Impact of Protein and Alkali Supplementation on Skeletal Muscle in Older Adults

Not Applicable

Completed

Conditions: Age-Related Sarcopenia
Muscle Loss

Interventions: Dietary Supplement: whey protein isolate
Other: maltodextrin powder
Other: microcrystalline cellulose
Dietary Supplement: potassium bicarbonate (KHCO3)

Registration Number: NCT04048616

Lead Sponsor: Tufts University

Brief Summary: The central hypothesis is that higher protein intake and a neutralizing alkaline salt supplement will improve muscle performance and mass, compared to their respective placebos, in older men and postmenopausal women.

Detailed Description: With aging, skeletal muscle mass and performance decline leading to an increased risk of falls and physical disability. There is ongoing research on whether increasing dietary protein intake in older adults improves indices of muscle health and thus translates to a reduction in physical disability. A main concern is that high protein results in a large dietary acid load from the breakdown of protein to acidogenic byproducts, which could in turn promote muscle degradation particularly in older adults with age-related declines in renal excretion of acid. The scientific premise of this project is that the balance between the amount of protein in the diet (anabolic component) and the net acid load of the diet (catabolic component) in part determines whether the diet as a whole has a net anabolic or catabolic effect on muscle. Preliminary data have suggested that a daily alkaline salt supplement (potassium bicarbonate, KHCO3) lowered the dietary acid load and improved lower extremity muscle power in postmenopausal women.

The investigator's central hypothesis is that higher protein intake and a neutralizing alkaline salt will improve muscle performance and mass, compared to their respective placebos, in older men and postmenopausal women. To test the hypothesis, the investigators conducted a randomized, double-blind, placebo-controlled, 2x2 factorial study in underactive men and women age 65 and older on baseline lower protein diets. Participants were assigned to one of four groups: either a whey protein supplement (to raise protein intake to 1.5 g/kg/d) with or without KHCO3 81 mmol/d or an isocaloric placebo supplement with or without KHCO3 81 mmol/d for 24 wks.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 141

Inclusion Criteria

ability to sign informed consent form
ambulatory community-dwelling men and women
age 65 years and over
habitual dietary intake of protein of ≤0.8 g/kg/d
underactive
estimated glomerular filtration rate ≥ 50 ml/min/1.73 m2

Exclusion Criteria

participation in a diet or intensive exercise program during the study
vegetarian (no animal protein)
oral glucocorticoid use for > 10 days in the last 3 months
anabolic and gonadal hormones in the last 6 months
Tamoxifen/raloxifene in the last 6 months
regular use of alkali-producing antacids (> 3 times per week)
potassium-containing supplements or products
non-steroidal anti-inflammatory medications >3 times per week
antacids containing calcium carbonate, aluminum hydroxide, magnesium hydroxide, or calcium acetate
insulin
sulfonylureas
SGLT2 inhibitors
a lower extremity fracture in the last year
kidney stones in the past 5 years
hyperkalemia
elevated serum bicarbonate
hypercalcemia
uncontrolled diabetes mellitus defined as having fasting blood >150 or hemoglobin A1c >8%
untreated thyroid or parathyroid disease
significant immune disorder
current unstable heart disease
Crohn's disease
active malignancy or cancer therapy in the last year
alcohol use exceeding 2 drinks/day
current peptic ulcers or esophageal stricture
other condition or abnormality in screening labs, at discretion of the study physician

Study & Design

Study Type: INTERVENTIONAL

Study Design: FACTORIAL

Arm && Interventions

Group	Intervention	Description
maltodextrin powder + microcrystalline cellulose	maltodextrin powder	isocaloric placebo maltodextrin powder and identical placebo microcrystalline cellulose capsules
whey protein isolate + KHCO3	whey protein isolate	1.5 gm/kg/day of whey protein and 81 mmol/day of KHCO3
whey protein isolate + microcrystalline cellulose	microcrystalline cellulose	1.5 gm/kg/day of whey protein and identical placebo microcrystalline cellulose capsules
maltodextrin powder + KHCO3	maltodextrin powder	isocaloric placebo maltodextrin powder and 81 mmol/day of KHCO3
whey protein isolate + KHCO3	potassium bicarbonate (KHCO3)	1.5 gm/kg/day of whey protein and 81 mmol/day of KHCO3
whey protein isolate + microcrystalline cellulose	whey protein isolate	1.5 gm/kg/day of whey protein and identical placebo microcrystalline cellulose capsules
maltodextrin powder + KHCO3	potassium bicarbonate (KHCO3)	isocaloric placebo maltodextrin powder and 81 mmol/day of KHCO3
maltodextrin powder + microcrystalline cellulose	microcrystalline cellulose	isocaloric placebo maltodextrin powder and identical placebo microcrystalline cellulose capsules

Primary Outcome Measures

Name	Time	Method
Double Leg Press Peak Power at 70%	24 weeks	Double leg press peak power at 70% of the 1 repetition maximum

Secondary Outcome Measures

Name	Time	Method
Double Leg Press Peak Power at 70%	12 weeks	Double leg press peak power at 70% of the 1-repetition maximum
Double Leg Press Peak Power at 40%	12 weeks	Double leg press peak power at 40% of the 1 repetition maximum
Knee Extension Peak Torque	12 weeks	Knee extension peak torque at 60 degrees/s using Biodex Isokinetic Dynamometer
Handgrip Strength	24 weeks	Measure maximum handgrip strength in either hand using handheld Jamar+ dynamometer
Appendicular Lean Body Mass/Height Squared	24 weeks	Dual energy X-ray absorptiometry (DXA) lean mass of arms plus legs divided by height squared
Physical Performance Battery Score	24 weeks	Performance score (range 0-4 with higher values representing a better performance) based on Health Aging and Body Composition-Physical Performance Battery
24 Hour Urinary Total Nitrogen Excretion	24 weeks	Measure based on 24 hour urine total nitrogen excretion