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International Electronic Journal of Medicine (IEJM)
June 2014, Volume 3, Issue 1, Pages: 3-11
ISSN: 2251-8304
Original Article The Effect of High Fiber Diet on Sex Hormones in Early
Pubertal Obese Girls; a Randomized Crossover Clinical

Zeinab Piraloo 1, Sedighe Forouhari 2, Seyede Zahra Ghaemi 3, Parisa Rostambeigy 4, Zahra Mohammadi 5,6, Seyed Shojaeddin Namazi 7, Mostafa Mohammadi 8, Moosa Salehi 9 ,Azam Jokar 10, Najaf Zare 11, Sareh Roosta 1 Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran Infertility Research Center, Community Based Psychiatric Care Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Department of Midwifery, Estahban Branch, Islamic Azad University, Estahban, Iran Department of Nursing, Estahban Branch, Islamic Azad University, Estahban, Iran Shahid Beheshti University of Medical Sciences, Tehran, Iran Infertility Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Student Research Committee, Hormozgan University of Medical Sciences, Bandar Abbas, Iran Yasuj University of Medical Sciences, Yasuj, Iran Nutritional Science Center, School of Nutrition and Food , Shiraz University of Medical Sciences, Shiraz, Iran 10. Community Based Psychiatric Care Research Center, College of Nursing & Midwifery Hazrat Fatemeh(PBUH), Shiraz University of Medical Sciences, Shiraz, Iran 11. Infertility research center, Department of Biostatistics, Shiraz University of Medical Sciences, Shiraz, Iran
Please cite this paper as: Piraloo Z, Forouhari S, Ghaemi SZ, Rostam Beigy P, Mohammadi Z, Zolghadr J,
et al. The Effect of High Fiber Diet on Sex Hormones in Early Pubertal Obese Girls; a Randomized
Crossover Clinical Trial. Int Elec J Med. 2013;2(4):35-45.

Corresponding author:
Sedighe Forouhari, Infertility Research Center, Community Based Psychiatric
Care Research Center, Shiraz
University of Medical Sciences, Shiraz, Iran,
The aim of the present study was to investigate the effectiveness of high-fiber diet on
sexual hormones in obese and overweight female adolescents.
Methods: This randomized crossover clinical trial was conducted among 56 obese or overweight girls in
Shiraz, Iran. All subjects were randomly divided into two groups. A list containing high (25 g/day green
leafy vegetables or fresh fruits) and low fiber diets were prepared for case and control groups,
respectively. Each group consumed their special diet for two months. After a month of cleanup period,
the intended diet was replaced between the two groups. Blood sample of participants were taken in
third to fifth day of the spontaneous menstrual cycle. After the end of each step, the serum levels of
SHBG, DHEA, estradiol and testosterone were measured. Data was analyzed by SPSS (V.19) using paired

International Electronic Journal of Medicine (IEJM)
June 2014, Volume 3, Issue 1, Pages: 3-11
ISSN: 2251-8304
sample t-test and independent t-test. Significant level was considered below 0.05 IRCT ID; 2012120811699N1. Results: The results showed that high-fiber diet significantly reduced the serum levels of testosterone,
estradiol, and DHEA compared to low fiber diet (P = 0.0001). Nevertheless, the changes of SHBG level
were not significant between the two diets (P > 0.05).
Conclusions: This study demonstrated that the use of high-fiber diet can decrease the sex hormones in
adolescent girls. Consuming a high fiber diet is recommended for obese and overweight patients.
Keywords: Vegetables, Fruit, Obesity, Overweight, Gonadal Steroid Hormones, Female.


Overweight or obesity has led to increased prevalence of numerous diseases and disorders such as
coronary and cerebrovascular diseases, type 2 diabetes mellitus, hypertension, osteoarthritis, gout,
asthma and dementia (1).
Obesity is also associated with increased risk of different types of cancers such as endometrial cancer
and breast cancer in postmenopausal women. Hormonal imbalance, including sex hormones and insulin
can lead to obesity and raise the risk of various cancers (2).
There is strong evidence that puberty is also the leading cause of ovarian dysfunction. As well as, many
investigators have demonstrated that obesity can lead to a variety of hormonal disorders such as
hyperandrogenism (3).
Additionally, several studies have indicated that obesity has direct interaction with hormonal imbalance.
Obesity can affect the fertility potential of women. Two different mechanisms has been reported for this
effect; the first is increased androgen-estrogen conversion and the second is direct effect of obesity on
estrogen circulation in human body (3, 4).
However, evidence regarding the role of diet on serum level of estrogen and androgens are inconsistent
(4, 5). Few studies have shown that high fiber diet such as beans, vegetables, fruits and whole grains
may be useful for treatment of metabolic, hormonal and lipid abnormalities (6). This study aimed to
investigate the influence of high-fiber diet on the sex hormones in obese and overweight girls.

