Dairy Product Consumption and Oligo-Astheno-Teratozoospermia Risk: A Hospital-Based Case-Control Study in China

How Food Choices Impact on Male Fertility

PURPOSE OF REVIEW

Increasing evidence on the significance of nutrition in reproduction is emerging from both animal and human studies, suggesting an association between nutrition and male fertility. Here, we have highlighted the impact of the various food groups on reproductive hormones and on spermatogenesis, and the effects of classical and latest dietary patterns such as Mediterranean diet, Western diet, intermittent fasting, ketogenic diet, and vegan/vegetarian diet on male fertility.

RECENT FINDINGS

Nutrients are the precursors of molecules involved in various body's reactions; therefore, their balance is essential to ensure the correct regulation of different systems including the endocrine system. Hormones are strongly influenced by the nutritional status of the individual, and their alteration can lead to dysfunctions or diseases like infertility. In addition, nutrients affect sperm production and spermatogenesis, controlling sexual development, and maintaining secondary sexual characteristics and behaviors. The consumption of fruit, vegetables, fish, processed meats, dairy products, sugars, alcohol, and caffeine importantly impact on male fertility. Among dietary patterns, the Mediterranean diet and the Western diet are most strongly associated with the quality of semen. Nutrients, dietary patterns, and hormonal levels have an impact on male infertility. Therefore, understanding how these factors interact with each other is important for strategies to improve male fertility.

Dietary fat and fatty acid consumptions and the odds of asthenozoospermia: a case-control study in China

STUDY QUESTION

Are dietary fat and fatty acid (FA) intakes related to the odds of asthenozoospermia?

SUMMARY ANSWER

Plant-based fat consumption was associated with decreased asthenozoospermia odds, while the consumption of animal-based monounsaturated fatty acid (MUFA) was positively related to asthenozoospermia odds.

WHAT IS KNOWN ALREADY

Dietary fat and FA are significant ingredients of a daily diet, which have been demonstrated to be correlated to the reproductive health of men. However, to date, evidence on fat and FA associations with the odds of asthenozoospermia is unclear.

STUDY DESIGN SIZE DURATION

The hospital-based case-control study was performed in an infertility clinic from June 2020 to December 2020. Briefly, 549 asthenozoospermia cases and 581 controls with normozoospermia were available for final analyses.

PARTICIPANTS/MATERIALS SETTING METHODS

We collected dietary data through a verified food frequency questionnaire of 110 food items. Asthenozoospermia cases were ascertained according to the World Health Organization guidelines. To investigate the correlations of dietary fat and FA consumptions with the odds of asthenozoospermia, we calculated the odds ratios (ORs) and corresponding 95% CIs through unconditional logistic regression models.

MAIN RESULTS AND THE ROLE OF CHANCE

Relative to the lowest tertile of consumption, the highest tertile of plant-based fat intake was inversely correlated to the odds of asthenozoospermia (OR = 0.68, 95% CI = 0.50-0.91), with a significant dose-response relation (OR = 0.85, 95% CI = 0.75-0.97, per standard deviation increment). Inversely, animal-based MUFA intake (OR = 1.49, 95% CI = 1.04-2.14) was significantly correlated to increased odds of asthenozoospermia, and an evident dose-response relation was also detected (OR = 1.24, 95% CI = 1.05-1.45, per standard deviation increment). Subgroup analyses showed similar patterns of associations to those of the primary results. Moreover, we observed significant interactions on both multiplicative and additive scales between animal-based MUFA and cigarette smoking.

LIMITATIONS REASONS FOR CAUTION

Selection bias and recall bias were unavoidable in any of the observational studies. As we failed to obtain the information of trans-fatty acid (TFA) consumption, the relation of TFA intake and asthenozoospermia odds was unclear.

WIDER IMPLICATIONS OF THE FINDINGS

This study indicated that different sources of fat and FAs might exert different effects on the etiology of asthenozoospermia, and cigarette smoking could exacerbate the adverse effect of high animal-based MUFA intake on asthenozoospermia. Our findings provide novel evidence pertaining to the fields of prevention of asthenozoospermia through decreasing animal-derived fat and FA consumptions and smoking cessation.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the JieBangGuaShuai Project of Liaoning Province, Natural Science Foundation of Liaoning Province, Clinical Research Cultivation Project of Shengjing Hospital, and Outstanding Scientific Fund of Shengjing Hospital. All authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Phytochemical consumption and the risk of teratozoospermia: findings from a hospital-based case-control study in China

STUDY QUESTION

Are dietary phytochemicals associated with the risk of teratozoospermia?

SUMMARY ANSWER

Dietary intake of carotene, including total carotene, α-carotene, β-carotene as well as retinol equivalent, and lutein + zeaxanthin, were inversely correlated with the risk of teratozoospermia.

WHAT IS KNOWN ALREADY

Phytochemicals are natural plant derived bioactive compounds, which have been reported to be potentially associated with male reproductive health. To date, no study has investigated the association between phytochemical intake and the risk of teratozoospermia.

STUDY DESIGN SIZE DURATION

This hospital-based case-control study, which included 146 newly diagnosed teratozoospermia cases and 581 controls with normozoospermia from infertile couples, was conducted in a hospital-based infertility clinic in China, from June 2020 to December 2020.

