The participants took either cinnamon (0.12 to 6 grams) or a placebo daily for 1.5 to 12 months.

Compared to a placebo, cinnamon reduced total cholesterol (large effect size) and reduced fasting blood glucose, blood pressure, triglycerides, and LDL-C (each with a moderate effect size). However, cinnamon had no meaningful effects on weight, BMI, HDL-C, HbA1c, or markers of insulin resistance.

In a subgroup analysis, higher doses (greater than 1.5 grams daily) and shorter durations (2 months or less) showed greater improvements.

Adverse events were rare and mild and included occasional rash, hives, or mild stomach discomfort.

Cinnamon might improve blood sugar and cholesterol in metabolic diseases Original paper