Role of Zinc (Zn) in Human Reproduction: A Journey from Initial Spermatogenesis to Childbirth.

Zinc (Zn), the second-most necessary trace element, is abundant in the human body. The human body lacks the capacity to store Zn; hence, the dietary intake of Zn is essential for various functions and metabolism. The uptake of Zn during its transport through the body is important for proper development of the three major accessory sex glands: the testis, epididymis, and prostate. It plays key roles in the initial stages of germ cell development and spermatogenesis, sperm cell development and maturation, ejaculation, liquefaction, the binding of spermatozoa and prostasomes, capacitation, and fertilization. The prostate releases more Zn into the seminal plasma during ejaculation, and it plays a significant role in sperm release and motility. During the maternal, labor, perinatal, and neonatal periods, the part of Zn is vital. The average dietary intake of Zn is in the range of 8-12 mg/day in developing countries during the maternal period. Globally, the dietary intake of Zn varies for pregnant and lactating mothers, but the average Zn intake is in the range of 9.6-11.2 mg/day. The absence of Zn and the consequences of this have been discussed using critical evidence. The events and functions of Zn related to successful fertilization have been summarized in detail. Briefly, our current review emphasizes the role of Zn at each stage of human reproduction, from the spermatogenesis process to childbirth. The role of Zn and its supplementation in in vitro fertilization (IVF) opens opportunities for future studies on reproductive biology.

Adherence to diet quality indices in relation to semen quality and reproductive hormones in young men.

STUDY QUESTION: Is adherence to an a priori defined diet quality indices [Alternate Healthy Index 2010 (AHEI-2010), relative Mediterranean diet score (rMED) or dietary approaches to stop hypertension (DASH)] associated with semen quality and reproductive hormone levels in young men? SUMMARY ANSWER: Greater adherence to the DASH diet is related to higher sperm counts. WHAT IS KNOWN ALREADY: Studies assessing the relationship between dietary intake and male reproductive function have mainly been focused on specific nutrients, food groups or data-driven dietary patterns, but the evidence on a priori defined dietary indices is still scarce. STUDY DESIGN, SIZE, DURATION: Cross-sectional study of 209 male university students recruited from October 2010 to November 2011 in Murcia Region (Southern Spain). PARTICIPANTS/MATERIALS, SETTING, METHODS: Healthy young men aged 18-23 years were included in this study. Diet was assessed using a validated food frequency questionnaire and three a priori-defined dietary indices (AHEI-2010, rMED and DASH) were calculated. Linear regression was used to analyze the relation between the three dietary indices and semen quality parameters and reproductive hormone levels accounting for potential confounders and covariates. MAIN RESULTS AND THE ROLE OF CHANCE: We found statistically significant positive associations between the DASH index and sperm concentration (P, trend = 0.04), total sperm count (P, trend = 0.04) and total motile sperm count (P, trend = 0.02). No associations were observed for other semen parameters or male reproductive hormones. LIMITATIONS, REASONS FOR CAUTION: Even though we adjusted for several known and suspected confounders we cannot exclude the possibility of residual or unmeasured confounding or chance findings. Subjects were blinded to the study outcomes thus reducing the potential influence on their report of diet. Our sample size may be too small to rule out associations with other semen parameters or reproductive hormones. Causal inference is limited, as usual with all observational studies. WIDER IMPLICATIONS OF THE FINDINGS: The results suggest that greater adherence to the DASH may help improve sperm counts. This study was carried out on young men from the general population. However, results may differ among other populations (e.g. infertile men). Therefore, further research is needed to confirm these findings and extend these results to other populations. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by Fundación Séneca, grants No 08808/PI/08 and No 19443/PI/14; Ministerio de Ciencia e Innovación, Instituto de Salud Carlos III (AES), grants No PI10/00985 and No PI13/01237; and grant P30DK046200 from the National Institutes of Health. Authors have no competing interests to declare.

Do Popular Diets Impact Fertility?

Infertility affects 15% of the population in developed countries, and its prevalence is increasing. Fertility can be influenced by different factors. Although key factors like maternal age cannot be changed, there is growing evidence that other modifiable factors, such as diet, can have an impact on fertility. Diet has become increasingly important in recent years for a number of reasons: the new trend toward a healthy lifestyle, the higher prevalence of certain digestive disorders, a lack of time that leads people to consume more prepared and processed food, and personal choice to not eat meat, among others. To meet these needs, several diets have recently become popular, such as the Mediterranean diet, known as the gold standard of health; the DASH diet, known for preventing hypertension; the Western diet, characterized by processed food; the ketogenic diet, characterized by low carbohydrate intake; and the vegetarian diet, which is the choice for people who do not eat meat or animal by-products. Diets present a unique composition characterized by the presence or absence of specific nutrients, which have also been associated with male and female fertility individually. This review assesses the impact of these diets and of macro- and micronutrients on both female and male fertility.

