Bone density and the female cyclist: Mum was right about drinking your milk

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Bone health is not an issue often discussed over post ride coffees. But you may have heard some whispers through the peloton about bone mineral density and pro cyclists. Of course, what the pros know, you should know.

I spoke with Dr. Eric Haakonssen, a senior AIS physiologist who’s worked with Orica-AIS women’s team, the Australian Women’s road team and the BMX high performance unit. He has spent the past four years examining issues surrounding body composition in female cyclists for a PhD. Today I’m going to examine why bone health is a big deal, what Dr. Haakonssen’s newly released research can tell us about bone density in relation to cycling and why Mum was right when she said drink your milk.

No bones about it

Bone density (or bone mineral density) refers to the amount of minerals within the bone and is used as an indicator of a bone’s strength. In the general population, issues with bone density aren’t common until after the age of 50. However research has been accumulating that shows young, fit cyclists are susceptible to the health problem. A review of the literature released on BioMedCentral in 2012 indicated that up to two-thirds of professional and masters road cyclists had significantly low bone density. “Pretty quickly we saw that they did appear to be on the low side,” said Dr. Haakonssen, in reference to when the Australian Institute of Sport (AIS) staff began screening their cyclists, male and female.

Having low bone density can lead to a condition called Osteoporosis, where the matrix structure of the bone deteriorates and becomes brittle. Once diagnosed, the Australian Government predicts a lifetime risk of future fractures of up to 29% in males and 56% in females. Fractures can be caused by even the slightest fall, yet too few Australians are actually diagnosed or properly treated for the condition.

Going down with a bang  

“That is one of the concerns. You have a population with low bone mineral density who are susceptible to high impacts. It’s generally a case of not if they crash but when,” Dr. Haakonssen said. Perhaps more concerning, the previous released research found that the bones of the lower spine and hips were most significantly affected, areas that are highly vulnerable in a crash.

Given that bone density peaks in the early twenties and slowly begins to deteriorate from there, discovering that cycling can cause lower bone density has long-term health implications. Years after the medals are won, cyclists may have chronic injuries caused by brittle bones, especially after menopause when bones deteriorate more rapidly.

Despite having higher risk factors, female cyclists are currently underrepresented in the literature. Of the thirty-two participants Dr. Haakonssen recruited for his study, seven had bone density scores classified significantly below that of the normal population. Road cyclists are the worst affected, with mountain and BMX riders suffering less bone density losses.

What’s up, Doc?

“Cyclists seem to be the perfect storm for low bone density,” said Dr. Haakonssen. Accepted risk factors for poor bone health include a lack of weight bearing activity, insufficient calcium intake and vitamin D, low body weight, smaller statured people, hormonal suppression, certain medications and smoking.  Cyclists, unfortunately, have extra risk factors. All risk factors can be classified as modifiable or non-modifiable, which helps us understand how to better manage them.

Based on his research, Dr. Haakonssen classifies risk factors specific to riders as extended training durations, reduced energy availability, poor weight loss practices, a lack of weight bearing exercise and calcium losses through sweat. Dr. Haakonssen and his team were interested in the last factor for his latest study.

Enter the Matrix

Calcium plays an important role in many body functions. The majority of it is found bound to the skeleton in salt form, where it gives strength to the bone matrix and acts as a mineral reservoir. A tiny but significant amount is found in extracellular fluids and blood. This is calcium’s most vital place, as in cells it acts as a trigger for heart muscle function, transmits nerve impulses and is used in muscular contractions. The balance of calcium in the bloodstream is maintained vigorously by the body.

“If it gets too high or gets too low, we have problems with the nerves firing and the heart functioning,” Dr. Haakonssen explained. “What we notice is that with athletes when they sweat a bit they do lose a small but probably significant amount of calcium. So if there is no other calcium available through dietary sources, the only way to maintain that level is to leech it from the bones. That’s where we got concerned about the cyclists routinely doing three, four, five-hour rides.”

Increasing calcium intake seems like the most obvious thing to do, however previous studies indicate that cyclists who eat high levels of calcium have similar risks as those who eat low levels calcium. Dr. Haakonssen believes the missing link might be the timing. “We got to thinking based on previous research in male cyclists and basketball players that it might not be a case of the total daily calcium intake but the timing of it for athletes. So we wondered if we introduced it prior to exercise if we’d be able to create a protective effect.”

