Adherence to DASH Dietary Pattern and Polycystic Ovarian Syndrome: A Case-control Study

Objective: Polycystic Ovary Syndrome (PCOS) as one of the endocrine and metabolic abnormalities is prevalent in reproductive-aged women. This study aimed to investigate the relevance between adherence to the DASH diet and PCOS. Results: This is an age and BMI-matched case-control study including (n=108) new diagnosis PCOS women as a case group and women without PCOS as a control group (n=108). Also, the validated 168-item food frequency questionnaire was used to determine the usual dietary intake. The method of Fung et al. was used to calculate the DASH score. Moreover, logistic regression was assessed to evaluate the relationship between adherence to the DASH diet and the odds of PCOS. After adjustment for potential confounders, an increase in adherence to the DASH diet signicantly reduced the odds of PCOS (OR for the highest vs. lowest quartile = 0.18; 95% CI 0.07, 0.47). There was a signicant decreasing trend in the odds of PCOS across increasing quintiles of the DASH diet (p-trend <0.001). The results showed that adherence to the DASH diet could reduce the odds of PCOS by 82 percent. It’s worth noting that more prospective studies are required to conrm the ndings of the current study. circumference; FFQ:food frequency questionnaire; TLGS:Tehran Lipid and Glucose Study; CI:condence interval.


Introduction
Polycystic ovary syndrome (PCOS) is one of the most multifactorial disorders and frequent endocrine abnormalities among women in reproductive age [1,2], which prevalence between 10-15%, depending on diagnostic criteria [3,4]. Based on the Rotterdam criteria, the prevalence of PCOS in Iran has been reported to be 19.5% [5]. Infertility, endometrial carcinoma, anxiety, impaired hemorrhage, sleep apnea, and metabolic disorders such as obesity, hypertension, type 2 diabetes, impaired gonadotropin secretory activity, insulin resistance, cardiovascular diseases, and metabolic syndrome may be complications of this syndrome [6][7][8][9][10]. Previous studies have indicated that adherence to physical activity and diet treatment recommendations are very important to achieve therapeutic goals [11]. A combination of using medication and lifestyle modi cations are treatment plans for this chronic condition [12]. Given that the exact etiology of PCOS is not clear yet, but the interactions between genetic and environmental factors such as diet are considered as effective factors on PCOS [13][14][15][16]. Therefore, diet management and weight loss as lifestyle modi cations, have been suggested as the primary strategy in the treatment of PCOS [17,18].
Dietary Approaches to Stop Hypertension (DASH) dietary pattern is a low-glycemic index and low energydense diet which has rstly been considered for the regulation of blood pressure [19]. This dietary pattern is rich in vegetables, fruits, whole grains, and low-fat dairy with a reduced content of sodium, saturated and total fat [19]. Therefore, due to these useful ingredients, favorable effects of the DASH diet on insulin resistance, lipid pro les, biomarkers of in ammation and oxidative stress, and PCOS women have also been reported repeatedly [20][21][22][23]. Besides, Some studies indicated bene cial effects of the DASH diet on androgens, antioxidant status, body composition, weight loss, AMH (anti-Müllerian hormone), lipid, and metabolic pro les in PCOS women [21,24,25]. Also, a randomized controlled trial study conducted by Azadi-Yazdi et al. indicated that adherence to the DASH diet had bene cial effects on androstenedione, SHBG, and antioxidant capacity in women with PCOS [26]. DASH diet contains higher amounts of dietary ber, phytoestrogens, potassium, calcium, magnesium, folic acid, and other bene cial nutrients [20,27], which justi es the bene cial effects of this dietary pattern on PCOS. For example, the useful effect of high-ber and phytoestrogens food on the regulation of testosterone levels in women with PCOS have been mentioned before [28]. As well as, this diet is rich in monounsaturated fatty acids which improve glycemic control and lipid pro les by improves insulin sensitivity [29]. Another related mechanism is the bene cial effect of magnesium on incremental of SHBG level, which correlates with insulin sensitivity and decreases the free fraction of androgens [30]. Therefore, investigating the DASH diet based on other dietary quality indices to clarify other useful features of this healthy diet, will be helpful.
To the best of our knowledge, this study is the rst investigation aimed to evaluate the association between adherence to the DASH diet and odds of PCOS in new diagnosed patients in Middle Eastern countries. Also, we adjusted for a wide range of confounding variables including body composition such as body fat percentage in addition to energy intake.

