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Strength and power

Everything in the library studied for it, medical and holistic together. Within each kind, what was shown to help comes first, strongest evidence first. What was tested and not shown to help stays on the list.

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Medication4 Hormone therapy6 Peptides and SARMs4 Supplements29 Therapies1 Practices7 Daily life1 Food and drink2 Lab markers1

Medication

AcetaminophenLimited

Muscle growth with resistance training

One small trial found 4 g a day raised muscle and strength gains from 12 weeks of resistance training in older adults.

The numbers and sources

Effect: Over 12 weeks of knee extensor training, quadriceps volume rose 12.5% on acetaminophen 4 g a day and 8.6% on placebo, and strength rose 19 kg against 15 kg. Muscle protein content, water content and fiber type distribution did not differ between groups [18].
Population: 36 adults aged about 64 to 67, 11 on acetaminophen, 13 on ibuprofen and 12 on placebo [18].
Sources: [18]
Caveats: One small trial in older adults. The dose, 4 g a day, is above the 6 caplets (3,000 mg) in 24 hours given in the over-the-counter directions [19].

AlbuterolModerate

Strength and sprint performance in people without asthma

Mixed results: beta-agonists improved strength and sprint performance by about 5% overall in people without asthma, mostly with oral, weeks-long or prohibited use. Inhaled approved doses barely differed.

Compared with placebo [11]

The numbers and sources

Effect: Overall, beta-agonists improved anaerobic performance by about 5% (SDM 0.29, 95% CI 0.16 to 0.42). The effect was 0.14 (95% CI 0.00 to 0.28) for drugs and doses approved in sport and 0.46 for prohibited ones, 0.16 for inhaled and 0.51 for oral use, and 0.20 for a single dose against 0.50 over weeks. Strength (0.35) and sprint (0.17) both improved [11].
Population: 34 randomized placebo-controlled studies with 472 participants without asthma [11].
Sources: [11]
Caveats: The authors state it is uncertain whether doses approved in sport improve performance. Results are pooled across beta-agonists [11].

NSAIDsLimited

Muscle growth and strength with resistance training

Small trials found mixed results: ibuprofen raised muscle gains in older adults, lowered them in young adults against aspirin, and made no difference in another.

The numbers and sources

Effect: Results differ by trial. In older adults training for 12 weeks, ibuprofen 1.2 g a day increased quadriceps volume 10.9% against 8.6% on placebo, and strength 19 kg against 15 kg [6]. In young adults training for 8 weeks, ibuprofen 1,200 mg a day increased quadriceps volume 3.7% against 7.5% on low-dose aspirin, and strength gains on the maximal-effort leg were smaller [7]. In young adults training for 6 weeks, ibuprofen 400 mg after each session did not change biceps thickness or strength against placebo [8]. A systematic review of 7 athlete trials found NSAIDs did not raise collagen synthesis or satellite cell activity after exercise [9].
Population: 36 adults aged about 64 to 67 [6]; 31 adults aged 18 to 35 [7]; 18 adults aged about 24, each arm its own control [8]; 346 athletes in 7 RCTs [9].
Sources: [6], [7], [8], [9]
Caveats: Small trials with different doses, ages and comparators. [7] compared ibuprofen with 75 mg aspirin, not placebo. No meta-analysis of training adaptations was sourced.

RapamycinLimited

Physical function with exercise in older adults

Small trials found no gain in physical function with exercise, and one found smaller chair-stand gains on sirolimus than placebo in some analyses.

The numbers and sources

Effect: Over 13 weeks of home exercise, chair-stand repetitions rose in both groups. The difference was -2.13 repetitions (95% CI -4.61 to 0.34) for sirolimus 6 mg weekly against placebo. Complete-case (-2.46) and per-protocol (-3.44) analyses favored placebo significantly. Six-minute walk and grip strength also favored placebo, not significantly [3]. Handgrip and timed walk did not change on rapamycin 1 mg daily in the pilot [2].
Population: 40 sedentary adults aged 65 to 85, mean 72.2 [3]; 25 adults aged 70 to 95 [2].
Sources: [3], [2]
Caveats: Small exploratory trials. [3] was funded by Dr Brad Stanfield Ltd.

Hormone therapy

Growth hormoneModerate

Lean mass and leg strength in orthopedic patients

Shown to raise lean body mass about 3.6% and leg strength about 3.2% in orthopedic and sports medicine patients.

The numbers and sources

Effect: Across orthopedic studies, lean body mass rose in 15 of 23 studies, a mean difference of 3.63% against placebo, and leg extension strength rose by a mean difference of 3.17%. IGF-1 rose by a mean of 133.2%, in a dose-dependent way [5].
Population: 1,157 patients, mean age 54.3, in 22 studies of orthopedic surgery and sports medicine settings, mean dose 1.49 mg per day [5].
Sources: [5]
Caveats: The review rated its studies as moderate quality and pooled only where it could [5]. These were patients, not healthy athletes.

Testosterone therapyLimitedStudied in men

Muscle size and strength at high doses in young men

One small 1996 trial at high doses found more muscle size and strength in young men with normal testosterone, most with training.

The numbers and sources

Effect: Over 10 weeks without exercise, men on testosterone gained more triceps area (424 vs -81 mm²), quadriceps area (607 vs -131 mm²), bench press (9 vs -1 kg) and squat (16 vs 3 kg) than men on placebo. With training, the testosterone group gained 6.1 kg of fat-free mass, 22 kg on bench press and 38 kg on squat, more than either non-exercise group. Mood and behavior did not change in any group [5].
Population: 43 healthy men with normal testosterone, in 4 groups, for 10 weeks [5].
Sources: [5]
Caveats: One small trial from 1996 at a dose the authors describe as supraphysiologic. It does not address men with low testosterone or use over years.

Testosterone therapyLimitedStudied in men

Muscle strength in middle-aged and older men

Limited evidence: strength gains in middle-aged and older men were small and varied widely across trials.

The numbers and sources

Effect: Strength results were heterogeneous. Leg and knee extension and dominant-hand grip showed a pooled effect size of 0.3 SMD (95% CI 0.0 to 0.6) [2].
Population: Middle-aged and older men in the strength subset of 29 RCTs [2].
Sources: [2]
Caveats: The interval reaches zero, and trials varied widely.

Menopausal hormone therapyStrongStudied in women

Muscle strength

Not shown to increase muscle strength in postmenopausal women, though very high variation leaves a small effect possible.

