Clinical Inquiries

Do complementary agents lower HbA1c when used with standard type 2 diabetes therapy?

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No, there is no high-quality evidence that supports using complementary or alternative agents to lower hemoglobin A1c (HbA1c) in patients with noninsulin-dependent type 2 diabetes. Oral chromium in widely varying doses reduces HbA1c a small amount (strength of recommendation [SOR]: C, meta-analysis of low-quality randomized, controlled trials [RCTs] of disease-oriented outcomes, with inconsistent results).

Oral cinnamon 1 to 3 g/d causes a small (<0.1%) drop in HbA1c (SOR: C, meta-analysis of low-quality RCTs of disease-oriented outcomes).

Fenugreek, milk thistle, safflower oil, and sweet potato extract may also reduce HbA1c (SOR: C, small, low-quality RCTs of disease-oriented outcomes).


Almost all complementary and alternative agents reviewed here were tested against placebo, and most were used in combination with standard therapy, usually identified as diet with or without oral hypoglycemic agents (TABLE).1-8

Meta-analyses evaluate effects of chromium and cinnamon

A meta-analysis of 13 RCTs evaluating the effect of oral chromium in patients with type 2 diabetes (age range not given) found a small improvement in HbA1c.1 Limitations of the meta-analysis included a wide range of chromium dosages and preparations. Ten studies showed no benefit, and of the 3 showing improvement, the researchers rated 2 as poor-quality.

A meta-analysis of 5 RCTs assessing the effect of oral cinnamon in patients with type 2 diabetes, 42 to 71 years of age, found that cinnamon produced a clinically irrelevant but statistically significant decrease in mean HbA1c.2 After analyzing the 2 RCTs with the largest effects, the researchers concluded that cinnamon might have a greater effect in patients with poorly controlled diabetes (baseline HbA1c>8.2%).

When they evaluated these RCTs for study homogeneity, they found significant differences among the studies in subject age, gender, ethnicity, body mass index, disease duration, concurrent medications, and baseline HbA1c levels, as well as variations in cinnamon dose, preparation, and therapy duration. Furthermore, only one of the studies reported randomization methods and whether allocation was concealed.


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