Conducted over 12 weeks, the study offered a promising and simple dietary approach to tackling muscle loss — also known as sarcopenia — among community-dwelling seniors. This applied specifically to those who followed vegetarian diets or struggled to meet protein intake requirements.
The findings emphasise the effectiveness of a plant-based intervention in improving mobility, physical function, and sarcopenia risk scores, even without major changes to body composition or muscle mass.
Focus on real-world elderly nutrition challenges
The researchers enrolled 100 participants aged 65 and older, all at risk of both malnutrition and sarcopenia, and randomly split them into two groups. One received a daily serving of soup containing 24g to 30g of protein, while the other continued their usual diet with no supplements. The soup was designed for lacto-vegetarians, meaning it included dairy-based proteins but no meat, fish or eggs.
The intervention targeted seniors who were not only losing muscle mass but also not eating enough protein — an particularly common issue among vegetarians and older adults with reduced appetite or dietary restrictions.
The researchers assessed physical performance, nutritional status and muscle-related health markers at the beginning and end of the 12-week study period. While the study was open-label, researchers minimized bias through randomisation and regular follow-up.
Stronger legs, faster mobility, better nutrition
Those who consumed the soup showed statistically significant improvements in two key mobility tests. Their average score on the Short Physical Performance Battery (SPPB) — a widely used tool to assess balance, walking speed, and leg strength — improved by 0.83 points compared to those in the control group.
Additionally, these participants completed the five-time chair-rise test, which measures lower body strength and functional movement, 2.25 seconds faster than those who did not receive the soup. Even though muscle strength (measured by hand grip) did not change significantly, the boost in physical function could still translate into better quality of life and lower fall risk.
The intervention group also saw lower sarcopenia risk. Their SARC-F scores (used to identify muscle weakness, mobility issues and fall risk) dropped by nearly 0.7 points, a statistically significant difference. The Mini Nutritional Assessment Short Form (MNA-SF) score, which evaluates malnutrition risk, also rose by 0.44 points. This meant they were more likely to meet their daily nutritional needs and less likely to suffer from severe muscle decline.
No significant gains in muscle mass or biomarkers
While functional performance and nutritional status improved, there were no major changes in skeletal muscle mass or body composition, as measured by bioelectrical impedance. The same applied to blood biomarkers related to cholesterol, inflammation, and kidney function, though some within-group improvements were seen.
For instance, triglyceride levels and total cholesterol decreased slightly in the intervention group, but those changes were not statistically significant when compared to the control group.
The researchers noted that this could be due to the short trial period or participants’ relatively healthy baseline status. As such, more time may be needed to see significant physiological changes in muscle or metabolism.
Protein supplementation may supplement exercise
While resistance exercise remains the gold standard for improving muscle mass and strength in older adults, not all seniors can — or will — follow regular fitness routines, which is where dietary strategies come in.
Previous studies using animal-based protein powders or amino acid supplements showed mixed results. Some increased muscle protein synthesis but also raised inflammatory markers or had limited long-term benefits. This trial suggests that plant-based proteins (especially in easy-to-consume formats like soup) can offer a viable alternative without the risks sometimes associated with animal proteins.
Limitations and next steps
The researchers acknowledged several limitations. The trial was open-label, so participants knew whether they were receiving the soup. This could have influenced behaviour and reporting. Physical activity was not monitored, and dietary intake outside the study supplement was not tracked in detail. Also, the study duration may have been too short to detect muscle mass changes.
Moreover, nearly half participants were already vegetarians, which may limit how generalisable the findings are to the broader older adult population. Future studies should aim for a longer duration, include physical activity tracking, and explore if tailored dosing based on body weight improves results. Comparing animal- and plant-based protein supplements side-by-side would also add value.
A simple step toward healthier ageing
This study shows that a daily serving of protein-enriched vegetarian soup can improve mobility and reduce the risk of muscle loss in older adults, especially those at risk of malnutrition or who follow plant-based diets. While muscle mass gains were not significant, the improvements in physical performance and nutritional status were enough to suggest real-world benefits.
The researchers concluded: “Future investigations are warranted to elucidate the long-term effects of lacto-vegetarian protein-enriched soup supplementation on cardiometabolic and inflammatory biomarkers, alongside a comprehensive assessment of muscle health.”
Source: The Journal of Nutrition, Health and Aging
“Daily Supplementation with Protein-Enriched Lacto-Vegetarian Soups and Muscle Health in Community-Dwelling Older Adults: A Randomized Controlled Trial”
https://doi.org/10.1016/j.jnha.2024.100477
Authors: Sheng-Lun Kao, et al.