The numbers and sources

Effect: Hormone therapy was not associated with strength gain (SMD 0.352, 95% CI -0.098 to 0.803, I² 95.3%). Results were unchanged by treatment type, muscle group and duration [10]. A 2025 systematic review found 2 of 6 RCTs suggesting better grip strength and 1 of 6 better physical performance, with no consistent evidence of benefit [9].
Population: 9 RCTs with 2,476 postmenopausal women [10]; 15 RCTs and 28 observational studies [9].
Sources: [10], [9]
Caveats: Heterogeneity was very high, so a small effect cannot be ruled out. The systematic review rated risk of bias high to severe [9].

DHEAModerate

Strength and physical function in older adults

Not shown to change strength or physical function in most studies of adults aged 50 and older, including a 2-year trial.

The numbers and sources

Effect: A systematic review of 8 studies found single improvements in grip, chest press, leg press and knee strength, with similar numbers of studies showing no effect on each. Four of five studies of physical function found no difference from control [4]. Over 2 years, DHEA did not change muscle strength or peak oxygen uptake [3].
Population: 661 adults aged 50 and older in 8 studies [4]; 144 elderly men and women [3].
Sources: [3], [4]
Caveats: The review was not pooled, and its trials differed in population and exercise.

Growth hormoneModerate

Strength and performance in healthy young athletes

Not shown to improve strength or exercise capacity in healthy young athletes, though lean body mass rose about 2 kg, mostly water. Sprint capacity rose slightly.

The numbers and sources

Effect: Lean body mass rose 2.1 kg (95% CI 1.3 to 2.9) against no growth hormone, but strength and exercise capacity did not appear to improve. Lactate during exercise was higher in 2 of 3 studies that measured it [2]. In recreational athletes given growth hormone for 8 weeks, sprint capacity rose 0.71 kJ (3.9%, 95% CI 0.0 to 7.7%), and 8.3% in men given testosterone as well. Endurance, strength and jump height did not change. The lean mass gain came from extracellular water, and the sprint gain was gone 6 weeks after stopping [3].
Population: 27 study samples with 303 treated participants aged 13 to 45, mean 27, mean treatment 20 days [2]; 96 recreational athletes, 63 men and 33 women [3].
Sources: [2], [3]
Caveats: Few studies measured performance, and trial doses may differ from covert use [2][3]. [3] was funded by the World Anti-Doping Agency.

Peptides and SARMs

SermorelinLimitedStudied in men

Strength in older men

One small study without placebo found 2 of 6 strength measures improved over 6 weeks in men aged 64 to 76. Muscle mass did not change.

The numbers and sources

Effect: Over 6 weeks, nightly sermorelin raised nighttime growth hormone release, with no change in IGF-1. Two of six strength measures (upright row and shoulder press) and one endurance test (abdominal crunch) improved. Muscle by DEXA and muscle histology did not change [4].
Population: 11 healthy, non-obese men aged 64 to 76 with low baseline IGF-1 [4].
Sources: [4]
Caveats: One small study with no placebo group, comparing each man with his own baseline. The authors note that single nightly doses produced smaller hormone effects than multiple daily doses in earlier work [4].

SARMsGrey marketLimited

Physical function and strength

Limited evidence: one trial found better physical function in healthy older adults, and a review found improvement inconsistent across trials.

The numbers and sources

Effect: In healthy older adults, physical function improved on enobosarm against placebo (P = 0.013) [2]. The 2026 review reports that physical function improved inconsistently across trials [4].
Population: 120 healthy older adults over 12 weeks [2]; trials summarized in a review [4].
Sources: [2], [4]
Caveats: One phase 2 trial plus a narrative review.

MK-677Grey marketLimited

Strength and physical function

Limited evidence: added fat-free mass did not change strength in older adults, and after hip fracture only gait speed improved over placebo.

The numbers and sources

Effect: In healthy older adults, the gain in fat-free mass did not change strength or function [1]. After hip fracture, stair climbing power rose 12.5 W more than placebo (95% CI -10.95 to 35.88, not significant), and gait speed improved by a 0.7-point score difference (95% CI 0.17 to 1.28). Several other functional measures did not improve [3].
Population: 65 older adults [1]; 123 older adults recovering from hip fracture, 24 weeks [3].
Sources: [1], [3]
Caveats: The older-adult trial was not powered for function [1]. The hip fracture trial was stopped early [3].

CJC-1295 and ipamorelinGrey marketNo research yet

Muscle and strength

We haven't sourced research on this yet.

Supplements

CaffeineStrong

Muscle strength and power

Shown to improve maximal strength and jump power slightly in mostly resistance-trained young men. Lower body strength alone did not reach significance.

The numbers and sources

Effect: Across 10 studies, 1RM strength improved by SMD 0.20 (95% CI 0.03 to 0.36) and vertical jump power by SMD 0.17 (95% CI 0.00 to 0.34). Upper body strength improved (SMD 0.21, 95% CI 0.02 to 0.39); lower body did not reach significance (SMD 0.15, 95% CI -0.05 to 0.34) [6]. The umbrella review rated strength, muscular endurance and anaerobic power evidence moderate quality [2].
Population: Mostly resistance-trained young men [2][6].
Sources: [2], [6]
Caveats: Effects are small. The authors flag that blinding was rarely checked, and caffeine is often detectable by its feel [6].

CreatineStrong

Strength

Shown to add a small amount of strength on upper and lower body lifts, including in older adults.

The numbers and sources

Effect: For upper body exercises under 3 minutes, the effect size for bench and chest press at the end of supplementation was 0.265 (95% CI 0.132 to 0.398) [6]. For the lower body, effect sizes were 0.336 (95% CI 0.047 to 0.625) for squat and 0.297 (95% CI 0.098 to 0.496) for leg press [7]. In older adults, leg press SMD was 0.24 (95% CI 0.05 to 0.43) [2]. Postmenopausal women gained 7.5 kg more on leg press 1RM (95% CI 2.2 to 12.8, 3 trials, 111 women) [3].
Population: 53 trials with 1,138 people for upper limb [6]; 60 trials with 1,297 people for lower limb [7]; older adults [2]; postmenopausal women [3].
Sources: [2], [3], [6], [7]
Caveats: Effect sizes in the 0.24 to 0.34 range are small by conventional thresholds. The strength trials pool short protocols and long training blocks together. In 69 studies (1,937 participants), creatine with resistance training raised bench press by 1.43 kg and squat by 5.64 kg over placebo, and handgrip and leg press did not differ. Gains were significant in younger adults and men, and not in older adults or women [8]. A 2026 analysis limited to adults aged 60 and over found a small strength gain (g 0.31, 95% CI 0.18 to 0.45, moderate certainty) [5].

