How healthy plant-based diets enhance strength and function in aging adults

Explore how nutrient-rich plant-based eating supports physical performance and combats age-related decline.

Study: Plant-Based Diets and Their Associations with Physical Performance in the Baltimore Longitudinal Study of Aging. Image Credit: MarinelaM / Shutterstock

A recent study published in the journal Nutrients assessed associations between plant-based diets and physical performance in an aging population.

Physical performance is vital for promoting healthy aging and mitigating the risk of disability and morbidity in older adults. Physical performance is often measured through handgrip strength, balance, mobility, and lower body strength, which are related to skeletal muscle mass, function, and strength.

Age-related decreases in muscle strength and mass typically start in adulthood and accelerate with aging. Muscle mass decreases by 1% to 3% annually, while muscle strength declines by 2.5% to 4% annually. Malnutrition and disuse may exacerbate these reductions. Diets play a significant role in supporting muscle health and alleviating age-related decreases in physical performance.

Dietary patterns characterized by plant-based foods have been associated with enhanced physical strength and function in older adults. While the health benefits of plant-based diets on diabetes, cancer, and cardiovascular disease are well documented, their effects on physical performance and function, especially in aging individuals, are less studied. However, recent findings highlight that the quality of plant-based foods significantly influences their impact on physical performance.

About the study

The present study investigated the relationship between plant-based diets and physical performance in an aging population. They obtained data from the Baltimore Longitudinal Study of Aging (BLSA), initiated in 1958. Participants were recruited from the Baltimore-Washington area in the United States (US). Laboratory tests, interviews, and clinical examinations were performed during follow-up assessments.

Further, the BLSA began collecting dietary data in 2005 using a semi-quantitative food frequency questionnaire. The present study analyzed data collected from 2015 to 2018. Participants with missing data or energy intake < 600 kcal/day or > 4800 kcal/day were excluded. Adherence to a plant-based diet was ascertained by the overall plant-based diet index (PDI), healthful PDI (hPDI), and unhealthful PDI (uPDI).

These indices comprised 18 food groups: seven were healthy plant-based foods, five were unhealthy plant-based foods, and six were animal-based. The indices were scored and stratified into tertiles (T1:T3), with T3 indicating higher adherence to the diet. The short physical performance battery (SPPB) was used to examine physical function. Grip strength was assessed using a Smedley hand dynamometer. Gait speed was measured over a fixed distance (6 meters).

Covariates included age, race/ethnicity, sex, education, smoking status, physical activity, body mass index (BMI), chronic diseases, average energy intake, and alcohol consumption. Analysis of covariance and chi-squared test were used to examine differences in sample characteristics among the tertiles. The associations between adherence to the plant-based diet and grip strength, gait speed, and SPPB were assessed using multivariable linear regression models.

The researchers also conducted sensitivity analyses among participants aged ≥65 years to strengthen the findings.

Findings

The study included 1,398 participants with valid FFQ data. Their baseline age was 68.3 years, on average. Most participants were female (53.2%) and non-Hispanic White (72.3%). About 23.4% were obese, and 38.7% were overweight. Older age correlated with higher hPDI and PDI but not uPDI. Further, higher PDI tertiles were associated with greater consumption of whole grains, fruits, vegetables, beans, nuts, and vegetable oils.

Higher PDI tertiles were also associated with a greater intake of unhealthy foods, such as sugar-sweetened beverages, sweets, and juices. Individuals in the highest hPDI tertile had significantly increased intake of healthy food groups and reduced intake of less healthy food groups relative to those in the highest uPDI tertile. The consumption of fish, seafood, animal fat, and eggs was comparable between uPDI and hPDI tertiles.

In addition, SPPB and gait speed did not differ across PDI tertiles. However, participants in the highest hPDI tertile had higher SPPB scores and gait speed, while those in the highest uPDI tertile showed lower SPPB scores. Participants in the highest PDI tertile had significantly lower grip strength. There were no significant associations between physical performance and overall PDI.

Nevertheless, hPDI was positively associated with physical performance measures, whereas uPDI was negatively associated. For instance, participants in the highest hPDI tertile had grip strength values 1.14 kg higher than those in the lowest tertile, highlighting the importance of nutrient-dense foods. A sensitivity analysis restricted to a subsample of individuals aged ≥65 yielded results consistent with the primary analysis; higher adherence to a healthy plant-based diet was associated with higher grip strength and SPPB in this subsample.

Conclusions

The findings reveal that general adherence to a plant-based diet did not significantly improve physical performance in a cohort of middle-aged and older adults. However, adherence to a healthy plant-based diet was associated with physical function and strength. Conversely, an unhealthy plant-based diet was negatively associated with physical function. These results emphasize the need to prioritize the quality of plant-based foods in dietary recommendations.

Further studies are required to corroborate these results, uncover mechanisms, and refine dietary recommendations to optimize plant-based diets for aging populations. Additionally, future research could explore how specific plant-based nutrients, such as antioxidants and short-chain fatty acids, contribute to physical performance and muscle health.