The World Health Organization lists four semen quality parameters in its latest manual of 2010: concentration (ie, count, which should be a minimum of 15 million sperm cells per ml semen); progressive motility (32% minimum); vitality (58%); and morphology (4%). These are the main parameters measured to evaluate semen quality within a normal range. At the molecular level, the genetic integrity of each sperm cell is essential for successful fertilisation; if DNA strands in the cell become damaged or fragmented, they will be unable or less likely to fertilise an egg and maintain embryonic development. It is believed that this DNA fragmentation is caused by oxidative stress as a result of environmental and lifestyle factors.
The nuts like walnut, cashew nut, almonds, etc in a regular diet can significantly improve the quality and function of human sperm. The background of a general decline in quantity and quality of human sperm, attributed in industrialised countries to "pollution, smoking, and trends toward a western-style diet." The consumption of nuts have significant improvements in the sperm count, vitality, motility and morphology (shape); these are consistent with the statistics and medical examinations. The diets rich in omega-3, antioxidants (eg, vitamin C and E, selenium and zinc), and folate are helpful in building the sperm quality and quantity. Nuts are dense foods containing many of these nutrients and other phytochemicals.