Protein powderStrong

Muscle mass and strength during resistance training

Shown to add about 2.5 kg of strength and 0.3 kg of fat-free mass during resistance training, with no extra gain above 1.62 g per kg of total protein.

The numbers and sources

Effect: Across 49 RCTs (1,863 participants), protein supplements increased 1RM strength by 2.49 kg (95% CI 0.64 to 4.33) and fat-free mass by 0.30 kg (95% CI 0.09 to 0.52) over control. Gains in fat-free mass did not rise further once total protein intake passed 1.62 g per kg a day. The effect fell with age and was larger in trained lifters (0.75 kg, 95% CI 0.09 to 1.40) [1]. An earlier meta-analysis of 22 RCTs (680 people) found 0.69 kg more fat-free mass (95% CI 0.47 to 0.91) and 13.5 kg more leg press 1RM (95% CI 6.4 to 20.7) [2]. In 12 studies of adults aged 18 to 30 (261 participants), whey raised bench press by 8.87 kg (95% CI 5.95 to 11.79) and squat by 9.60 kg (95% CI 5.61 to 13.60), and neither whey nor soy significantly changed lean body mass [3].
Population: Healthy adults in resistance training programs of 6 weeks or longer [1][2]. Young adults [3].
Sources: [1], [2], [3]
Caveats: The supplement effect depends on how much protein the diet already provides; the 1.62 g per kg breakpoint is total intake from food plus powder [1]. Trials mix whey, casein, soy and blends. The smaller 2025 review of young adults did not find the lean mass gain the two larger reviews report [3].

AshwagandhaModerate

Strength

Shown to raise muscle strength in physically active people but not in untrained people. Results leaned on single trials and certainty was low.

The numbers and sources

Effect: A Bayesian meta-analysis reported ashwagandha outperformed placebo on strength and power [11]. Across 20 trials, muscle strength rose (SMD 0.58, 95% CI 0.12 to 1.04, I² 56.9%), in physically active people (SMD 1.03, 95% CI 0.56 to 1.49) but not in untrained or special populations [8]. In 3 resistance-training trials, gains exceeded placebo for 1-RM bench press (SMD 0.60, 95% CI 0.20 to 1.01) and lower-body 1-RM (SMD 0.52, 95% CI 0.19 to 0.86), and body fat did not change [13]. In the three-level analysis, strength effects were positive but uncertain [12].
Population: Healthy men and women [11]. 1,249 participants [8]. 161 healthy adults in structured resistance training [13].
Sources: [11], [8], [13], [12]
Caveats: Under Hartung-Knapp-Sidik-Jonkman adjustment, both resistance-training estimates lost statistical significance, and each depended on one influential trial. Certainty was low [13].

BCAAs and EAAsModerate

Muscle mass and strength in older adults

Shown to improve strength and muscle mass modestly in older adults, for supplements rich in BCAAs, including EAA and whey products.

The numbers and sources

Effect: Across 35 RCTs in older people, BCAA-rich supplements, a category that included EAA and whey protein products, improved strength (SMD 0.35, 95% CI 0.15 to 0.55), muscle mass (SMD 0.25, 95% CI 0.10 to 0.40) and physical performance (SMD 0.29, 95% CI 0.00 to 0.57). EAA supplements improved handgrip strength more than whey protein in subgroup analysis [7]. In 52 patients having knee replacement, 9 g a day of EAAs from 1 week before to 2 weeks after surgery left rectus femoris area at 134% of baseline at 2 years against 114% on placebo, and quadriceps strength at 159% against 125%. Clinical outcomes did not differ [8]. In 10 RCTs and one prospective study of people with sarcopenia, leucine groups differed from placebo in handgrip strength (p = 0.03), appendicular muscle mass and gait speed (p = 0.008) [9].
Population: Older adults [7]; knee replacement patients [8]; 1,133 people over 65 with sarcopenia [9].
Sources: [7], [8], [9]
Caveats: High heterogeneity, and 14 of 35 trials had potential bias [7]. The pooled supplements are not pure BCAA products. The leucine review rated its evidence low quality and found leucine alone of limited benefit without other therapy [9].

CitrullineModerate

Strength and power during high-intensity sets

Shown to slightly improve resistance sets and short sprints in mostly strength-trained adults, with about 6% more repetitions to failure on 6 to 8 g.

The numbers and sources

Effect: Across 12 studies (13 samples, 198 participants) using at least 3 g taken at least 30 minutes before testing, citrulline improved resistance sets and sprints of 30 seconds or less by SMD 0.20 (95% CI 0.01 to 0.39), with no heterogeneity (I² 0%) [1]. In 8 studies (137 participants), 6 to 8 g of citrulline malate 40 to 60 minutes before training added 3 ± 5 repetitions to failure, 6.4% over placebo (SMD 0.196). Lower body trended up (SMD 0.27, p = 0.051) and upper body did not change (SMD 0.16) [2].
Population: Healthy, mostly strength-trained adults [1]; 101 trained men, 26 trained women and 9 untrained men in [2].
Sources: [1], [2]
Caveats: Every individual study's confidence interval crossed zero; only the pooled estimate did not [1].

Protein powderModerate

Muscle and strength in older adults

Shown to raise lower-body strength slightly in older adults, with lean mass gains only when combined with resistance training.

The numbers and sources

Effect: In 25 trials (1,454 adults aged 64 to 84), whey raised lower-body strength (SMD 0.16, 95% CI 0.04 to 0.28, 19 trials) and did not change upper-body strength or body composition overall. Combined with resistance training, whey raised lean body mass [4].
Population: Older adults, with or without resistance training [4].
Sources: [4]
Caveats: One meta-analysis. The lean mass finding comes from a subgroup [4].

TMGModerate

Muscle strength and power

Shown to raise maximal strength modestly, mostly lower body, in healthy people. Upper-body strength, sprint power and muscular endurance did not change.

The numbers and sources

Effect: Across 17 studies, betaine raised maximal strength (SMD 0.47, 95% CI 0.04 to 0.89), mostly in the lower body (SMD 0.49, 95% CI 0.01 to 0.98). Upper-body strength, cycling sprint power, bench throw power and muscular endurance did not change. Vertical jump improved (SMD 0.36, 95% CI 0.03 to 0.69) after one low-quality study was excluded [3].
Population: 317 healthy people aged 15 to 60, 21% female, supplementing for at least 7 days [3].
Sources: [3]
Caveats: Small trials. The lower bounds of the intervals sit close to zero.

FenugreekLimited

Muscle strength with training

Limited evidence: 4 of 6 small trials reported gains in strength, lean mass or lower body fat with fenugreek extracts alongside exercise.

