Association between tea consumption and semen quality among 1385 healthy Chinese men (original) (raw)

Introduction

Tea is the most widely consumed beverage in the world next to water (Liu et al., 2016). The global tea planting areas cover approximately 4.89 million hectares, with China's tea planting area accounting for 62.6% of the world (3.06 million hectares) (Li et al., 2021). China has the highest tea production (2.61 million tons), accounting for 45% of the global total (Wu et al., 2020). According to the Report on China's Tea Production and Marketing Situation in 2020 (Chen et al., 2020a), the Chinese population consumed about 2.21 million tons of tea. Tea consumers in China have expanded to 4.24 billion (Chen et al., 2020a). Currently, the lifestyle of drinking tea is no longer predominantly loved by the elderly in China, being more and more favored by the young and middle-aged (Li, 2022). Based on the large consumption of tea in China and worldwide and its potential to promote health (Yi et al., 2019), as well as the negative relationship between tea drinking and the risk of asthenozoospermia (Eslamian et al., 2016), tea drinking was not associated with reduced fecundability (Wesselink et al., 2016), exploring the impact of tea consumption on semen quality may provide clues to address reproductive health issues.

To date, more than 500 kinds of chemical substances have been identified in tea, including tea polyphenols, amino acids, carbohydrates, proteins, chlorophyll, volatile compounds, minerals and other unidentified compounds (Li et al., 2020). Fresh leaf tea is unusually rich in tea polyphenols known as catechins (catechin, epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate), which may constitute up to 30% of the dry leaf weight (Seo et al., 2016). Several biological properties have been reported for tea polyphenols including antioxidant (Khan and Mukhtar, 2018), antimicrobial (Nikoo et al., 2018), anti-atherosclerotic (Yamagata et al., 2015), anti-inflammatory (Huang et al., 2021), anti-angiogenic and anticancer effects (Fassina et al., 2004). A growing body of epidemiological and clinical studies suggests that tea consumption has significant protective effects against cancer (Filippini et al., 2020) and other diseases such as diabetes (Nunes et al., 2014), neurological (Kuriyama et al., 2006) and cardiovascular diseases (Chung et al., 2020). However, there are few studies on the effect of tea consumption on reproductive health, especially male semen quality.

Previous studies have shown that tea polyphenols are generally considered as strong antioxidants, having a protective effect against sperm damage caused by toxic substances and other factors such as alcohol (Rahman et al., 2018). Notably, the unique properties of tea polyphenols may potentially improve reproductive health (Roychoudhury et al., 2017). Pokhrel et al. reported that a healthy lifestyle affects male fertility. For example, regular tea consumption increased sperm concentration, especially drinking tea more than three times a week was found to be superior to drinking it 1–2 times a week (Pokhrel et al., 2019). De Amicis et al. suggested that epigallocatechin gallate (EGCG) significantly improved human sperm motility and viability at low concentrations (2–20 μM) (De Amicis et al., 2012). In addition, tea extract has been used in cryodiluent media to reduce oxidative stress and avoid peroxidation damage, thereby improving in vitro semen quality and preserving fertility potential (Ahmed et al., 2020; Alqawasmeh et al., 2021; Gadani et al., 2017; Kaedei et al., 2012; Wittayarat et al., 2012). Although in vivo and in vitro experiments have investigated tea polyphenols as potentially improving semen quality, there are a lack of well-designed epidemiological studies to confirm the association between tea consumption and semen quality. Taken together, the current evidence on the association between tea drinking and semen quality is limited and inconclusive, and further studies are needed. In this study, we conducted a large observational study to evaluate the association between tea consumption and semen quality parameters, using a large-scale, repeated measure design.

Section snippets

Study population

The study participants were men providing semen samples to the Hubei Province Human Sperm Bank; the detailed information is the same as our previous reports (Chen et al., 2020b, c; Ma et al., 2019; Sun et al., 2019). The inclusion criteria were as follows: (1) Chinese nationality; (2) voluntary donation activity; (3) aged between 22 and 45 years; (4) without systemic disease and severe organic diseases (such as heart disease, diabetes, tuberculosis, liver diseases, blood system diseases, high

Ethical approval

This study was approved by the Ethics Committee of the Reproductive Medicine Centre, Tongji Medical College, Wuhan, China. All donors were fully aware of the donation process and provided signed informed consent before participation.

Basic characteristics

A total of 1385 participants with 6466 sperm donation samples were included in the research, of which 389 were tea drinkers. The tea drinker had a mean (SD) age of 29.2 years (6.0 years), body mass index of 23.4 kg/m2 (3.1 kg/m2) and abdominal circumference of 81.5 cm (8.3 cm), which was higher than that of non-tea drinkers (P < 0.001). Overall, 23.4% of tea drinkers earned an income of no less than 4000 CYN, while 55.0% of tea drinkers were smokers and 56.0% were occasional alcohol users. Some

Discussion

In this study, we explored the relationship between tea consumption and semen quality. Based on mixed-effects models with repeated measures of semen quality, we found that when the duration of tea drinking was 10 years or longer, it was significantly associated with higher sperm concentrations. When stratified for BMI, sperm concentration was significantly increased in men with low BMI or in the normal range, but not in men with a high BMI. In addition, when the frequency of tea drinking was 3

Conclusion

In conclusion, our findings suggest that maintaining a habit of tea drinking may improve semen quality parameters, especially in men with smoking, alcohol intake habits or abnormal weight. This study provides valuable clues for future research, and the protective mechanism of tea drinking on male fertility in humans requires further study.

Authors contributions statement

Xia ren Liu: Writing - original draft, Writing - review & editing. Xue lin Wang: Writing - original draft, Writing - review & editing, data analysis and interpretation. Jun Zhao: data analysis and interpretation, administrative, technical, or material support, Writing - review & editing. Chun hui Hu: Funding acquisition, Writing - review & editing. Nan nan Cao: Writing - review & editing. Heng-gui Chen, Bin Sun & Cheng-Liang Xiong: Acquisition, Investigation, Resources, Supervision. Yi-Xin Wang

Funding/support

This work was supported by research grants from the National Natural Science Foundation of China (81,901,567, 81,903,281), the Natural Science Foundation of Hubei Provincial Department of Education (Q20202105), the Scientific and Technological Project of Xiangyang City of Hubei Province (2020ZD16, 2021YL25 and 2021YL29), the Innovative Research Programme of Xiangyang No.1 People's Hospital (XYY 2021S02, XYY 2021M02), and the Innovative Research Program for Graduates of Hubei University of

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The paper has not been published previously.

Acknowledgements

We thank all the funding support. The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. We thank all of the participants for their willingness to participate in the study and the time that they devoted to the study.