There is increasing evidence that the acid-base balance of diet plays an important role in the health of bones and muscles. An excess of acid in the body can result in calcium loss and muscle breakdown. Potassium bicarbonate, a base supplement, can neutralize acid within the body. The purpose of this study is to determine the effectiveness of potassium and bicarbonate, alone and combined, at reducing bone loss and preventing muscle wasting in older adults.

The typical American diet of dairy products, grains, and meats results in excess acid build-up in the body. The kidney is often unable to remove this excess acid quickly enough, resulting in mildly elevated blood acidity. In an attempt to neutralize the acidity, the body releases calcium from its bones. Over time, however, this calcium loss can lead to decreased bone density and possibly osteoporosis. Excess acid in the body also stimulates the breakdown of muscle. The combination of osteoporosis and reduced muscle strength sets the stage for falls, fractures, and ultimately functional decline. At least 30% of older adults fall once a year and, of those falls, 5% result in fractures. Preserving muscle mass and strength is an effective way to lower the risk of falling and to maintain independence among older people. Potassium bicarbonate is a base supplement that can neutralize acid. The purpose of this study is to determine the effectiveness of potassium and bicarbonate, alone and combined, at reducing bone loss and preventing muscle wasting in older adults.

This study will last 3 months. Participants will be randomly assigned to one of four treatment groups:

• Group 1 will receive potassium bicarbonate supplements
• Group 2 will receive potassium chloride supplements
• Group 3 will receive sodium bicarbonate supplements
• Group 4 will receive placebo supplements

All participants will take three pills of their assigned supplement after each meal; this will occur on a daily basis throughout the study. Participants will also take a multivitamin and a 600-mg calcium tablet daily. Participants will not be required to alter their usual diet in any way, but they will be requested to not take their usual calcium and vitamin D supplements during the study. Study visits will occur on Days 1, 21, 49, and 84. Days 1 and 84 study visits will include a review of medical history and physical activity, blood collection, and evaluation of weight, blood pressure, calcium absorption, and muscle function. Collection of both a 24-hour urine sample and a calendar depicting compliance with the supplement schedule will also occur at these two visits. The other study visits, on Days 21 and 49, may include blood collection, calendar compliance checking, and weight and blood pressure measurements. Supplements will be handed out on Days 1, 21, and 49.

Inclusion Criteria:

• Body mass idex less than 35
• Not currently on a weight gain or weight loss diet
• Willing to maintain usual level of physical activity
• Willing to refrain from taking own calcium supplements, antacids, or salt substitutes

Exclusion Criteria:

• Vegetarian
• Use of glucocorticoids for more than 10 days in the 3 months prior to study entry
• Use of estrogen, raloxifene, or calcitonin in the 6 months prior to study entry
• Use of bisphosphonate or teriparatide in the 2 years prior to study entry
• Current use of diuretics, nonsteroidal anti-inflammatory drugs (NSAIDS), beta-blockers, anabolic drugs (steroids or other), angiotensin converting enzyme (ACE) inhibitors, or angiotensin receptor blockers (ARBs)
• Renal disease, including kidney stones in the 5 years prior to study entry or creatinine clearance less than 50 ml/min/1.73 m2 of body surface area
• Hyperparathyroidism
• Untreated thyroid disease
• Significant immune disorder
• Current unstable heart disease
• Active malignancy or cancer therapy in the year prior to study entry
• 24-hour urine calcium levels greater than 300 mg/d after 1 week of being off calcium supplements
• Hypertension, congestive heart failure, arrythmias, or myocardial infarction in the 12 months prior to study entry
• On a salt-restricted diet
• Bone density total hip T score of less than -2.5
• Abnormal serum calcium
• Alkaline phosphatase levels greater than 10% above the upper end of the reference range
• Adrenal insufficiency, primary aldosteronism, or Bartter's syndrome
• Diabetes mellitus
• Alcohol use exceeding two drinks/day
• Peptic ulcers or esophageal stricture
• Screening serum 25(OH)D levels below 16 ng/ml