Clinical Assistant Professor, Department of Family Medicine, University of Wisconsin; Clinical Assistant Professor of Medicine, Arizona Center for Integrative Medicine, University of Arizona, Tucson
Dr. Kiefer reports no financial relationships relevant to this field of study.
- This was a double-blind, placebo controlled trial that included 80 women with mild-moderate menstrual pain.
- Research subjects were given 1,000 mg of the cinnamon spice (presumed true cinnamon) or 1,000 mg of matching starch capsule three times daily for the first three days of menstruation for two cycles.
- Both groups improved over time, but there was a more pronounced pain-relieving effect in those taking cinnamon.
- Several significant methodological flaws in this paper compromised the believability of the results.
SYNOPSIS: Cinnamon, three grams daily, for the first few days of menstruation may help attenuate menstrual pain in women suffering from dysmenorrhea, although an improved follow-up clinical trial is necessary to corroborate this.
SOURCE: Jahangirifar M, Taebi M, Dolatian M. The effect of cinnamon on primary dysmenorrhea: A randomized, double-blind clinical trial. Complement Ther Clin Pract 2018;33:56-60.
Premenstrual disorders, which encompass a variety of affective and somatic symptoms, are common, with some estimates that 12% of women meet the criteria for premenstrual syndrome (PMS).1 Several classes of medications are available to treat PMS, but some women also turn to integrative therapeutics for symptomatic relief.1 To explore one treatment that falls under the latter category, Jahangirifar et al focused on the effects of cinnamon. Cinnamon, an omnipresent spice, is a common name that refers to several species of plant that yield products with culinary and medicinal use. It is likely that these authors used true, or Ceylon, cinnamon (Cinnamomum verum, Family Lauraceae), considered more “delicate” and “complex” in flavor.2 Another commonly sold cinnamon species, and one that also can be called “cinnamon” legally in the United States, is cassia cinnamon (Cinnamomum aromaticum, synonym Cinnamomum cassia). It is sweeter and stronger in flavor than true cinnamon and often is less expensive.3
Jahangirifar et al focused on documented and cited anti-inflammatory effects of cinnamon as justification for undertaking this PMS study. This study was conducted at Isfahan University of Medical Sciences in Iran, and the researchers recruited 80 female students from the university. Inclusion and exclusion criteria are listed in Table 1, but research participants had to complete a “verbal multidimensional scoring system” (VMS) rating during the recruitment process showing “mild” or “moderate” menstrual pain. No scale was provided to determine these VMS categories.
Eighty women were randomized to receive either capsules of cinnamon (n = 40) or placebo (n = 40). Each cinnamon capsule contained 1,000 mg cinnamon, while the placebo capsules contained 1,000 mg starch (presumably corn starch, but this was not specified). Patients took each capsule three times daily for three days, starting on the first day of the menstrual period. The three-day treatment was administered for two menstrual cycles. Women were asked to rate their menstrual pain using a visual analog scale (VAS) from 0 (no pain) to 10 (severe pain) at baseline and after each of the three-day treatments.
After the allocation to treatment or placebo, no women were lost to follow-up, although 12 in the cinnamon group and 10 in the placebo group stopped the protocol for one of four reasons: “irregular consumption,” taking pain medications, allergic reaction, or “missing drugs.” The researchers only analyzed data from those who completed the protocol (28 in the cinnamon group and 30 in the placebo group).
At baseline, the two groups were similar with respect to age and other demographic features. VAS results are shown in Table 2. There was a statistically significant decrease in VAS scores over time for both groups (P < 0.001), although the cinnamon group decreased more over time (P = 0.02). Also, the VAS score was less in the cinnamon group after both the first cycle (P = 0.001) and the second cycle (P = 0.002). Adverse effects were not discussed.
