BACKGROUND The last decade has seen increased research on the relationship between diet and male fertility, but there are no clearly defined nutritional recommendations for men in the preconception period to support clinical fertility outcomes. OBJECTIVE AND RATIONALE The purpose of this scoping review is to examine the extent and range of research undertaken to evaluate the effect(s) of diet in the preconception period on male clinical fertility and reproductive outcomes. SEARCH METHODS Four electronic databases (MEDLINE and EMBASE via Ovid, CAB Direct, and CINAHL via EBSCO) were searched from inception to July 2023 for randomized controlled trials (RCTs) and observational studies (prospective/retrospective, case–control, and cross-sectional). Intervention studies in male participants or couples aiming to achieve dietary or nutritional change, or non-intervention studies examining dietary or nutritional components (whole diets, dietary patterns, food groups or individual foods) in the preconception period were included. Controls were defined as any comparison group for RCTs, and any/no comparison for observational studies. Primary outcomes of interest included the effect(s) of male preconception diet on clinical outcomes such as conception (natural or via ART), pregnancy rates and live birth rates. Secondary outcomes included time to conception and sperm parameters. OUTCOMES A total of 37 studies were eligible, including one RCT and 36 observational studies (prospective, cross-sectional, and case–control studies; four studies in non-ART populations) published between 2008 and 2023. Eight reported clinical outcomes, 26 reported on secondary outcomes, and three reported on both. The RCT did not assess clinical outcomes but found that tomato juice may benefit sperm motility. In observational studies, some evidence suggested that increasing fish or reducing sugar-sweetened beverages, processed meat or total fat may improve fecundability. Evidence for other clinical outcomes, such as pregnancy rates or live birth rates, showed no relationship with cereals, soy and dairy, and inconsistent relationships with consuming red meat or a ‘healthy diet’ pattern. For improved sperm parameters, limited evidence supported increasing fish, fats/fatty acids, carbohydrates and dairy, and reducing processed meat, while the evidence for fruits, vegetables, cereals, legumes, eggs, red meat and protein was inconsistent. Healthy diet patterns in general were shown to improve sperm health. WIDER IMPLICATIONS Specific dietary recommendations for improving male fertility are precluded by the lack of reporting on clinical pregnancy outcomes, heterogeneity of the available literature and the paucity of RCTs to determine causation or to rule out reverse causation. There may be some benefit from increasing fish, adopting a healthy dietary pattern, and reducing consumption of sugar-sweetened beverages and processed meat, but it is unclear whether these benefits extend beyond sperm parameters to improve clinical fertility. More studies exploring whole diets rather than singular foods or nutritional components in the context of male fertility are encouraged, particularly by means of RCTs where feasible. Further assessment of core fertility outcomes is warranted and requires careful planning in high-quality prospective studies and RCTs. These studies can lay the groundwork for targeted dietary guidelines and enhance the prospects of successful fertility outcomes for men in the preconception period. Systematic search of preconception diet suggests that increasing fish and reducing sugary drinks, processed meats and total fat may improve male fertility, while consuming healthy diets, fish, fats/fatty acids, carbohydrates and dairy and reducing processed meat can improve sperm health.

中文翻译：

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评估孕前饮食对男性生育能力的影响：系统范围综述


背景 过去十年中，关于饮食与男性生育能力之间关系的研究有所增加，但没有明确定义的针对孕前男性的营养建议来支持临床生育结果。客观和基本原理 本范围综述的目的是检查为评估孕前饮食对男性临床生育力和生殖结局的影响而进行的研究的范围和范围。检索方法 从建库到 2023 年 7 月，检索了四个电子数据库 （MEDLINE 和 EMBASE 通过 Ovid、CAB Direct 和 CINAHL 通过 EBSCO） 的随机对照试验 （RCT） 和观察性研究 （前瞻性/回顾性、病例对照和横断面）。纳入了旨在实现饮食或营养改变的男性参与者或夫妇的干预研究，或检查孕前饮食或营养成分（全饮食、饮食模式、食物组或个体食物）的非干预研究。对照定义为 RCT 的任何比较组，观察性研究定义为任何/无比较。感兴趣的主要结局包括男性孕前饮食对临床结局的影响，例如受孕（自然或通过 ART）、妊娠率和活产率。次要结局包括受孕时间和精子参数。结果 共有 37 项研究符合条件，包括 2008 年至 2023 年间发表的 1 项 RCT 和 36 项观察性研究（前瞻性、横断面和病例对照研究;4 项针对非 ART 人群的研究）。8 例报告了临床结局，26 例报告了次要结局，3 例报告了两者。 RCT 没有评估临床结局，但发现番茄汁可能有益于精子活力。在观察性研究中，一些证据表明，增加鱼类或减少含糖饮料、加工肉类或总脂肪可能会提高繁殖力。其他临床结局的证据，如妊娠率或活产率，显示与谷物、大豆和乳制品没有关系，与食用红肉或 “健康饮食 ”模式的关系也不一致。对于精子参数的改善，有限的证据支持增加鱼、脂肪/脂肪酸、碳水化合物和乳制品，并减少加工肉类，而水果、蔬菜、谷物、豆类、鸡蛋、红肉和蛋白质的证据不一致。一般来说，健康的饮食模式被证明可以改善精子健康。更广泛的影响 由于缺乏关于临床妊娠结局的报告、现有文献的异质性以及缺乏确定因果关系或排除反向因果关系的 RCT，因此排除了提高男性生育能力的具体饮食建议。增加鱼类、采用健康的饮食模式以及减少含糖饮料和加工肉类的消费可能会有一些好处，但目前尚不清楚这些好处是否延伸到精子参数之外，以提高临床生育能力。鼓励在男性生育能力的背景下进行更多探索全饮食而不是单一食物或营养成分的研究，特别是在可行的情况下通过随机对照试验。有必要进一步评估核心生育率结局，并且需要在高质量的前瞻性研究和 RCT 中仔细规划。 这些研究可以为有针对性的饮食指南奠定基础，并提高男性在孕前成功生育结果的前景。对孕前饮食的系统搜索表明，增加鱼类和减少含糖饮料、加工肉类和总脂肪可能会提高男性生育能力，而食用健康饮食、鱼类、脂肪/脂肪酸、碳水化合物和乳制品以及减少加工肉类可以改善精子健康。