have conflicting results, and alpha-lipoic acid is covered by a Health Canada claim with clear warnings. In all cases, choose a product with an NPN, introduce it on its own, and talk to your doctor if you are being treated for diabetes.
You'll find magnesium, chromium and several other minerals in our vitamins, minerals and amino acids section. And to build an approach suited to your blood test results and habits, our certified naturopaths welcome you at our four Gatineau locations: discover our naturopathy service.
References
- Complementary and Alternative Medicine for Diabetes (Chapter 22). Diabetes Canada. 2018. https://www.diabetes.ca/for-professionals/full-guidelines/chapter-22
- Insulin Resistance and Prediabetes. National Institute of Diabetes and Digestive and Kidney Diseases (NIH). https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance
- Dietary fibre and its benefits. La Boîte à Grains. https://laboiteigrains.com/en/blogs/regimes/les-fibres-alimentaires-et-leur-bienfaits
- A systematic review and meta-analysis of randomized controlled trials on the effects of magnesium supplementation on insulin sensitivity and glucose control. Simental-Mendía LE et al. Pharmacological Research. 2016. https://pubmed.ncbi.nlm.nih.gov/27329332/
- Magnesium, a common deficiency in Canada. La Boîte à Grains. https://laboiteigrains.com/en/blogs/supplements-naturels/le-magnesium-une-carence-courante-au-canada
- Natural health product monographs: Multi-Vitamin/Mineral Supplements, Cassia, Cinnamon (Cinnamomum verum), Alpha-Lipoic Acid and Psyllium. Health Canada. https://webprod.hc-sc.gc.ca/nhpid-bdipsn/
- Systematic review and meta-analysis of the efficacy and safety of chromium supplementation in diabetes. Suksomboon N et al. Journal of Clinical Pharmacy and Therapeutics. 2014. https://pubmed.ncbi.nlm.nih.gov/24635480/
- Effect of chromium supplementation on glycated hemoglobin and fasting plasma glucose in patients with diabetes mellitus. Yin RV, Phung OJ. Nutrition Journal. 2015. https://link.springer.com/doi/10.1186/1475-2891-14-14
- Product information, NPN 80020089 (chromium picolinate). Licensed Natural Health Products Database, Health Canada. https://health-products.canada.ca/lnhpd-bdpsnh/info?licence=80020089
- Psyllium fiber improves glycemic control proportional to loss of glycemic control: a meta-analysis. Gibb RD et al. American Journal of Clinical Nutrition. 2015. https://pubmed.ncbi.nlm.nih.gov/26561625/
- Vitamin D Supplementation for Prevention of Type 2 Diabetes Mellitus: To D or Not to D? Pittas AG et al. Journal of Clinical Endocrinology and Metabolism. 2020. https://pubmed.ncbi.nlm.nih.gov/32844212/
- In the News: Berberine. National Center for Complementary and Integrative Health (NIH). 2023. https://www.nccih.nih.gov/health/in-the-news-berberine