Eating peanut butter builds muscle power in older adults, study finds

The act of rising from a chair may seem like a simple task for most, but it is actually a significant effort for many older adults. This small movement serves as an everyday way to gauge overall strength, balance, and confidence, as well as what may ultimately determine how much assistance an individual requires in order to live independently.

According to a new research study from Deakin University in Melbourne, Australia, there is one food product that may be an unexpectedly easy solution: peanut butter. In this study, conducted over a period of six months, older adults consuming one serving of peanut butter on a daily basis, as opposed to those who did not, exhibited improvements in their lower body strength. Improvements were measured in relation to the speed at which individuals could rise from a chair after five repetitions.

The study was formally titled "Capacity of Older Individuals after Nut Supplementation" (COINS) and was conducted by Dr. Sze-Yen Tan, PhD, Associate Professor and Nutrition Researcher, at Deakin University's Institute for Physical Activity and Nutrition (IPAN). In total, 120 community-dwelling older adults between the ages of 66 and 89 years, who were considered to be at an increased risk of falling, participated in this study.

All participants were randomly assigned to one of two groups. One group received 43 grams (three tablespoons) of natural peanut butter daily, provided at no charge; the other group was instructed to refrain from eating nuts during the study and follow their typical dietary regimen. Participants in both groups were instructed to maintain their usual levels of physical activity and exercise during the course of the study.

The trial period ran from May 2023 until July 2024 and took place at Deakin University's Burwood Campus. Researchers collecting data for outcome measures and conducting statistical analyses were blinded to the participants' group allocations. However, the study participants were not blinded to their group assignments. Gait speed was the primary outcome for this study, measured via timing over four meters.

In regard to this primary outcome, peanut butter did not affect participants' gait speed. After six months, there were no significant changes within or between groups.

One of the most significant differences that resulted from consuming peanut butter was the five-times sit-to-stand test; essentially, this simulates a common activity that people perform every day. The test consists of a participant standing and sitting five times in the least amount of time, with their arms crossed over their chest. Although there was a significant change in time (1.23 seconds) from baseline to six months, there were again no other significant differences between the control and peanut butter groups.

This change in time from the five-times sit-to-stand test was also used to estimate muscle power. The peanut butter group had significant increases in both their absolute and relative muscle power based on the five-times sit-to-stand test. The estimated treatment effect for absolute power was 22.0 watts and 0.27 watts per kilogram for relative power, with corresponding p-values of 0.004 and 0.002, respectively.

In summary of the remaining results in this report, the authors were cautious when interpreting these data, as there were no significant between-group differences on any of the other physical function measures. These were assessed using the timed up-and-go test, the four-square step test, and the 30-second sit-to-stand. Similarly, there were no significant between-group differences with respect to measured muscle strength (hand grip strength and knee extensor strength), as well as no differences as assessed with DXA scans (lean mass and fat mass).

Thus, peanut butter was not an effective means for improving overall strength in participants. It was observed that peanut butter aided them in reaching their feet quicker than they would have done without it. Since one aspect of strength is how quickly one can get to their feet, this is a significant finding.

Therefore, it was hypothesized that peanut butter would provide the energy needed to enable faster completion of the five-time sit-to-stand test (5STS) but would not increase other types of physical function measures. The authors of the article provided a basic rationale for why this might be the case. Muscle power has two components: force and speed. In this case, individuals finished the 5STS at a faster speed compared to those in the reference group, even though there were no measurable increases in strength among participants due to the use of peanut butter as a low-protein energy source.

Authors noted in the discussion section of the research paper that while a 1.23-second difference is small, it is nonetheless clinically meaningful. They referenced studies demonstrating that approximately a one-second change in five-time sit-to-stand (5STS) test scores reflects significant differences in future disability risk.

As Tan explained, this result is significant when translated into layperson terms. "If you had increased the rate of completing this 5STS test you developed greater levels of muscle power," she said. "Muscle power gives senior adults the ability to perform daily living activities, walking up and down stairs, and rising up from the chair. Greater muscle power can minimize fall risks, which is a major reason for losing the ability to live independently, a reduction in quality of life, and potentially premature death."

This means that the stakes were high concerning a rather simple motion. However, in this research project, the direct assessment of fall occurrences was not evaluated. Also, the tool used to screen for fall risk did not possess reliable or valid predictive validity for predicting future falls, even though it was adapted from prior work conducted by the research group.

Even though participants in the study increased their caloric intake and protein consumption through daily use of peanut butter, they did not experience any increase in their body weight or in their fat mass compared with participants in the control group. The authors concluded that increasing caloric intake with nut supplementation does not always lead to weight gain, and there are several potential explanations for that finding. Researchers also cautioned that energy expenditure was not measured, and therefore the mechanism cannot be confirmed.

There were several limitations reported by the authors, most of which suggested that the group studied was quite healthy prior to the start of the trial. The participants in the study appeared to be well nourished, and the average protein intake at baseline was approximately 1.12 grams per kilogram, which already exceeded recommendations for daily protein intake. There also appeared to be a higher level of physical functioning at baseline for participants, which may have contributed to difficulty detecting changes in some of the outcomes, such as gait speed.

The control group was provided with standard care without any associated placebo food, and participants were aware of what treatment they were receiving. This could possibly have created expectancy or behavior changes, despite being measured at baseline and six months (diet and physical activity), with no difference noted.

Adherence was determined through returned containers, a method that is common but not accurate enough to provide total confidence in evaluating dietary adherence. Biomarkers, such as plasma vitamin E, were considered a better measure of adherence but were not utilized in this study.

Further, the authors did not conduct any adjustments for multiple comparisons that would increase the likelihood of an erroneous finding of significance among the secondary study outcomes. Additionally, there were no inflammatory or oxidative stress biomarkers measured. Therefore, the mechanism of how peanut butter may provide a benefit remains unknown.

The authors also identified questions regarding the funding source of the study. Funding for the study was provided by The Peanut Institute Foundation and did not play any role in designing, implementing, analyzing, or writing the manuscript.

For older adults who experience difficulties when standing from a seated position, the data from this trial suggest that consuming three tablespoons of natural peanut butter daily may increase the lower body power necessary for this specific activity without resulting in a gain of body weight over a six-month period.

It should not be viewed as an alternative to strength and resistance training, as Tan describes these as important elements of fall prevention for those at a high risk of falls. The results should instead be viewed as a supportive intervention for older adults to improve their nutrition, thereby positively stimulating one area of functional capacity.

It may also provide an alternative for older adults who prefer not to consume costly or unappealing commercial oral nutrition supplements because of the soft texture of peanut butter, which is more acceptable to individuals with dental issues.

Research findings are available online in the Journal of Cachexia Sarcopenia and Muscle.

The original story "Eating peanut butter builds muscle power in older adults, study finds" is published in The Brighter Side of News.

Like these kind of feel good stories? Get The Brighter Side of News' newsletter.