A few tablespoons of unsweetened peanut butter each day can mitigate some aspects of age-related muscle decline, according to a new study of 120 community-dwelling elders by researchers at the Deakin University School of Exercise & Nutrition Sciences in Geelong, Victoria, Australia.

In general, nuts as a good dietary source of protein, healthy fats, and fiber. Pistachios and peanuts are particularly rich in anti-inflammatory and anti-oxidant phytochemicals that can attenuate chronic inflammation and oxidative stress, which are key drivers of muscle loss.

There’s some evidence from population studies that increased nut consumption is associated with a reduced risk of musculoskeletal and cognitive decline among older people. But until now, the direct impact of daily nut consumption on muscle strength and function had never been evaluated in a randomized intervention trial.  

Ilili Feyesa and a research team based at Deakin University aimed to rectify that. They recruited 120 generally healthy, non-exercising, community-dwelling people over age 65, to participate in a 6-month study of the effects of daily peanut butter consumption on a range of biometric and functional assessments.

Simple, Practical, Inexpensive

They randomized the participants to two groups: the control subjects were instructed to simply maintain their usual dietary and lifestyle habits over the 6-month period; the intervention group also maintained their usual routines but with the addition of 43 grams per day of peanut butter, supplied by the researchers at no cost. This daily “dose” of peanut butter is equivalent to roughly 2.7 tablespoons.

Feyesa and colleagues chose peanut butter as the mode of nut delivery because “a butter form is simple, practical, age-appropriate and inexpensive.”  Barring allergies or sensitivities, most people like peanut butter, and its soft texture makes it ideal for people who have dental problems–a common issue among elders.

After 6 months, those in the peanut butter group showed better times on the 5STS test, as well as improved muscle power compared with those in the control group.

The 43-gram serving, equivalent to about 1.5 ounces of whole peanuts, supplied ~250 kcal, 20 g of fat (over 90% unsaturated), and 10 g of protein.

At baseline, the investigators ran the subjects through a wide variety of questionnaires and tests of muscle function. These included:

• Falls risk screening using a standardized protocol comprised of 6 parameters: age; history of slips or trips (without falling) in the past year; feeling unsteady while standing, walking, or doing daily activities; subjectively feeling at risk for falling; difficulty rising from a chair or toilet without using arms; using 4 or more prescription drugs.

• Gait speed, measured by timing the participants while they walked a 4-meter distance at their usual pace.

• Five Times Sit-to-Stand (5STS) test: For this test, a participant is asked to stand up from a chair, with arms crossed over chest, five times, as quickly as possible. The time needed to complete the task is an indicator of leg muscle strength and power.

• 30-second STS: a closely related test which measures the total number of times someone can rise from a chair, arms crossed, during a 30-second period.

• Four-Square Step Test (FSST): In this test, participants step forwards, sideways and backwards as quickly as possible over two rods arranged in a cross formation. The investigators record the time needed to complete the task.

They also assessed upper and lower body muscle condition via handgrip strength and knee extensor strength measurements.

A total of 108 subjects (76 women, 32 men; mean age 76 years) completed the full 6-month trial. At baseline there were no major differences between the control and intervention groups in terms of BMI, or general dietary and lifestyle habits. Full compliance with the peanut butter intervention was 86%.

Better Muscle Power

Peanut butter was by no means a magical elixir for muscle strength, but it did have statistically and clinically significant impacts on some of the aforementioned assessments.

After 6 months, those in the peanut butter group showed better times on the 5STS test, as well as improved muscle power compared with those in the control group. Muscle power, which reflects both muscle force and velocity of action, was calculated using a validated formula that divides body weight, height, and chair height by the total STS time.

On average, the peanut butter group showed a 1.23 second improvement on the 5STS, a finding the authors considered “small yet clinically meaningful.” Age-related declines in 5STS performance correlate strongly with increased disability and impairment in daily activities. Improvements in 5STS, even if incremental, could help in averting disability.

The participants in the peanut butter group also showed a 0.25 W/kg increase in muscle power compared to the people in the control group. That may not sound like much, but again incremental improvements do matter. Feyesa and colleagues note that low relative muscle power is linked to greater impairment of mobility, especially difficulty in walking.

They explain that muscle power, defined as muscle strength multiplied by velocity, may be a more significant indicator of overall functionality and personal independence than muscle strength alone (Carbone S, et al. Mayo Clin Proceedings, 2025). Further, as people age, muscle power tends to decline earlier and faster than muscle mass and muscle strength.

“An improvement in muscle power documented in our study is of clinical importance.”

Important Questions

That said, peanut butter consumption did not have any statistically significant effect on muscle, strength, muscle mass, or gait speed. This raises interesting an interesting question: why did muscle power increase, while other measures of muscle function showed no changes?

Ilili and her collaborators address that seeming paradox, explaining that the participants in the peanut butter group were able to complete the 5STS task in a shorter time, indicating a higher velocity. Since velocity is a key factor in the muscle power equation, this increased the power calculation even though there was no change in muscle strength as indicated by knee extensor strength measurements.

But why no increase in strength?

The authors explain that the recommendation that elders increase their protein intake so as to preserve muscle mass and strength is “based on the premise that aged muscle requires a greater supply of amino acids to optimally stimulate muscle protein synthesis, particularly in the context of anabolic resistance, which is characterised by a reduced muscle protein synthesis response to anabolic stimuli.”

The 43-gram daily peanut butter serving tested in this trial provided roughly 13 g of protein which may not be enough to counterbalance the age-associated anabolic resistance. Add to that the fact that most participants in this trial were eating, on average, 1.12 g/kg of protein daily, which is well above the 0.8 g/kg Recommended Daily Allowance for protein in this age bracket. This likely blunted the potential effect of the additional protein intake.

Further, the study participants were not exercising regularly. Ilili and colleagues point to a systematic review and network of meta-analyses of 38 RCTs showing that protein supplementation combined with consistent exercise is the most effective for improving muscle mass, strength and physical function in older people. Increasing protein intake in the absence of regular exercise may not do much.

The peanut butter supplementation did add calories—an average of 256 kcal—to the participants’ daily intake. It also added fat—approximately 21 grams—along with the protein. But this did not lead to any net weight gain or body fat increase in the intervention group compared with the controls.

Why not? The authors hypothesize that the high levels of mono- and polyunsaturated fatty acids in peanuts are more easily oxidized by the body and have greater thermogenic effects. They add that their findings are consistent with other studies of nut consumption showing that increased intake does not automatically lead to weight gain.

The recommendation that elders up their protein intake is “based on the premise that aged muscle requires a greater supply of amino acids to optimally stimulate muscle protein synthesis, particularly in the context of anabolic resistance.

The peanut butter intervention was well-tolerated. In fact, many participants said they liked it, and planned to continue eating peanut butter daily after the trial ended.

There were no incidents of allergy or serious adverse effects, though one subject reported diarrhea and bloating, and another experienced troublesome burping. One individual dropped out of the intervention because of concerns about potential cholesterol elevation.

“Peanut butter supplementation is a feasible dietary strategy” for boosting dietary protein in older adults,” the authors state. “Peanut is a nutrient-dense food, and peanut supplementation in a butter form is a simple, practical, age-appropriate and inexpensive dietary strategy that can be easily adopted by older adults.”

It may not be a cure-all for age-associated sarcopenia. But it’s an inexpensive and tasty way to preserve muscle power and function, while attenuating potential risk of disability.

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