{"paper_id":"bc2f2a64-2b6e-47b9-8826-87e5f577a2bf","body_text":"www.ogscience.org 99\nIntroduction\nEndometriosis is defined as the presence of functioning en -\ndometrial glands and stromal cells outside the endometrial \ncavity, affecting 5–15% of women of child-bearing age, \namong whom 30–50% develop infertility [1,2]. Many theo\n-\nries have been proposed to explain the pathophysiologic \ndevelopment of endometriosis; however, the etiology of the \ndisease is still unclear [3,4]. Most researchers agree that en\n-\ndometriosis is an estrogen-dependent chronic inflammatory \nprocess in the pelvic cavity. Accordingly, endometriosis is as\n-\nsociated with pelvic pain and infertility, especially in the case \nof ovarian endometrioma, which directly affects the ovarian \nreserve [5].\nDietary pattern and risk of endometrioma in Korean \nwomen: a case-control study\nHyun Joo Lee, MD, Hye Kyung Noh, MD, Seung Chul Kim, MD, PhD, Jong Kil Joo, MD, PhD,  \nDong Soo Suh, MD, PhD, Ki Hyung Kim, MD, PhD\nDepartment of Obstetrics and Gynecology, Medical Research Institute, Pusan National University Hospital, Pusan National University School of \nMedicine, Busan, Korea\nObjective\nThe aim of this study was to investigate and compare the dietary patterns of Korean women diagnosed with \nendometrioma or other benign ovarian cysts.\nMethods\nA total of 66 patients, comprising 39 patients who were surgically diagnosed with ovarian endometrioma and \n27 control patients with other benign ovarian cysts, were included in this case-control study. Trained interviewers \nidentified and interviewed the case patients and controls on the day before the laparoscopic ovarian surgery, using a \nsemiquantitative food frequency questionnaire developed by the Ministry of Health and Welfare of Korea. Statistical \nanalysis was performed using the Wilcoxon sum-rank test for continuous variables and the χ\n2\n test or Fisher’s exact test \nfor categorical variables.\nResults\nThe calcium intake from daily food consumption was significantly lower in patients with endometrioma than in those \nwith other benign ovarian cysts. The dietary intakes of vitamin D, iron, and zinc were also relatively lower in patients \nwith endometrioma than in patients with other benign ovarian cysts, although they did not reach the statistical \nsignificance threshold.\nConclusion\nThe risk of endometrioma is significantly associated with a lower dietary intake of calcium. Future studies including a \nlarger number of patients on a nationwide scale are urgently required for further clarification.\nKeywords: Diet; Calcium; Endometrioma; Benign ovarian cyst\nReceived: 2020.08.06.   Revised: 2020.11.03.   Accepted: 2020.11.09.\nCorresponding author: Jong Kil Joo, MD, PhD\nDepartment of Obstetrics and Gynecology, Medical Research \nInstitute, Pusan National University Hospital, Pusan National \nUniversity School of Medicine, 179 Gudeck-ro, Seo-gu, Busan \n49241, Korea\nE-mail: jongkilj@hanmail.net\nhttps://orcid.org/0000-0002-6338-1512\nArticles published in Obstet Gynecol Sci are open-access, distributed under the terms of \nthe Creative Commons Attribution Non-Commercial License (http://creativecommons.\norg/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, \nand reproduction in any medium, provided the original work is properly cited.