Sperm Numbers Are Falling!
By: David Karabinus, Ph.D., HCLD
The adult human testis is a busy place: on a given day each one produces approximately 45,000,000 sperm. Not bad for an organ that is about the size and weight of a walnut. Sperm production is neither simple nor speedy: the process, called spermatogenesis, takes place over a period of about 64 days and is a sequence of meiotic and mitotic divisions plus final maturational steps. The result is 256 mature spermatozoa being produced from one spermatogonial stem cell. Spermatogenesis takes place within the seminiferous tubules, the little hollow tubes about the diameter of a hair that compose most of the testicular tissue. Testicular function is regulated by intricate hormonal feedback interactions between the testis, hypothalamus, and pituitary gland to assure normal spermatogenesis occurs.
Declining sperm production in humans has received much media attention recently, accompanied by dire predictions of widespread infertility, jabs at the collective competence of males and snickers about the extinction of men. In reality, such reports are not new: as far back as the mid 1970s there have been such reports in the scientific literature. However the results are not as clear-cut as they may appear. An Italian study reported a decline in sperm concentration between the 1970s and today. A French study also reported a reduction in sperm concentration from 1973 and 1992. There were two US studies that showed that sperm density in the US had decreased 1.0-1.5% per year between the mid- to late 1930s and early to mid 1990s. During the same period, sperm densities were reported to have declined ~3% per year for European/Australian subjects. A US study indicated that sperm counts had actually increased between 1974 and 1994 while another study showed that sperm numbers declined for those born after 1974 compared with those born before 1959. A Japanese study showed sperm concentrations were steady to increased in 1998 compared to the period between 1975 and 1980. A study in India showed that sperm concentration had not declined between 1990 and 2000. A Danish study showed no change in sperm numbers among volunteers whose semen was periodically evaluated between 1996 and 2001.
The results of these studies do not present clear cut evidence that sperm production is declining in humans. The statistical and sampling methods employed by the studies showing sperm reductions have been called into question. There are indications that geographical differences in sperm production may reflect variations in diet, environmental exposure, pollution, etc. Is there anything we need to be concerned about? Maybe. Sperm production can be affected by a multitude of things such as medication, illness, trauma, and stress. Exposure to environmental pollutants, too much heat and too much cold can also impact testicular function. Hormonal supplements can significantly disrupt the feed back mechanism between testes, pituitary and hypothalamus. The chemotherapy or radiation that kills the cancer and saves your life can eliminate the testes’ ability to produce sperm. Alcohol and recreational drug use also have adverse effects.
There is no evidence that males are becoming inherently less capable of producing adequate numbers of sperm. However, since we do know that lifestyle and environmental factors can impair sperm production, avoiding such factors is prudent. In unavoidable situations, such as medical treatment, obtain a physician’s advice about potential reproductive impacts. Healthy habits such as eating a balanced diet, regular exercise, taking a multi-vitamin, and avoiding environmental toxicants are probably the most effective actions that can be taken to maintain the male’s inherent ability to produce sperm.
The adult human testis is a busy place: on a given day each one produces approximately 45,000,000 sperm. Not bad for an organ that is about the size and weight of a walnut. Sperm production is neither simple nor speedy: the process, called spermatogenesis, takes place over a period of about 64 days and is a sequence of meiotic and mitotic divisions plus final maturational steps. The result is 256 mature spermatozoa being produced from one spermatogonial stem cell. Spermatogenesis takes place within the seminiferous tubules, the little hollow tubes about the diameter of a hair that compose most of the testicular tissue. Testicular function is regulated by intricate hormonal feedback interactions between the testis, hypothalamus, and pituitary gland to assure normal spermatogenesis occurs.
Declining sperm production in humans has received much media attention recently, accompanied by dire predictions of widespread infertility, jabs at the collective competence of males and snickers about the extinction of men. In reality, such reports are not new: as far back as the mid 1970s there have been such reports in the scientific literature. However the results are not as clear-cut as they may appear. An Italian study reported a decline in sperm concentration between the 1970s and today. A French study also reported a reduction in sperm concentration from 1973 and 1992. There were two US studies that showed that sperm density in the US had decreased 1.0-1.5% per year between the mid- to late 1930s and early to mid 1990s. During the same period, sperm densities were reported to have declined ~3% per year for European/Australian subjects. A US study indicated that sperm counts had actually increased between 1974 and 1994 while another study showed that sperm numbers declined for those born after 1974 compared with those born before 1959. A Japanese study showed sperm concentrations were steady to increased in 1998 compared to the period between 1975 and 1980. A study in India showed that sperm concentration had not declined between 1990 and 2000. A Danish study showed no change in sperm numbers among volunteers whose semen was periodically evaluated between 1996 and 2001.
The results of these studies do not present clear cut evidence that sperm production is declining in humans. The statistical and sampling methods employed by the studies showing sperm reductions have been called into question. There are indications that geographical differences in sperm production may reflect variations in diet, environmental exposure, pollution, etc. Is there anything we need to be concerned about? Maybe. Sperm production can be affected by a multitude of things such as medication, illness, trauma, and stress. Exposure to environmental pollutants, too much heat and too much cold can also impact testicular function. Hormonal supplements can significantly disrupt the feed back mechanism between testes, pituitary and hypothalamus. The chemotherapy or radiation that kills the cancer and saves your life can eliminate the testes’ ability to produce sperm. Alcohol and recreational drug use also have adverse effects.
There is no evidence that males are becoming inherently less capable of producing adequate numbers of sperm. However, since we do know that lifestyle and environmental factors can impair sperm production, avoiding such factors is prudent. In unavoidable situations, such as medical treatment, obtain a physician’s advice about potential reproductive impacts. Healthy habits such as eating a balanced diet, regular exercise, taking a multi-vitamin, and avoiding environmental toxicants are probably the most effective actions that can be taken to maintain the male’s inherent ability to produce sperm.
posted by Kathleen, Contributing Editor at
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