Background: The incidence and severity of primary dysmenorrhea are influenced by various factors. The aim of the present study was to review nutritional factors influencing primary dysmenorrhea. Methods: Academic databases including Web of Science, EMBASE, Scopus, and PubMed (including Medline) were searched using keywords of nutrition, diet, and primary dysmenorrhea. In this study, observational studies that were published in English from 1990 to April 2018, which focused on nutritional factors affecting primary dysmenorrhea, were selected. The evaluation of studies was performed using a modified STROBE checklist with 10 items. Results: Out of 5,814 retrieved studies, 38 articles met inclusion criteria and were included for final data synthesis. The increased consumption of fruits and vegetables as the sources of vitamins and minerals, as well as fish and milk and dairy products have positive associations with less menstrual pain. Inconsistent results were reported on the consumption of other nutritional groups. Studies showed negative associations of meal skipping and following diet to lose weight with severity of dysmenorrhea. Conclusion: A few studies showed inconclusive findings due to methodological heterogeneities for assessing nutritional habits and different methods of measuring dysmenorrhea pain. Therefore, further analysis and future interventional studies with stronger methodologies are required.
Dysmenorrhea is the most common health-related problem (60%) in women in the reproductive age [1, 2]. It can reduce the quality of life and hinders social activities in young women, especially when it is accompanied by symptoms such as headache, fatigue, nausea and vomiting, diarrhea, boredom, chills and muscle cramps [3‒5]. Primary dysmenorrhea is responsible for disability and inefficiency in terms of absence from the school or workplace. It has been reported that about 1% of women in the reproductive age lose their active work hours for 1–3 days per month. Also, about 14% of girls are absent from the school due to painful uterus contractions [6, 7]. The feelings of shame and mood changes due to dysmenorrhea influence women’s social relationships . Also, the consequences and economic losses of medications may happen . Therefore, dysmenorrhea is considered important in terms of its economic and social effect on women.
The increased production or unbalanced levels of prostaglandins creates pain due to increased uterine contractility, decreased uterine blood flow, and increased sensitivity of peripheral nerves [2, 7]. Age, family history, body mass index, socioeconomic status, education, smoking, and alcohol use can influence the severity of primary dysmenorrhea [1, 7‒17]. Non-steroidal anti-inflammatory drugs and oral contraceptive pills have been listed as common treatments for women with dysmenorrhea . The goal of treatment is to provide adequate pain relief and reduction of symptoms with least adverse effects. Marjoribanks et al.  in a systematic review reported that non-steroidal anti-inflammatory drugs were more effective than placebos, but some adverse effects including mild neurological (e.g., headache, drowsiness, dizziness) and gastrointestinal symptoms (e.g., nausea, indigestion) were increased. In another systematic review study, Proctor et al.  reported that COX-2 specific inhibitors effectively reduced dysmenorrhea, but they are not used in many countries due to cardiovascular effects.
Potential side effects of some drugs make some women with dysmenorrhea to seek alternative medicine such as herbal drugs, diet, fish oil supplements, vitamin E, and low-fat diets and vegetables to control their symptoms [21‒23]. Two Cochran systematic reviews investigated the efficacy of dietary supplements including vitamin and herbal drugs on dysmenorrheal pain relief. They found that primary studies had low quality evidence to support the effectiveness of any dietary supplement for dysmenorrhea, and there was a lack of evidence of their safety [24, 25].
Besides the above-mentioned relative risk factors of dysmenorrhea, the potential role of women’s daily diet in association with the severity of dysmenorrhea has been reported. Abdul-Razzak et al.  reported the positive effect of calcium on controlling primary dysmenorrhea. Di Cintio et al.  showed a poor positive relationship between egg and cheese consumption and dysmenorrhea. Balbi et al.  believed that an excessive consumption of fish, eggs, and fruits had a negative relationship with the reduction of dysmenorrhea. A study at Dumlupinar University reported that coffee consumption and family history of dysmenorrhea were some significant risk factors of dysmenorrhea . In the study by Ozerdogan et al. , the prevalence of dysmenorrhea was higher in students who consumed tea, Coca cola, or Pepsi. The severity of dysmenorrhea was higher in women with excessive sugar intake.