The numbers and sources

Effect: A systematic review of 6 RCTs found 4 reported gains in muscle strength, repetitions to failure, lean mass or lower body fat with fenugreek extracts. Of two small glycogen trials, one found faster resynthesis and one did not [7].
Population: Participants in 6 RCTs of exercise or sport [7].
Sources: [7]
Caveats: Narrative synthesis without pooled effect sizes. Two of the trials had fewer than 10 participants [7].

Fish oilLimited

Muscle mass and function in older adults

Limited evidence: omega-3 added about 0.33 kg of muscle mass and slightly improved timed up and go in older adults.

The numbers and sources

Effect: Across 10 trials in older adults, omega-3 added 0.33 kg of muscle mass (95% CI 0.05 to 0.62) and shortened timed up and go by 0.30 seconds (95% CI -0.43 to -0.17). Above 2 g a day the muscle mass gain was 0.67 kg (95% CI 0.16 to 1.18) [34]. In 94 healthy older adults, 4 g a day of krill oil for 6 months increased muscle strength and size against a control oil, with similar responses by age, sex and BMI [35].
Population: Older adults in 10 RCTs [34]; adults 65 and older doing less than 1 hour of structured exercise a week [35].
Sources: [34], [35]
Caveats: Few trials, and the dose subgroup is post hoc. The search ended in July 2018 [34]. The krill oil report is a secondary analysis of one trial [35].

Protein powderLimited

Pre-sleep casein

Limited evidence: pre-sleep casein raised overnight muscle protein synthesis, with gains in size and strength in young men but not older men.

The numbers and sources

Effect: 20 to 40 g of casein about 30 minutes before sleep raised overnight protein synthesis rates in young and older men. Over 10 to 12 weeks of training, pre-sleep protein increased fiber size, strength and muscle mass in young men but not in older men [8]. In 24 trained soccer players, 30 g of casein before sleep and the same dose right after training both improved next-day anaerobic performance against no casein, and the two timings did not differ [9]. After sleeve gastrectomy, casein-enriched milk before sleep or during the day did not change body composition, strength or physical performance over 12 weeks compared with no supplement [10]. In 9 trained adults, 40 g of casein before sleep did not change sleep measures against a carbohydrate control, while the same dose of whey shortened sleep onset and lengthened sleep [11].
Population: Nine studies, mostly men [8]. 24 male soccer players [9]. 45 adults after bariatric surgery [10]. 9 young adults, crossover [11].
Sources: [8], [9], [10], [11]
Caveats: Reference [8] is a systematic review without pooling. Its authors note uneven total protein intake between groups, so the timing effect cannot be separated from extra protein [8]. The three newer trials are small [9][10][11].

ReishiLimitedStudied in women

Stress and fitness

One small trial found better VO2 max, grip strength and mood scores than placebo in sedentary female students over 30 days.

The numbers and sources

Effect: In 78 female college students in India, 1,000 mg a day for 30 days improved heart rate, VO2 max, physical work capacity and right-hand grip strength against placebo, and anxiety, depression and well-being scores improved. The 500 mg dose differed from the 1,000 mg dose on VO2 max and work capacity [6].
Population: 78 sedentary female students, mean age 20.6 [6].
Sources: [6]
Caveats: One small trial. The abstract does not report effect sizes or funding.

Tongkat aliLimited

Muscle strength

One small study without placebo found higher testosterone and grip strength over 5 weeks in active adults aged 57 to 72. The maker funded it.

The numbers and sources

Effect: In 25 physically active adults aged 57 to 72, 400 mg a day for 5 weeks raised total and free testosterone and handgrip force in men and women [7].
Population: 13 men and 12 women, single group [7].
Sources: [7]
Caveats: No placebo group. Funded by Biotropics Malaysia [7].

HMBModerate

Muscle mass and strength in older adults and patients

Mixed results: HMB raised muscle mass and strength slightly in older adults and patients, but not when added to resistance training.

The numbers and sources

Effect: In 9 RCTs (448 older adults), HMB raised fat-free mass (ES 0.37, 95% CI 0.16 to 0.58), with no change in fat mass. HMB alone raised fat-free mass (ES 0.59); HMB added to exercise did not (ES 0.06, 95% CI -0.26 to 0.38) [5]. In 21 RCTs (1,935 people over 50), HMB raised appendicular muscle mass by 1.56 kg (95% CI 0.03 to 3.09), lean mass by 0.28 kg, handgrip strength by 0.54 kg and gait speed by 0.06 m/s [6]. In 5 RCTs in sarcopenia, muscle mass index (SMD 0.32, 95% CI 0.00 to 0.64) and handgrip strength (SMD 0.65) rose, and gait speed did not change [7]. In 15 RCTs (2,137 patients with muscle-wasting conditions), HMB or HMB-containing supplements raised muscle mass (SMD 0.25, 95% CI -0.00 to 0.50) and strength (SMD 0.31, 95% CI 0.12 to 0.50) [8].
Population: Older adults [5][6]; people with sarcopenia [7]; hospital and clinical patients [8].
Sources: [5], [6], [7], [8], [9], [10]
Caveats: Many trials gave HMB in multi-ingredient nutrition drinks, so the effect of HMB alone is unclear [8]. No trial in [8] had low risk of bias in every category. Review [6] searched Chinese databases. Added to resistance training, HMB did not change muscle mass (SMD 0.05, 95% CI -0.10 to 0.20, 13 RCTs, 561 adults over 50) or strength [9], and a second review of 10 trials (596 older adults) found no change in lean mass, a borderline handgrip gain (SMD 0.24, 95% CI 0.00 to 0.48) and better physical performance scores (SMD 0.54), with half the trials at high risk of bias [10].

NMNModerate

Muscle and physical function

Mixed results: one review found no change in muscle mass, strength or gait speed in older adults, while others found better endurance or gait speed.

