When I saw that headline on the News Medical site it clearly caught my attention. Here is a summary of the article or a link to it if you’d like to read more about the study.
The article covers a randomized controlled trial examining whether daily peanut butter supplementation can improve physical function in adults aged 65 and older, with the key finding being that while one specific measure of lower-body power improved, the study’s primary walking test showed no change.
The scientific backdrop for the study is the well-established decline in muscle mass and strength that accelerates after age 50, with lifetime losses of 20–30% in muscle mass and up to 40–50% in strength. After 65, physical function can drop to less than half its peak capacity, raising the risk of falls, fractures, hospitalization, and loss of independence.
The rationale for focusing on peanut butter stems from its nutritional profile — it is rich in protein, unsaturated fats, vitamins, minerals, antioxidants, and fiber — and from observational data suggesting that regular nut consumption may reduce inflammation and oxidative stress, both of which contribute to muscle decline with aging. Nut butters are also practical for older adults because they are soft, affordable, and easy to incorporate into daily meals.
The trial recruited 120 community-dwelling adults aged 65 and over who were assessed as being at risk of falling. Half were assigned to consume 43 grams of peanut butter per day — roughly 1.5 nut servings, providing 10 grams of protein and 250 calories — while the other half continued their usual diet without nuts, for a period of six months.
The primary outcome — 4-meter gait speed (a standard walking test) — did not improve in the peanut butter group, nor did most other measures of physical function, strength, or body composition. However, there was a meaningful improvement in the five-times sit-to-stand test, with participants completing it about 1.2 seconds faster and showing notable gains in both absolute and relative muscle power.
The researchers note that this improvement in muscle power is potentially clinically significant. Low relative muscle power is a known predictor of limited mobility, and a gain of 0.2–0.3 watts per kilogram can shift someone from a low to a medium or medium to high power category — levels that are more closely tied to independence and survival in older people than peak strength alone. Notably, participants did not gain weight despite the additional calories, which the authors speculate may relate to the high unsaturated fat content of peanut butter and possible effects on energy balance.
Can peanut butter improve mobility after 65? The study had several limitations worth noting, including a relatively high baseline protein intake among participants (which may have limited the room for additional benefit), a comparatively high baseline physical function that could create ceiling effects, no placebo food for the control group, and no measurement of inflammatory or oxidative stress markers to test the proposed biological mechanisms. The authors conclude that while the findings are modest, the simplicity and strong adherence (86%) of the intervention make it worthy of further investigation, particularly among older adults with low muscle mass or those at risk of malnutrition.
