Study by UCLA School of Nursing Finds Cycling May Negatively Affect Male Reproductive Health
A new study conducted by UCLA School of Nursing researchers has found that serious leisure male cyclists may experience hormonal imbalances that could affect their reproductive health. The study, “Reproductive Hormones and Interleukin-6 in Serious Leisure Male Athletes,” was published in the European Journal of Applied Physiology.
The UCLA study explored the associations between exercise intensity and circulating levels of reproductive hormones in serious leisure male athletes (triathletes and cyclists) and recreational athletes. UCLA researchers studied 107 healthy male athletes ages 18 to 60 and divided them into three groups: 16 were triathletes, 46 were cyclists and 45 were recreational athletes. Participants completed the International Physical Assessment Questionnaire to obtain an objective estimate of time spent participating in different levels of physical activity and inactivity during the previous seven days. Blood samples were then collected from each participant to measure total testosterone, estradiol, cortisol, interleukin-6 and other hormones.To date, an extensive amount of research has been performed documenting the positive effects of long-term exercise on health. These studies have shown that while moderate exercise can lead to enhanced cardiovascular and metabolic function and reduced body fat, ultra-endurance levels of exercise can also adversely affect the neuroendocrine system and reproductive health. Although most research studying the effects of exercise on reproductive health has focused on female athletes, there are few studies that have looked at male endurance-trained athletes.
“Plasma estradiol and testosterone levels were significantly elevated in serious leisure male cyclists, a finding not previously reported in any type of male athlete,” notes Leah Fitzgerald, PhD, FNP-BC, assistant professor at the School of Nursing and principal investigator and senior author of the study. Plasma estradiol concentrations were more than two times higher in the cyclists than in the triathlete and recreational athletes, and total testosterone levels were about 50 percent higher in cyclists than in the recreational athletes. “These effects were accompanied by little or no compensatory shift in circulating reproductive hormone levels.”
Estradiol is a form of estrogen and, in males, is produced as an active metabolic product of testosterone. Possible conditions associated with elevated estrogen in males include gynecomastia, a condition that may result in the loss of male pubic hair and enlarged breast tissue. “Although preliminary, these findings warrant further investigation to determine if specific types of exercise may be associated with altered sex hormone levels in men that could affect general health and reproductive well-being,” said Fitzgerald.
One of the interesting findings of the study related to the use of chamois cream. Some cyclists apply chamois cream to their perineum area to help prevent chaffing and bacterial infections related to bicycle saddle sores. However, many such commercial creams contain a variety of ingredients including lubricants, polymers and oils; and some also contain parabens, which are anti-microbial preservatives and weak estrogen agonists. In the study 48.5 percent of cyclists compared to 10 percent of triathletes reported using a paraben-containing chamois cream. The study found an association between an increase in estrogen levels and increasing years of chamois cream use, particularly for male cyclists using the cream for more than four years. At this time, however, no direct cause and effect has been found.
The study was funded by the UCLA School of Nursing, UCLA General Clinical Research Center and Kaiser Foundation. Other authors of the study included Wendie A. Robbins, also of the School of Nursing, and James S. Kesner, Division of Applied Research and Technology, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.
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