Given the probable relationship between the nutritional status (excluding supplements) and primary dysmenorrhea, as well as significance of knowledge of nutrition-related methods for the management of dysmenorrhea, this systematic review investigated the relationship between dietary habits and nutritional status with the intensity of primary dysmenorrhea.
In accordance with the PRISMA guideline for designing and implementing systematic review studies , the following steps were taken to perform this study: systematic literature search, organization of documents for review, abstracting and quality assessment of documents, synthesizing data, and writing the final report.
A systematic literature search was performed in databases including Web of Science, Embase, Scopus, and PubMed (including Medline). The Boolean search method was used using keywords that were connected together via AND, OR, and NOT: ([Risk factor OR Associate factor OR contributing factor] OR [Food OR nutrient OR Diet OR Nutrition Status OR Nutrition Assessments OR Nutrition OR Nutrition Indexes OR Nutritional Indices OR Prognostic Nutritional Index OR Mini Nutritional Assessment]) AND (Dysmenorrhea OR Menstruating Disturbances OR Menstrual Disorders OR Menstrual Disorder OR Pelvic Pain OR Painful Menstruation OR Painful Period OR Period Pain OR Primary Dysmenorrhea OR Menstrual Pain OR Menstrual Cramps). Also, the reference list of included studies and previous systematic reviews were searched to increase the search coverage.
Type of Studies
Observational studies including cross-sectional, case-control, and cohort studies published in English language from 1990 to April 2018 were included. The studies published before 1990 and in languages other than English were excluded. Moreover, case reports, letters to the editor, and review articles were excluded. Trial studies on dietary supplements and herbal drugs were excluded because of the presence of a recent published systematic review on this topic .
They were from all age ranges which were suffering from primary dysmenorrhea in their menstrual cycles. Those subjects with secondary dysmenorrhea who used contraceptive methods such as intrauterine contraceptive device or oral contraceptive pills were excluded. If the type of dysmenorrhea was not specified (due to a higher prevalence of primary dysmenorrhea in comparison to secondary dysmenorrhea), data was included.
Observational studies on nutritional habits, daily food consumption, or nutrients in the daily diet were included. Trial studies on dietary supplements and herbal drugs were excluded.
Intensity of dysmenorrheal pain was assessed using a visual analogue scale. Also, other valid scales or dichotomous measurements were other main outcomes measured in this systematic review.
The title and abstract of all articles retrieved during the search process were studied using the inclusion criteria. The full texts of the articles were examined using the above-mentioned criteria independently by 2 authors. Disagreements were resolved through discussions.
The modified STROBE checklist was used to assess the quality of selected observational studies with cohort, case-control, and cross-sectional designs. The STROBE as a valid instrument with 22 items was used for reporting or evaluating observational studies . For the quality assessment of this review, the modified STROBE checklist with 10 items was used in relation of the methodological assessment of studies. The modified checklist consisted of objectives (specific objectives), study design (key elements of the study design), setting (the setting, location, relevant date, period of recruitment, exposure, follow-up, and data collection), subjects (eligibility criteria and the sources and methods of samples’ selection), definition and measurement of all variables (outcomes, exposures, predictors for each variable of interest, sources of data, and methods of measurement), potential sources of bias and confounders (efforts taken to address potential sources of bias), sample size (final sample size), quantitative variables (handling variables during analyses, group selections, and reasons), and statistical methods (methods used to control confounding variables, methods used to examine subgroups and interactions, addressing missing data). Next, the studies were scored as “low risk”, if the above mentioned criteria were unmet they were scored as “high risk”, and if these items were not explained at all, they were rated as “not clearly defined”. The quality assessment process was performed independently by 2 authors and disagreements were resolved through discussions.
