According to the WHO estimation, fertility problems have become an increasing medical problem affecting ~60–80 million couples, and male factors account for almost 50% of cases (1). As one of the principal types, asthenoteratozoospermia is defined as low sperm vitality or even malformation (2). In addition to genetic factors, environmental factors, lifestyle habits, and dietary factors may be relevant to sperm quality (3). Epidemiological studies have reported that sweetened beverages, red meat, and organ meat consumption are negative and that fish, egg, nut, and low-fat dairy consumption are positively correlated with sperm quality (4–7).

In reality, however, individuals eat combinations of food as meals instead of a single food, which makes it difficult to distinguish their individual effects (8). To overcome this challenge, dietary patterns were used to assess the effect of overall diet on sperm quality. A meta-analysis reported that individuals with the highest adherence to the healthy dietary pattern (highly related to fruit, vegetables, tomatoes, whole grain, legumes, and fish) had a significantly higher level of sperm concentration than those who had the lowest adherence to the healthy dietary pattern (9). Given that these dietary patterns (data-driven) do not apply to another population, the diet quality scores (priori-defined) are easier to calculate and compare across studies (10).

Dietary inflammatory index (DII) scores, as one of a priori-defined score, have been reported to not be associated with asthenozoospermia risk in our previous study (11). Other priori-defined diet scores have been reported to associate with overall sperm quality, such as the Healthy Eating Index-2005 (HEI-2005), the Alternate Healthy Eating Index-2010 (AHEI-2010), and dietary approaches to stop hypertension (DASH) (1, 12, 13). Studies have shown that HEI, AHEI, and DASH diet scores were associated with better overall sperm quality in Israel (1), and adherence to the DASH diet scores was related to a higher sperm count and concentration in southern Spain and Poland (12, 13). However, it is unknown whether this association can be extrapolated to Chinese populations. In addition, the relationships between the Chinese Healthy Eating Index (CHEI), which is used to assess overall diet quality among Chinese populations (14), and overall sperm quality have been unclear.

Therefore, to explore the diet quality scores appropriated for the Chinese population that can be used as a tool to improve sperm quality, we conducted a hospital–based case–control study to investigate the associations between DASH, AHEI-2010, and CHEI diet quality scores and asthenoteratozoospermia risk in China.

In the current study, we found that the inverse association between diet quality scores and asthenoteratozoospermia risk was evident for CHEI, AHEI-2010 and DASH scores overall, when the SD of diet quality scores was considered a continuous variable. In the stratified analyses, significant inverse associations for these three diet scores only appeared for individuals at a younger age.

There has been no study investigating the association between multiple diet quality scores and asthenoteratozoospermia risk. We found that higher adherence to the AHEI-2010 and DASH scores was inversely associated with asthenoteratozoospermia risk. Our results are partially consistent with a cross-sectional study conducted in Poland that reported that adherence to AHEI-2010 and DASH scores may have higher sperm concentration, normal sperm morphology, and total sperm count (12). Some similarities may also be found with observations conducted in Israel reporting that men in the highest quartiles of AHEI-2010 and DASH scores had significantly higher sperm concentrations and normal sperm morphology (1).

The AHEI-2010 and DASH scores were characterized by high intakes of fruit, vegetables, whole grains, and legumes and low intakes of sugar-sweetened, red/processed meat, and sodium. These high intake food groups were found to be positively associated with sperm count (3, 19), concentration (19), sperm motility (20, 21), and morphology (3, 19). These food groups serve as major sources of vitamins, minerals, and polyphenols, which are be considered antioxidant and anti-inflammatory. The antioxidants in male reproductive health may be positively associated with semen parameters (22–24), as these oxidants may reduce oxidative damage to sperm (25, 26), DNA maintenance, transfer RNA, and protein synthesis (27), and reduce the negative effects of inflammation (26, 28). Moreover, these two dietary scores recommend reduction in sugar-sweetened beverage, red/processed meat, and fat consumption. The relatively high content of sugars, saturated/trans fatty acids, and sodium may adversely affect sperm count (19), concentration (29, 30), sperm motility (3, 20), and morphology (3, 31).

