While exercise is generally good for bone, a study of male endurance cyclists reports that serious cyclists lose significant hip bone mineral density during the biking season. This new research as well as earlier studies document that over time many endurance cyclists end up with low bone density.
If exercise is good for bone, why do endurance cyclists lose hip bone during the biking season?
Researchers report several factors which contribute to bone loss among serious cyclists. These include:
(1) Cycling is not weight-bearing and yields comparatively low skeletal strain (the skeletal strain of exercise encourages bone formation).
(2) Endurance cyclists do a great deal of this non-weight-bearing exercise, averaging over 13 hours per week, and perhaps do this activity instead of other exercise which might be weight-bearing and bone-building.
(3) Cyclists experienced an increase in parathyroid hormone, likely subsequent to excessive loss of calcium through the skin with sweating. Excess parathyroid hormone tends to increase bone breakdown.
(4) Cyclists likely did not consume enough calories for their heavy training. Also, I would add that they likely did not consume enough of the 20 key bone-building nutrients.
(5) The physiological stress of such training produces bone-damaging stress hormones and pro-inflammatory cytokines.
The Better Bones perspective on this research finding would include, but also go beyond, the above five proposed causal factors. As we see it, intense physical activity places various stresses on the body resulting in increased oxidative damage, increased bone-depleting low grade metabolic acidosis, and increased losses of many nutrients in the sweat. All these factors suggest the need for a higher level of not only calcium, but of all the 20 key bone nutrients. Further, ample antioxidants should be consumed by endurance athletes. These nutrients should be taken, perhaps in liquid form, just before or during the exercise itself. In addition, special attention should be given to reducing any exercise-induced metabolic acidosis with the Alkaline for Life® Diet and the use of alkalizing mineral compounds as necessary.
Barry, DW, and Kohrt, WM. 2008. BMD decreases over the course of a year in competitive male cyclists. J Bone Miner Res, 23(4):484-491.
Does being Asian-American really increase your risk of fracture? Being “Asian or Asian-American” always figured high on the standard list of osteoporosis risk factors. So naturally, one is led to think that Asians and Asian-Americans are at high risk for osteoporotic fracture—particularly Asian-American women who are in or past menopause.
When we actually look at the fracture statistics, however, we find that postmenopausal Asian-American women have the lowest fracture rate of women in any US ethnic group. In a study of nearly 200,000 women, Asian-Americans were found to experience one-third the osteoporotic fractures of Caucasian and Hispanic women, and they even fractured much less than Native American and African-American women.
So, why is being Asian-American always listed as a big risk factor for osteoporosis? This is because Asian-Americans are generally thinner and have lower bone density than other ethnic groups. Yet the study shows that although they have lower bone density, they still fracture much, much less often.
This interesting paradox supports my long-standing position that bone mineral density is not a good predictor of fracture risk. As I have been saying for years now, many factors influence fracture risk, not just bone density. In fact, over half of all women who fracture do not have very low bone density.
To learn about the variety of risk factors contributing to osteoporotic fracture, take a look at my article, Rethinking the Causes of Osteoporosis.
Barrett-Conner, E. et al. 2005. Osteoporosis and fracture risk in women of different ethnic groups. J Bone Miner Res, 20(2):185-194.
My recent blog on the bone-building action of prunes drew a lot of attention and generated several interesting follow-up questions. Let me answer your questions as best I can.
Q. Wouldn’t eating 9-10 prunes a day cause diarrhea and/or gas?
A. As we well know, prunes have a laxative effect. The studies using 9-10 prunes a day, however, found that if people introduce the prunes slowly, taking a few to start and adding more over time, they do not experience excessively loose stools. Also, at the Center for Better Bones we find that soaking or lightly cooking the prunes also helps improve their digestibility, as does eating them warmed a bit, if necessary. Another tip is to spread your prunes out over at least 2 meals. Incidentally, prunes make a tasty dessert or sweet addition to hot cereal.
Q. Will eating all these prunes each day cause me to gain weight?
A. As it appears, consuming prunes did not cause weight gain and, in fact, prune researcher, Dr. Bahram Arjmandi specifically addresses this question, suggesting that prunes are so satisfying that they can actually aid in weight control. Also, recent work at the San Diego State University found snacking on prunes twice a day curbed the appetite while improving blood lipids, which actually aids weight management.
Q. I try to keep my blood sugar under control. Wouldn’t eating these prunes harm my blood sugar?
A. As Dr. Arjmandi reports, “Because prunes are low on the glycemic scale, they should not be a problem for people with diabetes.”
Q. Does drinking prune juice have the same effect as eating prunes?
A. All of the research I have found uses whole prunes, so I have to say that we simply do not know if prune juice would have the same bone-building impact.
Q. You list prunes as being an “acid-forming food.” So how can they help bones?
A. We have to remember that foods have many qualities, and not all acid-forming foods are bad for bones. In fact, protein is acid forming and yet adequate protein is essential for optimum bone health. Although prunes are slightly acid-forming, they contain phenolic and flavonoid plant compounds, which increase bone growth factors, so overall their impact on bone is very positive.