Nutritional strategies for bone health in female endurance athletes

Are you a constant sufferer of stress related bone injuries? An endurance athlete? Female?

There are many different contributing factors of stress fractures in endurance athletes. Overcoming these challenges and working toward the prevention of these injuries is so important in order to continue with our training and competition schedule. In this article ,I will discuss why female endurance runners are more susceptible to these injuries along with some modifiable risk factors (i.e. nutrition interventions) that can be manipulated to reduce your risk of suffering one!

(Men, I did not forget about you. Stay tuned for an article on stress fractures in male endurance athletes!)

Possible Reasons for Stress Fractures

There are many endurance athlete-specific reasons why stress fractures may occur. One reason for this is the fact that distance running has a high metabolic demand. It costs a lot of energy to run fast for long periods of time and thus increases our need for a higher caloric intake. This can put us at risk if we are inadvertently under consuming calories. Inadequate food intake including both overall energy and micronutrient intake, can play a role in increasing our risk of fractures.

Excessive negative energy balance aside, runners seem to be especially at risk compared to other endurance athletes who also consume lots of calories. Although running does indeed increase bone mineral density (bone strength) with the proper balance of training and recovery, the repetitive nature of high-volume running often leads to the athletes not taking adequate rest days and/or programming in periodized reduced training weeks. This can lead to insufficient recovery and healing of the bone in between bouts of stress and therefore not enough time for the bone to adapt and become stronger. I would refer you to my colleagues, Dr. Sean and Kayla Ng, at the clinic to find out more about how to structure your training schedule.

 On top of inadvertent negative energy balances and insufficient recovery, some endurance athletes neglect the inclusion of a strength program into their training schedule. Lifting will act as a stimulus to increase bone mineral density. Not only this, but strength training can also aid in enhancing hours muscles ability to direct forces optimally through bones (i.e. compressive vs. sheer forces). For more on this, again I would encourage you to discuss this with my colleagues Dr. Sean and Kayla Ng.

Another risk factor is related to how in some circles, runners are often pressured to fit into the very thin and light body category. First off, low BMI or low weight in itself can be correlated with low bone mineral density. In addition, if that low weight is combined with weight loss efforts and low energy intake, this can wreak havoc on your bone health due to hormonal changes (i.e. decreased estrogen production) and resulting menstrual dysfunction (which can act as an early sign that your are consuming insufficient calories).

BUT, all is not lost!  There is a lot we can do to overcome our bone health challenges. Nutrition, for one, is an easily modifiable risk factor that can have positive outcomes for our bone health.

Nutrition & Bone Related Injuries

To put the need for proper nutrition in maintaining bone health in perspective, here are the results of 3 interesting and very applicable studies on the topic:

1. Negative energy balance and estrogen: Low energy availability, which is the amount of energy left over after exercise for normal physiological function expressed in calories/kg fat free mass, decreases estrogen levels. This results in a 4x greater risk of bone injury compared to those who have adequate energy availability.
2. Insufficient calcium: Low calcium intake (800mg) resulted in 6x more risk for bone injury compared to high calcium (1500mg).
3. NFL players and Vitamin D: In NFL male players, players with 1+ fractures had higher rates of inadequate levels of circulating Vitamin D.

Practical Applications:

So, here’s what you can do:

1. Make sure nutrition intake closely matches energy demand of sport & daily life.
2. Consume enough bone building materials (i.e. calcium, vitamin D, and magnesium)
3. Weight loss tactics should be introduced at appropriate times (likely in the low training/off season) to reduce risk of injury close to race season.

I hope these statistics and general tips reinforce how important nutrition planning is for endurance female athletes. If you still have questions or need guidance on planning for your race season, come visit me at the clinic!  You can check out more about me on my profile HERE.

References:

Tenforde AS et al., 2016. Association of the female athlete triad risk assessment stratification to the development of bone stress injuries in collegiate athletes. The American Journal od Sports Medicine 45(2), 302-310.

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.

Barrack et al., 2014. Higher incidences of bone stress injuries with increasing female athlete triad-related risk factors. The American Journal of Sports Medicine. 42(4). 949-958.

Papageorgiu M, Dolan E, Elliot-Sale KJ, Sale C. 2018. Reduced energy availability: implications for bone health in physically active populations. Eur J Nutr. 57:847-859.

Maroon JC, Mathyssek CM, Bost JW, Amos A, Winkelman R, Yates AP, Duca MA, Norwig. 2015. Vitamin D profile in National Football League players.