The numbers and sources

Effect: In adults with a mean age over 60, NMN did not change skeletal muscle index (MD -0.42, 95% CI -0.99 to 0.14), grip strength, gait speed (MD -0.01 m/s, 95% CI -0.08 to 0.06) or chair-stand time. Knee extension strength, SPPB scores and thigh muscle mass did not improve [4]. A network meta-analysis of NAD precursors reported higher endurance with NMN at medium dose (SMD 0.66, 95% CI 0.09 to 1.23) and high dose (SMD 1.02, 95% CI 0.43 to 1.60), with no change in strength [5]. One trial reported a longer six-minute walk on 300 to 900 mg a day than placebo [1]. A 2025 meta-analysis of 9 RCTs (412 middle-aged and older adults) found faster gait speed on NMN (SMD 0.34, 95% CI 0.03 to 0.66) and lower ALT (SMD -0.29, 95% CI -0.55 to -0.03) [6].
Population: Randomized trials in adults with mean ages of 60.9 to 83 years [4]; 27 studies with 1,599 adults across NR, NMN, NADH and nicotinamide [5]; 80 middle-aged adults [1]; 412 middle-aged and older adults [6].
Sources: [4], [5], [1], [6]
Caveats: The reviews disagree on endurance and on gait speed [4][5][6]. The pooled muscle analysis included 2 to 5 studies per measure [4]. The network analysis mixes precursors and populations [5].

Vitamin DModerate

Muscle strength

Shown to raise muscle strength slightly in older adults and those with low vitamin D, with no change in younger people. A newer review found no change.

The numbers and sources

Effect: Across 30 RCTs (5,615 people, mean age 61.1), vitamin D raised global muscle strength by an SMD of 0.17. Muscle mass (SMD 0.058) and power (SMD 0.057) did not change. The effect was larger with baseline 25-hydroxyvitamin D below 30 nmol/L and at 65 or older (SMD 0.25, 95% CI 0.01 to 0.48) than in younger people (SMD 0.03, 95% CI -0.08 to 0.14) [23]. Across 7 RCTs in adults 60 and older, vitamin D did not raise skeletal muscle mass index, lean mass or handgrip strength [24]. In 152 postmenopausal women with 25-hydroxyvitamin D below 30 ng/mL, 20 µg calcifediol or 3,200 IU vitamin D3 a day for 6 months did not differ from placebo on gait speed, knee strength and sit-to-stand tests (success in 53.6%, 55.5% and 61.4%) [25].
Population: Adults in 30 RCTs, with or without calcium [23]; adults with mean age 60 to 74 in 7 RCTs of 3 to 36 months [24]; women aged 50 to 70 with osteopenia or osteoporosis [25].
Sources: [23], [24], [25]
Caveats: An SMD of 0.17 is small, and the search for that review ended in January 2014 [23]. The newer review did not find a change in handgrip strength [24].

Alpha-GPC and choline supplementsLimitedStudied in men

Strength and power

Small trials found mixed effects on strength and power in young men, with one gain in lower body pull force. All were funded by alpha-GPC makers.

The numbers and sources

Effect: In 13 college-aged men, 600 mg a day for 6 days raised mid-thigh pull peak force by 98.8 N versus a 39.0 N fall on placebo. Upper body force did not differ significantly [9]. In 48 men over 7 days, 250 mg or 500 mg a day did not change isometric strength or psychomotor vigilance. Countermovement jump velocity and power differed between groups, with the largest change at 250 mg [10]. Jumps, bench throws and growth hormone did not differ after single doses [8].
Population: Young men [8][9][10].
Sources: [8], [9], [10]
Caveats: All three trials were funded by alpha-GPC manufacturers (Chemi Nutra [9][10], NNB Nutrition [8]). Samples were small and outcomes were mixed.

CollagenLimited

Muscle mass and strength with training

Limited evidence: one review found gains in fat-free mass and strength with training, while 8 training trials found collagen added no strength gain.

The numbers and sources

Effect: Across 19 RCTs (768 healthy adults) training for 8 weeks or more, collagen peptides improved fat-free mass (SMD 0.48), muscle architecture (SMD 0.39), maximal strength (SMD 0.19) and 48-hour reactive strength recovery (SMD 0.43) [1]. A 2025 meta-analysis found muscle performance improved (SMD 0.60, 95% CI 0.05 to 1.15) [10]. In 8 training RCTs, strength rose with training in every trial, and collagen added no further gain [2].
Population: Healthy adults over 17 in exercise programs [1]; people in RCTs of collagen with or without calcium and vitamin D [10]; trained adults aged 18 to 52 [2].
Sources: [1], [10], [2]
Caveats: Sources disagree on strength. GRADE certainty was moderate for body composition and low for the other outcomes [1]. A systematic review found collagen did not raise muscle protein synthesis compared with isonitrogenous higher-quality proteins [3].

Fisetin and quercetin (senolytics)Limited

Physical function and cognition

Small trials found mixed results: walking improved in an uncontrolled pulmonary fibrosis study, cognition did not change in Alzheimer disease, and quercetin results in older adults varied.

The numbers and sources

Effect: In idiopathic pulmonary fibrosis, six-minute walk distance, 4 m gait speed and chair-stand time improved significantly after 3 weeks of intermittent dosing [5]. In mild Alzheimer disease, cognitive and brain imaging outcomes did not differ from baseline after 12 weeks [6]. With quercetin alone, 26 older adults doing 6 weeks of resistance training on 200 mg a day of quercetin glycosides gained more knee extension force than on placebo (115.1% against 105.3% of baseline), with no change in muscle mass [7]. In 38 older adults, a single 500 mg dose before low or moderate intensity resistance exercise produced a larger drop in electrically elicited muscle torque afterward than placebo, and not at high intensity [8].
Population: 14 adults with idiopathic pulmonary fibrosis [5]; 5 adults with early Alzheimer disease, mean age 76 [6]; healthy older adults [7][8].
Sources: [5], [6], [7], [8]
Caveats: The dasatinib plus quercetin studies were open-label with no placebo group, built to test feasibility [5][6]. The two quercetin-only trials are small and from one research group [7][8].

L-arginineLimited

Exercise performance

Limited evidence: one review reported better aerobic and anaerobic performance but was found to contain errors, and strength trials found no effect.

The numbers and sources

Effect: A meta-analysis of 15 studies reported improved aerobic performance (SMD 0.84, 95% CI 0.12 to 1.56, I² 89%) and anaerobic performance (SMD 0.24, 95% CI 0.05 to 0.43) [10]. A 2025 published comment identified errors in that analysis, including outlier effect sizes, effect estimates that needed recalculating with standard deviations, and one included study that appeared to compare arginine with citrulline rather than placebo [11]. A meta-analysis of 3 trials of acute arginine alone in strength training found no effect on muscular endurance (0.26, 95% CI -0.13 to 0.65) or peak torque [12]. In a crossover trial of 4 days at 3.2 to 9.6 g a day, total biceps curl repetitions, volume load, fatigue and plasma nitric oxide did not differ from placebo [13].
Population: Athletes and active adults [10][12]. 16 recreationally trained young men [13].
Sources: [10], [11], [12], [13]
Caveats: Sources disagree. Aerobic results had very high heterogeneity [10].