\nCopyright © 2021 Korean Society of Obstetrics and Gynecology \nOriginal Article\nObstet Gynecol Sci 2021;64(1):99-106\nhttps://doi.org/10.5468/ogs.20230\neISSN 2287-8580\n\nwww.ogscience.org100\nVol. 64, No. 1, 2021\nThe major risk factors based on such estrogen-dependent \nfeatures of endometriosis include increased estrogen expo -\nsure frequently leading to early menarche, prolonged dura -\ntion of menstrual flow, shorter menstrual cycle interval, and \nnulliparity [1,6,7]. One of the factors that could influence \nphysiologic estrogen activity and exposure is the dietary \npattern of a patient, which is a valuable, modifiable factor \nnot only for disease management but also for prevention \nwhen well understood [1,8]. A number of studies have been \npublished, although they reported rather inconclusive data. \nSome studies have reported that a plant-based and high-\nfiber diet increases estrogen excretion and decreases the \nconcentration of bioavailable estrogen. However, the effects \nof vegetable consumption on the risk of ovarian endome -\ntrioma are unknown [1,9-11]. Moreover, studies investigating \nthe association between red meat consumption and the risk \nof endometrioma development have reported contradictory \nresults [12].\nWhen evaluating the relationship between certain diets \nand diseases, it is important to note that the effect of diet \non the hormone levels or inflammatory status of the body \ncould be influenced by the cooking method, storage tech\n-\nniques, and/or management of food resources (e.g., use of \npesticides) [13]. Because of such variables, the precise evalu\n-\nation of the relationship between dietary patterns and the \noccurrence of a specific disease requires statistical analysis \nbased on a homogeneous population with a shared culinary \nculture. Thus, this case-control study investigated the dietary \npatterns of Korean women diagnosed with ovarian endome\n-\ntrioma (histologically confirmed after laparoscopic surgery) \ncompared with patients with other benign ovarian cysts with \nsurgical and histologic confirmation.\nMaterials and methods\n1. Study population\nThe current case-control study included a total of 66 patients \nreferred to a single, tertiary, national university hospital from \nSeptember 2018 to August 2019. Of these, 39 patients diag\n-\nnosed with unilateral or bilateral ovarian endometrioma were \nassigned as the case group. Another 27 patients with other \nbenign ovarian cysts, such as teratomas or cystadenomas, \nwere selected as the control group. The other benign ovar\n-\nian cysts were not further distinguished because they were \nless likely to be associated with estrogen exposure [14]. All \npatients underwent routine preoperative examinations and \nmedical history taking for laparoscopic surgery, after which \nthe ovarian pathology was diagnosed with histologic confir -\nmation. In the review of the patients’ medical records, men-\nstrual irregularity was defined as a menstrual cycle length \nof less than 21 days and/or more than 35 days with varying \nintervals, and history of smoking included both present and \nprevious smoking. For the case group, only patients who \nwere diagnosed with endometrioma for the first time were \nincluded; those with recurring endometrioma were excluded. \nPatients who had been previously requested to restrict food \nintake because of their medical history, such as diabetes, \nwere also excluded, as were women who had been taking \nhormonal contraceptives for contraception or dysmenorrhea \ntreatment. The control group was composed of patients with \nsurgically and histologically confirmed ovarian teratomas or \nserous or mucinous cystadenomas. Patients who were diag\n-\nnosed with coexisting endometriosis during the operation \nwere excluded from the control group, as were those who \nhad been preoperatively diagnosed with comorbid myoma \nuteri and/or adenomyosis with imaging modalities such as \ncomputed tomography or magnetic resonance imaging. \n2. Dietary assessment\nFood intake data were collected using a validated semiquan-\ntitative food frequency questionnaire (SQFFQ) about the \npatients’ dietary patterns for the