This randomized cross over clinical trial was conducted in Shiraz University of Medical Sciences (SUMS).
The study population consisted of all early adolescent obese girls who lived in Shiraz city from April 2012
to September 2012.

International Electronic Journal of Medicine (IEJM)
June 2014, Volume 3, Issue 1, Pages: 3-11
ISSN: 2251-8304
A number of 56 early adolescent girls (between 15-19 years old) with body mass index (BMI) of over 25 kg/m2 were randomly selected and assigned into two groups. The research project protocol and the advantages and limitations of the diet described for all participants. All subjects provided informed consent, and the Study was approved by ethic committee of SUMS and registered in Iranian Clinical Trial Registry (IRCT ID; 2012120811699N1). Exclusion criteria consisted of any medical disease including PCOS, hyperthyroidism, hypothyroidism, adrenal hyperplasia, known renal and hepatic failure, irregular menstruation, use of oral corticosteroids and tetracycline, consumption of minerals and vitamins supplements, suspected or documented pregnancy, gastrointestinal disorders, vegetarian diet or a diet containing high levels of phytoestrogens. However, they could use low amounts of acetaminophen or aspirin. All participants started their diets 3 days before the first day of study. After 12 h fasting, participants' weight was measured with minimal clothing, and the standing height was measured without shoes. All subjects were asked to consume diets containing a mixture of 55% carbohydrates, 15% protein and 30% fat. For the case group, a list of high-fiber diet was prepared (including lettuce, cabbage, fresh fruits and other green leafy vegetables). Case subjects were asked to consume at least one meal per day from these high-fiber foods (equaling 25 g/day). Participants of the control group were asked not to consume the intended list of foods that contain high amounts of fiber. In the first step of study, the group A considered as experimental group and group B as control group. The diet selected for each group was asked to be used for two months. Afterwards, for a month, both groups were advised to use their usual diets (clean phase). In the second step of the study, the diet was replaced between the two groups for two months again. During the study, participants were asked not to alter their common diets and do not use of hormonal drugs such as oral contraceptives. At the end of each step (before study, after the first two months, after the clean phase and after the second two months) 10 ml of blood was taken from peripheral veins of the participants within the third to fifth days of the spontaneous menstrual cycle and the serum levels of sex hormone-binding globulin (SHBG), dehydroepiandrosterone (DHEA), estradiol and testosterone were measured. Serum and plasma were separated by centrifugation for 15 minutes at 1,465 × g (3,200 rpm) and 4° C, and stored at −80°C for further analysis. Serum levels of testosterone, estradiol and DHEA were determined by radioimmunoassay using commercial reagents (Aria Farmed Company). SHBG was

International Electronic Journal of Medicine (IEJM)
June 2014, Volume 3, Issue 1, Pages: 3-11
ISSN: 2251-8304
measured by electroimmunoassay electrophoresis (Aria Farmed Company). Analytical sensitivity for the factors assays were: testosterone 2.5 ng/dl, estradiol 0.6 ng/dl, DHEA 6 µg/dl and SHBG 0.02 IU/l. The analyses were performed using SPSS software version 19 and NCSS software version 11. Descriptive statistics such as mean and standard deviation were used. Paired T-test and Independent T-test were employed for continues and quantitative variables between groups. The P-value less than 0.05 were considered significant. Results:
The mean age of participants was 16.97 ± 1.05. The age, BMI, testosterone, DHEA, SHBG and estradiol of
the participants of both groups did not have significant differences before the intervention (P> 0.05).
The basic characteristics of the subjects are listed in Table 1.
Table 1: Comparison of the basic characteristics of participants Estradiol (pg/ml) Testosterone (ng/ml) *NS: not significant
The difference of DHEA, estradiol and testosterone levels were significant (P<0.05), but the changes of
SHBG levels were not statistically significant. (P =0.86). (Table 2).
The results showed that mean reduction in group B patients were lower than group A subjects. The
mean reduction of DHEA, estradiol and testosterone after the first step (Group A) were 17 ng/ml
(8.99%), 20 pg/ml (19.96%) and 0.15 ng/ml (25%) and after the second step (Group B) were 42 ng/ml
(23.59%), 32 pg/ml (30.47%) and 0.18 ng/ml (28/12 %), respectively.

