Effect of dietary trace element zinc on male fertility

Galina Nenkova¹, Rossen Stefanov², Dimitrina Kacheva ² , Paulina Taushanova, Boyko Georgiev, Albena Alexandrova^1,3

¹Laboratory of Free Radical Processes, INB-BAN,
²Institute of Biology and Immunology of Reproduction Acad. "Kiril Bratanov“
³National Sports Academy “Vassil Levski”

 

            Keywords: zinc, food, spermatozoa, fertility

 

            Zinc is an essential trace element necessary for the proper development and physiological balance of living organisms, particularly human. It is found in nearly 200 enzymes in the human body and is relevant to both male and female fertility. Up to one-fifth of the world's people may lack sufficient zinc in their diet. Zinc deficiency is a recognized health problem. In the U.S., the Recommended Dietary Allowance (RDA ) is 8mg/day for women and 12 mg/day for men. Oysters, lobster and red meats, especially beef, lamb and liver have some of the highest concentrations of zinc in food. Zinc is less concentrated in eggs and cheese The food plants that contain the most zinc are wheat and sesame. Zinc is also found in beans and nuts, almonds, pumpkin seeds, sunflower seeds.

            Zinc deficiency in men leads to reduced sperm concentration, poor motility and morphology of male germ cells. The earliest sign of zinc deficiency is an arrest at spermiogenesis with lack of elongated spermatozoa. Zinc is incorporated into the sperm nucleus and is important for compact DNA packing. The exchange of somatic histones into basic protamines helps this compaction and protects the DNA by reducing the access of a potential source of free radicals. Antioxidant enzymes are located primarily in the cytoplasm but in sperm lack of cytoplasm results in decreased antioxidant defense. Therefore sperm are very sensitive to oxidative stress and need enough zinc to protect their chromatin. If there is not enough zinc the sulfhydryl (thiol) groups (SH) in protamines interact with iron which is a prerequisite for the formation of free radicals. Therefore insufficient intake of dietary zinc can have a negative effect on male fertility.