previous year. The SQFFQ, \nwhich covered 112 food groups derived from the Korean \nNational Health and Nutrition Examination Survey, was de\n-\nveloped by the Ministry of Health and Welfare [15]. Food \nintake frequency was divided into the following 9 categories \nfor all 112 items: never or seldom, once per month, 2 to \n \n3 times per month, once or twice per week, 3 to 4 times per \nweek, 5 to 6 times per week, once per day, twice per day, \nand 3 or more times per day. The participants indicated the \nfrequency of intake of each food item based on the pro\n-\nvided definitions of portion sizes. The respondents indicated \nwhether the amount of food they consumed in 1 sitting \nwas more than, equal to, or less than 1 portion, based on \npictures of the food items. Daily intake was calculated using \nthe midpoint of the assigned frequencies of each category \nfor each food item. Food intake was calculated by multiply\n-\ning the midpoints of the frequencies for each food category \nby the number of times each food item was consumed. By \n\nwww.ogscience.org 101\nHyun Joo Lee, et al. Dietary pattern and risk of endometrioma\nusing the SQFFQ food intake data, the consumption of en -\nergy and nutrients, such as protein, carbohydrates, fat, fiber, \ntotal vitamin A, vitamin B1, vitamin C, calcium, and iron, was \ncalculated using Can-Pro 2.0 software (The Korean Nutrition \nSociety, Seoul, Korea) [16]. Trained interviewers identified \nand supervised the patients throughout the completion of \nthe questionnaire. All interviews were conducted in a hospi -\ntal setting.\n3. Statistical analysis\nStatistical analyses were performed using SAS software (ver -\nsion 9.4; SAS Institute, Cary, NC, USA). The frequency distri-\nbutions of categorical demographic and personal behavior-\nrelated variables were obtained according to the presence of \nendometrioma or other benign ovarian cysts, and statistical \nsignificance was determined using the χ\n2\n test. The median \nand interquartile range (IQR) of the dietary intake of each \nnutrient, as determined using the SQFFQ method, were \ncalculated. Statistical significance was determined using the \nWilcoxon rank-sum test for continuous variables.\nResults\n1.   Patient characteristics of the endometrioma and \nother benign cyst groups\nThe background characteristics of the patients are presented \nin Table 1. No statistical differences were found in the pa\n-\ntients’ age, body mass index, age at menarche, and parity \nbetween the groups. The median serum level of carbohy\n-\ndrate antigen 125 in the endometrioma group was 34.80 U/\nmL that in the benign ovarian cyst group was 18.20 U/mL. \nNone of the patients in either group had a history of diabe\n-\ntes, hypertension, or dyslipidemia.\n2.   Results of semiquantitative food frequency \nquestionnaire in the endometrioma and other \nbenign cyst groups\nTable 2 shows the results of the SQFFQ in both groups. The \ndietary calcium intake was significantly lower in the endome-\ntrioma group than in the other benign ovarian cyst group, \nwith median (IQR) values of 530.83 (406.89–725.23) mg and \n779.40 (518.52–867.18) mg, respectively (P=0.047). Vitamin \nD, iron, and zinc intakes were also relatively lower in the \nendometrioma group than in the other benign cyst group, \nbut without statistically significant differences. No other \nstatistically significant difference was observed in the rest of \nthe evaluated nutrients: carbohydrates, lipids, proteins (both \nplant-based and animal-based), dietary fibers (both soluble \nand insoluble), vitamins, minerals (including phosphorus, so\n-\ndium, chlorine, potassium, and magnesium), cholesterol, to -\ntal fatty acids, saturated fatty acids, unsaturated fatty acids, \nother fatty acids (including caproic acid, caprylic acid, and \npalmitic acid), and amino acids (including isoleucine, cyste\n-\nine, phenylalanine, and aspartate).