Diet and Male Fertility 饮食对男性生育水平的影响

Diet and obesity are two important lifestyle factors that can influence spermatogenesis. Accompanying modern Westernized lifestyles are changes in diets and eating habits that are a result of a fast paced lifestyle. People are eating more highly refined carbohydrate rich foods and simultaneously consuming less fresh fruits and vegetables. The importance of fresh vegetables in a well-balanced diet was noted in a study that decreased subjects intake of certain nutritional substances, like fruits and vegetables; a correlation between this lack of nutrients and sub fertility was found (1-4). Besides containing antioxidants and essential nutrients, vitamins and folate are found in fruit and vegetables; these substances are involved in DNA and RNA synthesis and thus play an important role in spermatogenesis by protecting the sperm’s DNA from free radical damage (3).

饮食和肥胖是影响精子产生的两个重要的生活方式相关因素。伴随着现代西式生活方式的是饮食和饮食习惯的改变，这些改变是由于快节奏的生活方式造成的。 人们现在摄入更多的是富含碳水化合物的高精食品，同时较少食用新鲜的水果和蔬菜。 在一项减少受试者摄入某些营养物质(如水果和蔬菜)的研究中，研究者发现新鲜蔬菜对均衡饮食起到了非常重要的作用。营养缺乏与亚生育力之间存在相关性(数据参考见1-4)。除了含有抗氧化剂和必需营养素外，水果和蔬菜中还含有维生素和叶酸;这些物质参与DNA和RNA的合成，通过保护精子的DNA免受自由基的破坏，在精子的生成中起着重要的作用(数据参考见3)

Nutritionally deficient diets, lacking antioxidant vitamins and synergistic minerals do not enable the quenching of reactive oxygen molecules. For example, vitamin C and vitamin E are essential antioxidants that protect the body’s cells from damage due to oxidative stress and free radicals. Vitamin C is the most abundant antioxidant in the semen of fertile men and contributes to the maintenance of healthy sperm by protecting the sperm’s DNA from free radical damage (1-4). Vitamin E is a fat-soluble vitamin that helps protect the sperm’s cell membrane from damage. Studies show that vitamin E improves sperm motility and morphology while vitamin C regenerates vitamin E; thereby these vitamins work together to improve sperm function (1-4). Selenium is a mineral that also functions as an antioxidant; Selenium supplements have also been shown to increase motility. Combinations of these three nutrients have been shown to improve sperm parameters in infertile men (5).

营养不足的饮食，缺乏抗氧化维生素和协同矿物质，无法使活性氧分子猝灭。 例如，维生素C和维生素E是必不可少的抗氧化剂，可保护人体细胞免受氧化应激和自由基的损害(数据参考见1-4)。 维生素C是可育男性精液中最丰富的抗氧化剂，通过保护精子的DNA免受自由基的破坏来维持精子的健康。维生素E是脂溶性维生素，有助于保护精子的细胞膜免受损害。 研究表明，维生素E可以改善精子的活力和形态，而维生素C可以使维生素E再生。因此，这些维生素可以共同作用以改善精子的功能(数据参考见1-4)。硒是一种矿物质，也可以用作抗氧化剂。 硒还表现出其可提高精子活力的能力。 这三种营养素的组合可改善不育男性的精液指标(数据参考见5)。

Obese and overweight individuals with high body mass index(BMI) are at risk of infertility (6-8). Men with a BMI higher than 25 are considered three times more at risk of infertility due to the reduction in sperm count and increase of DNA fragmentation.

