Assessment of Intake of Cinnamon Supplements on Hemoglobin A1c Levels in Prediabetics

Abstract

Introduction:

One in three adults in the United States 20 years of age or older has prediabetes mellitus (pre-DM), and many pre-DM patients will develop type 2 diabetes mellitus within 5 years. Cinnamon is used to lower blood sugar levels; however, results on its effectiveness are mixed. Diabetic blood glucose control is mainly monitored by either fasting blood glucose or hemoglobin A1c (HbA1c). The HbA1c test reflects the average blood glucose levels over the past 2–3 months. In this study, we investigated whether cinnamon supplements would influence HbA1c levels in prediabetic subjects.

Methods:

Fifty-two prediabetic subjects 18–70 years old qualified for this study. The treatment (TX) group (n = 30) received two 500 mg capsules of cinnamon daily, while the CON group (n = 22) did not receive any cinnamon supplement. Thirty-three subjects completed this study in 10 weeks (TX, n = 20; CON, n = 13). At the beginning and end of the study, HbA1c levels, body mass index (BMI), and percent body fat (PBF) of the subjects were also determined.

Results:

The Mann-Whitney U test for use with two independent groups indicated no statistically significant difference between the TX and CON groups based on HbA1c levels U = 123.50, p = 0.810; BMI U = 112, p = 0.507; and PBF U = 119, p = 0.685.

Conclusion:

The results of this pilot study showed that there were no statistically significant differences between the TX group taking the cinnamon supplements versus the CON group not taking cinnamon supplements in regard to HbA1c levels, BMI, or PBF. Future studies with longer study duration for HbA1c testing are warranted to determine the effects of cinnamon on lowering HbA1c in prediabetics.

Introduction

According to the Center for Disease Control and Prevention (CDC), more than 30 million Americans have diabetes mellitus (DM), while more than 84 million Americans are prediabetic (pre-DM).¹ One in three adults in the United States 20 years of age or older has pre-DM, and many pre-DM patients will develop type 2 diabetes mellitus (T2DM) within 5 years.¹ In the national diabetes statistics report of 2020, which reflected an estimate for 2018, 7.3 millions of adults 18 years of age or older did not report having diabetes or were not aware of having diabetes.²

Chronic complications of uncontrolled blood glucose in DM patients can lead to an increased risk for damage to the heart, kidneys, blood vessels, and peripheral nerves. Those affected by T2DM can suffer from myocardial infarctions, stroke, kidney disease, and neuropathy (often leading to amputations).³ To minimize complications associated with T2DM, the primary focus is on control of blood glucose levels.

Consistent maintenance of blood glucose concentration within levels at or near the non-DM range and the avoidance of significant blood glucose fluctuations are imperative for maintaining the health of DM patients. Diabetic blood glucose control is mainly monitored by either fasting blood glucose or hemoglobin A1c (HbA1c).⁴ The HbA1c test reflects the average blood glucose levels over the past 2–3 months. It measures the percentage of hemoglobin proteins in the blood that are coated with sugar.^5,6 The higher the HbA1c measurement, the higher the risk for diabetic complications due to poor glycemic control.⁷

An advantage of HbA1c versus fasting blood glucose is that HbA1c is not subject to fluctuations based on diet before the testing. HbA1c measurements are crucial for monitoring the health of DM patients and serve as a principal consideration when tailoring medication and treatment (TX) plans. Risk factors to develop T2DM include being obese or overweight, African American, Hispanic/Latino, Alaska Native, American Indian, Native Hawaiian, or Pacific Islander, ≥45 years old, or sedentary lifestyle.