\nDiscussion\nIn this study of a homogeneous population of Korean wom-\nTable 1. Patient characteristics in the endometrioma group and the other benign ovarian cyst group\nCharacteristics Endometrioma group (n=39) Other benign ovarian cyst group (n=27) P-value\nAge (yr) 33.18 (9.35) 35.67 (11.27) 0.350\nHeight (cm) 160.66 (4.58) 160.64 (5.59) 0.991\nWeight (kg) 54.40 (8.06) 56.91 (8.14) 0.221\nBMI 21.08 (3.04) 22.08 (3.18) 0.207\nNulliparous (%) 29 (74.36) 15 (55.56) 0.186\nb)\nAge at menarche (yr) 13.33 (1.58) 13.48 (1.60) 0.712\nCA-125 (U/mL)\na)\n34.80 (23.10–60.10) 18.20 (12.05–28.85) 0.001\nc)\nMenstrual irregularity (%) 7 (17.95) 5 (18.52) 1.000\nb)\nSmoking (%) 1 (2.56) 0 (0.00) 1.000\nb)\nData are presented as mean (standard deviation) or median (interquartile range). \na)\nP<0.05; \nb)\nχ\n2\n test or Fisher’s exact test for categorical variables; \nc)\nWilcoxon rank-sum test for continuous variables.\n\nwww.ogscience.org102\nVol. 64, No. 1, 2021\nTable 2. Dietary intake of each nutrient in the endometrioma group and the other benign ovarian cyst group\nCharacteristics Endometrioma group (n=39) Other benign ovarian cyst group (n=27) P-value\nEnergy (kcal) 2,235.43 (1,795.43–2,658.01) 2,495.67 (1,811.78–3,298.20) 0.217\nCarbohydrate (g) 325.33 (246.10–391.47) 364.93 (275.13–507.93) 0.164\nLipid (g) 62.08 (49.26–84.29) 67.74 (42.27–107.69) 0.717\nVegetable lipid 31.94 (23.57–40.83) 30.48 (22.32–48.31) 0.756\nAnimal lipid 29.77 (25.16–42.35) 29.99 (19.05–53.84) 0.877\nProtein (g) 74.84 (61.63–93.08) 82.45 (62.39–121.77) 0.287\nVegetable protein 40.31 (32.36–46.35) 44.07 (30.80–56.69) 0.318\nAnimal protein 38.32 (25.75–50.11) 38.38 (23.70–66.60) 0.525\nFiber (g) 25.71 (20.01–36.46) 31.29 (22.49–40.99) 0.350\nSoluble dietary fiber 3.43 (2.52–5.23) 4.78 (2.63–6.29) 0.248\nInsoluble dietary fiber 14.22 (11.36–20.28) 17.62 (11.18–20.85) 0.414\nVitamins\nVitamin A (µg RAE) 602.61 (410.65–949.52) 656.85 (442.93–893.96) 0.707\nβ-Carotene (µg) 3,859.46 (3,066.85–4,910.98) 4,506.81 (3,065.18–5,404.64) 0.399\nVitamin D (µg) 2.58 (1.90–3.86) 3.49 (2.29–5.72) 0.149\nVitamin E (mg) 20.68 (16.92–28.38) 26.20 (17.60–33.04) 0.385\nVitamin K (µg) 165.36 (116.86–215.94) 203.76 (114.16–283.23) 0.305\nVitamin C (mg) 115.64 (79.33–198.67) 144.29 (86.26–287.52) 0.264\nThiamin (mg) 2.19 (1.69–2.82) 2.39 (1.80–3.07) 0.452\nRiboflavin (mg) 1.63 (1.36–2.38) 1.98 (1.51–2.56) 0.232\nNiacin (mg) 12.77 (10.53–16.81) 16.53 (11.24–19.79) 0.185\nVitamin B6 (mg) 2.04 (1.50–2.45) 2.42 (1.53–3.28) 0.128\nFolate (µg) 586.10 (445.53–856.39) 677.76 (523.42–1,000.34) 0.337\nVitamin B12 (µg) 8.99 (6.02–11.18) 7.22 (5.96–15.50) 0.766\nPantothenic acid (mg) 5.49 (4.62–6.84) 6.60 (4.90–9.82) 0.138\nVitamin B7 (µg) 2.63 (1.42–4.98) 3.40 (1.33–6.66) 0.437\nMinerals\nCa (mg)\na)\n530.83 (406.89–725.23) 779.40 (518.52–867.18) 0.047\nP (mg) 1,195.35 (944.14–1,480.49) 1,410.78 (1,103.60–1,853.43) 0.152\nNa (mg) 3,664.52 (3,058.92–4,994.28) 4,723.70 (3,243.69–5,720.62) 0.141\nCl (mg) 122.35 (59.89–180.92) 134.85 (72.26–281.58) 0.357\nK (mg) 2,860.00 (2,353.87–4,419.42) 3,769.45 (2,872.51–5,199.46) 0.152\nMg (mg) 141.09 (95.72–177.36) 143.61 (106.71–187.22) 0.452\nFe (mg) 17.39 (13.47–20.02) 21.32 (15.03–27.09) 0.141\nZn (mg) 11.40 (9.36–13.94) 14.24 (9.04–18.13) 0.198\nCu (µg) 819.59 (562.48–1,117.10) 937.58 (650.70–1,182.37) 0.517\nCholesterol (mg) 416.89 (299.02–552.22) 443.85 (266.84–686.51) 0.484\nTotal fat (g) 40.22 (29.97–51.67) 42.73 (25.45–66.49) 0.669\nSaturated fat (g) 11.14 (8.39–14.36) 11.54 (7.57–18.81) 0.542\nMonounsaturated fat (g) 13.55 (10.52–18.27) 15.29 (8.92–24.79) 0.613\nPolyunsaturated