The choice of diagnosis is compelling, but the justification for studying cinnamon is not. In many cases with herbal medicine research, there are preclinical data or traditional use that steers researchers toward taking the next step in exploration, the randomized, controlled clinical trial. For “cinnamon,” most of the research has been done on cassia cinnamon, a different species than what was used in this study. Furthermore, the cassia data seem most convincing for use in people with diabetes.4,5,6 Their primary reason for studying cinnamon in PMS (more specifically, dysmenorrhea) was that it had not been studied for that before. It appears, then, that the researchers hit the jackpot and demonstrated a positive effect.
There were some “red flags” in the methodology of this study. Those participants who did not follow the treatment protocol apparently were excluded. A more accepted approach to lack of adherence would be to include them in the original randomized group, and then statistically analyze their outcome as intention-to-treat, as if they had completed the protocol. To exclude after randomization may create bias in the research results. Also, there was some sloppy writing or record keeping, or both: It is unclear whether women with menstruation duration of 39-44 days were included or excluded. In addition, women were included in the trial if, as per the VMS, they had mild or moderate dysmenorrhea, but the specifics of that scale were not discussed (although other scholarly articles provide that it ranges from 0-9, 0-3 on three different pain subsets). In addition, they recorded a “baseline” VAS score, but would this have been at the start of painful menstruation or some other time? It is unclear. This lack of attention to detail makes one wonder what else might have been overlooked or mistakenly addressed.
Another important aspect to this paper is the proper identification of the intervention itself. More well-designed clinical trials investigating herbal medicines would have expanded on the herbal identification in the methods section. It was only in the Discussion section that a reference was made to the species name, zeylanicum, the not-so-common synonym of C. verum, one of the common spice species. The story is slightly confusing in that, unless expressly stated, spice cinnamon also could be cassia cinnamon, C. aromaticum, synonym C. cassia. Many clinical trials have been conducted on cassia cinnamon as referenced above. Does it matter? As with any herbal medicine, there are interspecies chemical nuances that can produce physiological effects. Clinicians can accurately base their recommendations only on this chemical specificity and the clinical trials that have been done on a particular species. Ideally, the researchers in this study would have provided information about the source of the cinnamon, as well as shown how the identification was made, either by laboratory techniques such as mass spectrometry, or, if the whole plant was available, corroborating the plant used in the study with a definitive authentication in an herbarium.
Looking past the methodological flaws, are the results clinically significant? Both groups improved over the two cycles studied, which the researchers mention could have been due to the “psychological support” (not detailed) offered during the study. Two cycles probably are not enough to conclude whether this is a trend or outlier; the next study should be longer. The treatment group showed an improvement in menstrual pain beyond the placebo group, a roughly 40% improvement during the course of the study. If these results hold up to more rigorous analyses, this could be welcome relief to women suffering from PMS symptoms. With some of the mechanistic work cited by the researchers demonstrating cinnamon’s anti-inflammatory effects, the physiological benefit is concordant with these results.
All told, the issues with this paper obscure the addition of a new tool to clinicians’ treatments for dysmenorrhea. There is the hint of a plant anti-inflammatory alternative to the pharmaceuticals available for dysmenorrhea, but a new study, with fewer dropouts, an intention-to-treat analysis, and in-depth herbal identification, is necessary.
- Hofmeister S, Bodden S. Premenstrual syndrome and premenstrual dysphoric disorder. Am Fam Physician 2016;94:236-240.
- Chen P, Sun J, Ford P. Differentiation of the four species of cinnamons (C. burmannii, C. verum, C. cassia, and C. loureiroi) using a flow injection mass spectrometric (FIMS) fingerprinting method. J Ag Food Chem 2014;62:2516-2521.
- Aggarwal B, Yost D. Healing Spices. Sterling: NY; 2011.
- Bi X, Lim J, Henry CJ. Spices in the management of diabetes mellitus. Food Chem 2017;217:281-293.
- Medagama AB. The glycaemic outcomes of cinnamon, a review of the experimental evidence and clinical trials. Nutr J 2015;14:108.
- Ríos JL, Francini F, Schinella GR. Natural products for the treatment of type 2 diabetes mellitus. Planta Med 2015;81:975-994.