The DASH diet and sodium reduction to improve markers of bone turnover
Does the DASH (Dietary Approaches to Stop Hypertension) diet decrease the risk of osteoporosis? When we think of osteoporosis prevention, increased calcium and vitamin D are the first two things that normally come to mind. This study by Lin PH and others, PMID: 14519796, however, looks at the effect of reducing dietary intake of sodium as a potential beneficial factor in preventing osteoporosis. The DASH diet has been shown to significantly reduce the risk of hypertension due to its daily reduction of sodium intake and due to other positive dietary benefits that it entails. I have mentioned the effect of increased sodium on calcium metabolism in several newsletters, mainly that it increases the loss of calcium in the urine, thus potentially increasing the risk of osteoporosis. In this study, they compared three different daily intakes of sodium and their effects upon markers of bone turnover and calcium metabolism in adults. Two markers of bone turnover were reduced by the DASH diet: Serum osteocalcin (OC) and C-terminal telopeptide of type I collagen (CTX) by 8-11% and 16-18% respectively. The authors suggest that, "A reduced sodium intake reduced calcium excretion in both diet groups and serum OC in the DASH group. The DASH diet and reduced sodium intake may have complementary, beneficial effects on bone health."
Comments. This is very interesting to me since I've recently been looking at my dietary sodium intake trying to track down whether or not I have slightly elevated blood pressure. Having been a "health nut" to varying degrees since the late 1960s, I've always felt that my diet and exercise programs were excellent. I've never added salt to any food since about 1981 and thus assumed I've been on a low-sodium diet since then. However, now that I'm looking more closely at my sodium (not salt) intake, I've been surprised by the results. I eat a mainly vegetarian diet that includes lots of visits to the Chinese buffets where they put plentiful vegetables in with the various dishes on the serving line. I also eat lots of canned or processed vegetables, soups, Thai foods, etc. Now as I look at those labels, I realize that I was getting much more than the DASH diet recommendation of 2,500 mg/day or less of sodium. In fact, a couple of days ago I started a very low sodium diet and noticed an almost immediate four pound weight loss, which had to be retained water, since my caloric intake is not particularly reduced. Unfortunately, the problem is that sodium is added to virtually everything processed that we eat, so it isn't a simple change to reduce sodium intake from your diet. The Website I mentioned above does have recipes and simple guidelines wherein they try to make the changes as pain free as possible. For those of us with osteoporosis these modifications may be well worth the effort. Potential benefits appear to be at least two fold in nature: Reduce your sodium intake and improve your bone density while you decrease your chances of hypertension.
More on resistance exercise and BMD
Resistance exercise training in heart transplant recipients. This is another study, PMID: 14550817, by Braith RW and others from the University of Florida in Gainesville similar to the one that I highlighted in a recent Update. The previous study was on lung transplant recipients, but it appears that both heart and lung transplant patients get roughly equal doses of glucocorticoids which rapidly reduces their bone mineral density (BMD). Note there was an almost 12% reduction in all groups in the lumbar spine two months post transplantation. Alendronate was able to stop further reduction, while the control group continued to lose BMD. The resistance exercise group who also took alendronate had significantly increased BMD over the six-month study period compared to the two-month low, once again with about a 9% improvement in the lumbar spine. The authors conclude: "Our results indicate that anti-osteoporosis therapy in this population should include both an anti-resorptive agent as well as an osteogenic stimulus, such as mechanical loading."
Comments. The interesting element of this remarkable improvement in BMD is that the participants only used the MedX resistance exercise machine once-weekly for the lumbar spine. It would be wonderful if there was a way to duplicate the effects of the MedX machine at home, but for now there are no studies to indicate that is possible. Thus, access to the MedX machine appears to be your only way to try to improve lumbar BMD if you want to do it without medications, or faster than medications alone can do it. If you can get a copy of the first study, you will see that the MedX is able to stabilize the entire lower body while the spine moves through a 72 degree plane, all the while working against a resistance force. This combination of stabilization and resistance force are virtually impossible to duplicate without some mechanical device.