fat (g) 14.05 (11.30–19.24) 15.52 (8.89–23.31) 0.727\n\nwww.ogscience.org 103\nHyun Joo Lee, et al. Dietary pattern and risk of endometrioma\nCharacteristics Endometrioma group (n=39) Other benign ovarian cyst group (n=27) P-value\nFatty acids (g)\nn3 fatty acid 0.66 (0.44–0.99) 0.50 (0.32–1.27) 1.000\nn6 fatty acid 4.42 (3.22–5.72) 4.46 (2.62–7.60) 0.707\nCaproic acid 0.01 (0.00–0.01) 0.01 (0.00–0.03) 0.701\nCaprylic acid 0.01 (0.00–0.01) 0.01 (0.00–0.02) 0.895\nLauric acid 0.12 (0.07–0.25) 0.12 (0.05–0.29) 0.969\nMyristic acid 1.17 (0.86–1.75) 1.60 (0.85–2.18) 0.281\nMyristoleic acid 0.20 (0.13–0.27) 0.23 (0.10–0.32) 0.429\nPalmitic acid 38.79 (31.64–47.00) 41.63 (28.29–54.57) 0.476\nPalmitoleic acid 3.31 (2.38–4.72) 3.66 (2.72–6.57) 0.305\nStearic acid 10.71 (7.68–13.50) 12.24 (6.42–17.63) 0.414\nOleic acid 52.26 (38.78–63.20) 59.50 (32.41–84.62) 0.444\nLinoleic acid n6 44.73 (34.03–55.30) 46.96 (27.32–52.17) 0.604\nLinoleic acid n3 4.83 (3.95–6.28) 5.06 (3.32–6.78) 0.678\nγ linoleic acid 0.00 (0.00–0.00) 0.00 (0.00–0.00) 0.938\nStearidonic acid 0.02 (0.01–0.05) 0.02 (0.01–0.07) 0.201\nArachidic acid 0.28 (0.23–0.37) 0.31 (0.18–0.45) 0.660\nEicosenoic acid 0.88 (0.61–1.20) 0.95 (0.70–1.57) 0.392\nDocosanoic acid 0.16 (0.01–0.27) 0.17 (0.03–0.68) 0.185\nTetracosanoic acid 0.02 (0.01–0.03) 0.02 (0.01–0.03) 0.492\nOther fatty acid 1.68 (1.13–2.08) 1.89 (0.97–2.62) 0.500\nAmino acids (mg)\nIsoleucine 1,883.74 (1,543.83–2,196.70) 2,164.41 (1,591.59–2,991.26) 0.305\nLeucine 3,605.33 (2,888.95–3,951.05) 3,881.38 (2,889.01–5,644.90) 0.330\nLysine 2,411.76 (1,935.49–3,217.77) 2,540.66 (1,845.83–3,938.08) 0.509\nMethionine 822.83 (667.78–992.84) 983.05 (715.21–1,338.48) 0.189\nCysteine 497.84 (401.54–622.37) 545.18 (389.52–943.23) 0.350\nPhenylalanine 2,053.00 (1,670.79–2,259.90) 2,236.80 (1,602.91–3,223.99) 0.437\nTyrosine 1,536.10 (1,221.48–1,660.01) 1,642.90 (1,231.48–2,396.93) 0.378\nAromatic amino acids 474.97 (360.99–651.23) 479.12 (285.65–930.04) 0.846\nThreonine 1,638.82 (1,349.37–2,009.12) 1,739.02 (1,294.78–2,652.56) 0.460\nTryptophan 388.88 (309.66–513.61) 405.13 (338.92–608.15) 0.650\nValine 2,271.37 (1,872.81–2,562.71) 2,604.35 (1,910.10–3,561.50) 0.194\nHistidine 1,260.01 (1,006.30–1,556.34) 1,389.06 (1,089.44–2,014.45) 0.287\nArginine 3,227.83 (2,443.01–3,697.55) 3,406.15 (2,299.44–5,259.51) 0.551\nAlanine 2,459.03 (1,962.48–2,891.14) 2,580.99 (1,838.04–3,872.93) 0.421\nAspartic acid 4,332.92 (3,443.94–5,561.76) 4,561.69 (3,277.35–6,916.76) 0.569\nGlutamic acid 8,246.09 (7,098.08–9,473.94) 9,252.80 (6,689.90–13,033.56) 0.437\nGlycine 1,756.50 (1,329.30–2,147.21) 1,785.72 (1,171.84–2,841.09) 0.746\nProline 2,672.18 (2,383.42–3,307.90) 3,177.45 (2,527.83–3,789.80) 0.217\nSerine 1,945.67 (1,658.40–2,238.09) 2,166.25 (1,524.05–3,081.65) 0.460\nTaurine 119.53 (73.52–202.41) 127.72 (65.55–192.33) 0.877\nData are presented as median (interquartile range).\na)\nP<0.05.\nTable 2. Continued\n\nwww.ogscience.org104\nVol. 64, No. 1, 2021\nen living in a local city with a shared culinary culture, the \ndietary intake of calcium was significantly lower in the endo-\nmetrioma group. Moreover, although statistical significance \nwas not reached, the dietary intakes of vitamin D, iron, and \nzinc were relatively lower in the endometrioma group than \nin the control group. Our data did not provide supporting \nevidence for a relationship between endometriosis and any \nof the other nutrients or food groups examined, except for \ncalcium, vitamin D, iron, and zinc.