Hypothesis: Neutralization of acid production induced by the Western diet with oral administration of potassium citrate increases bone mineral density and bone mass as well as skeletal muscle mass and strength in elderly people (> 65y).

We will perform a prospective, randomized, placebo-controlled trial evaluating the effect of K citrate on bone mineral density, microarchitectural composition of bone,nutritional parameters, lean body mass, parameters of skeletal muscle mass and strength, 24h and exercise induced blood pressure changes in otherwise healthy, elderly ambulatory subjects of both genders.

Potassium citrate (60 mEq) is supplied as tablets with a wax matrix (10 mEq of citrate per tablet) and ingested in three doses/day. All subjects will receive daily oral 500 mg of calcium and 400 IU of vitamin D to ensure adequate calcium and vitamin D supply.

Inclusion Criteria:

• Men and women, 65 to 80y, tscores at L2-L4 0 to -2.5

Exclusion Criteria:

• Treated or necessity to treat low BMD (t-score L2 to L4 <-2.5)
• Any major medical illness that would possibly need hospitalization and/or be followed by foreseeable complications within 12 months and/or have a life-expectancy of less than 5 years
• Stable serum creatinine > 150 umol/l and/or known Type IV renal-tubular acidosis (hyperkalemia)
• vegetarians
• concommitant drug prescriptions: systemic and topical glucocorticoids, systemically acting estrogens (topical allowed): both within the last 6 months. antiosteoporosis drugs: bisphosphoponates, fluoride, calcitonin, all within the previous 12 months.
• vitamin D deficiency at screening visit
• technical difficulties to delineate bone area of interest during the screening visit