Similar to a phenomenon already well documented in women, inadequate nutrition appears to be linked to hormonal abnormalities and potentially preventable tibial cortical bone density loss in athletic men, according to results of a small, prospective study.
Based on these findings, “we suspect that a subset of male runners might not be fueling their bodies with enough nutrition and calories for their physical activity,” reported Melanie S. Haines, MD, at the annual meeting of the Endocrine Society.
This is not the first study to suggest male athletes are at risk of a condition equivalent to what has been commonly referred to as the female athlete triad, but it enlarges the objective data that the phenomenon is real, and it makes insufficient availability of energy the likely cause.
Dr. Melanie S. Haines
In women, the triad is described as a lack of adequate stored energy, irregular menses, and bone density loss. In men, menstrual cycles are not relevant, of course, but this study like others suggests a link between the failure to maintain adequate stores of energy, disturbances in hormone function, and decreased bone density in both men and women, Dr. Haines explained.
RED-S vs. male or female athlete triad
“There is now a move away from the term female athlete triad or male athlete triad,” Dr. Haines reported. Rather the factors of failing to maintain adequate energy for metabolic demands, hormonal disturbances, and bone density loss appear to be relevant to both sexes, according to Dr. Haines, an endocrinologist at Massachusetts General Hospital and assistant professor of medicine at Harvard Medical School, both in Boston. She said several groups, including the International Olympic Committee (IOC), have transitioned to the term RED-S to apply to both sexes.
“RED-S is an acronym for relative energy deficiency in sport, and it appears to be gaining traction,” Dr. Haines said in an interview.
According to her study and others, excessive lean body mass from failure to supply sufficient energy for physiological needs “negatively affects hormones and bone,” Dr. Haines explained. In men and women, endocrine disturbances are triggered when insufficient calories lead to inadequate macro- and micronutrients.
In this study, 31 men aged 16-30 years were evaluated. Fifteen were in the athlete group, defined by running at least 30 miles per week for at least the previous 6 months. There were 16 control subjects; all exercised less than 2 hours per week and did not participate in team sports, but they were not permitted in the study if their body mass index exceeded 27.5 kg/m2.
Athletes vs. otherwise healthy controls
Conditions that affect bone health were exclusion criteria in both groups, and neither group was permitted to take medications affecting bone health other than dietary calcium or vitamin D supplements for 2 months prior to the study.
Tibial cortical porosity was significantly greater – signaling deterioration in microarchitecture – in athletes, compared with control subjects (P = .003), according to quantitative computed tomography measurements. There was also significantly lower tibial cortical bone mineral density (P = .008) among athletes relative to controls.
Conversely, tibial trabecular measures of bone density and architecture were better among athletes than controls, but this was expected and did not contradict the hypothesis of the study.
“Trabecular bone refers to the inner part of the bone, which increases with weight-bearing exercise, but cortical bone is the outer shell, and the source of stress fractures,” Dr. Haines explained.
The median age of both the athletes and the controls was 24 years. Baseline measurements were similar. Body mass index, fat mass, estradiol, and leptin were all numerically lower in the athletes than controls, but none were significant, although there was a trend for the difference in leptin (P = .085).