In this cross-sectional study, 400, newly diagnosed (<6 months), infertile men, according to clinical diagnosis by an andrologist, participated in this study, between July 2019 and December 2019, from Yazd Reproduction Research Institute. Inclusion criteria included: individuals with age between 20 to 55 years, and abnormal semen parameters, including sperm count less than 15 million per milliliter and/or normal morphology less than 4% and/or semen volume less than 1.5 ml and/or progressive motility less than 40% . Also, exclusion criteria included: chronic diseases, testicular atrophy, ejaculatory disorder, hypospadiasis, stenosis, varicocele, adherence to specific diets, such as weight loss diet, diet for athletes/athletic competition, or any other diets which change the usual dietary intake of individuals, non-response to more than 35 items of food frequency questionnaire, and under-reporting and over-reporting of energy intake (less than 800 and more than 4,200) (Supplemental figure 1). General and dietary information was collected by a trained nutritionist. All participants signed informed consent preceding study commencement.
Physical examination and lifestyle variable
Physical activity data were collected using a validated and reliable questionnaire (International Physical Activity Questionnaire) . The IPAQ provides information about levels of inactivity, moderate activity, strenuous activity, and walking. In addition, we gathered the data regarding frequency (days per week) and duration (minutes per day) for all types of activities.
Socioeconomic status (SES) of the study participants was determined according to variables, such as homeownership (landlord-tenant), washing machine and dishwasher (yes-no), number of overseas trips, has a car (yes-no), individual occupation, and education (number of years of study).
Anthropometric data were measured according to standard methods. The body mass index (BMI) and waist to hip ratio (WHR) were calculated according to the standard protocol of the World Health Organization (WHO), based on minimal clothing and no shoes, using Falcon scales (Seca, Hamburg, Germany), measured to the nearest 0.1kg for weight, and the nearest 0.1 cm for length/height. Hip circumference (HC) was measured at the widest part of the buttocks, and waist circumference (WC) was measured at the midpoint between the last rib and the iliac crest (umbilical level). BMI and WHR were calculated based on the following formula: weight (kg)/height (m2), and WC (cm)/HC (cm), respectively .
Dietary intake was assessed by using a semi-quantitative Food Frequency Questionnaire (FFQ). The validity of this questionnaire has previously been confirmed in Iranian populations . The FFQ included 168 food items, which was designed according to the frequency of consumption of the common foods of one’s country during the preceding 12 months (number of times consumed daily, weekly, monthly, and annually). The FFQ was filled out by a trained dietitian, through remote interviewing. The total meat consumption was defined as red meat, poultry, fresh fish, canned fish, processed meats, and organ meats. Information on alcohol use was not collected for cultural reasons and was therefore not analyzed. The dietary habits of each person were assessed one year prior to infertility diagnosis.
Semen samples were collected following 3 days of abstinence. Before transferring the samples into the container, the temperature of the container was matched to the body temperature of 37 ° C. Semen samples were kept in sterile containers at 37 ° C for 30 minutes, and were then evaluated and analyzed according to the WHO fifth edition laboratory guidelines . Four parameters related to semen and sperm, including semen volume, sperm concentration, normal sperm morphology, and sperm motility were measured.
In the present study, the consumption of different types of meat was divided into four categories (quartiles). Then, the relationship between these four categories with the variables of age, body mass index, education, smoking, physical activity, and the social-economic index was measured by Chi-square and One-way Analysis of Variance (ANOVA) tests. Next, the relationship between meat consumption and semen quality indicators of participants was investigated by using Linear mixed models, adjusted for age, BMI, WHR, physical activity, smoking, and SES status, using pesticides, as well as macro and micro-nutrients intake. A P-Value of less than 0.05 was considered to represent statistical significance. All statistical analyses were performed using SPSS software (version 22, Chicago, IL, USA).