A 12-Week Randomized Double-Blind Placebo-Controlled Clinical Trial, Evaluating the Effect of Supplementation with a Spinach Extract on Skeletal Muscle Fitness in Adults Older Than 50 Years of Age
What this study found
Spinach extract supplementation plus a 12-week resistance training program produced greater improvements in knee isokinetic and isometric strength and in muscle quality than placebo. Lean/muscle mass increased and fat mass decreased in both groups, with larger magnitudes in the spinach group. Quality of life in role physical and role emotional domains improved with the spinach extract. Adherence was high and no adverse events were reported. No dietary intake changes were observed. Conclusion: spinach extract may enhance exercise-induced muscle adaptations and support healthy aging when…
- Study & population
- Design: single-center, randomized, double-blind, placebo-controlled trial with two parallel arms.
- Intervention
- Spinach extract (Spinacia oleracea L.), four capsules per day (500 mg each, total 2 g/day) taken in two divided doses (breakfast and lunch) for 12 weeks.
- Key limitation
- Small sample size; single-center; predominantly female sample (8 men, 37 women); exploratory gender analyses with limited male representation; dietary intake not tightly controlled; 12-week duration; findings may not generalize to broader populations; potential confounding from the concurrent exercise program.
View source
Open PDFOriginal abstract
The aim of a 12-week randomized double-blind placebo-controlled study was to assess the effect of daily supplementation with a natural extract of Spinacia oleracea L. (4 × 500 mg capsules/day; total 2 g per day) combined with a moderate-intensity training program (1 h session/3 times a week) on skeletal muscle fitness in adults over 50 years of age. Muscle strength assessed by isokinetic and isometric dynamometry improved significantly in the experimental (n = 23) and the placebo (n = 22) groups, but the magnitude of improvement was higher in the experimental group, with between-group differences in almost all variables, including isokinetic at 60° s−1 in knee extension, peak torque (p < 0.007); total work per repetition maximum (p < 0.009); isokinetic at 180°s−1 in knee extension, peak torque (p < 0.002); total work (p < 0.007); total work per repetition maximum (p < 0.005); average power (p < 0.027); isometric in knee extension, peak torque (p < 0.005); and average peak torque (p < 0.002). Similar findings were observed for muscle quality. Changes in quality of life (SF-36) were not found, except for improvements in the role physical (p < 0.023) and role emotional (p < 0.001) domains, likely as a result of the physical training sessions. A nutritional survey did not revealed changes in dietary habits. No adverse events were recorded. In subjects over 50 years of age, moderate-intensity strength training combined with daily supplementation for 12 weeks with a natural extract of Spinacia oleracea L. improved muscle-related variables and muscle quality. Maintaining muscle health is a key component of healthy aging.