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

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.

Urinary Excretion of Ecdysterone and Its Metabolites Following Spinach Consumption

“…[26] Similarly to the results in young men, a recently published study reports an increase of skeletal muscle fitness after spinach extract administration for 12 weeks in adults over 50 years of age. [18] In previous studies, the urinary elimination and metabolism of ecdysterone were reported following the administration of ecdysterone supplements or pure ecdysterone to humans. [27][28][29][30] Concerning an application in doping control analysis, the urinary elimination and metabolism of ecdysterone were reported following the administration of ecdysterone supplements or pure ecdysterone in humans.…”

“…Ecdysteroids have long been recognized for various potential beneficial effects on animal species and humans, including hypolipidemic, antidiabetic, hepatoprotective, adaptogenic as well as growth-promoting and anabolic effects. [12][13][14][15][16][17][18][19][20][21] In vivo and in vitro studies have shown that ecdysterone increases protein synthesis and muscle mass. [20,21] As reported in Parr et al, [21] this effect involves mediation by estrogen receptor beta (ER-𝛽).…”

“…[ 19 ] Following these results and considering the given literature for its anabolic activity, ecdysterone has been included in the Monitoring Program of the World Anti‐Doping Agency (WADA) since 2020 under the section “Anabolic Agents, In‐and Out‐of‐Competition.” [ 26 ] Similarly to the results in young men, a recently published study reports an increase of skeletal muscle fitness after spinach extract administration for 12 weeks in adults over 50 years of age. [ 18 ]…”

Metabolomics of Acute vs. Chronic Spinach Intake in an Apc–Mutant Genetic Background: Linoleate and Butanoate Metabolites Targeting HDAC Activity and IFN–γ Signaling

“…As noted above, (S)-2A2HB was not available commercially, but the presumed deacetylated metabolite (S)-2HB was viewed as a possible mechanism-based HDAC inhibitor, analogous to sulforaphane metabolites [8,34]. Using molecular docking in silico, favorable interactions were predicted for (S)-2A2HB, (S)-2HB and the enantiomeric metabolite (R)-2HB with allosteric sites in HDAC1-and HDAC3-containing corepressor complexes (Figure 5C).…”

“…Recent human clinical intervention trials have assessed diverse aspects of SPI intake, including anthropometric measures, muscle fitness, metabolic profiles, arterial stiffness, and urinary biomarkers [5,[34][35][36], extending prior research on the health benefits of green leafy vegetables and the functional properties of spinach-derived phytochemicals and bioactives [37][38][39][40][41]. We reported that long-term feeding of freeze-dried SPI at 10% w/w in the diet for 26 weeks exhibited significant antitumor efficacy in the Pirc model, resulting in >60% reduced tumor multiplicity in the colon and small intestine [6].…”