Spotlight on Dietary Supplements

Cinnamon, chromium, and alpha-lipoic acid are dietary supplements that have been studied for diabetes management, but are not commonly found in daily multivitamins. Chromium* and cinnamon have the least supportive evidence of efficacy, while some studies have found alpha-lipoic acid to be promising, at least subjectively, in reducing the discomforts of peripheral neuropathy.

Alpha lipoic acid, or ALA (not to be confused with alpha-linolenic acid, which has the same abbreviation), is a water- and fat-soluble antioxidant produced by the body to assist in energy metabolism. Foods rich in ALA include spinach, broccoli, and brewer’s yeast. ALA may increase insulin sensitivity and enhance glucose uptake in the muscle cells of people with type 2 diabetes.

The antioxidant chemical structure of alpha-lipoic acid may protect nerves from oxidative damage caused by hyperglycemia in people with diabetes. Improved blood flow around peripheral nerves and regeneration have been found in animal studies of ALA. Several small randomized controlled clinical trials have indicated that ALA noticeably reduces pain, numbness, and tingling compared to a placebo in patients with diabetic neuropathy. These studies used doses ranging from 500 to 1800 mg per day–600 mg was found to be optimal. Side effects of nausea, vomiting, and dizziness occurred at doses of 1200 mg per day and above.

The use of ALA as a supplement is not recommended for treatment or prevention of neuropathy, but may be considered by patients who are symptomatic despite use of approved medications. Patients with thiamine (vitamin B1) deficiency or a thyroid disorder, or who are undergoing chemotherapy, should avoid taking ALA.

Chromium is a trace mineral that the body normally uses to aid glucose metabolism. It is found in most foods in small quantities, around two micrograms per serving. Adequate dietary intake is 50 to 200 mcg per day. Clinical trials involving diabetic patients have shown conflicting or minimal reduction of A1C, a long-term indicator of glycemic control in diabetes, although chromium may reduce fasting blood glucose. Several of the studies concluded that the variation in responses to this mineral makes it unsuitable for patients with poor glycemic control, but possibly useful in patients with chromium deficiency.

The supplemental dose of chromium is 200 to 600 micrograms per day. Upset stomach may occur. Chromium supplementation may also increase side effects from the following drug classes and should be avoided in combination with them: beta-blockers, corticosteroids, nonsteroidal anti-inflammatories, insulin, and niacin.

Drugs that reduce stomach acid, such as antacids or proton-pump inhibitors, can decrease absorption of chromium. Chromium may cause problems for those with iron deficiency because it competes with iron for absorption and transport within the body. The picolinic acid found in chromium picolinate may adversely affect neurotransmitter metabolism in central nervous system disorders, including Parkinson disease and disorders treated with antidepressants.

Cinnamon is promoted as an herb that can lower blood sugar, possibly by mimicking the effect of insulin. A review of several clinical trials found that cinnamon lowered fasting blood sugar by a small amount, less than nine mg/dL, in patients with type 2 or prediabetes. The optimal adult dose is not yet known, but a half-teaspoon or one 500 mg standardized dose is thought to be safe. Larger doses may be unsafe because Cassia cinnamon contains coumarin, which is toxic to the liver. Cinnamon may alter the efficacy of drugs processed by the liver and may increased bleeding risk in patients using blood thinners.

Consult your physician before beginning any new dietary supplements. Because hypoglycemia may occur when using any of these supplements, monitor blood sugar carefully, especially if taking prescribed blood sugar-lowering drugs.

*This mineral is often added to multivitamins, particularly “weight-loss” formulations such as “Centrum Specialist Energy.” Check labels to avoid overdose.


1. Centrum, Our Products. Introducing Centrum Specialist Energy. Pfizer Consumer Healthcare, 2012. Available at:
2. Natural Standard, Bottom Line Monograph. Alpha-lipoic acid (1,2-dithiolane-3-pentanoic acid).
3.Lexi-Comp, Natural Products Database. Alpha-Lipoic Acid. 2012.
4. Natural Standard, Bottom Line Monograph. Alpha-lipoic acid (1,2-dithiolane-3-pentanoic acid)
5. Ziegler D, Ametov A, Barinov A, Dyck PJ, Gurieva I, Low PA, Munzel U, Yakhno N, Raz I, Novosadova M, Maus J, Samigullin R. Oral treatment with alpha-lipoic acid improves symptomatic diabetic polyneuropathy: the SYDNEY 2 trial. Diabetes Care. 2006 Nov;29(11):2365-70.
6. Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Chromium. 8 Aug 2005. Available at:
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10. Natural Standard, Professional Monograph. Cinnamon (Cinnamomum spp.). 2012.


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