We don’t think much about our bones until something breaks, but as with most health issues, prevention is key. Bone mineral density (BMD) is one of several indicators of how susceptible bones are to fracture, and it is measured using Dual X-Ray Absorptiometry (DXA). A DXA scan measures three components of body composition: bone mass, fat mass, and lean mass, making it not only the most accurate for BMD measurement but also for body fat percentage. Diagnosis of low bone mass is based upon age and gender comparisons using “T or Z scores” which are calculated by the DXA software.
When it comes to bone health, athletes are generally thought to be exemplary, but cycling is a non-weight bearing sport, thus it does not provide the stimulus needed to maintain or improve BMD. Research has shown that BMD values decrease during the racing season with minimal improvements during the off season. Compared to other sports, cyclists have lower BMD in the spine compared to runners and triathletes and often, they are at greater risk for low BMD than inactive individuals. As BMD is lost, it is an uphill battle to regain and increase it.
My interest in cyclists and bone stems from research I recently completed and presented at the American College of Sports Medicine (ACSM) annual meeting this past June. The research looked at the effect of a high impact jumping program, inadequate energy intake, calcium and vitamin D on BMD.
Energy and Bone
Most research on BMD has used premenopausal female runners to study the female athlete triad. If you are a male and reading this, do not tune out! As previous research has shown, energy deficits impair BMD so males are not completely off the hook. If you increase your training volume and intensity without increasing your caloric intake, your body will be in a state of energy deficit. Habitually existing in an energy deficit, intentional or not, suppresses physiological processes in the body and the effect on bone is the same: a faster rate of bone breakdown than bone rebuilding. This is due to subsequent compensations by the endocrine system. When we do not consume enough calories over the long term, axes that maintain hormonal balance in males and females can be disrupted. Decreased levels of estrogen as experienced during menopause are correlated with decreased BMD. The effect of low testosterone and estrogen on BMD in males is inconclusive.
Impact & Bone
It has been proven that impact to the bone (e.g. high vertical jumping/basketball, resistance training) provides the stimulus needed to maintain BMD. BMD improves in the areas to which the stimulus is applied which is why full body resistance training is recommended throughout the year with additional high impact exercises during the off-season. Bone metabolism adapts to stimuli, so plan on varying your workout and consider including trail and road running. Knowing that power-to-weight ratio is key to performance, if weight gain from resistance training is a concern, be sure to consume enough calories to fuel and recover from training.
Bone Building Nutrients
It is known that calcium is vital to build bone; to maximize calcium absorption both vitamin D3 and vitamin K are needed.
- Calcium
- The Recommended Dietary Allowance (RDA), created by the United Stated Department of Agriculture, recommends a 1000-1300 mg/day of calcium depending upon age and gender. Dermal calcium loss is also a consideration especially for athletes with high sweat rates who do not consume low-fat sources of calcium. Yes, greens contain calcium, but you will not consume as much as you need purely through a diet high in spinach, and chard due to decreased bioavailability from oxalic acid. If your diet is dairy-free, purchase non-dairy beverages that are fortified with vitamin D and calcium.
- Vitamin D3: Even if you live in a sunshine state, vitamin D (25[OH]D) levels decrease during winter and spring, so it is recommended you have your levels checked at the beginning of spring and end of fall.
- The RDA for vitamin D3 is 600 IU/day, however I make customized recommendations based upon serum values. Almost everyone should take a minimum of 1000 IU/day while athletes that have insufficient or deficient values of 25[OH]D may need up to 5000 IU/day for an average of five weeks, after which their values should be re-measured.
- Aim for >50 ng/mL – then change to a maintenance dose.
- Vitamin K is found is most leafy greens and consuming one cup per day will provide the recommended intake of 90-120 mcg/day.
There are several supplements on the market promoted for bone health that contain calcium, vitamin D3, and vitamin K. Work with a coach or dietitian to find a reputable brand, or simply avoid them.
BMD at Every Age
Male and female athletes in their teens and 20’s:
- Male cyclists and female runners with high training volume/mileage who do not consume enough calories or perform resistance training, are at risk of not attaining peak bone mass, repeated stress fractures, and disrupted menstrual cycle.
Males and Females in 30’s:
- Male cyclists who do not cross train, and all females should implement resistant training and supervised high impact exercises into their annual training plan.
Over 50: Males and females consider a DXA scan to know baseline BMD values. Often, only whole body BMD is discussed with patients, so be sure to get a copy of all body regions that are scanned.
Release provided by Regina Hammond.
Regina Hammond, MS (http://www.trismarter.com/staff/coaches/regina-hammond) is the Director of Nutrition at Trismarter Triathlon Coaching and Nutrition (http://www.trismarter.com). When she isn’t running up Pikes Peak Regina is creating custom hydration and fueling plans for age group athletes who successfully compete in half-ironman 70.3 and ironman triathlons including the World Championship. Staying abreast of the latest research she believes in an individualized approach to nutrition and works with clients on performance fueling plans, periodized nutrition plans, weight loss, and behavior change. Contact Trismarter Triathlon Coaching & Nutrition to make your triathlon dreams a reality!