By Annie Bothma, January 2023
Athletes should pay more attention to their bone health, whether this relates to their
longer-term bone health, the risk of osteopenia and osteoporosis or their shorter-term risk of bony injuries (like stress fractures or a stress response). Given that bone is a nutritionally modified tissue and diet has a significant influence on bone health across the lifespan, optimizing nutritional intake is a great way for athletes to build strong bones.
In this post, I will outline some key nutritional strategies athletes need to consider to protect their bones. There will be a follow-up post focused on what nutritional supplements can be utilized to optimize, as well as which key micronutrients need to be considered when it comes to maintaining good bone health.
WHY HAVING STRONG BONES MATTERS
Osteoporosis is defined, by the World Health Organization, as “a progressive systemic skeletal disease characterized by low bone mass and micro-architectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture”.
Consequently, bone mass and strength are important considerations in the
prevention of osteoporosis and its associated conditions. Having low bone mass in
itself is not necessarily a major clinical problem; the issues arise from the associated
increase in bone fragility and heightened risk of osteoporotic fracture. Most
importantly, it is clear that osteoporosis can significantly affect one’s quality and
quantity of life, given that around 50% of hip fracture patients do not return to
independent living and one fifth of individuals requiring hospitalization for fragility
fractures die within a 6-month period. As such, the potential for development of such
a bone condition in athletes requires careful consideration. (Sale, 2019).
There are two main considerations for athletes concerning their bone health:
Firstly, 90% of peak bone mass is achieved by the age of 20 years and the amount of bone accrued by the age of 30 years is about the maximum amount that will be attained.
Secondly, it is very difficult to generate a sufficient and sustained osteogenic stimulus to improve bone health to such a degree as to offset age-associated bone loss. As such, it is important for athletes to maximize and protect their bone health during their athletic career, rather than sacrificing this for their athletic performance.
CONTROL THE CONTROLLABLE
When it comes to bone health, some factors, such as genetics, race, age and sex are non-modifiable. However, some lifestyle factors provide a potential modifiable effect on the bone. Of these factors, mechanical loading has arguably the greatest effect. Bone responds to the magnitude, rate, total number and direction of loading cycles induced through activity. As such, manipulating the mode, duration and intensity of exercise could be useful ways to improve bone health in athletes. Strength training has also been shown to have positive impacts on building and maintaining bone density.
Nutrition is another modifiable factor that needs to be considered. Although,
nutritional requirements to support the skeleton during growth and development and
during aging are unlikely to be notably different between athletes and the general
population, but there are some key considerations of specific relevance to athletes,
Low energy availability
Low carbohydrate intake
AVOID LOW-ENERGY AVAILABILITY
The low energy availability experienced by some athletes can have adverse effects
on bone, including acute bony injuries and longer-term reduced bone mass and
strength. It seems that many highly active individuals, particularly elite and
recreational endurance athletes, might have some difficulties in matching their
dietary energy intakes to their exercise energy expenditure, which inevitably results
in low energy availability. It is clear that this is also an issue that can affect male
athletes as well as female athletes.
"Energy availability can be described as the amount of ingested energy remaining to support basic bodily functions and physiological processes, including growth, immune function, locomotion, and thermoregulation, once the energy needed for exercise has been accounted for." (Sale, 2019)
Studies suggested that low energy availability achieved through dietary energy restriction resulted in decreased bone formation, with no significant change in bone resorption. This means that there is more bone breakdown than build-up which can result in decreased bone mineral density and ultimately lead to a fracture.
Low energy availability achieved through exercise alone, on the other hand, did not significantly effect bone metabolism. This might suggest some bone protective effect of the mechanical loading induced by exercise in the short term, even when this might result in low energy availability. However, these results also suggest that the athlete must focus on adequate dietary intake during hard training periods to promote positive bone formation.
Given the potential for low energy availability to negatively influence the short-term responses of bone, it would seem sensible to suggest that if this state was maintained over longer periods, more serious consequences might be experienced like the development of osteopenia or osteoporosis.
ADEQUATE NUTRIENT AVAILABILITY
The effects of reduced nutrient availability on bone also needs to be considered. With low-energy availability nutrient intake is also reduced by the same relative amount, which begs the question of whether the effects on bone are only due to energy availability or whether the combination of the reduction in the availability of carbohydrate, protein, calcium, vitamin D and other micronutrients also contributes to the negative impact on bone.
In addition, there might also be an interaction between elements of RED-S (Relative energy Deficiency in Sport) and the Female Athlete Triad and certain nutrients that could exacerbate the effects on bone. The female hormone estrogen regulates bone metabolism. It is essential to bone health because it promotes the activity of osteoblasts, which are the cells that make new bone. Estrogen levels drop when an athlete is under-fuelling which leads to a decrease in bone density.
If you’re experiencing low energy availability or RED-S, it’s imperative to address the underlying issues. Stress reactions, stress fractures, and missing your period are huge warning signs that there’s something wrong, including the loss of bone density, from which you may never be able to recover.
SAY NO TO LOW-CARBOHYDRATE DIETS
It has also been shown that low-carbohydrate intake can reduce bone turnover and
has therefore been suggested that following a low-carbohydrate diet can negatively
influence an athlete’’s bone health in the long-term.
Carbohydrates are also a crucial part of meeting your energy demands as an athlete and will help you avoid low energy availability. Furthermore, it is has been well know that carbohydrate consumption before and during high intensity and prolonged duration exercise enhances performance. Therefore, athletes who are consuming a low-carbohydrate diet are not only negatively influencing their bone metabolism, but also compromising their performance.
ADEQUATE PROTEIN INTAKE
Sufficient protein intake is important for strong bones. Bone tissue is composed ~ 50% protein by volume and about a third by mass, given that it is an important constituent of the
structural matrix of bone. As such, athletes need to consume sufficient protein to support the increased rate of bone turnover caused by athletic training. Additionally, protein ingestion increases the production of a number of hormones and growth factors, such as IGF-1, which are also involved in the formation of bone. Of further relevance for the athlete is the fact that higher protein intakes also support the development of muscle mass and function; the associated increases in muscular force would likely act upon the bone to enhance bone mass and strength.
Not everything is in your control when it comes to building and maintaining strong bone density. However, athletes can take advantage of good nutritional strategies like maintaining good energy availability, avoiding nutrient deficiencies, saying no to low-carb diets, and ensuring they have an adequate protein intake.
Control the controllable and maintain a strong skeleton through a good diet!
Craig Sale1, Kirsty Jayne Elliott-Sale2, "Nutrition and Athlete Bone Health," Journal of Sports Medicine, 2017, available online at https://pubmed.ncbi.nlm.nih.gov/31696454/