We are back at it again, and this time I want to talk a little bit about nutrition concerns for the male endurance athlete. If you have been following along with my previous blogs (if you haven’t, you should be!), you will recall we discussed how nutrition impacts the health and wellbeing of female endurance athletes, especially regarding stress fracture risk. You can find it here, if you would like to take a look back for a refresher.
For a quick recap, we discussed how endurance running is a huge metabolic demand, meaning it costs a lot to run fast for long periods of time. This can result in accidental under consumption of macronutrients (carbohydrates, fat and protein), energy, and ultimately vitamin/mineral intake, or purposeful restriction of food intake to achieve a desired level of thinness or body shape. Chronic under consumption, whether accidental or not, of both nutrient and energy, can cause some physiological changes in the body and can greatly increase your risk of bone related injuries.
It was typically believed that low energy availability (LEA), in the past known as the female athlete triad, only was a complication females encountered in sport, however it is now known that males also experience negative health and performance effects of LEA. It is possibly harder to detect in males, as there is no clear sign, such as loss of menstrual cycle, however that is why we need to be careful not to miss the subtle signs. In this article we will discuss what happens physiologically with LEA, and its effects on bone mineral density (BMD).
Under consuming energy can be a difficult concept to understand because calculations of exercise energy expenditure, basil metabolic rate and even energy intake are difficult to assess. Current research defines “Energy Availability” (EA) as the left over energy to be used for normal physiological processes after accounting for energy expenditure, which is expressed as kcal/kg of FAT FREE mass.
The EA equation= [energy intake- exercise energy expenditure] / fat free mass (kg)
Physiological Changes With LEA
– Decreased metabolic rate
– Increased cortisol (stress hormone)
– Decreased testosterone
– Signs include fatigue and decreased sex drive
Bone Mineral Density
There is ample evidence to suggest that an active individual have higher BMD than sedentary individuals. Within the athletic population swimmers and cyclists tend to have fairly low BMD due to non-weight bearing nature of the exercise. A study by Viner et al. looked at male and female cyclists with lower than expected BMD. The found that 70% had LEA across the entire training cycle, including pre season, competition and post season. This points to the theory that this particular group may have had low BMD due to their LEA. They found that 40% of the participants had low bone mineral density in their lumbar spine, and 10% had low bone mineral density in the femoral neck. The athletes were followed for 1 year and their BMD stayed the same, which is positive. The researchers pointed to their previous interventions of increasing vitamin D & calcium intake and including weight training as a reason for the maintenance of BMD. This provides evidence that a good nutrition and training intervention can help maintain bone strength.
Another study in elite male endurance athletes showed that LEA resulted in low testosterone (although not clinically low) however it did not result in any differences in BMD compared to those with normal testosterone levels. There seems to be a caloric value threshold before we start to see negative health and bone effects. Interestingly, it seems as though women are more sensitive to changes in EA, where we see significant and detrimental effects in heath and bone when their EA reaches 30 kcal/kgFFM/day or below. There is evidence that this occurs at levels of 20-25 kcal/kgFFM/day in a male athlete, although more research is needed to confirm this. This study suggested that because they investigated athletes at ~30kcal/kgFFM/day that this was not enough of a deficit to result in decreased BMD. However, this does not mean you can neglect your nutrition planning because even though their BMD did not change, those with low testosterone had 4.5x more risk of sustaining a stress fracture and had 4.5x more missed training days due to injury.
In elite endurance athletes, 40% of males were found to have LEA. Even temporary low EA increases bone breakdown and decreases bone building, and chronic low EA has long lasting effects on bone health plus many more effects such as mental health and performance to name a few. Therefore, it is essential to stay on top of your nutrition as a part of stress fracture/injury risk reduction.
1. Negative energy balance and testosterone: studies show low testosterone results in 4.5x higher risk of bone injury and had 4.5x more missed training days due to injury
2. NFL players and vitamin D: In NFL players, low circulating vitamin D levels correlated with increased risk of core and lower muscle injuries; players with 1+ fractures had higher rates of inadequate levels of circulating vitamin D.
3. Military recruits with lower serum Vitamin D- correlated with higher risk of fractures
Viner RT, Harris M, Berning JR, Meyer NL. Energy availability and dietary patterns of adult make and female competitive cyclists with lower than expected bone mineral density. International Journal of Sports Nutrition and Exercise Metabolism. 2015. 25, 594-602.
Ruohola JP, Laaksi I, Ylikomi T, Haataja R, Mattila VM, Sahi T, Tuohimaa P, Pihlajamaki H. Association between serum 20(OH)D concentration and bone stress fractures in Finnish young men. Journal of Bone and Mineral Research. 2006. 21, 1483-1488.
Heikura IA, Uuitalo ALT, Stellingwerff T, Bergland D, Mero AA, Burke LM. 2017. Low energy availability is difficult to assess but outcomes have a large impact on bone injury rates in elite distance athletes. International Journal of Sport Nutrition and Exercise Metabolism.