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

Nutrients. 2021 Dec 6;13(12):4373. doi: 10.3390/nu13124373.


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.

Keywords: healthy aging; muscle health; natural spinach extract; randomized trial; strength training.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Age Factors
  • Aged
  • Dietary Supplements*
  • Double-Blind Method
  • Female
  • Healthy Aging / drug effects
  • Humans
  • Male
  • Middle Aged
  • Muscle Strength / drug effects*
  • Muscle, Skeletal / physiology*
  • Phytotherapy
  • Plant Extracts / administration & dosage*
  • Plant Extracts / pharmacology*
  • Sarcopenia / physiopathology
  • Sarcopenia / prevention & control*
  • Spinacia oleracea / chemistry*
  • Time Factors


  • Plant Extracts