Is There a Role for Dietary Potassium in Bone Health?
This chapter explores the question of the role of potassium in bone health, despite the speci„c reference to such an effect used in setting the current dietary reference intake recommendation for potassium by the Institute of Medicine (2005). Potassium has been associated with bone health (e.g., Lemann et al., 1989, 1991; Green and Whiting, 1994; Tucker et al., 1999; New et al., 2000; Jones et al., 2001; Sebastian et al., 2006) through its contribution to dietary alkalinity. Potassium is ingested mainly as a component of fruits and vegetables, but it is also found in lesser amounts in dairy foods, meats, and grains, especially whole grains. In Table 17.1, selected food sources of potassium in various food groups are shown. Unlike several nutrients that affect bone health directly through incorporation in bone mineral, such as calcium, phosphorus, magnesium, and —uoride, or through bene„cial effects in bone cells, such as vitamins A, D, and K, potassium is classi„ed as a nutrient which indirectly promotes bone health. Thus, uncertainty lies in whether a speci„c direct hypocalciuric effect of potassium exists or whether potassium serves primarily as a carrier for anions that promote bone health and also may possibly reduce sodium intake, assuming that potassium is consumed in its stead. In the former role, optimal potassium intake, but only as an alkaline salt, promotes the retention of calcium through countering the adverse effects of a mild metabolic acidosis that stimulates bone resorption. The latter role suggests that potassium itself plays no role and that several other cations (except sodium) are just as effective. This hypothesis is explored in this chapter in the context of bone health.