\nThe lower intakes of calcium in our patients with endo\n-\nmetrioma are partially consistent with previously reported \ndata from different ethnicities and population pools. Harris \net al. [17] reported that calcium, vitamin D, and magnesium \nintakes from food sources were inversely related to endo -\nmetriosis. In their study, participants with a higher quintile \nintake of calcium from food sources had a lower risk of en\n-\ndometriosis, with a trend of statistical significance. Moreover, \nTrabert et al. [1] suggested inverse associations between en\n-\ndometriosis and dairy product intake or calcium intake from \nfood sources, although the difference was not statistically \nsignificant (odds ratio, 0.7; 95% confidence interval, 0.4–1.2). \nThe authors suggested the ability of calcium and vitamin D \nto downregulate growth-promoting factors, such as insulin-\nlike growth factor-I, and to upregulate negative growth fac\n-\ntor regulators, such as transforming growth factor β. Further-\nmore, according to their study, dietary factors such as dairy \nproducts and several specific nutrients may be related to the \nphysiologic processes associated with endometriosis through \ntheir effects on systemic inflammation. The association \nbetween vitamin D and endometrioma seems more compli\n-\ncated to analyze than the association of other nutrients with \nendometrioma. As mentioned earlier, the dietary intake of \nvitamin D was inversely related to endometriosis, although \nonly a small proportion of vitamin D is obtained from dietary \nsources [17]. Nevertheless Ciavattini et al. [18] also reported \nthat a relatively high proportion of women with ovarian en\n-\ndometrioma showed hypovitaminosis D. Similarly, Abbas et \nal. [19] observed that vitamin D treatment induced a reduc\n-\ntion in the endometriosis cyst dimension in a rat model. To \nclarify the role of vitamin D in endometriosis, further studies \nare urgently required.\nIn our study, the dietary intake of zinc was also lower in the \nendometrioma group (median [IQR] = 11.40 [9.36–13.94] mg \nin the case group and 14.24 [9.04–18.13] mg in the control \ngroup, P=0.198). Similar patterns were observed in the study \nby Messalli et al. [20], who reported that patients with endo\n-\nmetriosis presented a lower serum zinc concentration than \nthe control group (1,010±59.24 µg/L vs. 1,294±62.22 µg/L, \n \nP<0.05). They also suggested that zinc interferes in the \npathogenic processes of endometriosis, such as inflammation \nand immunity.\nOther important dietary factors known to be related to \nthe risk of endometriosis development are red meat, trans \nfats, and omega-3 fatty acids. Large studies have been con -\nducted to reveal such relationships, and their results have \nshown that increased intakes of red meat and trans fats, \nand decreased intake of omega-3 fatty acids were related \nto an increased risk of endometriosis [2,8,21]. In our study, \nthe intake of animal fat and protein showed no difference \nbetween the 2 groups. Such results may be due to the small \nnumber of patients included in this study; however, they \ncould also result from the inclusion in the current study of \nan East Asian population with eating habits that differ from \nthose of Western populations analyzed in previous studies. \nTraditionally, Asian populations are known to consume lower \namounts of meat than their Western counterparts. Although \nthe general dietary patterns have been showing similarities \nworldwide, owing to the increasing cultural exchanges and \nthe faster and easier internal trades of food products, the \ndaily eating habits still considerably differ across different \ncountries [22,23]. Thus, the red meat consumption in our \nKorean population may have been too low to present any \nsignificant effect on the risk of endometriosis, compared \nwith previous data from Western populations. Moreover, \nthe current study was conducted in a local port city in South \nKorea, where the population had easy and frequent access \nto fish products containing omega-3 fatty acids. Accordingly, \nboth the case and control groups had been exposed to and \nconsumed higher levels of omega-3 fatty acids than the gen\n-\neral population, which could have affected the results of the \ncurrent study.