MacaLimited

Physical performance

Limited evidence: large effects came mostly from animal tests, and a small trial in basketball players found no difference from placebo.

The numbers and sources

Effect: A meta-analysis of 16 studies reported large effects on forced swimming, rota-rod and grip strength tests and lower blood lactate [8]. In a crossover trial in 10 well-trained college basketball players, 2,000 mg a day for 2 weeks did not differ from placebo in jump height, shooting accuracy, repeated sprints, fatigue index or lactate clearance [9].
Population: Animal and human studies [8]. 10 male basketball players [9].
Sources: [8], [9]
Caveats: The outcomes are largely animal tests. The abstract does not report a separate human effect [8]. The basketball trial was small and short [9].

HMBStrong

Strength and fat-free mass in trained athletes and young lifters

Not shown to change strength, fat-free mass or fat mass in trained athletes or young adults in resistance training.

The numbers and sources

Effect: In 6 RCTs of trained and competitive athletes (193 participants), effect sizes were trivial and not significant for bench press (0.00), leg press (0.09), fat-free mass (0.16) and fat mass (-0.20) [1]. In 11 studies of adults aged 18 to 45 in resistance training, HMB raised total body mass slightly but did not change fat-free mass, fat mass or strength [2]. In 5 studies of athletes, fat-free mass trended up (0.30, 95% CI -0.07 to 0.68, p = 0.08), apparently only when protein intake was under 1.6 g per kg a day [3].
Population: Trained and competitive athletes [1][3]; young adults in training [2].
Sources: [1], [2], [3]
Caveats: Small pooled samples. The ISSN position stand [4] reports body composition improvements across ages and training levels, but several of its authors disclose employment, consulting or patents tied to HMB.

Protein powderStrong

Plant protein compared with animal protein

Not shown to differ in strength by protein source. Soy matched milk protein for muscle, while non-soy plant proteins trailed animal protein in 5 trials.

The numbers and sources

Effect: In 16 RCTs, protein source did not change absolute lean mass or strength; adults under 50 gained 0.41 kg more lean mass (95% CI 0.08 to 0.74) on animal protein [5]. In 30 RCTs, plant protein produced lower muscle mass than animal protein (SMD -0.20, 95% CI -0.37 to -0.03). Soy and milk protein did not differ (SMD -0.02, 17 RCTs). Non-soy plant proteins such as rice, oat and potato trailed animal protein (SMD -0.58, 5 RCTs). Strength (14 RCTs) and physical performance (5 RCTs) did not differ [6].
Population: Adults of all ages, most with protein intakes above the RDA [5][6].
Sources: [5], [6]
Caveats: Few trials tested pea, rice or other non-soy powders, so the non-soy estimate rests on 5 trials [6].

ChromiumModerateStudied in men

Strength and muscle with resistance training

Not shown to add to strength or muscle gains from resistance training in men, in two small trials.

The numbers and sources

Effect: Over 8 weeks, strength, fat-free mass and muscle mass rose with training, and chromium chloride or picolinate did not add to the gains [10]. Over 12 weeks in older men, 924 µg a day did not add to strength, muscle size or lean mass. The placebo group gained more knee-extension power [11].
Population: 36 men [10]; 18 men aged 56 to 69 [11].
Sources: [10], [11]
Caveats: Both trials were small.

D-aspartic acidModerateStudied in men

Strength and muscle with training

Not shown to add to strength or muscle gains from resistance training in trained men over 28 days to 12 weeks.

The numbers and sources

Effect: Over 28 days of heavy resistance training, body composition and strength rose in both groups and did not differ between 3 g of D-aspartic acid and placebo [2]. Over 12 weeks of supervised training, isometric strength rose 17% and quadriceps and calf muscle size increased similarly in both groups on 6 g a day or placebo [4].
Population: Resistance-trained men [2][4].
Sources: [2], [4]
Caveats: Small samples, 22 randomized in [4].

TribulusModerateStudied in men

Strength and sport performance

Not shown to improve strength, body composition or sport performance in active men. One small trial found a larger bench press gain.

The numbers and sources

Effect: In 30 CrossFit-trained men over 6 weeks, body composition and four of five workout tests did not differ from placebo. Bench press rose 19.2% with tribulus against 8.5% with placebo [5]. A systematic review of 7 studies in physically active men found no clear benefit on muscle damage markers or hormones, some lipid improvements and no reported toxicity [4]. A review of athlete use found that tribulus alone did not improve androgen status or physical performance [9].
Population: Physically active men [4][5][9].
Sources: [4], [5], [9]
Caveats: Few and small trials.

CholineLimited

Endurance and strength performance

One small trial found choline citrate did not change run time to exhaustion or squat performance in 14 soldiers.

The numbers and sources

Effect: Choline citrate before and during 4 hours of loaded treadmill marching raised plasma choline 128% and did not change run time to exhaustion, squat performance or perceived exertion [10].
Population: 14 soldiers in a crossover trial [10].
Sources: [10]
Caveats: One small trial. Trials of alpha-GPC and citicoline, including memory and power output, are on the alpha-GPC page.

CitrullineLimited

Maximal strength

Limited evidence: 4 studies found no effect of citrulline malate on maximal muscle strength in resistance-trained adults.

The numbers and sources

Effect: In 4 studies (69 citrulline malate and 69 placebo assessments), there was no overall effect on muscle strength (SMD 0.13, 95% CI -0.21 to 0.46), for lower (0.06) or upper (0.17) limbs [3].
Population: Resistance-trained adults [3].
Sources: [3]
Caveats: Four studies. This and the repetition analysis [2] measure different things: maximal force versus reps to failure.

MagnesiumLimited

Muscle strength and performance

Limited evidence: no significant change in strength or power across trials. One small trial in exercisers found lower VO2max and sprint power on magnesium.

The numbers and sources

Effect: Across 14 RCTs, magnesium did not significantly change isokinetic peak torque (WMD 0.87, 95% CI -1.43 to 3.18), muscle strength (WMD 0.87, 95% CI -0.12 to 1.86) or muscle power (WMD 3.28, 95% CI -14.94 to 21.50). Benefits appeared more pronounced in older adults and people with alcoholism than in athletes [11].
Population: 215 athletes or active people, 95 untrained adults, and 232 older adults or people with alcoholism [11].
Sources: [11], [12]
Caveats: Fixed-effects pooling across mixed populations and outcomes. In a 2025 crossover RCT of 15 regular exercisers, 600 mg a day of magnesium chloride for 9 days lowered VO2max (44.4 vs 41.3 mL/kg/min, p = 0.005) and 30 second sprint power (439 vs 415 W, p = 0.03) against placebo, with no change in a 10 km time trial [12].

