Potassium, The Hidden Bone Guardian

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Potassium is a mineral of great importance to the body, in fact the adult A.I. for potassium at 4,700 mg is nearly four times that of calcium (at 1,200 mg). While it is widely known that potassium serves along with sodium to maintain critical fluid balance within the body, it’s role in bone health is less well appreciated.

As it occurs, the body has its own system of priorities for ensuring survival. Maintaining proper fluid balance inside and outside of the cells is indeed a high priority. The maintenance of systemic acid-base (pH) homeostasis is also held in very high priority, as alterations in blood pH balance can result in death within minutes. As the body produces various acids through its metabolic processes, there is a need to neutralize or buffer these acids with alkali (base) compounds. To ensure acid-base balance, the body maintains diet-derived alkali reserves in the blood, other fluids and tissues. In addition, bone stores extra back-up alkali reserves available for transfer into the blood when alkali compounds in the blood, other fluids and tissue run short.

Bone, and the hydration layer around bone, provides the only substantial extra reservoir of base available to titrate excess metabolic acids. When we exhaust all other available alkali reserves, alkalizing compounds are drawn from in and around bone. This drain of alkalizing compounds from bone leads in turn to enhanced bone breakdown and loss of both bone mineral and bone matrix.

The role of potassium in bone health relates to the ability of selected potassium salts to neutralize bone-depleting metabolic acids. As discussed in previous E-Bone Health Newsletters, metabolic acidosis “eats away” at bone much like acid rain eats away at a
limestone statue. Metabolic acidosis, however, is largely neutralized, by potassium compounds, and to a lesser degree magnesium compounds, obtained from fruits and vegetables.

Fruits, vegetables, seeds and most spices contain high amounts of potassium compounds. These potassium compounds (known as potassium salts) include alkalizing forms of potassium including potassium citrate, potassium malate and potassium gluconate.

Within the body these potassium salts are metabolized to yield potassium bicarbonate, which in turn provides the body with bicarbonate for neutralizing metabolic acids.1 If these mineral salts are not consumed in adequate amounts, alkalizing bone mineral compounds are drawn upon to help reduce low-grade metabolic acidosis, causing increased bone resorption and enhanced loss of minerals in the urine.

A variety of population-based studies now document the positive association between high intake of base-forming potassium and magnesium foodstuffs and bone health. For example, several studies with adults have found a positive association between fruit and vegetable intake and bone mineral density.(2-5) In addition, urinary potassium, as a marker of potassium intake, is positively associated with bone mineral density in children.6 Overall, a beneficial effect on bone mass from high potassium fruit and vegetable intake has been shown in premenopausal and postmenopausal women, in the elderly, in children and in men.(7, 8)

By neutralizing metabolic acids, potassium conserves calcium within the body and reduces urinary calcium loss. Potassium bicarbonate supplements equivalent to that found in 7-8 servings of fruits and vegetables were found to reverse the urinary calcium loss induced by high salt intake.9 Along the same lines, the Dash Intervention Trial found that simply increasing fruits and vegetables from 3.6 to 9.5 servings a day decreased urinary calcium loss from 157 mg day to 110 mg per day.10 Looking at it another way, bone health expert Dr. Robert Heaney explains that eating one medium baked potatoes or one large banana can conserve about 60 mg of calcium within the body. To put this into perspective, a urinary loss of an extra 60 mg calcium per day would result in a 18 to 21% loss of total skeletal calcium over a decade.

Further, Drs. Sebastian, Frassetto and colleagues at the University of California were able not only to decrease urine calcium and phosphorus loss, but also able to decrease bone breakdown, and stimulate new bone formation in postmenopausal women by adding enough alkalizing potassium salts to neutralize metabolic acids.11

Fruits and vegetables provide mineral salts with alkalizing compounds (as potassium citrate) useful for neutralizing net endogenous acid. In addition to promoting an alkaline environment, a diet high in fruits, vegetables and legumes provides nutrients such vitamins C, E, A and the B’s, quercitin and many other phytochemicals which also promote bone health. Increasing vegetable and fruit intake is the preferred way to increase potassium intake and carries multiple benefits for blood pressure normalization, stroke risk reduction and weight control in addition to being bone-protective.

The current U.S. “Adequate Intake” recommendation for potassium is 4,700 mgs/day, (the equivalent of about 13 half cup servings of fruits and vegetables a day). The average adult daily potassium intake in the U.S. is much below the AI and is reported to average around 2,200 mgs for women and 3,200 mgs for men.

Unquestionably potassium is one of the most important key bone nutrients and consuming the recommended amount of 4,700 mg potassium a day should be a top priority for everyone.

Editor’s Note:

· NOW’s Potassium Gluconate Powder (Item #1472) can be used as a source of alkaline potassium and contains 550 mg potassium per level teaspoon.

· NOW’s Potassium Chloride Powder (item #1450) is a richer source of potassium with
712 mg potassium per ¼ level teasponn, but is not alkaline.

References:

1 Remer T, Manz K F. Dietary protein as a modulator of the renal net acid excretion capacity: Evidence that an increased protein intake improves the capability of the kidney to excrete ammonium. J Nutr Biochem 1995;6(8):431-7.

2 New SA, Robins SP, Campbell MK, et al. Dietary influences on bone mass and bone metabolism: further evidence of a positive link between fruit and vegetable consumption and bone health. Am J Clin Nutr 2000;71(1):142-51.

3 Tucker KL, Hannan MT, Chen H, Cupples LA, Wilson PW, Kiel DP. Potassium, magnesium, and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women. Am J Clin Nutr 1999;69(4):727-36.

4 New SA, Millward DJ. Calcium, protein, and fruit and vegetables as dietary determinants of bone health. Am J Clin Nutr 2003;77(5):1340-1; author reply 1.

5 New SA, MacDonald HM, Campbell MK, et al. Lower estimates of net endogenous non-carbonic acid production are positively associated with indexes of bone health in premenopausal and perimenopausal women. Am J Clin Nutr 2004;79(1):131-8.

6 Jones G, Riley MD, Whiting S. Association between urinary potassium, urinary sodium, current diet, and bone density in prepubertal children. Am J Clin Nutr 2001;73(4):839-44.

7 New SA. Impact of Food Clusters on Bone. In: Burckhardt P, Dawson-Hughes B, Heaney RP, eds. Nutritional Aspects of Osteoporosis. San Diego: Academic Press; 2001:379-98.

8 McGartland CP, Robson PJ, Murray LJ, et al. Fruit and vegetable consumption and bone mineral density: the Northern Ireland Young Hearts Project. Am J Clin Nutr 2004;80(4):1019-23.

9 Sellmeyer DE, Schloetter M, Sebastian A. Potassium citrate prevents increased urine calcium excretion and bone resorption induced by a high sodium chloride diet. J Clin Endocrinol Metab 2002;87(5):2008-12.

10 Appel LJ, Moore TJ, Obarzanek E, et al. A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group [see comments]. New England Journal of Medicine 1997;336(16):1117-24.

11 Sebastian A, Harris ST, Ottaway JH, Todd KM, Morris RC, Jr. Improved mineral balance and skeletal metabolism in postmenopausal women treated with potassium bicarbonate. New England Journal of Medicine 1994;330(25):1776-81