Additional predisposing risk factors for T2DM include a family history of DM, having hypertension, low high-density lipoprotein levels, hypertriglyceridemia, history of heart disease or stroke, depression, or polycystic ovary syndrome.⁸

In pre-DM patients, blood glucose levels are higher than normal, but not as high as in DM patients. In pre-DM patients, HbA1c levels are between 5.7% and 6.4%, while in individuals who are not pre-DM, HbA1c levels are lower than 5.7%. The higher the individual's body mass index (BMI) and percent body fat (PBF), the higher their risk of prediabetes and T2DM.⁹

The development of pre-DM or subsequent T2DM is linked to one's body weight and body fat.⁹ Body fatness, as assessed indirectly through measuring BMI or directly through bioelectrical impedance for the percent of fat weight, is linked to insulin resistance. Body fatness makes one more susceptible to an increased risk of pre-DM and T2DM.⁹ One of the nutritional supplements on the market that seems to enhance insulin sensitivity is cinnamon.¹⁰ Previously published research suggests the possible use of cinnamon to lower blood glucose levels by reducing insulin resistance in DM individuals.^10,11

Because cinnamon seems to enhance insulin senstivity, it may help reduce blood sugar levels. The purpose of this study was to determine if cinnamon capsules taken as a dietary supplement would reduce HbA1c levels in pre-DM individuals.

Methods

Subjects

Individuals were excluded from the study if pregnant or nursing, diabetic, or they had neurological disease, chronic fatigue, fibromyalgia, chronic medical conditions, bleeding disorders, impaired hepatic function, frequent headaches, and implanted device such as pacemaker, or a psychiatric diagnosis. In addition, subjects who were prone to gastrointestinal disturbances or allergic to cinnamon were excluded from the study. Subjects on antihypertensive medications, blood thinners, or hepatotoxic drugs, or those who consumed high amounts of alcohol were excluded from the study as well.

One hundred and thirty-seven subjects, 18–70 years of age, were recruited and screened randomly for pre-DM. Out of the 137 subjects, 52 individuals were determined to be pre-DM. For this pilot study, the control (CON) group did not receive any cinnamon supplement. Thirty individuals were placed in the TX group and received cinnamon supplements, while 22 subjects were placed in the CON group and did not receive any cinnamon supplement. Out of 52 pre-DM subjects, 33 individuals completed the study (TX, n = 20; CON, n = 13) while 19 individuals did not complete the study. Among 33 individuals who completed the study, there were 10 males and 23 females.

The ethnicities of participants who completed the study were 36% African American, 33% Hispanic, 21% Caucasian, and 6% Asian, and 1 subject was mixed Caucasian/African American. All subjects were informed of the risks and benefits associated with the investigation. Subjects gave written consent to participate in the study. Approval of the University's Institutional Review Board (IRB), the Institutional Biosafety Committee (IBC), and the U.S. Food and Drug Administration (FDA) were secured before the start of the study.

Experimental design

This study utilized a pretest/post-test design. Pre-DM subjects who completed the study were the TX group, received cinnamon capsules (n = 30), or the CON group, received no cinnamon capsules (n = 13), for a 10-week duration. During the preliminary screening, subjects completed a general health history questionnaire, and had their HbA1c levels assessed by finger stick measurement, and anthropometric measurements were obtained.

The supplement used for this study was Nature's Bounty^® 1000 mg pure cinnamon (cinnamon burmannii). According to the manufacturer's label, the supplement contained non-genetically modified organism, no artificial color, no artificial flavor, no artificial sweetener, no preservatives, no sugar, no starch, no milk, no lactose, no soy, no gluten, no wheat, no yeast, and no fish, and was sodium free.

Other ingredients in the cinnamon supplement contained gelatin, and < 2% of Silica, and Vegetable Magnesium Stearate. Participants in the TX group ingested two 500 mg capsules of cinnamon daily for 10 weeks.

The CON group did not take the cinnamon supplements or any other supplement during the study. Anthropometric measurements were taken in lightweight clothing and bare feet. Height was measured using a tape measure, while subjects placed their heels, buttocks, and head against a wall. Weight, PBF, and BMI were assessed using a bioelectrical impedance scale (Tanita Analyzer TBF-300A; Arlington Heights, IL, USA). After anthropometric measurements, each subject's blood was drawn using a capillary fingerstick method for determination of HbA1c levels.