肥胖和超重的人身体质量指数(BMI)升高，有不孕风险((数据参考见6-8)。 BMI高于25的男性由于精子数量减少及DNA碎片率的增加而被认为不孕风险增加了三倍。

There are many links between obesity and infertility: firstly, excess adipose tissue leads to the conversion of more testosterone to estrogen. This subsequently results in the development of secondary hypogonadism through hypothalamic-pituitary-gonadal axis inhibition, thereby decreasing the levels of circulating testosterone and increasing the levels of estradiol. This decrease in testosterone is most likely responsible for impaired spermatogenesis. Secondly, accumulation of suprapubic and inner thigh fat in severely obese men can lead to infertility due to the insulating effects of fat deposits near the scrotum, which causes testicular heat stress. Fat deposits around scrotal blood vessels can impair blood cooling and elevate temperatures.Obese men also tend to be more sedentary which would exacerbate any temperature increases. Finally, obesity and several of its accompanying complications, namely insulin resistance and dyslipidemia, are associated with systemic pro inflammatory states and increased oxidative stress. Oxidative stress causes sperm membrane lipid peroxidation, which results in the impairment of sperm motility, DNA damage,and impaired sperm-oocyte interaction. Conversely, adipose tissue releases pro-inflammatory adipokines that increase leukocyte production of ROS, which negatively impacts sperm function.

肥胖与不育之间有许多关联：首先，过多的脂肪组织会导致更多的睾酮转化为雌激素。随后通过下丘脑-垂体-性腺轴抑制导致继发性腺功能减退，从而降低了循环睾酮素的水平并增加了雌二醇的水平。睾酮素的减少很可能是精子发生受损的原因。第二，严重肥胖男性的耻骨和大腿内侧脂肪的积聚可能会由于阴囊附近脂肪堆积(这会引起睾丸热应激)的绝缘作用而导致不孕。阴囊血管周围的脂肪沉积会损害血液冷却的能力，会导致温度的升高。肥胖的男性也往往久坐不动，这会加剧体温升高。最后，肥胖及其伴随的一些并发症，即胰岛素抗性和血脂异常，与全身炎症状态和氧化应激增加有关。氧化应激导致精子膜脂质过氧化，导致精子活力受损，DNA损伤和授精作用减弱。相反，脂肪组织释放促炎性脂肪因子，增加白细胞中活性氧的产生，从而对精子功能产生负面影响。

Poor endocrine and exocrine functions of the testis are believed to be directly proportional to increased BMI and obesity in men around the world. Lowering BMI in obese men can be asolution to some infertility issues.

我们认为睾丸的内分泌和外分泌功能差与全世界男性的高BMI和肥胖症成正比。 降低肥胖男性的BMI可以解决某些不育问题。

References数据参考：

Eskenazi B, Kidd SA, Marks AR, Sloter E, Block G, Wyrobek AJ.Antioxidant intake is associated with semen quality in healthymen. Human reproduction (Oxford, England) 2005; 20 (4) : 1006-12.51.

Fraga CG, Motchnik PA, Shigenaga MK, Helbock HJ, Jacob RA, Ames BN. Ascorbic acid protects against endogenousoxidative DNA damage in human sperm. Proceedings of theNational Academy of Sciences of the United States of America1991; 88 (24) : 11003-6.

Song GJ, Norkus EP, Lewis V. Relationship between seminal ascorbic acid and sperm DNA integrity in infertile men.International Journal of Andrology 2006; 29 (6) : 569-75.

Therond P, Auger J, Legrand A, Jouannet P. alpha-Tocopherol in human spermatozoa and seminal plasma: relationshipswith motility, antioxidant enzymes and leukocytes. MolecularHuman Reproduction 1996; 2 (10) : 739-44.

Hawkes WC, Turek PJ. Effects of dietary selenium on spermmotility in healthy men. Journal of Andrology 2001;22(5):764-72.

Koloszar S, Fejes I, Zavaczki Z, Daru J,Szollosi J,Pal A. Effectof body weight on sperm concentration in normozoospermicmales. Archives of Andrology 2005; 51 (4) : 299-304.

Kort HI, Massey JB, Elsner CW, Mitchell-Leef D, Shapiro DB,Witt MA, et al. Impact of body mass index values on spermquantity and quality. Journal of Andrology 2006;27(3):450-2.

Nguyen RH, Wilcox AJ, Skjaerven R, Baird DD. Men’s body massindex and infertility. Human Reproduction (Oxford, England)2007; 22 (9) : 2488-93.