After screening and examining the quality of selected studies, data was extracted and recorded in forms independently by 2 authors. The forms were consisted of questions about the name of the first author, year, study design, country of the study, sample size, age of subjects, associations between dysmenorrhea and nutritional groups, and nutritional habits.
The qualitative synthesis of findings was performed due to the heterogeneity of measures used to assess and report nutrition consumption and insufficiency in provided data. Also, different measures were used to report the intensity of dysmenorrhea.
The search process led to retrieving 5,814 potentially relevant articles. Of which, 157 articles were found related to the study topic during abstract and title checking, but 18 articles were duplicated and 3 articles were published in other languages than English. The full texts of 136 remaining articles were reviewed and 38 articles were selected based on the inclusion criteria. The reference list of the included studies was read to find potentially related studies, but no article was included in the search process. Figure 1 showed the search process according to the PRISMA flowchart.
Description of Selected Studies
Most articles (n = 27) had cross-sectional designs, 4 had prospective or cohort designs, and the remaining were case-control studies. A total of 19,626 women were studied in these studies. The largest number of samples was 2,166 individuals in the study by Fujiwara and Nakata  in Japan. Also, the study of Abdul-Razzak et al.  in Jordan had the lowest number of samples (n = 56). The studies were performed in the different parts of the world including the United States, China, Japan, Iran, Jordan, Nepal, Turkey, India, South Korea, Ethiopia, Georgia, Serbia, and Italy. Japan had the largest number of studies with 6 articles (Table 1).
Evaluation of the selected studies using the modified checklist of STORBE with 10 items showed that the studies mostly had a moderate quality level. The quality assessment scores were presented in Table 1. The majority of the studies had issues in reporting bias, sample size estimation, description of design, and statistical analysis of quantitative variables. Figure 2 showed the graphical representation of the quality of studies.
The findings of the selected studies were presented in 2 parts: (i) summarizing the results of the studies regarding the association between dysmenorrhea and dietary nutritional groups based on the food pyramid (Table 2) and (ii) abstracting the results of the studies based on nutritional and dietary habits (Table 3).
The Results of the Selected Studies According to the Dietary Nutritional Group
Carbohydrate Including Bread and Cereals: Consumption of pasta, rice, white bread, biscuits, pastry, potatoes, grains were studied by Di Cintio et al. , Balbi et al. , Tavallaee et al. , and Gagua et al. , but no association was reported between the consumption of food related to these groups and dysmenorrhea.
Fruits and Vegetables: The association between the consumption of fruits and vegetables were investigated in 4 studies, but Di Cintio et al.  and Abu Helwa et al.  found no associations. However, Tavallaee et al.  and Balbi et al.  reported that fruit consumption had negative associations with the level of menstrual pain.
Meat, Legumes, Eggs, and Nuts: This group consisted of a wide range of nutrients including meat, poultry, fish, legumes such as beans and soybean, eggs, and nuts. Fish consumption as a separate nutrient was studied by Deutch , Balbi et al. , and Grandi et al.  which reported inconsistent results. Deutch  found that a high intake of n-3 fatty acids through marine sources was associated with pain reduction; also Balbi et al.  found that women with dysmenorrhea significantly consumed less fish compared to healthy controls, but Grandi et al.  did not find any significant association. Egg as another nutrient was studied by Di Cintio et al.  and Balbi et al.  with completely contradicting results. Di Cintio et al.  reported that women with dysmenorrhea consumed eggs more frequently than healthy controls, but Balbi et al.  reported that women with dysmenorrhea consumed significantly less eggs compared to healthy controls. Other studies did not find significant results concerning the association between dysmenorrhea and the consumption of meat and its alternatives [16, 26, 27, 39, 52, 55].
Milk and Dairy: Milk and dairy consumption were reported in several studies. Four studies found a significant inverse association between the consumption of dairy products and dysmenorrhea [16, 21, 33, 59], Di Cintio et al.  found no relationship between the intake of milk and risk of dysmenorrhea, but cheese was more frequently used by women with dysmenorrhea than healthy controls.
