Trends in Endocrinology and Metabolism article debunks cancer rate and sperm count myths
There is a widely-held belief that sperm counts are decreasing globally and that rates of female breast cancer and male reproductive tract problems are generally increasing. However, Dr Stephen Safe, writing in the May issue of Trends in Endocrinology and Metabolism, argues that there is little evidence to suggest that either of these beliefs is true and that public concern regarding these issues, heightened by media reports, is ill-founded. Furthermore, he suggests that Endocrine Disrupting Chemicals (EDCs), long hypothesized to be linked to the above conditions, are unlikely to be causal factors.
There has been a great deal of research to investigate the potentially adverse effects of EDCs, synthetic and naturally occurring compounds such as environmental estrogens, human exposure of which results from dietary intake as trace contaminants in food. Safe writes that “humans are exposed to high levels of dietary endocrine-active compounds in fruit, vegetables and other food products and therefore, lower and even trace levels of contaminant EDCs would have a negligible impact on overall EDC exposure and impact.” The concept of the Precautionary Principle meant that research was set in motion to investigate how EDCs relate to conditions such as cancers and sperm counts. However, this research has proved largely inconclusive in establishing any harmful effects.
Results of studies during the past 12 years have indicated an overwhelming lack of evidence to support a link between exposure to EDC compounds and development of breast cancer. Several studies have shown that levels of EDCs in breast cancer patients are not significantly different to the matched controls, which would indicate that they are not a factor in incidence rates.
Research indicates neither an increase nor decrease in global sperm counts, although there is evidence of regional differences in sperm counts and quality within countries. However, a general population-based study of young men in Denmark showed no association between sperm count and certain EDCs. It is unlikely that EDCs are linked to regional differences in sperm counts or quality as exposure to EDCs is largely consistent within most countries and regions.
There are also large demographic variations in incidence rates of testicular cancer, which must also therefore be attributable to other etiological factors, especially since levels of organochlorine pollutants are decreasing in most locations. It has been estimated that more than 80% of the risk of most cancers is associated with genetic variables designated as environmental factors, which include exposure to contaminants, lifestyle and diet. Safe concedes that “there may be other human health problems linked to high exposure to organochlorine contaminants” but, in the absence of any evidence to suggest that EDCs affect rates of breast and testicular cancer, sperm counts and fertility, states that it is now time to propose new hypotheses to concentrate on other etiological factors.
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