Very Low Carbohydrate Diets & Endurance Events: Part 2

Welcome to part 2 of the my exploration of very low carb diets for endurance athletes.  My last article provided the basis for understanding this article as it explored how and when our body choses to use fat vs. carbs.  Check it out here.

In this article, I will now explore (1) do low carb diets actually enhance fat metabolism and (2) does that actually makes us faster.

Does VLCD increase fat burning capacity?

Short answer, yes, the body is forced to increase fat use to support the energy needs during exercise. Research clearly shows that after adapting to a keto diet for as little as 3 weeks results in significantly elevated rates of fat oxidation (0.6g/min to 1.5g/min) during exercise. Fat oxidation at moderate intensities (65% VO_2max) in elite ultra-endurance athletes on a keto diet contributed 88% of the fuel for exercise verses 56% in athletes consuming high carbohydrate diets. Now, if we remember what we discussed in the last article, we learned that as we increase intensity we increase the amount of carbohydrates burned. This begs the question “will those high fat oxidation rates continue at intense ecercise (80% VO_2max)?”. Another study investigated the fuel usage of elite race walkers at 80% VO2max, and they too found that fat oxidation was elevated to the same levels as previous research (1.5g/min).

Research Outcomes of VLCD and Performance:

The more important question in my mind (and likely yours as well) is “well that is fine and dandy- my body will burn more fat, but what will happen to my performance?!”. We will review some key research studies that have looked at fat adaption diets (high fat diets for 3-7days), keto diets and their effect on performance. The majority of high fat diet adaptation and keto diets find that performance decreased and a handful found they had no-statistically significant effect. Only two articles find a performance benefit.

Keto, Training and Performance

Louise Burke et al. (2017) conducted a large study investigating the effects of a keto diet, chronically high carbohydrate diet or periodised carbohydrate diet on race performance of elite race walkers after a 3 week intervention and training camp. Athletes on the keto diet perceived the training to be significantly more difficult and experienced an inability to complete the exercise training sessions planned. This is a very important point because if an athlete cannot train as hard as they could they won’t see much improvement in their sport.

After the 3 weeks of intense training, the keto group had higher fat oxidation compared to the two high carbohydrate groups. All groups had significant increases in their maximal oxygen uptake (VO_2max) as a result of the training. As we discussed in the previous article, burning fat is less efficient and this study clearly demonstrated that at all competition race speeds there was significantly more oxygen used in the keto group and there was no change in the fraction of VO_2max at various speeds. The high carbohydrate and periodised carbohydrate groups used less oxygen and were able to keep the same pace at lower fraction of VO_2max. In plain English, the two carbohydrate groups improved their running economy and efficiency with the training where the keto group did not reap the benefits of the training because the cost of burning fat is so high.

Lastly, this study compared pre and post training performance walk times in a real 10km race. They found that both carbohydrate groups had a reduction in their time by 5-6% (on average 190s and 124s faster for high carbohydrate and periodised carbohydrate group). There was no improvement in the keto group and on average their times were 23s slower. There was a wide variability in performance for the keto group, ranging from 162s faster to 208s slower, meaning that keto worked for some individuals but not others.

High Fat Diet With Carbohydrate Loading

What if we don’t go into ketosis and we use a fat adaptation strategy + carbohydrate load, best of both worlds right? Havemann et al. (2006) showed that when elite cyclists consumed a high fat diet (68%) for 6 days with 1 day of carbohydrate loading that there was no significant difference in time to complete a 100km simulated bike race compared to a traditional high carbohydrate diet. However, if we look at the time to completion, we find that the high carbohydrate trial was completed on average 3 minutes 44 seconds faster (likely significant in the real world), leading us to believe that on average high carbohydrate diet may be superior to high fat diets. Again, 3 out of 8 racers on the high fat diet did improve their time compared to high carbohydrate diet, demonstrating that there may be some athletes who may respond well to a high fat diet.

More importantly, this research included 1km sprints throughout the ride to simulate a race like situation and found that the power output was significantly lower in the high fat diet group which lead to slower sprint times. Despite having lower power output in the high fat trial, they perceived they were working as hard as they were in the high carbohydrate trial. There was no difference in muscle recruitment during the sprints, meaning the high fat trial worked just as hard as the carbohydrate trial but did not achieve the same results in the sprint performance. The researchers thought that the high fat diet + a carbohydrate loading period would result in glycogen sparing due to increased reliance on fat for fuel, thus improving sprint times as sprinting relies on glucose to provide fuel. This was not the case and it is possible that high fat/fat adaptation diets reduce the ability to effectively burn carbohydrates.

