Polycystic ovary syndrome (PCOS) is associated with irregular menstrual cycles, chronic anovulation, and hyperandrogenism, as well as metabolic aberrations such as insulin resistance (IR), hyperinsulinemia, and dyslipidemia. PCOS is diagnosed when a woman has two of the following conditions with no other medical explanation: hyperandrogenism, intermittent or absent menstrual cycles, and polycystic ovary indicated by ultrasound. Although its etiology is uncertain, PCOS appears to result from a combination of genetic and environmental factors.
IR is common in women with PCOS, may play a causal role in its development, and can contribute to the development of obesity, type 2 diabetes, and cardiovascular problems. Pharmaceutical treatments for PCOS are limited by contraindications, poor efficacy, and adverse effects. Cinnamon (Cinnamomum verum, Lauraceae) bark is used in traditional Persian medicine to regulate menstrual cycles in patients with PCOS, and it has been shown to lower blood glucose and reduce the homeostatic model assessment of insulin resistance (HOMA-IR) index, a measure of insulin sensitivity, in patients with diabetes.
Two recent double-blind, randomized, controlled clinical trials evaluated the effects of cinnamon supplementation on metabolic factors such as serum insulin, HOMA-IR index, lipid profiles, and levels of adiponectin (a protein hormone that regulates the metabolism of lipids and glucose) in women with PCOS.
Cinnamon Bark Supplementation Results in Improvements in Insulin and Lipid Profiles
Reviewed: Borzoei A, Rafraf M, Asghari-Jafarabadi M. Cinnamon improves metabolic factors without detectable effects on adiponectin in women with polycystic ovary syndrome. Asia Pac J Clin Nutr. 2018;27(3):556-563. doi: 10.6133/apjcn.062017.02.
From October 2015 to February 2016, investigators recruited 84 women with PCOS who visited the gynecology clinic at Moheb Yas Hospital in Tehran, Iran. Included patients were 20 to 38 years old and had a body mass index (BMI) of 25-40 kg/m2. The patients were categorized according to age and BMI and then randomly assigned to one of two groups of 42 participants each. At baseline, the patients’ height and weight were measured, and a three-day average for energy and macronutrient intake was determined (using a patient recall method) for each patient. The groups were similar in anthropometric, dietary, and biochemical characteristics at baseline.
Cinnamon bark was provided by the Iranian Institute of Medicinal Plants in Tehran and was ground and encapsulated by the investigators. Each capsule contained 500 mg cinnamon (Cinnamomum verum syn. C. zeylanicum, Lauraceae) bark powder. Placebo capsules were filled with wheat (Triticum aestivum, Poaceae) flour. Each group took three capsules daily for eight weeks.
Fasting blood samples were collected at baseline and after eight weeks to determine serum insulin, HOMA-IR, total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels.
All patients completed the study, with a 94% compliance rate. No adverse effects were reported.
In the cinnamon group, significant decreases were seen in weight (P < 0.01) and BMI (P = 0.002) after eight weeks compared to baseline, while no significant changes were seen in the control group. In the cinnamon group, intakes of energy (P = 0.02) and total fat (P = 0.04) decreased and intake of protein increased (P = 0.04) after eight weeks, compared with baseline values.
Significant improvements were seen in serum glucose (10.63% decrease; P < 0.01), insulin (12.63% decrease; P = 0.01), and HOMA-IR index (20.25% decrease; P < 0.01) in the cinnamon group after eight weeks, compared with baseline values. Changes in the control group were not significant. Significant improvements from baseline in all lipid variables were seen in the cinnamon group after eight weeks (P < 0.05 for all). No significant changes were seen in the control group.
With adjustments for energy intake, BMI, and other baseline values, significant between-group differences were observed in serum glucose (P = 0.001), insulin (P = 0.007), HOMA-IR index (P = 0.001), TC (P = 0.04), LDL-C (P = 0.04), and HDL-C (P = 0.001) over the length of the study, with greater improvements seen in the cinnamon group. Between-group differences in serum TG levels were not significant. Changes in serum adiponectin levels, which were within normal limits at baseline, were not significant between the groups after eight weeks. “It seems that detected favorable effects on serum glucose and lipid parameters in our study were not mediated via adiponectin,” wrote the authors.
Limitations of this study include its short duration, the use of a fixed dose of cinnamon, and the inclusion of patients whose BMI was 25 kg/m2 or greater. The results may not be applicable to underweight or normal weight patients with PCOS or to consumption of other doses or durations of cinnamon supplementation.
The authors concluded that “short term supplementation of cinnamon had some favorable effects on metabolic risk factors of women with PCOS and may be useful in management of PCOS complications.”