Comparing the effectiveness of infertility treatments by numbers needed to treat (NNT).

To compare the clinical efficiency of different modes of treatment of infertile couples and to estimate the possible benefit of nutraceutical food supplementation (NFS), the numbers needed to treat (NNT) was calculated in 4143 infertile couples based on controlled trials in recent literature and personal data. The NNT expresses the number of individuals who need to be treated to obtain one complementary pregnancy. In female infertility, the NNT of mild or moderate endometriosis was 8.4, and in anti-estrogens treatment of anovulation, it was 5.9. In tamoxifen treatment of idiopathic oligozoospermia, NNT was 3.9, and in antioxidant supplementation, it was 7.8. Treatment of varicocele yielded NNT of 6.3 and 6.8 after 1 year in multi- or single-centre trials, respectively, and NFS lowered the NNT after 3 months to 2.6. Adding NFS to the male partner increased the ongoing pregnancy rate by IVF with NNT of 8.3, and adding NFS to both partners reduced the NNT to 4.0. Although these results were obtained in heterogeneous trials and populations, it is suggested that the NNT should be useful for comparing the effectiveness of different modes of treatment of the infertile couple, and that complementary nutraceutical food supplementation may be beneficial.

Alleviation of Fertility Disorders Based on Probiotics Induced Immune System Improvement: A Review.

Infertility is a worldwide problem affecting a large percentage of the population. Several products and techniques have been adopted to alleviate infertility condition, but the most recent and promising result was obtained through supplementation of probiotics. Continuous research on probiotics opened up a previously unknown area of its role as a modern medicine in improving fertility. New research findings suggest a profertility effect of several probiotics strains through alleviation of various fertility based disorders and modulation of the immune system. The goal of this review is to cover all the major fertility based disorders, particularly highlighting the role of probiotics in improving fertility through alleviation of such fertility based disorders.

Application of dietetics in reproductive medicine.

In the light of up-to-date epidemiological data concerning the prevalence of infertility, and also considering the scale of the problem of obesity and proven cause-effect relationship between abnormal body weight and infertility, it is justifiable to undertake the task of systematization of the state of knowledge concerning nutritional correlates of infertility, in order to create a scientific basis for the formulation of the assumptions of a fertility diet. The study is an attempt to systematize the current state of knowledge concerning the importance of energy and structural (qualitative) aspects of nutrition in the prevention and treatment of infertility.

The preconception Mediterranean dietary pattern in couples undergoing in vitro fertilization/intracytoplasmic sperm injection treatment increases the chance of pregnancy.

OBJECTIVE: To investigate associations between preconception dietary patterns and IVF/intracytoplasmic sperm injection (ICSI) outcomes validated by biomarkers of the homocysteine pathway. DESIGN: Observational prospective study. SETTING: A tertiary referral fertility clinic at the Erasmus University Medical Centre, Rotterdam, The Netherlands. PATIENT(S): One hundred sixty-one couples undergoing IVF/ICSI treatment. INTERVENTION(S): No interventions other than the Dutch governmental recommendation of folic acid. MAIN OUTCOME MEASURE(S): Dietary patterns, blood and follicular fluid concentrations of folate, vitamin B12, vitamin B6, homocysteine, and fertilization rate, embryo quality, and pregnancy. RESULT(S): In women, two dietary patterns were identified. The "health conscious-low processed" dietary pattern (variation explained 12.1%) was characterized by high intakes of fruits, vegetables, fish, and whole grains and low intakes of snacks, meats, and mayonnaise, and positively correlated with red blood cell folate (ß=0.07). The "Mediterranean" dietary pattern (variation explained 9.1%), that is, high intakes of vegetable oils, vegetables, fish, and legumes and low intakes of snacks, was positively correlated with red blood cell folate (ß=0.13), and vitamin B6 in blood (ß=0.09) and follicular fluid (ß=0.18). High adherence by the couple to the "Mediterranean" diet increased the probability of pregnancy, odds ratio 1.4 (95% confidence interval 1.0-1.9). CONCLUSION(S): A preconception "Mediterranean" diet by couples undergoing IVF/ICSI treatment contributes to the success of achieving pregnancy.