Therapies

Massage therapyModerate

Strength, sprint and performance recovery

Mixed results: one meta-analysis found no effect on strength, jump, sprint or endurance, while others found small gains in force or short-term performance recovery.

Compared with no intervention [8]; control conditions the source abstracts do not describe [10][11]

The numbers and sources

Effect: Across 29 studies, massage did not improve strength, jump, sprint, endurance or fatigue [10]. In another pooled analysis, maximal isometric force (SMD 0.56) and peak torque (SMD 0.38) were higher after massage [8]. Across 22 trials, performance recovery effects were small: +6.6% with 5 to 12 minutes of massage and +1.0% with more than 12 minutes, larger for recovery periods of up to 10 minutes (+7.9%) than more than 20 minutes (+2.4%) [11].
Population: 1,012 participants in 29 studies [10]. 504 participants in 11 trials [8]. 22 randomized trials [11].
Sources: [10], [8], [11]
Caveats: The authors of [11] called the effects rather small and partly unclear, larger in untrained people than in trained athletes.

Practices

YogaModerate

Flexibility and leg strength in older adults

Shown to improve lower body flexibility and leg strength in older adults against both inactive controls and active exercise controls, in one meta-analysis.

Compared with inactive controls such as a waiting list or education booklets [7]; active controls such as walking or chair aerobics [7]

The numbers and sources

Effect: Against inactive controls, lower body flexibility improved (effect size 0.5) and lower limb strength improved (0.45). Against active controls, lower limb strength improved (0.49) and lower body flexibility improved (0.28) [7].
Population: Older adults with a mean age of 60 or above, not recruited for any condition, in 17 trials of physical function [7].
Sources: [7]
Caveats: The abstract gives no confidence intervals.

Cold water immersionModerate

Recovery of power and performance

Mixed results: pooled trials found small gains in next-day muscular power and no effect on strength recovery, and umbrella reviews call performance findings inconsistent.

The numbers and sources

Effect: Cold water immersion improved recovery of muscular power 24 hours after eccentric exercise (SMD 0.34, 95% CI 0.06 to 0.62) and high-intensity exercise (SMD 0.22, 95% CI 0.004 to 0.43), and lowered creatine kinase 24 hours after high-intensity exercise (SMD -0.85, 95% CI -1.61 to -0.08). Recovery of strength did not differ from passive recovery after either type of exercise [4]. An umbrella review of 15 meta-analyses reported better muscular power and jump performance at 24 to 48 hours despite impaired jumping in the first hours after immersion, and no improvement in strength performance [6]. A second umbrella review judged findings for objective performance inconsistent, time-dependent or comparator-dependent [5].
Population: Physically active people in 52 studies [4]. 161 unique studies across 15 meta-analyses [6]. 14 reviews [5].
Sources: [4], [6], [5]
Caveats: Certainty of evidence was rated low to very low, mainly for inconsistency and imprecision [6]. The lower confidence limit for power after high-intensity exercise sits at zero [4].

Red light therapyModerate

Exercise performance

Mixed results: pooled trials found small gains in muscle endurance and cycling time to exhaustion, and no effect on strength, sprinting, running or swimming performance.

The numbers and sources

Effect: Across 37 double-blind crossover studies (586 participants) of light applied before exercise, muscle endurance in single-joint exercise improved (SMD 0.27, 95% CI 0.12 to 0.41) and so did cycling time to exhaustion (SMD 0.35, 95% CI 0.10 to 0.59). Strength (p = 0.92), cycling sprints (p = 0.96), running and swimming measures did not change [17]. An earlier review of 39 trials (861 participants) found some effect in favor of phototherapy on time to exhaustion, repetitions, peak torque and lactate, at very low to moderate quality [18]. In athletes, a meta-analysis of 24 studies reported better lower-limb strength up to 8 weeks when laser was applied before exercise [19].
Population: Healthy young adults [17]. Healthy people in 39 trials [18]. Physically active athletes in 24 studies [19].
Sources: [17], [18], [19]
Caveats: The reviews disagree on strength. Light doses, wavelengths and exercise tests varied widely, and samples were small [18].

Whole-body cryotherapyLimited

Recovery of muscle function

Mixed results: a review counted better performance recovery in most studies, while a marathon trial found worse muscle function after cryotherapy than after cold water immersion.

The numbers and sources

Effect: In a review of 16 studies, measures of athletic capacity and performance improved in 71% of studies using controlled exercise [3]. After a marathon, cryotherapy had a harmful effect on muscle function compared with cold water immersion and was no better than placebo [4]. After resistance exercise, peak force at 48 hours was higher with cryotherapy than with cold water or placebo, and most other outcomes were trivial, unclear or favored placebo [5]. In 14 academy soccer players, peak power, soreness and perceived recovery did not differ from seated rest after one session [6].
Population: Physically active people in 16 studies [3]. 31 male marathon runners [4]. 24 resistance-trained men [5]. 14 professional academy soccer players in a crossover [6].
Sources: [3], [4], [5], [6]
Caveats: Small trials with different temperatures, timings and exercise models. Only the two Wilson trials used a placebo.

Whole-body cryotherapyLimited

Performance when used before exercise

Limited evidence: a systematic review of 12 controlled studies found the effect of cryotherapy before exercise on performance unclear.

The numbers and sources

Effect: Of 12 controlled studies of whole-body or partial-body cryotherapy before exercise, 6 tested performance, 4 oxidative stress and 2 lysosomal enzymes. The reviewers judged the potential for favorable physical responses unclear, with little high-quality research available [24].
Population: Healthy or athletic participants in 12 studies [24].
Sources: [24]
Caveats: No pooled estimate. Protocols were not standardized across studies.

Cold water immersionStrong

Strength gains from resistance training

Shown to reduce strength gains when used after resistance training sessions, in two meta-analyses. Whole-body immersion on its own showed no significant difference.