Cinnamon Powder Improves Insulin Resistance
Reviewed: Hajimonfarednejad M, Nimrouzi M, Heydari M, Zarshenas MM, Raee MJ, Jahromi BN. Insulin resistance improvement by cinnamon powder in polycystic ovary syndrome: A randomized double-blind placebo controlled clinical trial. Phytother Res. February 2018;32(2):276-283. doi: 10.1002/ptr.5970.
Conducted at Shiraz University of Medical Sciences in Shiraz, Iran, this study assessed the effects of cinnamon bark powder on insulin resistance in women with PCOS. Fresh cinnamon bark, purchased from a local market, was washed, dried, and ground into a powder, which was used to fill 500-mg capsules. Unfortunately, the authors did not mention the species of cinnamon* used in the study; they note only that the cinnamon sample “was identified by a botanist at the Shiraz School of Pharmacy with a specified voucher sample (no. 996).” Placebo capsules contained 450 mg of starch (heated until it turned brown) and 50 mg of cinnamon powder (used to produce similar taste and odor).
Patients at the University’s Shahid Motahari Outpatient Clinic who were aged 18 to 45 years, met the Rotterdam Criteria for PCOS, and had a BMI of 18 kg/m2 or greater were eligible for the study. Exclusion criteria included diabetes, hypertension, hyperprolactinemia, or thyroid problems, pregnancy or lactation, treatment for infertility, or use of hormones or any drug that affects insulin sensitivity. Enrollment took place between January 2016 and July 2016. Of 80 women screened, 66 were enrolled in the trial. For 12 weeks, 33 of those patients were instructed to take one cinnamon capsule three times daily after meals, for a total daily dose of 1,500 mg. The remaining 33 patients were instructed to take one placebo capsule three times daily. All patients also took a standard treatment of 10 mg daily of medroxyprogesterone for 10 days per month starting on day 15 of each menstrual cycle.
The primary outcome of the study was insulin resistance, as measured by the HOMA-IR index. Secondary outcomes were patients’ anthropometric profiles (weight, BMI, and waist circumference); biochemical parameters including fasting blood sugar (FBS), two-hour postprandial blood glucose, and lipid profile; and androgenic hormone assays to measure total serum testosterone and dehydroepiandrosterone sulfate levels.
Three patients in the cinnamon group and two in the placebo group were not included in the final analyses because they missed follow-up visits. One patient in the cinnamon group discontinued the treatment because of a rash and itching, and one patient in the placebo group withdrew from the study because of travel plans. Four others, one in the cinnamon group and three in the placebo group, were noncompliant (they missed more than three doses) but were included in the intention-to-treat analyses. The final analyses included 29 patients in the cinnamon group and 30 patients in the placebo group.
Compared with the placebo group, the cinnamon group had significantly greater reductions in fasting insulin (P = 0.024), HOMA-IR index (P = 0.014), and LDL-C levels (P = 0.049) after 12 weeks. Fasting insulin and HOMA-IR declined substantially over the course of the study in both groups, though significantly more so in the cinnamon group.
Improvements from baseline were observed in the cinnamon group in body weight, BMI, waist circumference, FBS, two-hour postprandial blood glucose, TC, TG levels, and serum androgenic hormone levels. However, the changes were mostly small, and final figures were not significantly different from those in the placebo group. Testosterone levels significantly decreased in the cinnamon group from 0.82 ± 0.82 ng/mL at baseline to 0.55 ± 0.28 ng/mL at the end of the study (P = 0.001); there was also a smaller significant decrease (P = 0.041) in the placebo group.
The rash and itching reported by one patient in the cinnamon group disappeared after the treatment was discontinued. No other serious adverse effects were reported.
The use of progesterone therapy as standard treatment along with the study intervention in both groups is a limitation of this study, as the authors could not evaluate the effects of cinnamon on the patients’ menstrual cycles. The therapy was used, however, because it was considered unethical to deprive any patient of standard medical treatment. Although the first evaluation of androgen was conducted during the follicular phase of all patients, final blood samples were drawn at the end of the study at 12 weeks, when some patients may have been in different phases of their menstrual cycle. According to the authors, this should be considered when interpreting the results of the androgenic hormone assays.
Other limitations of this study include the lack of an ultrasound of the patients’ ovaries at the end of the study, the small number of patients, the short duration, and the failure to report the species of cinnamon used. The fact that the placebo contained a small dose of cinnamon may have reduced differences between groups, although the differential in dosage was 10-fold. Nevertheless, previous clinical research has suggested a relatively wide variability in daily dosage of cinnamon having an impact on serum glucose levels and other hemodynamic factors.
The authors concluded that “cinnamon supplementation with the daily dose of 1.5 g for 12 weeks in combination with progesterone therapy was well tolerated and significantly improved insulin sensitivity and decreased insulin and LDL level[s] in women with PCOS.”
*A peer reviewer of this article noted that the species appears to be C. aromaticum based on the essential oil data included in the paper, but this has not been confirmed. The study authors did not respond to a request for more information.