Bone Health and the Female Athlete

Bone health is about more than just milk! Image from mommygoggles.com.

When I say the phrase “strong bones,” what is the first thing that pops into your mind? Milk? Calcium Supplements? Wolff’s Law? Stress Fractures? Hormone Imbalance? Poor diet? If you answered any of the above, you’ve come to the right place. As part two in a series on the female athlete triad, I’m tackling bone loss. I’ve developed somewhat of a fascination with this topic over the past year as a result of a few things. First, a runner friend of mine found out she had low bone mineral density in her back and arms. Hmmm. Since changing my diet to dairy-free and a 3-month layoff from running occurred simultaneously, I started to wonder whether my bone strength and health would be maintained while I lacked both calcium-rich milk and weight bearing exercise. Hmmmmmmm. Then, I read that osteoporosis is more about calcium loss than calcium intake. Ok bone health, you now have my undivided attention.

How do we measure bone health?

The measurement of bone loss is bone mineral density (BMD).  BMD is basically the strength of your bones. In fancy-pants, medical-land, it is the mineral content in one square centimeter of bone. The National Osteoporosis Foundation recommends testing for BMD be done via dual energy x-ray absorptiometry, also known as DEXA or DXA. I’m about to out-geek myself now, so please bear with me. DEXA results are expressed using the statistical measure of a T-score. This allows for comparison to normative values (derived from studying large numbers of people with healthy bones) for age, body part tested, and even race or gender. From the T-score, you can determine your risk for osteoporosis based on the distance of your T-score from the average value.

The highest point on the curve is the average. The colored sections show the deviation from the average. If your bone is in the purple area, your bone health is in jeopardy! Image from www.washington.edu

If you are within 1 unit (standard deviation) of the average, your bones are healthy! From 1 to 2.5 standard deviations below the average, your bones are considered osteopenic (or pre-osteoporotic). And if you T-score is more than 2.5 standard deviations below the average, your bones are osteoporotic. If your bones are osteoporotic, you are at an increased risk for fractures and stress fractures. A stress fracture in a lower extremity bone can mean 6-8 weeks without running. And a stress fracture in a vertebrae (medical term, Sponylolysis) can have neurological implications, if the vertebrae slides (spondylolithesis) towards nearby nerves or spinal cord. If I have sufficiently scared you into a bone health obsession, keep reading to find out what you can and should do to keep your bone strong and healthy!

 

The CDC is a great resource on bone health.

How do I know if I should have my bone density tested?

Bone loss, like so many other things in life, is about balance. Calcium intake (in) and calcium excretion (out/ or loss) both play a role. We intake calcium through our diet. According to the National Institutes of Health (NIH)  the recommended daily intake of calcium for women is 1000-1200 milligrams. A standard glass of milk has about 300 milligrams, but soy, salmon, sardines, almonds, leafy greens, seeds, and many other dairy-free foods have impressive calcium levels as well.

Recent research shows that the balance of acids/bases in the body as well as circulating protons (eek, chemistry!) can affect the excretion of calcium. An acidic environment can impair calcium absorption and an alkaline or basic environment can improve calcium absorption. Nutrients thought to increase calcium excretion include protein, sodium, and phosphorus. Just as some nutrients can affect calcium excretion, others can affect absorption including magnesium, vitamin D, vitamin K, and potassium. If you eat a balanced, variable diet without restrictions, you likely won’t have a problem with nutrient balance. But calcium intake can be difficult for individuals with food allergies, eating disorders, high alcohol consumption and gastrointestinal diseases all which can affect absorption as well as intake of nutrients. If any of these conditions affect you, it’s a good idea to have your BMD checked. But you may also want to see a dietitian or talk to your doctor about your calcium intake and bone health.

Excretion of calcium

Caffeine, smoking, alcohol, and hormones can all increase calcium loss. The first three are factors we can (and should) control, but hormones, particularly estrogen, can have a mind of their own. Amenorrhea or absence of menstruation for greater than 3 months indicates a decrease in estrogen production, which can decrease calcium absorption and increase calcium loss from bones. Amenorrhea is normal in conditions such as pregnancy, breast-feeding and menopause. However, if amenorrhea occurs due to training, weight loss, inadequate body fat or an eating disorder, it is considered pathologic and can cause irreversible bone loss. Amenorrhea is the third prong in the female athlete triad, and will have a segment of its own. However, if you experience loss of menstruation for greater than 3 months, you should absolutely contact your doctor to discuss hormone balance and bone health.

How can we prevent bone loss?

Like so many aspects of health, it’s much easier to be proactive or reactive when it comes to bone loss. Here are a few recommendations to keep your bones strong!

1. Weight bearing exercise. Anatomist Julius Wolff taught us that bone is highly adaptive to the stresses placed upon it. In response to stress, bone grows stronger. How do we stress the bones? By stressing our muscles. When a muscle contracts, it pulls on the bone and makes the bone stronger. Weight-bearing exercise (such as running) is a wonderful way to stress the muscles and build bone strength. Resistance training is also important, particularly for bone health in our spines and arms. Unless you are a champion at handstand races.  Exercise such as swimming, water jogging, and biking are not as effective at building strong bones. Try that line the next time a cyclist tells you to “save your knees” and take up cycling. I kid. I jest. Kind of. Moving on…

2. Eat a well-balanced diet with fruits, vegetables and protein. Track your calcium intake for a while by keeping a food diary such as www.FitDay.com or MyFitnessPal.com. Just don’t get too obsessive about it. Some of the Salty Runners have ‘fessed up to getting a little too obsessive when tracking food intake and we don’t want you to go there!

3. Get your bone density tested. Health fairs, science museums and college students with research studies sometimes offer free BMD testing. If you come across free testing, take advantage of it! If not ask your doctor to complete a screening. My friend (mentioned above) runs 75+ miles per week and eats a well-balanced diet without any restrictions and she had low density in her arms and spine. If that isn’t incentives to add some push-ups to your post run regimen, I don’t know what is!

For more on the importance of bone health and a very thorough explanation of how bone density is tested and what factors influence bone density, see Camille Herron’s recent post on the subject.

Have you had your BMD tested? What tips do you have for keeping your bones healthy?

 

I'm a pediatric physical therapist by day. Running mostly early am miles as I balance life as the mom of a toddler. With PR days in the past, my primary running goal is to be a lifelong runner. With 20+ years behind me, I still love the sport and I am truly grateful for every day I get to run.

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4 comments

  1. after less than a year of running, I got two stress fractures in my feet so i requested a bone density scan and learned I had osteopenia. I had been taking calcium supplements, though, so my family doc then tested my vitamin D levels and we learned they were negligible. After 8 weeks of uber-high vitamin D (50,000 iu/week), my vitamin D is back to normal.

    I think low vitamin D is an issue for many women, and would recommend testing for that as well.

  2. Great, well-written article. I hope in the future to see fewer of the “eek, chemistry!” disclaimers. You obviously did your research and know what you’re talking about. No need to dismiss yourself.