Other Products: Other products included sugar, fat, salt, caffeine, vitamins, and minerals:
A) Sugar: Consumption of sugar in 3 studies had a significant relationship with dysmenorrhea. It developed a significantly higher risk of dysmenorrhea in women consuming excessive amount of sugar [6, 29, 60]. Inconsistently, Tavallaee et al. , Grandi et al. , Mohamadirizi and Kordi , Abu Helwa et al.  found no association between the intake of sugar and dysmenorrhea.
B) Fats: Fat consumption was reported by 2 studies. Nagata et al.  found that only the intake of saturated fat had a positive association with lower menstrual pain. Also, Tavallaee et al.  reported that women with a low fat diet significantly experienced less pain during menstrual periods.
C) Salt: Three studies examined the relationship between excessive salt intake and dysmenorrhea. One study reported a higher prevalence of dysmenorrhea in women with moderate or excessive intake of salt compared with those with a minimal intake . Two other studies did not report a significant association between a high salt intake and dysmenorrhea [44, 55].
D) Caffeine Consumption: Caffeine consumption was the most studied nutrient including coffee, tea, Nescafe, carbonated soft drinks, chocolate, and hot chocolate. In 15 studies, the association between caffeine intake and dysmenorrhea was assessed. In some studies, some forms of caffeinated drinks were assessed separately such as tea, coffee, Nescafe, but others studies assessed this group as whole. Seven studies [16, 29, 38, 44, 48, 52, 55] did not find any significant association between caffeine intake and dysmenorrhea, but Faramarzi and Salmalian , Pejčić and Jankovic , and Hailemeskel et al.  found significant associations between caffeine consumption and higher intensity of menstrual pain. Drinking tea did not have a significant association with dysmenorrhea in 4 studies [28, 43, 45, 60], but Wang et al.  reported more tea consumption among women with dysmenorrhea. The association between coffee and menstrual pain was reported in 3 studies [28, 43, 60] indicating a positive association, but 7 studies  reported that coffee consumption had no association with dysmenorrhea.
Vitamins and Minerals: Venkata et al.  reported reduced blood levels of Vitamin E and C and primary dysmenorrhea. Consistently, Pramanik et al.  reported a higher daily intake of beta carotene, vitamin-E, and zinc in girls without dysmenorrhea than their counterparts with dysmenorrhea. No difference was reported with vitamin C. Weissman et al.  reported a lack of significant relationship between vitamin intake and dysmenorrhea. Only Abdul-Razzak et al.  reported that individuals with severe and very severe dysmenorrhea had vitamin D deficiency or had low calcium intake. Nevertheless, there was no relationship between the severity of menstrual pain, and vitamin D and plasma calcium levels.
Fiber Consumption: A study examined the association between fiber consumption and dysmenorrhea, and reported a negative and significant relationship between them .
Results of the Studies According to Nutritional Habits
Following Diet to Lose Weight: Montero et al. , Fujiwara , Rupa Vani et al. , and Hailemeskel et al.  studied the association between the current or previous attempts of going on a diet to lose weight and the intensity of dysmenorrhea. Consistently, a positive association between following a diet to lose weight and dysmenorrhea was reported.
Following Vegetarian Diet: Only one study focused on the relationship between having a vegetarian diet and dysmenorrhea. No significant difference was found in the prevalence of dysmenorrhea in vegetarian and non-vegetarian subjects .
Eating Behavior: Eating behaviors such as skipping breakfast, irregular eating, fast foods, or process foods were studied. Skipping breakfast was the most studied eating behavior and 6 studies found a significant correlation between skipping breakfast and the intensity of dysmenorrhea. Those women who skipped breakfast suffered from a higher intensity of dysmenorrhea [32, 36, 40, 41, 51, 55]. Conversely, Faramarzi and Salmalian  did not find a significant relationship between eating breakfast and dysmenorrhea. Also, no association was observed between the attitude toward eating breakfast and dysmenorrhea .