Study design and participants
This age-BMI matched case-control study was done on women with and without PCOS, to evaluate the association between adherence to the DASH diet and odds of polycystic ovarian syndrome. The participants were selected among those who referred to "Yazd Diabetes Clinic" Iran, from January 2018 to March 2019. Moreover, the endocrinology expert introduced several participants from different clinics in all parts of the city, who had the inclusion criteria. Also, the Rotterdam criteria was used for diagnosing women with PCOS [3]. The participants' recruitment procedures are indicated in Figure S1.
Two groups were age and BMI matched using a frequency matching method. After explained the study process, a signed written informed consent was provided by each participant.

Dietary intake assessment
Each participant using a 178-items semi-quantitative food frequency questionnaire (FFQ) with 551 questions by common dietary intake of the recent year was assessed. This FFQ was an adjusted model of the previously validated 168-item food frequency questionnaire, which was validated in the Tehran Lipid and Glucose Study (TLGS). Ten additional questions related to the consumption of Yazd speci c food items were added to the original 168-item FFQ leading to a questionnaire with 178 items.
A face to face interview with individuals was conducted by a blinded dietitian to ll out all of the questionnaires. To increase the precision and accuracy of the estimations, the portion sizes, and the frequency of food intake and beverage items, on average, were questioned. Then, the frequency was transformed into daily consumption, and portion sizes were converted to gram via household measurements. Finally, the actual food intake (g/day) was transferred to Nutritionist IV software (First Databank Inc., Hearst Corp., San Bruno, CA, USA) which is modi ed for Iranian foods to compute the total energy and nutrients intake. The overall energy and nutrients intake were investigated by transferring food intake (g/day) to Nutritionist IV.

Calculation of adherence to DASH diet indices
The DASH score was calculated to check the participant's adherence to the DASH diet using the method of Fung et al. [31] based on foods and nutrients that emphasized and focusing on eight components in the DASH diet: low intake of sugar-sweetened beverages and sweets, red and processed meats, and sodium, and a high intake of fruits, vegetables, whole grain, nuts and legumes, and low-fat dairy products, according to quintile categories. A score of 5 was given to participants with the highest quintile of low-fat dairy products, vegetables, fruits, nuts and legumes, and whole grains and a score of 1 was given to participants with the lowest quintile of mentioned foods. Also, Participants with a lower intake of sweetened beverages, sodium, and red and processed meats got higher points (ie, the score of 5 was for the highest quintile and the score of 1was for the lowest quintile). Eventually, the score of adherence to the DASH diet was calculated for each participant by Sum of the scores, ranging from 8 to 40.

Statistical analysis
Participants were divided into quartiles according to their scores of adherence to the DASH diet.
Comparing quantitative variables between cases and controls conducted by using an independent t-test whereas, for categorical variables, chi-square (χ2 test) was used. Kolmogorov-Smirnov test conducted to examine whether the distribution of variables is normal or not. Mean ± SD were presented for continuous variables while qualitative variables used frequency (percentage).
We compared the characteristics of participants (by Classi cation in quartiles) in the lowest and highest quartiles of adherence to the DASH diet scores using descriptive statistics. One-way ANOVA was used to compare general characteristics of quantitative variables across quartiles of adherence to the DASH diet, and for categorical variables used χ2 tests. We calculated Odds Ratio (OR) and 95% con dence interval (CI) for crude and adjusted models.
We used multivariable logistic regression in different models to evaluate the odds ratio for each of the three upper quartiles of adherence to the DASH diet (compared with the lowest quartile) and the prevalence of PCOS. In all of the analyses, the rst quartile of adherence to the DASH diet scores was considered as a reference. To assess the overall trend of odds ratios across increasing quartiles of adherence to DADH diet, we treated the quartile categories as an ordinal variable in the analyses. All analyses were conducted using the statistical software IBM SPSS Statistics version 24. P values < 0·05 considered statistically signi cant.

