A scoop of whey protein can change what shows up in the blood. But in a new trial of healthy older adults, that did not mean stronger legs, more muscle, or better physical performance.
Published in The American Journal of Clinical Nutrition, researchers tested whether boosting protein intake with whey could help protect aging muscles, especially because older bodies often respond less efficiently to protein than younger ones. They also tested potassium bicarbonate, an alkaline supplement meant to counter the acid load that can build up from protein metabolism.
After 24 weeks, neither supplement improved muscle power, physical performance, lean mass, or muscle mass compared with placebo. That was true even though both whey protein and potassium bicarbonate raised levels of IGF-1, a hormone involved in growth and muscle metabolism.
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Testing Whey Protein for Muscle Strength in Older Adults
With age, protein may not send the same muscle-building signal it once did. Even when older adults consume enough amino acids for repair and maintenance, their bodies may respond more weakly than those of younger adults, a problem often called anabolic resistance.
That has led some to suggest that older adults may need more protein than the current recommended daily allowance of 0.8 grams per kilogram of body weight per day. Whey protein is often used for this purpose because it is easy to consume and rich in amino acids involved in muscle protein synthesis.
The trial tested whether increasing intake well beyond that baseline would make a difference. Participants in the whey groups raised their protein intake to 1.5 grams per kilogram per day, nearly double the current recommendation.
Potassium bicarbonate was included for a different reason. Protein metabolism can add to the body’s acid load, and aging kidneys may become less able to clear that acid. Earlier work had shown that alkaline supplements might help reduce muscle breakdown by neutralizing some of the breakdown products.
Inside the 24-Week Supplement Trial
The trial included 128 healthy adults aged 65 and older. At the start, participants reported an average protein intake of 0.85 grams per kilogram per day, which was close to the current recommended amount.
They were assigned to one of four groups: whey protein plus potassium bicarbonate, whey protein plus placebo, placebo protein plus potassium bicarbonate, or double placebo. Researchers then compared the effects of whey protein against placebo protein and potassium bicarbonate against placebo potassium bicarbonate.
The main outcome was double-leg press power, a measure of lower-body muscle performance. Neither whey protein nor potassium bicarbonate produced a significant improvement. Researchers also found no meaningful differences in physical performance, lean mass, or muscle mass.
A Blood Marker Changed, but Muscle Size Did Not
IGF-1 levels rose in the whey protein and potassium bicarbonate groups, which may sound encouraging. The hormone is involved in growth, tissue repair, and muscle metabolism, so the increase indicates that the supplements positively affected the body.
That biological shift, however, did not lead to measurable changes in strength or muscle size.
These findings do not mean protein is unimportant for older adults, or that whey protein can never help. People with low protein intake, frailty, illness, poor appetite, or higher physical demands may have different needs.
The study narrows the takeaway rather than overturning it: Extra whey may be less useful for healthy older adults who are already meeting their basic protein needs.
This article is not offering medical advice and should be used for informational purposes only.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in The American Journal of Clinical Nutrition: Independent effects of whey protein and alkali supplementation on muscle health in healthy older adults: factorial randomized controlled trial