Measurement of levels (DCA 2000 Instrument; Elkhart, IN, USA) determined whether the volunteers were pre-DM. Pre-DM subjects with HbA1c levels between 5.7% and 6.4% were assigned to the TX or CON groups. HbA1c, BMI, and PBF levels were measured at the beginning and end of 10 weeks. The normal reference level for HbA1c is <5.7%, where 5.7–6.4% is considered pre-DM. The normal reference range for PBF is 8–24% and 21–35% for men and women, respectively. BMI normal reference range is 18–24.9 kg/m², with 25–29.9 kg/m² signifying overweight and >30 kg/m² obese.¹²

Statistical analysis

The software program used for the statistical analysis with this study was SPSS v. 26.0. A nonparametric Mann–Whitney U test used with two independent groups was conducted for the study's model. Descriptive statistics was performed to demonstrate the mean and standard deviation as described in the following Results section.

Results

This study explored whether there were statistically significant differences between the TX and CON groups based on A1c levels. Descriptive measures were summarized at baseline (day 1) and again at the end of the study (day 70). Subject characteristics for HbA1c, BMI, and PBF are shown in Table 1. The day 1 result of the mean HbA1c for the TX group was 5.88% (standard deviation [SD] = 0.21), while the CON was 5.83% (SD = 0.14).

Table 1.

Subject Characteristics on Days 1 and 70

	Day 1, TX (n = 20)	Day 70, TX (n = 20)	Day 1, CON (n = 13)	Day 70, CON (n = 13)	p
HbA1c (%)	5.88 ± 0.21	5.74 ± 0.39	5.83 ± 0.14	5.68 ± 0.27	0.810
BMI (kg/m²)	31.55 ± 8.13	31.03 ± 7.98	32.49 ± 7.40	32.55 ± 7.45	0.507
PBF (%)	34.1 ± 11.03	35.28 ± 10.86	38.3 ± 10.06	36.7 ± 8.47	0.685

Values are mean ± SD of characteristics of subjects receiving cinnamon (TX) or not receiving cinnamon (CON) at the beginning (day 1) and end of the study (day 70).

BMI, body mass index; CON, control; HbA1c, hemoglobin A1c; PBF, percent body fat; SD, standard deviation; TX, treatment.

The day 70 result of the mean HbA1c for the TX group was 5.74% (SD = 0.39) and for the CON group was 5.68% (SD = 0.27) (Table 1). The day 1 result of the mean BMI for the TX group was 31.15 (SD = 8.13), while for the CON was 32.49 (SD = 7.40). The day 70 result of the mean BMI for the TX group was 31.03 (SD = 7.98) and for the CON group was 32.55 (SD = 7.45) (Table 1). The day 1 result of the mean PBF for the TX group was 34.1 (SD = 11.03), while the CON was 38.3 (SD = 10.06). The day 70 result of the mean PBF for the TX group was 35.28 (SD = 10.86) and for the CON group was 36.70 (SD = 8.47) (Table 1).

The Mann–Whitney U test for use with two independent groups indicated no statistically significant difference between the TX and CON groups based on HbA1c levels U = 123.50, p = 0.810; BMI U = 112, p = 0.507; and PBF U = 119, p = 0.685.

Discussion

This pilot study examined the effects of cinnamon supplements on HbA1c levels in pre-DM subjects. The results of this study showed that there were no statistically significant differences between the TX group taking the cinnamon supplements versus the CON group not taking cinnamon supplements. There were also no statistically significant difference between TX and CON groups for BMI and PBF. It was not surprising that all the pre-DM subjects recruited for this study were either overweight or obese based on BMI and had PBF in excess of standard norms (Table 1). Elevations in both indirect (BMI) and direct measurements (PBF) of body fatness are consistent with insulin resistance seen with pre-DM and T2DM patients.⁹

To our knowledge, this was the first study to investigate the effects of cinnamon supplements on HbA1C in pre-DM individuals. The results of this study agree with our previous study performed in our laboratory on the effect of cinnamon on HbA1c levels, although the focus of the previous study was on nondiabetic adults (data not shown). The true efficacy of cinnamon supplementation as an adjunct therapy for lowering blood sugar levels remains questionable. At the 1000 mg dose, no deleterious side effect of cinnamon supplement was noted. While the current literature points to several studies showing cinnamon reduced fasting blood sugar in T2DM, the effect of cinnamon in reducing HbA1C levels remains mixed.^13,14 Kahn et al. found that cinnamon intake of 1, 3, or 6 g/day reduced fasting blood glucose levels in people with T2DM.¹³