The numbers and sources

Effect: Across 8 controlled studies, regular cold water immersion with resistance training reduced gains in one-repetition maximum, isometric strength and strength endurance (SMD -0.60, 95% CI -0.87 to -0.33) and in ballistic efforts (SMD -0.61, 95% CI -1.11 to -0.11) [7]. Across 10 studies (170 participants, 92% men), it attenuated strength gains (effect size -0.23, 95% CI -0.45 to -0.01). The effect was -0.31 (95% CI -0.61 to -0.01) when only the trained limbs were immersed and -0.08 (95% CI -0.53 to 0.38) with whole-body immersion [8]. In 21 men training for 12 weeks, strength rose more with active recovery than with 10 minutes of cold immersion after each session (P < 0.05) [9]. In 16 men training for 7 weeks, leg press gains were similar with and without 15 minutes at 10°C [10].
Population: Participants in 8 controlled studies of immersion at 15°C or colder [7]. 170 participants in 10 studies [8]. 21 physically active men [9]. 16 men [10].
Sources: [7], [8], [9], [10], [6]
Caveats: The two meta-analyses draw on an overlapping set of small trials, almost all in young men. The whole-body subgroup did not reach significance [8], and one trial found strength unaffected while muscle fiber growth was blunted [10]. An umbrella review reached the same conclusion on strength at low to very low certainty [6].

Infrared saunaLimitedStudied in women

Muscle growth and power

One trial found no added muscle growth from a 10-minute infrared sauna after training for 6 weeks in 40 female athletes. Loaded jump height improved.

The numbers and sources

Effect: Six weeks of strength and power training improved performance and muscle size in both groups. Hypertrophy measures by DXA and ultrasound showed no group by time interaction. Countermovement jump with 15% added load improved in the sauna group (interaction p = 0.002 for height and p = 0.010 for peak power) [23].
Population: 40 female team sport athletes, pair-matched to sauna (10 minutes at 50°C, 3 times a week) or control [23].
Sources: [23]
Caveats: Pair-matched, not described as randomized. One of several jump tests showed the effect.

Daily life

Strength trainingStrong

Muscle strength, lean mass and physical function

Shown to raise muscle strength by a large amount and lean mass by about 1.1 kg in older adults in pooled trials, with small gains in everyday physical function.

Compared with control groups in randomized trials [9]; before training, in the same people, in randomized and nonrandomized studies [10][11]

The numbers and sources

Effect: Progressive resistance training had a large effect on strength (SMD 0.84, 95% CI 0.67 to 1.00, 73 trials), a small effect on physical ability (SMD 0.14), a gait speed gain of 0.08 m/s and a moderate to large effect on rising from a chair (SMD -0.94) [9]. Strength rose 29% in leg press, 24% in chest press, 33% in knee extension and 25% in lat pull, more with higher intensity [10]. Lean body mass rose 1.1 kg (95% CI 0.9 to 1.2), more with higher volume and less in older participants [11].
Population: 6,700 older adults in 121 trials, mostly training 2 to 3 times a week at high intensity [9]. 1,079 adults 50 and older in 47 studies [10]. 1,328 adults 50 and older in 49 studies [11].
Sources: [9], [10], [11]
Caveats: Heterogeneity was high (I² 84% for lean mass) [11]. The two strength and lean mass reviews included nonrandomized studies and before-and-after changes [10][11].

Food and drink

Energy drinksModerate

Exercise performance

Shown to improve muscle strength and endurance, endurance tests, jumping and sport-specific actions after one energy drink, in pooled studies, with no significant effect on sprinting.

Compared with control or placebo conditions the abstract does not describe [4]

The numbers and sources

Effect: Energy drink intake improved muscle strength and endurance (effect size 0.49), endurance exercise tests (0.53), jumping (0.29) and sport-specific actions (0.51), and not sprinting (0.14, p = 0.06). Performance was associated with taurine dose and not with caffeine dose in a meta-regression [4].
Population: 34 studies published 1998 to 2015 [4].
Sources: [4]
Caveats: One review, with drinks varying in dose and ingredients. A different review found little evidence that ingredients other than caffeine improve performance [5]. Caffeine trials on their own are on the caffeine page.

Red meat and processed meatLimited

Muscle and strength with resistance training in older adults

Mixed results: one trial in older women found more lean mass and strength with lean red meat during training, while a larger trial found no added gain.

Compared with a daily serving of pasta or rice [5]; rice, pasta or potato on training days [6]

The numbers and sources

Effect: In women aged 60 to 90 doing resistance training twice a week, about 160 g of cooked lean red meat 6 days a week gave greater gains in total lean mass (0.45 kg, 95% CI 0.07 to 0.84), leg lean mass and strength (18%), and a 10% greater rise in IGF-1, over 4 months [5]. In adults 65 or older training 3 days a week, lean red meat on training days did not add to gains in lean mass, thigh muscle, strength or executive function over 24 weeks. Arm lean mass, gait speed and muscle density improved slightly more [6].
Population: 100 women in 15 retirement villages, cluster randomized [5]. 154 community-dwelling adults aged 65 or older [6].
Sources: [5], [6]
Caveats: Two trials from the same research group with different results. Both combined meat with exercise, so neither tests meat alone.

Lab markers

DHEA sulfate (DHEA-S)Strong

Body composition, physical performance and quality of life in trials that raised DHEA-S

Not shown to change body composition, physical performance, sexual function or quality of life in a meaningful way when DHEA-S was raised with DHEA in older adults.

The numbers and sources

Effect: In a 2-year trial in older adults with low DHEA-S, DHEA raised the level by a median of 3.4 µg/mL in men and 3.8 µg/mL in women, which is 340 and 380 µg/dL. It had no significant effect on body composition, and did not change peak oxygen consumption, muscle strength, insulin sensitivity or quality of life. Bone density rose at the femoral neck in men and at the ultradistal radius in women [8]. Across 25 trials in older men, DHEA reduced fat mass slightly (standardized mean difference -0.35, 95% CI -0.65 to -0.05), an effect that disappeared after adjusting for the rise in testosterone and estradiol, with no effect on blood lipids, blood sugar, bone, sexual function or quality of life [9]. A review of 8 trials called the effect on muscle strength and physical function inconclusive [10]. In postmenopausal women, 23 trials found no significant improvement in libido or sexual function (0.35, -0.02 to 0.73) and no significant effect on lipids, glucose, weight or bone density [11]. A Cochrane review found no improvement in quality of life (0.16, -0.03 to 0.34) and more androgenic side effects, mainly acne (odds ratio 3.77, 1.36 to 10.4) [12].
Population: 87 older men and 57 older women with low DHEA-S, treated for 2 years [8]. 1,353 older men in 25 trials, mean follow-up 36 weeks [9]. 661 adults aged 50 or older in 8 trials [10]. 1,188 postmenopausal women in 23 trials [11]. 1,273 women in 28 trials [12].
Sources: [8], [9], [10], [11], [12]
Caveats: A marker that tracks an outcome is not always one whose correction changes it. Low DHEA-S went with more deaths in cohorts. The trials measured body composition, function and quality of life, not deaths. The reviewers of the trials in women rated confidence in the evidence as low [11].