\nThe current study had several limitations. As this was a \nretrospective study that reviewed previously obtained medi\n-\ncal records, the baseline characteristics of the patients were \nlimited to 9 categories for the risk factors of endometrioma. \nAlthough such categories included major risk factors, more \ndetailed features of the patients still need to be investigated \nin future studies. In addition, most studies evaluating popu\n-\nlation dietary patterns in association with endometriosis use \nself-questionnaires; thus, some of the data are vulnerable \n\nwww.ogscience.org 105\nHyun Joo Lee, et al. Dietary pattern and risk of endometrioma\nto recall bias. However, in our study, all questionnaires were \ncompleted by medical professionals who had been educated \nabout the purpose and outline of the study. In addition, in \nepidemiologic studies, the diagnosis or exclusion of endo -\nmetriosis is typically determined solely by evaluating the \npatients’ medical records. In our study, all patients were diag\n-\nnosed with or ruled out from having endometriosis by lapa -\nroscopic surgery and histologic confirmation, thus obtaining \na more precise medical status for each patient.\nOther limitations include the potentially compromised ef\n-\nfects of a single nutrient according to the cooking method, \neven with the same amount of ingredients. Such variations \nare difficult to standardize in epidemiologic studies. However, \nit may be important to implement in certain areas in persons \nwith similar lifestyles, and our study included a homoge\n-\nneous population of only Korean women and local area resi-\ndents.\nFinally, the number of patients included in the present \nstudy was relatively small. To offset the size limitation, all \npatients included in the study were surgically diagnosed with \nthe ovarian pathology (endometrioma or a benign ovarian \ncyst), with histologic confirmation, and every food frequency \nquestionnaire interview was supervised by a medical profes\n-\nsional. Additionally, to our knowledge, this is the first study \nto analyze the effect of dietary patterns on the risk of endo\n-\nmetriosis in a Korean population.\nIn summary, the risk of endometriosis is significantly associ-\nated with a lower intake of calcium, and despite being statis-\ntically insignificant, lower intakes of vitamin D, magnesium, \nand zinc were observed in patients with ovarian endome\n-\ntrioma. Further studies including a larger number of patients \non a nationwide scale with detailed statistical analysis of \nsignificant nutrients are urgently required to determine the \nlink between dietary patterns and the risk of endometriosis, \nto enable the establishment of patient education programs \nand lifestyle consultation on population-based strategies for \npreventing the disease.\nConflict of interest\nNo potential conflict of interest relevant to this article was \nreported.\nEthical approval\nThe current study was officially exempted from ethical ap -\nproval by the institutional review board of the Human Re -\nsearch Protection Committee of Pusan National University \nHospital (committee reference No. 1912-014-086).\nPatient consent\nAll patients provided informed consent to the use of their \nmedical records and completed questionnaires for research \npurposes.\nFunding information\nNone.\nReferences\n  1.  Trabert B, Peters U, De Roos AJ, Scholes D, Holt VL. 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