Habits of regular eating or meal skipping were studied by Gagua et al.  and Jeon et al. . They showed that those subjects with irregular and skipped meal habits had a significantly higher intensity of dysmenorrhea. Also Bavil et al.  found significant differences between the groups with and without dysmenorrhea in terms of eating behaviors.
Studies on eating fast foods/process foods/junk foods reported inconsistent results. Fujiwara et al.  and Shinde and Laddad  reported a significantly higher level of dysmenorrhea in those subjects who ate fast foods and processed foods compared to their healthy counterparts. Mohamadirizi and Kordi  and Rupa Vani et al.  did not report such an association.
Dysmenorrhea is one of the main factors influencing the quality of life and social activities of women [1, 8]. Several factors can affect primary dysmenorrhea and its incidence and severity. Nutrition has not been adequately studied with regard to its effect on dysmenorrhea [21, 27]. Therefore, this systematic review aimed to investigate the association between primary dysmenorrhea and dietary habits.
Regarding dietary habits and the consumption of different nutritional groups, the consumption of carbohydrates including bread, cereals, meat, legumes, and nuts had no association with dysmenorrhea and its intensity. Consumption of fish and eggs as the alternatives of meat showed inconsistent results. Regarding the association between fish and dysmenorrhea, the consumption of fish was associated with less dysmenorrhea pain, but 2 studies found inconsistent results. This finding is consistent with results of recent studies indicating the effects of fish oil on primary dysmenorrhea [62, 63]. The prevention of prostaglandins synthesis is the major mechanism of fish oil . The protective role of fish is due to the content of omega-3 fatty acids. If more dietary omega-3 fatty acids are consumed, they enter the phospholipid membrane . During menstruation, omega-3 fatty acids compete with fatty acids containing omega-6 to produce prostaglandins and leukotriene. In addition, they can hinder the production of arachidonic acid . The effect of arachidonic acid in animal fats, especially meat, is the synthesis of prostaglandin . Prostaglandins produced from omega-3 fatty acids are less potent, and can reduce the contraction of the myometrium and vessels . A reduction of systemic symptoms is due to a poor leukotriene’s production. Egg can prevent dysmenorrhea due to its magnesium and calcium contents. Magnesium such as calcium plays a key role in the membrane fixation mechanism and can modulate synapses through calcium-dependent mechanisms. Reductions in magnesium levels increase synaptic transmission, resulting in myometric muscle contractions and, consequently, dysmenorrhea . Foods containing the high levels of magnesium can reduce the severity of dysmenorrhea through reducing the synthesis of prostaglandins and spasticity of small muscles and vessels . However, such findings are not consistent with that of the current systematic review. Such inconsistency may be due to small numbers of studies in this subgroup.
Studies on the association between the consumption of fruits and vegetables and dysmenorrhea were inconsistent. Two of 4 studies in this subgroup showed no significant association [26, 55], but 2 other studies confirmed that the increased consumption of fruits and vegetables are associated with the reduction of menstrual pain [16, 27]. Fruits and vegetables are important sources of vitamins and antioxidants . Therefore, the combination of these results with the findings of studies on the plasma level of vitamins confirmed that women with dysmenorrhea took less fruits and vegetables and had less plasma levels of vitamins [33, 42, 53]. Vitamins, beta-carotene, zinc, and minerals are diet antioxidants. Vitamin E is fat soluble and is primarily responsible for oxidant membrane injuries and is the first line of defense against the peroxidation of phospholipids. Vitamin C (ascorbic acid) is soluble in water and provides an antioxidant capacity by removing oxygen-free radicals. So vitamin C can convert vitamin-E-free radical back to vitamin E and are essential for the recycling of vitamin E to prevent fat peroxidation. Beta carotene inhibits oxidants. Zinc is an antioxidant factor . Reducing the level of antioxidants can increase the consumption of antioxidants or free radicals to detoxify the increased levels of oxidants in primary dysmenorrhea. A study on vitamins E and B (thiamine), magnesium, and fish oil suggests that these foods are important sources of vitamins E, A, and other nutrients . Women with primary dysmenorrhea who use non-steroidal anti-inflammatory drugs are suggested to use natural antioxidants such as vitamin E, vitamin C, and β-carotenoids for the reduction of pain [7, 53]. Single randomized controlled trials showed the effect of vitamin supplements on the reduction of menstrual pain reduction [63, 66, 67], but a Cochrane meta-analysis on the effect of dietary supplements for primary dysmenorrhea lacked high quality evidence to support the effectiveness and safety of any dietary supplement for dysmenorrhea. Therefore, more research with higher methodological qualities are required .
