LAUSR

Specimens were analyzed in the laboratory of the Fertility Clinic following, in part, the recommendations of the 2010 World Health Organization (WHO) criteria for the examination of human semen.8 Specifically, we strictly followed the WHO recommendations concerning sample collection, macroscopic evaluation, and sperm motility. However, we used a low-volume chamber (Makler, Sefi-Medical Instruments Ltd., Haifa, Israel) for determining sperm number. In addition, the patients answered a questionnaire to acquire data on their protein supplement intake and other relevant factors, including potential genetic and work-related factors. The questionnaires were thoroughly examined by the treating physician and, if needed, elaborated during consultation. Moreover, the men were retrospectively called by phone to provide further knowledge about their intake of protein supplementation, i.e., which product was used, the duration of intake (days, months or years), the frequency of intake (number of portions per day or week), and the concentration of protein supplement intake per portion. Finally, all men underwent a physical genital examination. All 20 men agreed to terminate their intake of dietary protein supplements, leading to an abstinence period of 2–16 (median 4.5 [interquartile range 2.0–8.5]) months before follow-up either if pregnant or when starting fertility treatment (Table 1). Following this washout period, a new semen sample was delivered and the sperm concentration and total sperm number were used as primary follow-up values (Table 1). Data were analyzed as two sample paired data based on paired t-test as the assumption of normality (QQ-plot) and variance (Bland–Altman plot) were confirmed after log-transformation of the data. The mean difference on the log-scale was transformed into a median ratio with a 95% confidence interval (CI). Patient number 9 (azoospermic) was excluded from the analysis as data could not be log-transformed. All calculations were made in Stata version 12.1 (Statacorp, Texas, USA). The study was approved by the Ethical Committee of Central Denmark Region. Patients had a mean age of 32.2 (standard deviation [s.d.] = 5.1) years, and mean body mass index (BMI) of 25.8 kg m−2 (s.d. = 9.2) with no relevant change during the follow-up period. Furthermore, Dear Editor, During the last decade, there has been an increase in the usage of dietary protein supplements for bodybuilding, especially among young men who work out in commercial gyms.1 Recently, it was shown that 23 of 24 dietary supplements available in fitness equipment and online shops contained anabolic steroids.2 However, these supposedly pro-androgenic supplements presumably differ from the more commonly used whey and soy protein supplements.3,4 Notwithstanding, both products are listed as dietary supplements rather than medical drugs; thus, they are not rigorously tested,5 do not necessarily list all contents,2 and consequently might contain known and unknown active components.3,6 In fact, it was shown that 14.8% of 634 nonhormonal nutritional supplements contained undeclared anabolic androgenic steroids.7 The impact of dietary protein supplements among young men remains poorly explored concerning their potential adverse effects on reproductive health. Although the present findings should be considered preliminary, we observed that abstinence from protein supplements was associated with improved sperm concentration but had no significant effect on total sperm number in a group of 20 subfertile men. This prospective observational study reports a cohort of 20 men who attended the Fertility Clinic Skive Regional Hospital due to subfertility between 2014 and 2016. The inclusion criteria for the study were (i) infertile men with a sperm concentration below 15×106 ml−1 at the time of enrollment,8 (ii) use of dietary protein supplements for bodybuilding on a regular basis (i.e., above two times per week for >3 months), (iii) nonsmokers, (iv) alcohol intake below the maximum intake of 14 units per week recommended by the Danish Health Authority;9 (v) no use of medication with potential gonadotoxic effect for at least 6 months prior to enrollment, (vi) absence of clinical varicocele. At the initial fertility consultation, patients provided a semen specimen on site after 2–5 days of ejaculatory abstinence. LETTER TO THE EDITOR