PARTICIPANTS/MATERIALS SETTING METHODS

Dietary information was collected using a validated semi-quantitative 110-item food frequency questionnaire. Unconditional logistic regression was applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between phytochemical (i.e. phytosterol, carotene, flavonoid, isoflavone, anthocyanidin, lutein + zeaxanthin, and resveratrol) intake and the risk of teratozoospermia.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed a decreased risk of teratozoospermia for the highest compared with the lowest tertile consumption of total carotene (OR = 0.40, 95% CI = 0.21-0.77), α-carotene (OR = 0.53, 95% CI = 0.30-0.93), β-carotene (OR = 0.47, 95% CI = 0.25-0.88), retinol equivalent (OR = 0.47, 95% CI = 0.24-0.90), and lutein + zeaxanthin (OR = 0.35, 95% CI = 0.19-0.66), with all of the associations showing evident linear trends (all P trend <0.05). In addition, significant dose-response associations were observed between campestanol and α-carotene consumption and the risk of teratozoospermia. Moreover, there was a significant multiplicative interaction between BMI and lutein + zeaxanthin intake (P interaction <0.05).

LIMITATIONS REASONS FOR CAUTION

The cases and controls were not a random sample of the entire target population, which could lead to admission rate bias. Nevertheless, the controls were enrolled from the same infertility clinic, which could reduce the bias caused by selection and increase the comparability. Furthermore, our study only included a Chinese population, therefore caution is required regarding generalization of our findings to other populations.

WIDER IMPLICATIONS OF THE FINDINGS

Dietary phytochemicals, namely carotene, lutein, and zeaxanthin, might exert a positive effect on teratozoospermia. These phytochemicals are common in the daily diet and dietary supplements, and thus may provide a preventive intervention for teratozoospermia.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by Natural Science Foundation of Liaoning Province (No. 2022-MS-219 to X.B.W.), Outstanding Scientific Fund of Shengjing Hospital (No. M1150 to Q.J.W.), Clinical Research Cultivation Project of Shengjing Hospital (No. M0071 to B.C.P.), and JieBangGuaShuai Project of Liaoning Province (No. 2021JH1/1040050 to Y.H.Z.). All authors declared that there was no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Intake of ultra-processed foods and asthenozoospermia odds: A hospital-based case-control study

Background

The intake of ultra-processed foods (UPFs) has increased rapidly in recent years. Evidence has suggested that UPFs has adverse effects on several health outcomes. This study aimed to first evaluate the association between the intake of UPFs and asthenozoospermia odds.

Methods

A hospital-based case-control study including 549 cases and 581 controls was performed in the infertility clinics of Shengjing Hospital of China Medical University from June 2020 to December 2020. Dietary intake was assessed using a validated food frequency questionnaire. Food items were categorized by the NOVA classification system based on the degree of processing. Semen parameters were analyzed according to the World Health Organization guidelines.

Results

The highest tertile of UPFs intake (% of total energy intake) was positively associated with the odds of asthenozoospermia (odds ratio [OR] = 1.53; 95% confidence interval [CI]: 1.12, 2.10; P for trend < 0.05), compared with the lowest tertile. Similar patterns were also found in subgroup analyses among participants with age ≥32 years (OR = 1.58; 95% CI: 1.04, 2.40), BMI ≥ 24 kg/m² (OR = 1.52; 95% CI: 1.04, 2.22), ever cigarette smoking (OR = 1.78; 95% CI: 1.14, 2.79), and ever alcohol drinking (OR = 1.65; 95% CI: 1.01, 2.72), and in sensitivity analyses by using absolute amount (g/day) to calculate the intake of UPFs.

Conclusion

Higher consumption of UPFs was positively associated with the odds of asthenozoospermia. More studies are needed to confirm our findings.

Associations between Meat and Vegetable Intake, Cooking Methods, and Asthenozoospermia: A Hospital-Based Case–Control Study in China

Background: The role of meat and vegetable intake in the development of asthenozoospermia has been controversial, and the role of cooking methods for meat and vegetables in the association has yet to be determined. The present study aimed to illuminate the relationship between the consumption and cooking methods of meat and vegetables and the risk of asthenozoospermia. Methods: In this hospital-based case–control study, we enrolled 552 patients with asthenozoospermia and 585 healthy controls. Dietary information was assessed using a validated self-administered food frequency questionnaire. Asthenozoospermia was diagnosed according to the fifth edition of the WHO laboratory manual for the examination and processing of human semen. Results: Participants in the highest tertile of total meat and unprocessed meat intake had a 44% and 39% lower risk of asthenozoospermia than those in the lowest tertile (OR = 0.56, 95% CI: 0.37, 0.87 and OR = 0.61, 95% CI: 0.40, 0.93), respectively. Participants with the highest processed meat consumption showed higher risk (OR = 1.44, 95% CI: 1.01, 2.06). Raw vegetable consumption was negatively associated with the risk of asthenozoospermia (OR = 0.67, 95% CI: 0.45, 0.98). The stir-frying cooking method for meat was associated with increased risk of asthenozoospermia (OR = 1.58, 95% CI: 1.02, 2.46). Conclusions: Intake of total meat, unprocessed meat, and raw vegetable may reduce asthenozoospermia risk, while higher consumption of processed meat may increase the risk. Cooking methods may play a role in these associations. These findings need to be confirmed in large and prospective cohort studies.