Summary

• VLCD do result in higher rates of fat oxidation during exercise
• VLCD may reduce response to training
• VLCD decreases economy in elite athletes
• VLCD decreases ability to work at maximal effort which is important when there is change in work intensity- ie running up a hill, breaking away from the pack
• Most studies show that on average VLCD negatively affect performance in endurance athletes, however there are some that may respond well
• Remember that VLCD are not the same as training fasted or temporarily low carb diets to train your body to use fat more effectively, as this is an effective training method

In my final article in this series, I will explore the roll of supplements, the keto diet, and how that relates to athletic performance.

References:

Volek JS, Noakes T, Phinney SD. Rethinking fat as a fuel for endurance exercise. Eur J Sport Sci. 2015;15(1):13- 20.

Volek JS, Freidenreich DJ, Saenz C, Kunces LJ, Creighton BC, Bartley JM, Davitt PM, Munoz CX, Anderson JM, Maresh CM, Lee EC, Schuenke MD, Aerni G, Kraemer WJ, Phinney SD. Metabolic Characteristics of keto-adapted ultra –endurance runners. Metabolism. 2016;65(3):100-10.

Burke LM, Ross ML, Garvican-Lewis LA, Welvaert M, Heikura IA, Forbes SG, Mirtschin JG, Cato LE, Strobel N, Sharma AP, Hawley JA. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J. Physiol. 2017;595(9):2785-2807.

Havemann L, West SJ, Goedecke JH, Macdonald IA, Gobson ASC, Noakes TD, Lambert EV. Fat adaptation followed by carbohydrate loading compromises high intensity sprint performance. J. Appl. Physiol. 2006;100: 194-202.

Leckey JJ, Ross ML, Quod M, Hawley JA, Burke LM. Ketone diester ingestion impairs time-trial performance in professional cyclists. Front. Physiol. 2017;8(806).

Protein Part II: How much and when to eat it

Welcome back to another protein-focused edition of Training & Performance! My last article looked at the evidence in support of avoiding protein while you run. Today, I will discuss one of the more common questions I hear at my practice: does protein timing and distribution matter? And should you be consuming protein directly after a workout?

Muscle/Protein Physiology

Our muscles are in a constant state of breakdown and renewal. For the average person (depending on factors such as age and level of activity), muscles are broken down and rebuilt at a rate of 1-2%/ day. To help support this renewal, the building blocks of muscle (amino acids) need to be taken in on a regular basis.

While the amino acids we ingest provide the raw material to support that 1-2% renewal rate, that is not all they do. The act of ingesting amino acids also triggers a physiological cascade that signals more muscle growth. So, when the body is being fed amino acids, not only does it have the material for muscle growth, but an anabolic muscle-building state is also put into action!

So it’s no surprise that ingesting protein is important to muscle growth. Now the question is, how much and how frequently do we need to ingest protein to optimize both of these benefits and maximize our gains?

Click HERE to read the rest in the Run Waterloo Magazine.

Does protein ingestion during an endurance activity enhance performance?

I have written many times(1, 2, 3, 4)  about the importance of ingesting carbohydrates during a race (if it’s long enough).

I’ve also discussed how taking in other sources of fuel, like protein, is not the best move due to it triggering an increased risk of GI distress. The reason: in part, protein is not absorbed and metabolized as quickly as carbohydrates. Delayed gastric emptying results in water diffusing into your guts and increasing the odds of needing to take a PB-killing washroom break! 

One thing I have heard in response to this tip from patients and athletes at H+P is that IF one is able to handle protein from a GI standpoint, is it worth experimenting with on top of carbohydrates as a fuel source? Is there an additional benefit to taking in protein during a race if it doesn’t bother your stomach? That is what we’ll be looking at with this article.

CLICK HERE to read the rest in the RunWaterloo magazine!

Are you maintaining your iron balance?

When it comes to performance, there’s no doubt that nutrition plays a significant role. In the past, I’ve really focused on acute nutrition: what you can do directly before or during your run to be faster (i.e. here).

An area I have neglected to focus on is what you should be doing from a nutritional standpoint on an on-going basis to stay healthy and perform at your best. One key area that I see as a recurring problem in my practice and athletes around me is iron deficiency anemia.

Iron has a number of roles in the human body. The most important function is how it is incorporated into hemoglobin and myglobin to facilitate oxygen transportation. If these proteins decline, our ability to transport oxygen to our working muscles also drops, and performance plummets along with it (such as here and here).

CLICK HERE to read more in the RW Magazine