Five studies assessed the association between the dairy consumption (calcium intake) and dysmenorrhea and they mostly (4 out of 5) reported a positive association between dairy consumption and the reduction of menstrual pain [16, 21, 33, 59]. Calcium intake in the diet has a protective effect on dysmenorrhea . Calcium is absorbed in the upper intestine and can regulate the ability of muscle cells to respond to nerve stimuli through various functions, which is called stabilizing [21, 27, 33]. Therefore, dairy and calcium consumption can reduce dysmenorrhea through controlling muscle nervous activities. Conversely, reduction of calcium concentrations can increase muscle spasm, spasticity, and muscle contractions . The possible explanation for this relationship is that the absorption and metabolism of vitamins and minerals are endangered by the use of sugar leading to muscle spasm and menstrual pain .
Sugar consumption had an inconsistent association with dysmenorrhea. Excessive sugar intake was increased by the absorption of certain vitamins and minerals and led to a food instability. It creates muscle spasm and pain in the menstrual cycle. Also, certain nutrients directly influence the circulation status of sexual steroids and cause muscle spasm [6, 29, 48, 56]. The relationship between caffeine intake and dysmenorrhea has been reported in many studies due to its effect on vasoconstriction and pelvic pain . On the other hand, caffeine can stimulate stress and irritability [28, 37, 49, 56].
Nutritional deficiencies are the most important factors that disrupt the hypothalamic-pituitary-ovarian axis. Nutritional deficiencies such as not eating breakfast contribute to the development of gynecological disorders especially endometriosis . The nutritional status influences sexual steroids. Insufficient nutrition causes a change in hormonal levels due to reduced levels of energy . Menstrual pain occurs only during ovulation. Progesterone affects the synthesis of prostaglandins and their attachment to myometrium receptors. Prostaglandins affect the uterine muscle and vascular tone, and dysmenorrhea is caused by an imbalance in prostaglandins. In addition, progesterone has some effects on the concentration of prostaglandin in myometrium .
The majority of the studies had issues in reporting potential source of bias, sample size estimation, description of design, and statistical analysis of quantitative variables. So there is a need to design and implement studies with stronger methodologies.
The most important limitation of this review study was methodological heterogeneity of studies. The heterogeneity in the assessment and report of consumption of nutritional groups and habits limited the data synthesis to qualitative synthesis. Performing meta-analysis was impossible. Qualitative synthesis has limitations in terms of providing conclusive findings. A lack of pre-registration protocol and exclusion of studies publications prior to 1990 and published in other languages are the other limitations of this study.
This systematic review showed the relationship between some nutritional factors and primary dysmenorrhea, indicating the need for further studies on this topic. The increased consumption of fruits and vegetables as the sources of many vitamins and minerals, fish and milk, and dairy can have a positive association with less menstrual pain. Other findings are related to nutritional habits, but most studies showed a negative association between dysmenorrhea and meal skipping and following diet to lose weight. Therefore, attention should be paid to the correction of female nutritional behaviors for having enough and balanced diet. Given the negative effects of dysmenorrhea on the quality of life, measures should be taken to increase the knowledge of women about dysmenorrhea and make appropriate lifestyle changes to control it. Designing and implementing interventional studies on nutrition education and modification are recommended.
The authors declare no conflicts of interest.