Characteristics of the study population
Characteristics of the subjects across quartiles of adherence to the DASH diet scores are indicated in adherence to the DASH diet had an inverse association with mean of BMI, waist circumference, waist-tohip ratio, body fat percentage, and visceral fat and had a positive association with physical activity, but none of them were statistically signi cant (p> 0.05).
The average intake of macronutrients, vitamins, and minerals in different quartiles of the adherence to the DASH diet scores indicated in Table 2. As shown in Table 2, the increase in adherence to the DASH diet had a signi cant relationship with a higher intake of carbohydrate, protein, EPA, DHA, vitamin D, vitamin C, and vitamin A(p<0.05). This table also showed that individuals with higher adherence to the DASH diet had a signi cant decrease in the consumption of fat, Zinc, and vitamin B12. Besides, the strong following of this dietary pattern had a signi cant association with an increase in the intake of chromium, potassium, and iron (p<0.05). One-way ANOVA was used to compare quantitative variables between quartiles of DASH Diet 0.47; p-trend = 0.000). As it was indicated in all models, this decreasing trend was signi cant and p-trend <0.05. Table 3 Multivariate adjusted odds ratio (OR) and 95% con dence interval (CI) for PCOS among Quartile of DASH diet scores

Discussion
This study scrutinized the association between adherence to the DASH diet and the risk of PCOS. As we found, this study indicated that an increase in adherence to the DASH diet had a signi cant relation with 82 percent decreasing the chances of developing polycystic ovary syndrome. Also, this study indicated higher following of this dietary pattern had a signi cant association with an increase in intake of EPA [32], DHA [33], vitamin D [34,35] Other studies in line with our ndings were two randomized clinical trial study demonstrated that adherence to the DASH diet had bene cial effects on BMI, anti-Müllerian hormone (AMH), insulin metabolism, SHBG [39], losing weight, reduction in serum androstenedione, and increase in antioxidant status [23]. As it was found, some components of the DASH diet including vegetables, fruits, nuts and legumes, and low-fat dairy products, contain high amounts of antioxidants, dietary ber, phytoestrogens, magnesium, and calcium, that their useful effects on PCOS which have been mentioned in previous studies [22,40]. On the other hand, calcium as an important micronutrient, which is found abundantly in low-fat dairy products, can increase insulin sensitivity [41]. Moreover, increased intake of calcium can be effective on weight loss which in turn would result in fecal fat excretion. weight loss can decrease insulin resistance [42] which may decrease the P450c17a enzyme activity and as a result decrease in ovarian androgen production occurs [43]. Insulin resistance and hyperinsulinemia as two pathogenesis factors in PCOS, by stimulation of androgen synthesis through Theca cells and reducing SHBG, may lead to hyperandrogenaemia [44,45]. Therefore, as a possible mechanism DASH diet which is rich in nuts that contain omega-3, has a protective effect on PCOS by increasing insulin sensitivity and SHBG level [45][46][47].
There are several strengths in this study. First of all, to the best of our knowledge, this study is one of the rst investigations in progress which to assess the relationship between adherence to DASH diet score and risk of PCOS in newly diagnosed patients in a Middle Eastern country.
Moreover, we considered newly diagnosed PCOS women as the case group to reduce the possibility of a conscious choice of a healthy diet by women with PCOS. Furthermore, a wide range of confounders, especially body composition in addition to energy intake was examined in this study that was not controlled in other similar articles. To reduce the self-reporting error, FFQ was lled out by a blinded trained dietitian to decide whether participants be in a case or a control group.

Conclusion
In conclusion, we found that adherence to a DASH diet had a reduction and protective effect on the chance of getting PCOS in Iranian women. Also, the high adherence to this dietary pattern had an association with increased intake of some vitamin, minerals, and macronutrients which have a great effect on increasing insulin sensitivity and reproductive chances.

Limitations
The current study has some limitations, such as the risk of recall bias that may occur while using the semi-quantitative FFQ. Also, given that the present study is a case-control study and there is no ability to respond to the causality, so prospective studies need to be done.

Declarations
Ethics approval and consent to participate