In addition, we found that CHEI scores were inversely associated with asthenoteratozoospermia risk. As the instrument in China to assess diet quality overall, the CHEI score was developed according to the updated Dietary Guidelines for Chinese (14). The main components recommended by the CHEI score are higher intakes of total grains, whole grains, and mixed beans, tubers, total vegetables, dark vegetables, fruits, dairy, soybeans, fish and seafood, poultry, eggs, seeds, and nuts and limitation of red meat, cooking oils, sodium, added sugars and alcohol (14). Evidence from epidemiological studies has reported that high intakes of dairy (4), fruits and vegetables (19, 32), cereals (32), fish (5, 6), nuts (6), and eggs (6) were related to higher sperm quality. In addition, high consumption of red meat (6, 32), processed meat (5), habitual alcohol consumption (33), sugar-sweetened beverages (34), and fish was found to be associated with low semen quality. The apparent benefit of CHEI may be attributable to a high intake of foods containing antioxidants and carotenoids. Reactive oxygen species production has been associated with increased cellular damage and the rate of sperm ATP depletion, which leads to insufficient axonemal phosphorylation, lipid peroxidation, and loss of motility and viability (35). In addition, the CHEI pattern also contains a high amount of nutrients with good anti-inflammatory properties, such as omega-3 fatty acids, fruit, and vegetables, and a low amount of proinflammatory nutrients, such as red meat and unhealthy fat. Inflammation may affect reproduction through anatomical or functional changes in the male accessory gland and/or direct negative impacts on spermatozoa (28).

In the stratified analyses, we found that the favorable associations between the three diet quality scores and asthenoteratozoospermia risk persisted across participants whose age was below 32 years, which indicated that adhering to the latest dietary guidelines for Americans or Chinese individuals is more likely to decrease asthenoteratozoospermia risk for young participants. The reason may be that young participants often show less healthy eating habits than general participants (36, 37). In addition, smoking can have a harmful effect on semen quality through a variety of toxic substances and chemical substances (38). However, the beneficial substances produced by diet cannot compensate for the harm to semen quality caused by smoking, which may explain the negative correlations between the CHEI score and asthenoteratozoospermia risk in non-smokers.

Our study has several strengths. To our knowledge, this is the first study to investigate the association between CHEI, AHEI-2010, and DASH and the risk of asthenoteratozoospermia in a Chinese population. Furthermore, we not only adjusted for several confounding factors but also carried out numerous subgroup analyses, which ensured the authenticity and reliability of our research results. However, some limitations occurred in our study. First, we cannot exclude the possibility of reverse causality with a case–control design. However, we provided strong evidence of a positive association by eliminating the effect of potential confounders. Second, dietary information collected by the FFQ may induce recall bias. To reduce this bias, we used the FFQ, which has acceptable reproducibility and validity, to collect dietary information in a face-to-face manner. Third, there are some dietary components that are not included in the diet score, such as oil and salt, which may affect our results. In the future, we need to consider these factors to improve these studies.

Our findings suggested that higher adherence to the CHEI, AHEI-2010, and DASH diet quality scores may reduce the risk of asthenoteratozoospermia, especially for younger participants. Well-designed prospective cohort studies and randomized clinical trials are required to confirm these results.

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding authors.

The studies involving human participants were reviewed and approved by the Ethics Committee of Shengjing Hospital of China Medical University. The patients/participants provided their written informed consent to participate in this study.

QC, H-HW, Q-JW, QD, and B-CP conceived the study. B-CP contributed to the design. QD, X-BW, R-HG, XL, and B-CP collected the data. QC and Q-JW cleaned the data, checked the discrepancy, and analyzed the data. QC, H-HW, Q-JW, X-BW, R-HG, XL, X-LT, and B-CP interpreted the data. All authors read the manuscript and approved the final vision.

This work was supported by the Shengjing Hospital Clinical Research Project (No. M0071 to B-CP).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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