Bone health for athletes

What role does nutrition play in bone health for athletes?

As an athlete, your nutrition with regards to bone health can make or break you – quite literally! Bone health is a great passion of mine, because it is one of the things that lead me on the path of dietetics in the first place.

When I was in high school, I used a lot of cortisone as treatment for chronic asthma issues. Little did I know that the high dosages would be absorbed systemically, leading to lower bone density. Coupled with this I had a very active lifestyle and was training very had for athletics. In 2015, I experienced my first stress fracture, and after doing a DEXA scan, we found out that I had osteopenia, which is pre-osteoporosis.

For years I had to work really hard with dietitians, sport psychologists, biokineticists and sport doctors in order to try and increase my bone density. This year (2020), five years later, I finally got the good news that my bone density is in normal ranges. It was a process, and probably one of the hardest journeys of my life, but in this time I learnt just how important nutrition is – not only for performance, but also for health.

In this article, I’m going to share not only what I learnt during the past 5 years but also what the science says about bone density. We are going to look at what you can do to treat and prevent low bone density (when your bones are broken down faster than they can be remodeled) with regards to nutrition and why it is important to do so.

What are the risks of low bone density?

• Stress Fractures
  Up to 15% of runners visiting a sports clinic in the USA present with stress fractures, according to the National Collegiate Athletic Association. Other sports have incidence rates of 1% – 2.6%. Running causes repetitive impact forces to act on the bone, which increases the risk for stress fractures if an athlete’s bone density is not adequate. However, stress fractures can occur in many different sports, like netball, hockey, gymnastics and tennis. And trust me, taking time off training in order to recover from stress fractures is NOT fun.
• Osteoporosis
  Not all athletes with poor bone health will necessarily experience a stress fracture. Some sports like swimming and biking have lower impact, which reduces the risk of a stress fracture even if bone density is low. In this case, decreasing bone density may occur due to a lack of calcium, vitamin D or hormonal imbalance, leading to osteoporosis or osteopenia. Osteoporosis can really affect your quality of life further down the road.

How does nutrition affect bone density?

1. Energy availability

Energy availability is the amount of energy that is left after subtracting the energy you used for training from your total daily energy intake. This energy is what is available for your body to perform a variety of normal functions like reproductive function, growth and bone formation.

Energy availability affects bone health both directly and indirectly:

• Lower energy availability leads to a reduction in bone protein synthesis. When energy availability drops to below 30kcal/kg fat free mass, bone mineralization and concentrations of hormones playing an important role in bone formation (insulin-like growth factor-1 and tri-iodothyronine) declines.
• Low energy availability can also lead to a decreased oestrogen concentration in females, which also leads to low bone density.

Elevate your plate: Make sure you are eating enough! At least 30 – 45kcal/kg fat free mass is required to prevent a decreased bone density. For more information on low energy availability and how to address it, click here.

A note on oral contraceptives

Oral contraceptive pills (OCPs) are often prescribed for female athletes who lost their menstrual cycle (this is called “amenorrhea”). However, this should not be the first route to try and treat the problem. Even though it may appear that a person has a “normal” cycle while using oral contraceptives, it is important for athletes and coaches to realize that it does not fix the underlying problem – low energy availability. Therefore, oral contraceptives does not treat hormonal and growth factor suppression that occurs in amenorrhea.

Research on the effect of oral contraceptives on increasing bone density remain mixed and often are influenced by “confounding factors”, which is other factors like weight that also may have had an impact on the end result.

2. Calcium intake

Calcium supports vital metabolic function such as cardiac function, nerve transmission, intracellular signalling, and hormonal secretion. The largest “reservoir” for calcium is in the bone tissue. Because calcium plays such a big role in critical body functions, the level of calcium in the blood needs to be very tightly regulated. Therefore, when not enough calcium is taken in, the bone will be broken down in order to maintain serum calcium.

What increases the risk of low calcium intake?

• Avoiding of dairy products and other calcium-rich foods
• Limiting energy intake
• Vegans/vegetarians- Data shows that vegans consume less calcium than omnivores and other vegetarians. If you are a vegan athlete, try consuming plant-based sources of calcium like as beans, pulses and green vegetables in order to meat your recommended amounts. While broccoli, bok choy and kale are particularly high in calcium, some green vegetables such as spinach and arugula contain oxalate which can interfere with calcium absorption. Calcium-fortified foods are a good option, like calcium-fortified soy, nut milks and fruit juices.

Elevate your plate: the RDA for males is 800mg/d and for females is 1000mg/d (ages 19 – 50). This amount increases to 1500 – 2000mg per day to optimise bone health in athletes who had low energy availability or menstrual dysfunction. You can meet this requirement by incorporating calcium rich foods like dairy or fortified dairy alternatives (like soy milk), beans, pulses, green vegetables, and fish with its bones still intact like pilchards or sardines.

3. Vitamin D intake

Vitamin D plays an important role in bone health by promoting bone growth and enhancing calcium absorption.

Elevate your plate: the RDA for vitamin D is 5 mcg/d (age < 51). Vitamin D is made in the skin when exposed to UVB rays from the sun. Vitamin D made in the skin lasts twice as long in the blood as vitamin D found in food. Food sources of vitamin D includes fish like salmon, tuna, mackerel and fish oils, as well as beef, liver, cheese and egg yolks.

4. Vitamin K intake

Vitamin K supplementation (10 mg/d) in elite female athletes has been reported to be beneficial to improve bone health.

Elevate your plate: The RDA for males is 120 mcg/d and Females 90 mcg/d, which can be obtained from green leafy vegetables, broccoli, asparagus, and beef liver.

Conclusion

Nutrition is very important for athletes to optimize bone health, and there are many things to look at when trying to increase bone density. If you are an athlete struggling with bone issues, I strongly advise seeking help from a dietitian to help you become the strongest, most injury resistant athlete you can be.

References

Scofield, Kirk & Hecht, Suzanne. 2012. Bone Health in Endurance Athletes: Runners, Cyclists, and Swimmers. Current sports medicine reports. 11. 328-34. 10.1249/JSR.0b013e3182779193.

Kerksick CM, Wilborn CD, Roberts MD, et al. 2018. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 15(1):38. Published 2018 Aug 1. doi:10.1186/s12970-018-0242-y

Rogerson, D. 2017. Vegan diets: practical advice for athletes and exercisers. J Int Soc Sports Nutr 14, 36. https://doi.org/10.1186/s12970-017-0192-9