International Electronic Journal of Medicine (IEJM)
June 2014, Volume 3, Issue 1, Pages: 3-11
ISSN: 2251-8304
Table 2: Comparison of the levels of DHEA, Estradiol, SHBG and Testosterone (Mean ± S.D) in the various steps of the study 172.14 ± 41.64 195.32 ± 40.91 174.57 ± 41.73 178.11 ± 38.84 102.48 ± 25.35 105.83 ± 27.09
*NS: not significant

To the best of our knowledge this study was the first randomized cross over clinical trial that assessed
the effectiveness of high fiber diets on decreasing serum levels of sex hormones in early pubertal obese
girls. Evidence have demonstrated that high fiber diets and starch-rich foods lead to slow motility of
gastrointestinal tract and even delay absorption and digestion (4).
The results of cross-sectional study by Dorgan et al. indicated that energy intake in premenopausal
women was inversely associated with plasma concentrations of androstenedione and DHEAS averaged
across the three menstrual cycles (7).
In the similar study conducted among 286 pre-pubertal girls in which dietary fat reduced from 33% to
27% of energy per day for 7 years, the authors have concluded that by year 5, the serum levels of
estrone, estrone sulfate, and E2 (estradiol) of studied population were 21–30% lower than general
population with normal diets. This differences were statistically significant (8).

International Electronic Journal of Medicine (IEJM)
June 2014, Volume 3, Issue 1, Pages: 3-11
ISSN: 2251-8304
Another study by Rose et al (9) concluded that 30 g/d consumption of high fiber supplementations for 2 months showed significant reductions in serum estrone and estrad iol. The acceptable cause for this reduction may be the effect of high fiber supplementations on the enterohepatic circulation of esterone. They also concluded that high fiber intake is related to decrease breast cancer and attributed to reduced serum estrogen concentration which is seen in these patients. Woods et al. showed that after 21st, day dietary modification with lower fat (20%) and higher fiber (40 g/d) can result in a lowering of serum estrogens. Also, the values of serum estrogens reducing were significantly lower in non-Hispanic white than African American women (10). In the study on 213 healthy, premenopausal women aged 20–40 years were consumed a low-fat (20%), high-fiber diet (25–30 g/d) and daily servings of fruits and vegetables for 1 year. the participants serum E2 and free E2 levels were 7–8% lower than the control group (11). Several studies conducted by Katcher et al. (12), Mehrabani et al. (13) and Goldin et al. (14) showed that high fiber diet could decrease testosterone levels in women. These findings are in consistent with the results of the present study. Also, the results of our study demonstrated that serum level of SHBG was not statistically different when high fiber diets are employed compared with normal diet. This finding which was consistent with other reports of several studies (4, 9, 12, 15). Nevertheless, some studies revealed that high fiber diets had significant reduction in serum concentrations of SHBG (14). On the other hand, studies have reported that the serum level of SHBG has inverse relationship with weigh and protein intake (12). There is evidence that dietary factors including fructose, glucose, sucrose, and insulin affect SHBG expression and secretion (16, 17). The increased in SHBG levels with consumption of hypocaloric diet has been reported after a long-term period (2–7 months) (18, 19). The lack of change in SHBG after a eucaloric diet suggests that manipulating diet composition during short-term observation may not be enough to dramatically alter SHBG serum levels (12). After more than 20 years of intervention, evidence showed that low-fat and high-fiber diets affect serum levels of E2, testosterone, SHBG, DHEA and free E2 levels among girls, premenopausal women, and postmenopausal women. However, results were not usually statistically significant, and specific hormonal changes, did not remain over time. These differences could be due to several factors including using different types and amounts of high fiber diets (4, 10, 20), racial differences (10), measuring the sex hormones during the various phases of menstrual cycle (9, 21-23), participants age (8, 9, 14), duration and population size of the study (8, 12).

International Electronic Journal of Medicine (IEJM)
June 2014, Volume 3, Issue 1, Pages: 3-11
ISSN: 2251-8304
A limitation of the present study is that it is not possible to determine what specific dietary component affects hormones and SHGB levels. Despite limitations, our results indicated that meal composition affects postprandial DHEA, estradiol and testosterone levels in early pubertal obese girls. Since puberty is important period in life and affected other life periods, the relationship between diet and sex hormones in adolescents with obesity in a few studies has been investigated. We concluded that 30 g of green leafy vegetables, starch reach foods and fresh fruits can significantly decrease the sex hormones in obese and overweight patients. Based on our results and previous studies, consumption of high fiber diet is recommended at least once a day in order to prevent and decrease the prevalence of diseases which are related to low fiber intake. This matter is more important for western populations in which the subjects prefer high protein and high fat diet than high fiber dietary and face more with several cancers compared with Asian peoples (15, 24-27). In this study, we evaluated the relationship between high fiber diet and sex hormone changes and we hope this study help further projects to provide new information on the relationship between sex hormones, diet and obesity in adolescents. Acknowledgements: The present article was extracted from the thesis written by Ms. Zeinab Piraloo
MSc and was financially supported by Shiraz University of Medical Sciences. The Code of Ethics CT-91-
6315 from the vice chancellor for research affair of Shiraz University of Medical Sciences.

Conflicts of Interest: The authors of this article declare that they have no conflicts of interest.

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June 2014, Volume 3, Issue 1, Pages: 3-11
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