However, the effectiveness of cinnamon does appear to be enhanced if the fasting or HbA1c levels are high at the beginning of TX.^15–17 Crawford showed that supplementation of 1 g of daily cinnamon lowered HbA1c levels by 0.83% in patients with T2DM. However, the HbA1c reduction in the Crawford study was likely attenuated by the lack of purity in the cinnamon capsules used.¹⁵ In contrast, other studies have shown that intake of cinnamon supplements had no significant change on fasting blood plasma glucose levels.^18,19 While Mang et al. showed that the intake of aqueous cinnamon extract, which corresponded to three grams of cinnamon powder, resulted in a moderate effect in reducing fasting plasma glucose levels, their study observed no significant intragroup or intergroup difference for HbA1c levels.¹⁴

A meta-analysis and updated systemic review conducted by Allen et al. showed that, while cinnamon consumption statistically and significantly correlated in reducing levels of fasting plasma glucose, total cholesterol, and triglyceride, no significant effect on HbA1c was demonstrated. Furthermore, the authors discussed that the time since diagnosis, cinnamon dose and duration of use, cinnamon formulations used, and scientific name of cinnamon species used are factors that should be considered for the evaluation of cinnamon effects.²⁰ The meta-analysis identified that the variation in cinnamon purity and in manufacturing processes could affect the quantity of active ingredients since a herbal supplement does not undergo the same manufacturing oversight as pharmacological products. The sample size and study population are some limitations for the studies as well.²⁰

Furthermore, conflicting outcomes of previous publications could be due to the differences in prescribed antidiabetic medications concurrently taken by the study participants, while participating in cinnamon supplement studies.

The exact mechanism of action of cinnamon on blood glucose levels needs to be determined. The reported effects of cinnamon have been mostly focused on fasting blood sugar levels with only few studies focusing on HbA1c measurements in DM individuals. This study explored the effect of cinnamon supplements on reducing blood sugar levels using HbA1c as the biomarker in pre-DM individuals. It makes it difficult at the current time to determine the long-term effect that cinnamon can have as a supplement and as an adjunct therapy for hyperglycemic control.

Although many clinical studies regarding the use of cinnamon supplements have focused on the possible effect in DM individuals, based on the results of this study, it would be premature to recommend cinnamon supplements as an adjunct therapy for reducing HbA1c levels in pre-DM individuals. Future studies with longer study duration for HbA1c testing, including fasting blood sugar testing, are needed to further elucidate the effect of cinnamon supplements in pre-DM individuals.

Limitations of the study

This was a small pilot study, which was performed over 70-day period. Also, there was no placebo used for the CON group.

Conclusion

The results of this study showed that there were no statistically significant differences between the TX group taking the cinnamon supplements versus the CON group not taking cinnamon supplements in regard to HbA1c levels, BMI, or PBF.

Footnotes

Authors' Contributions

The author's responsibilities were as follows: M.S. was the principle investigator and was responsible for the conceptualization of the study, study design, data collection, and writing the initial draft of the article. J.L. was responsible for research design, data analysis, and article analysis. D.W. was responsible for statistical analysis, data, and article analysis. H.M. and E.K. were responsible for data collection. Authors of this article have reviewed the final version, and approve it for publication and take responsibility for its content.

Acknowledgment

The authors would like to thank Ms. Lyndsey McMahon for her assistance and work in the study.

Disclaimer

To safeguard the participants and research team, the IRB (Protocol No. HS16-0265, approval date: September 8, 2016) and IBC (No. S16-0005, approval date: May 20, 2016) were approved. FDA approval was sought based on the recommendation from IRB (electronic approval from FDA; approval date: August 11, 2016).

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This study was supported by the funds from College of Health and Human Sciences of Northern Illinois University to Dr. Masih Shokrani.

Abbreviations Used

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