Protein2026-05

Independent effects of whey protein and alkali supplementation on muscle health in healthy older adults: factorial randomized controlled trial.

Ceglia Lisa, Konieczynski Elsa, Danico Elise, Trinquart Ludovic et al. — The American journal of clinical nutrition

Summary

This study investigated whether adding whey protein or an alkali supplement could improve muscle strength and mass in healthy older adults. Despite increasing a growth-related hormone, the supplements did not show significant benefits for muscle power, physical performance, or overall muscle mass over 24 weeks in participants already meeting daily protein recommendations.

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Key points

Healthy older adults took either whey protein, an alkali supplement, both, or placebos for 24 weeks.
The study aimed to see if these supplements could improve muscle strength, physical ability, or muscle mass.
Neither whey protein nor the alkali supplement improved muscle power, physical performance, or muscle mass.
However, both supplements did increase levels of a hormone linked to growth, called IGF-1.

What the study looked at

As people age, muscle strength and mass can decline, partly due to changes in how the body builds muscle and increased acidity. This study explored whether supplementing with whey protein, known for its muscle-building properties, or an alkali (to counteract acidity) could help maintain or improve muscle health in older adults. Researchers recruited healthy individuals aged 65 and older and randomly assigned them to one of four groups for 24 weeks. Groups received either a high dose of whey protein, an alkali supplement, both, or inactive placebos. Participants' muscle power, physical abilities, and muscle mass were measured at the start and end of the study. The study found that neither the whey protein nor the alkali supplement, taken independently or together, led to improvements in muscle power, physical performance, or overall muscle mass. While both supplements did increase levels of a growth-related hormone called IGF-1, this increase did not translate into measurable benefits for muscle function or size in these healthy older adults.

Dietary takeaway

For healthy older adults already consuming adequate protein, simply adding more whey protein or an alkali supplement might not be enough to boost muscle strength or mass. While protein is crucial for muscle health, this study suggests that increasing intake beyond current recommendations through supplements may not always yield further benefits for muscle function. Remember, this is just one study, and individual needs can vary.

Abstract

BACKGROUND: Aging is accompanied by reduced muscle protein synthesis and increased circulating acid, both of which contribute to declines in muscle health. OBJECTIVES: To determine the effects of whey protein (WP) and alkali (potassium bicarbonate, KHCO) supplementation on muscle performance and mass in healthy older adults. METHODS: In this randomized, 2 × 2 factorial, placebo-controlled study, healthy adults aged ≥65 years were assigned to either WP (1.5 g/kg/d) plus KHCO (81 mmol/d), WP plus placebo-KHCO, placebo-WP plus KHCO, or double placebo. Double leg press muscle power (primary outcome), physical performance, lean mass by dual energy x-ray absorptiometry, muscle mass by D-creatine dilution, and serum insulin-like growth factor 1 (IGF-1) were measured at baseline and 24 weeks. Primary analyses estimated main effects of WP compared with placebo-WP and KHCO compared with placebo-KHCO using factorial comparisons "at-the-margins," following CONSORT/SPIRIT recommendations for factorial trials. Between-group differences in the 24-wk outcomes were estimated using analysis of covariance adjusted for baseline value, age, and sex. RESULTS: In the intention-to-treat sample (n = 128), 47.7% were female, mean ± SD age was 74 ± 6 y, and baseline protein intake was 0.85 ± 0.30 g/kg/d. Neither WP nor KHCO affected muscle power compared with their respective placebo {WP to placebo-WP difference 4.7 watts [95% confidence interval (CI): -21.1,30.5; P = 0.72]; KHCO to placebo-KHCO difference -13.6 watts [95% CI: -39.6, 12.4; P = 0.30]}. No group differences were noted in physical performance or muscle mass. However, 24-wk mean IGF-1 level was higher in the WP and KHCO groups compared with their respective placebo [WP to placebo-WP difference 14.2 ng/mL (95% CI: 7.5, 21.0; P < 0.01); KHCO to placebo-KHCO difference 7.2 ng/mL (95% CI: 0.4, 13.9; P = 0.04)]. CONCLUSIONS: In healthy free-living older adults reporting a protein intake at the current recommended daily allowance, neither increasing protein to 1.5 g/kg/d with WP nor adding a KHCO supplement for 24 wk improved measures of muscle power, physical performance, or muscle mass despite achieving higher circulating IGF-1 levels. CLINICAL TRIAL REGISTRY NUMBER: This trial was registered as NCT04048616 at https://clinicaltrials.gov/study/NCT04048616?term=ceglia&rank=1.

View on PubMed →DOI: 10.1016/j.ajcnut.2026.101257