Men's Osteoporosis Support GroupAdverse effects of sodium chloride on bone J Nutr. 2008 Feb;138(2):419S-422S. Adverse effects of sodium chloride on bone in the aging human population resulting from habitual consumption of typical American diets. Frassetto LA and others. PMID: 18203914. This article was presented at a recent acid-base symposium, Nutrition-Health-Disease, in Munich, Germany. Frassetto and others have another study on this topic that you might want to read at PMID: 11842945. First I will summarize my general understanding of this article. Excess sodium chloride (table salt), and a diet that is lacking in potassium, combine to cause an acidic environment in the human body. Particularly as we age, this acidic environment can cause osteoporosis and many other pathological conditions, such as, sarcopenia, nephrolithiasis (kidney stones), hypertension, stroke, some types of cancer, insulin resistance, thyroid and growth hormone disturbances, and progressive renal insufficiency. The article is full of complex biochemical, metabolic and physiological terms, and is thus not easy to read, so I will try to present its high points as I understand them. Evolutionary diet override causes acidosis. Basically what has happened is that humans evolved with a diet that was high in potassium and low in sodium. Homo Sapiens have existed about 200,000 years and ate that high-potassium low-sodium diet for all but about 10,000 of those years. When the cereal-based diet started to be eaten about 10,000 years ago that changed the potassium-to-sodium ratio negatively and has only worsened in orders of magnitude with the advent of the highly processed fast-food diet Americans eat now. This creates a condition known as metabolic acidosis, which is conducive to acidic resorption of bone, kidney stones, etc. Three major things contribute to the acidosis: 1) cereal grains yield a net acid after metabolism, 2) energy-dense nutrient-poor fats and sugars lead to lower intakes of potassium-rich plant foods and 3) the ratio of potassium to sodium intake has been reversed in our diets. Early humans ate foods that led to about a 5:1 ratio of potassium to sodium whereas today that ratio is about 1:2. Evolutionary changes don't occur rapidly enough to enable humans to adequately cope with these acidic environmental changes, thus disease results. So those diseases I mentioned in the paragraph above are diet-induced, which means they can be prevented or treated by diet changes, mainly ones that increase the potassium-to-sodium ratio back to normal dietary levels that existed over 10,000 years ago. Bone and dietary sodium chloride. The authors note that other factors contribute to osteoporosis and osteopenia: genetics, insufficient sunlight exposure and hormonal changes, to name a few. There are studies that suggest the problem with salt intake is not that detrimental to bone and others that implicate it. The authors cite at least five studies that concluded that excess salt intake had detrimental effects on bones, including one they did on 166 post-menopausal women. They used biochemical markers of bone formation and resorption and related those to salt intake. They concluded the findings indicated that dietary sodium chloride magnitude-dependently drives urine calcium excretion, increases bone resorption rate, and increased bone resorption rate relative to bone formation rate. It has been suggested that rather than reducing salt intake people could just increase calcium intake. This is a problem in older individuals because they don't have the elevated levels of vitamin D needed to increase calcium absorption from the gut. Thus reducing salt intake is the better way to go. To test their hypothesis that increased potassium-to-sodium ratios should stop the acid loss of calcium from bone, the authors point to a study which used potassium citrate on 60 women who were first adapted to a low-salt diet, then switched them to high-salt with placebo or with potassium citrate. The citrate addition was found effective. The authors concluded: "Thus, the addition of oral potassium citrate to a high-salt diet prevented the increased excretion of urine calcium and the bone resorption marker caused by a high salt intake." The authors suggest, ". . . it behooves us to consider both the inordinate dietary sodium chloride load and the habitual dietary net acid load of contemporary American diets among many factors contributing to the pathogenesis of osteopenia and osteoporosis in the aging population." They note there is a balance needed between potassium and sodium intakes that might be affected either with increased potassium intakes, reduced sodium chloride intakes or a combination of both. Finally they state, "However, both decreasing sodium chloride intake and increasing potassium- and bicarbonate-rich precursors may likely not just help the aging skeleton but provide other potential health benefits as well." Editor's comments. In a recent Update on kidney stones, you'll notice that the diet recommended to prevent kidney stone formation would be very much like the one suggested by Frassetto and others here. Note that there is a link there to foods that are high in potassium content. I would also suggest this link to look up individual foods to find their nutritional information as displayed on the food label. NOTE: You may need to scroll down below the ads to find the exact item you are searching for if it doesn't show up as the label. Here is a summary of that diet: rich in vegetable fiber and alkaline potassium, normal calcium content, reduced sodium chloride content, reduced animal protein content, limited sugar and fat, and limited oxalate intake (not a factor in bone health, just kidney stone formation). Frassetto and others didn't mention the issue of reduced animal protein in this article since their main emphasis was on sodium chloride. Even though meat is moderately high in potassium, the proteins in meat are acid-forming, thus potentially negating the benefit of the potassium, and explaining why reducing meat would be beneficial to bone health while reducing the risk of kidney stone formation. Grains and cereals are generally low in potassium, particularly if they are processed to remove the fiber. For instance, white rice has 17.6 mg of potassium per cup while brown rice has about 83 mg of potassium per cup. However, crude rice bran has 1752.3 mg of potassium per cup. Thus highlighting what the authors said about how the switch to the cereal grain diet led the way to low potassium intake about 10,000 years ago. If you want to eat cereals/grains and keep your potassium intake high, it looks like you'll need to eat the whole grain and add some fiber, too. Or you can add vegetables and/or fruit, depending upon the type of grain used. I recently read two interesting books that relate to the information presented here that you might want to read. They were diet/health oriented and made dietary recommendations similar to Frassetto and others to promote overall health and longevity, not just bone health. They are "The Okinawa Program" by Bradley J. Willcox, M.D. Craig Willcox, M.D. and Makoto Suzuki, M.D. and "The China Study" by T. Colin Campbell and Thomas M. Campbell II.
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