At last research has identified that a subset of male athletes may suffer from undiagnosed low bone density which may predispose them to developing stress fractures. Maintaining peak bone mass or high bone density is extremely important for strong bones and preventing fractures. We’ve known for years that female athletes are at high risk of developing stress fractures if they limit their food intake too severely, but this research has been lacking for their male counterparts.
In this article:
- What affects bone health
- How not eating enough can cause low bone density in females
- Do low food/energy intake mess with male hormones?
- Summary: Dietary strategies to prevent stress fractures
What affects bone health
The biggest factor by far is your genetics. If your grandparents or parents suffered from frequent fractures or osteoporosis it may be worth your while to have your bone density checked. This is done through a DEXA scan which your GP can organise.
Your body requires Vitamin D to absorb the minerals (calcium and phosphorus) that you use to build strong bones. A lack of this vitamin may thus cause your bones to be weaker than what they should be and break more easily.
The research seems to suggest that most of us in the UK do not get enough Vitamin D – especially in the winter months. You can read more about Vitamin D deficiency in athletes and how much you should be taking here.
High impact activities like running or walking usually stimulate bones to grow stronger and people who take part in these sports have been shown to have higher than normal bone density levels.
However, this is not necessarily true for endurance athletes. Studies on endurance athletes have found that they can often display lower bone densities than sedentary controls! The sections below may explain why.
Your diet plays a very important role in maintaining good bone health. It should firstly include enough calcium and Vitamin D – the building blocks for strong bones. Secondly, it should also provide enough energy to replace what you use during the day.
An insufficient diet (too few calories) messes with a women’s hormone levels which in turn leads to poor bone health – a phenomenon that has been investigated for at least 20 years. Because hormone disturbances in female athletes produces easily observable changes (changes in menstruation), lots of research has been done on this topic. The research on their male counterparts have been mostly lacking until now. I’ll explain this in detail below.
How not eating enough can cause low bone density in females
Athletes of all genders are forever striving to reach the “perfect” racing weight and shave seconds off their time. The problem is that when a woman limits her food/energy intake too severely, her body perceives it as starvation and shuts down her reproductive function in an effort to increase her chances of survival.
This messes with her hormone levels (easily detected by very patchy or absent menstruation) which in turn messes with her ability to build strong bones leading to poor bone density (osteopenia or osteoporosis). Add to this a high volume or high impact training and you have the perfect recipe for a stress fracture.
Do low food/energy intake mess with male hormones?
Several studies have shown that male athletes who take part in sports that emphasise leanness (cycling, running, wrestling, horse racing etc.) tend to chronically under-eat. Some report up to a 25% higher prevalence of disordered eating patterns in these types of sport.
Male endurance athletes have been shown to have lower levels of reproductive hormones, including testosterone. When these hormone levels fall below the normal range it appears to be associated with low bone density for these men. What is unknown is whether these changes in male hormone levels are due to insufficient energy levels (not eating enough for what you are using) or other factors.
There are a few studies available that hint at a similar relationship between diet restriction and changes in male hormone levels as in females, but more research is needed. One study that may be worth mentioning, despite its small sample size, was performed by Zanker and Swaine in 2000.(3)
They tested a group of 8 male runners, after 3 consecutive days of 60 minutes hard treadmill running, under 2 conditions. In condition one they allowed them to replace all the energy they used, but for condition two they only allowed them to replace 50% of the energy they used.
Their results showed that the hormones in charge of bone turnover was reduced under the second condition.
There is also strong evidence in the non-athletic male population that chronic under-eating leads to poor bone health. Boys who suffer with anorexia nervosa have been found to have decreased bone density when compared to their peers.(1)
Summary: Dietary strategies to prevent stress fractures
- Take a Vitamin D supplement – especially if you live in less sunny countries or wear sunblock when outside.
- Eat enough Calcium
- Do not chronically under-eat. A short period of calorie restriction to make race weight may be OK, but you are predisposing yourself to all sorts of injuries if you do not refuel your body properly after exercise.
- Tenforde AS, Barrack MT, Nattiv A, et al. Parallels with the female athlete triad in male athletes. Sports Med 2016;46(2):171-82.
- Tenforde AS, Nattiv A, Ackerman K, et al. Optimising bone health in the young male athlete. British Journal of Sports Medicine 2017;51(3):148-49. doi: 10.1136/bjsports-2016-097000
- Zanker CL, Swaine IL. Responses of bone turnover markers to repeated endurance running in humans under conditions of energy balance or energy restriction. Eur J Appl Physiol 2000;83(4):434-40.
Maryke is an expert sports physiotherapist who provides online physio consultations using Skype. She is registered with the Chartered Society of Physiotherapy as well as the Health and Care Professions Council.