Time trials

The result was a study to determine if consuming a high calcium, dairy-based meal could alter bone resorption levels after a stationary trainer session. What they found was that elite female cyclists showed an increase in markers indicating bone resorption after a ninety minute ride. However, after eating a high calcium meal, cyclists had much lower levels of bone resorption markers then when they ate a normal breakfast. This indicates that eating a calcium rich meal prior to exercise has a protective effect on the bones.

The research found other results too. Markers of bone resorption were still elevated in athletes two hours after the trial, indicated that the process of bone uptake was ongoing. It was also noted that markers indicating that new bone was being laid down were not stimulated at all.

“If you see disturbances in calcium homeostasis leading to increased resorption of bone during just a 90-minute-bout of exercise, we would expect that you would see at least that much of a disturbance during longer rides. And if athletes are doing that almost daily, if not twice daily, we were concerned that over the career of a cyclist [it] could be one of the factors that contributes to low bone mineral density later in life,” said Dr. Haakonssen.

The game plan

As a result of this study, Professor Louise Burke and Louise Cato, dietitians at the AIS, created new guidelines for their athletes. The new calcium recommendations for pre-ride intake are approximately 1000 milligrams or three standard dairy serves. In a breakfast, this might look like porridge made with one cup of milk plus a handful of nuts and a tub of yogurt. Not only does this provide a good hit of calcium, dairy pre-ride also provides a quality source of protein.

If the ride is over three hours, additional calcium intake is recommended. Suggestions include cheese sandwiches, calcium fortified protein shakes and yogurts. Coffees, smoothies and milkshakes also make the cut. Despite any misgivings about upset tummies, Dr. Haakonssen has also released a study showing that eating a dairy heavy meal doesn’t appear to cause stomach discomfort during rides. For those with lactose intolerances or who can’t eat dairy products, many fortified products exist. Other dietary sources of calcium include almond and brazil nuts, tofu, tahini and leafy green vegetables.

Milking it

Dr. Haakonssen is quick to point out that this research is not professing to provide the ultimate solution to low bone density in cycling, and further research is required. Instead, this strategy is one of many that should be considered by cyclists. As Dr. Haakonssen said: “ If there is something very easy that we can change, such as the meal you eat before you go out and train, and that could potentially have a protective effect over the career of a cyclist, that could be something useful to try and implement.”

I’ll raise my milk glass to that!

With Dr. Haakonssen’s help, I have developed five tips looking at the modifiable factors of low bone density. These can be used as part of a broader protective program for cyclists.

My Tips

  • Eat your dinner – Making sure daily nutritional requirements are being met allows your body to have the resources to complete tasks essential for longevity-such as building strong bones. This means kilojoules, carbs, proteins, vitamins and minerals should all meet the requirements of the training you do. (Try Loren Rowney’s post-training epic omelette!)
  • Calcium load – As in the article, the AIS now recommends increasing calcium around the time of your training sessions. It’s important to note this is in addition to everyday calcium recommendations, which is ~1000mg.
  • Walk this way – Cyclists can be sedentary when off the bike. Dr. Haakonssen suggests that athletes should simply start with walking more frequently. The World Health Organisation (WHO) recommends 10,000 steps a day. Pedometers and phone apps can help gauge your daily activity levels.
  • Jump around – Weight lifting and high impact activity have a positive effect on laying down new bone when there is adequate nutrition to do so. Dr. Haakonssen reports he includes running and weight lifting in his female cyclists programs for this and other benefits. Easy exercise ideas include squats, box jumps and skipping.
  • Talk to a pro – If you are looking at reducing body fat levels, make sure your coach and a qualified sports dietician are on board. Dr. Haakonssen cites extreme and extended weight loss practices including kilojoule restriction and large training volumes as having detrimental effects to many aspects of female cyclists’ health, including bone health.

Thanks to Dr. Haakonssen and the researchers at the AIS and also to all the athletes who volunteered to take part in the studies. Is increasing your dairy pre-ride a move you might try? Do you have any high calcium recipes to share with your fellow readers? Please share them in the comments below.

Alana Crimeen is a qualified physiotherapist and Australian Physiotherapy Association member. Her professional background involves working in the public system including as an independent practitioner in an emergency department and in outpatient injury rehabilitation. She was introduced to riding in a velodrome, fell in love with riding on the road and learnt healthy fear for riding on the mountain. She likes to keep up with recent research relating to athletes in order to hassle her training partners about cross-training from a more educated point of view.

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