Energy and fatigue
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
Medication
Daytime sleepiness in narcolepsy
Shown to reduce daytime sleepiness in adults with narcolepsy, about 3 points on the Epworth scale and 3 minutes longer awake on a lab test, but not cataplexy.
Compared with placebo [1][2][3]; sodium oxybate in one comparison [1]
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- Against placebo, modafinil lowered Epworth Sleepiness Scale scores by 2.73 points (95% CI 2.08 to 3.39) and lengthened time to fall asleep on the Maintenance of Wakefulness Test by 2.82 minutes (95% CI 2.40 to 3.24). It did not change the number of cataplexy attacks a day. Its effect on sleepiness was similar to sodium oxybate's [1]. An updated meta-analysis found 3.56 more minutes on the Maintenance of Wakefulness Test (95% CI 2.25 to 4.86) and a 3.34-point drop on the Epworth scale (95% CI 2.56 to 4.13) [2]. In the two label trials, 58% to 72% on modafinil were rated improved against 37% to 38% on placebo [3].
- Population
- 1,054 patients in 9 randomized trials [1]; 997 adults in 5 trials pooled, out of 9 studies reviewed [2]; 558 adults in two 9-week US trials [3].
- Sources
- [1], [2], [3]
- Caveats
- The 2026 review notes the randomized trials date mostly from the 1990s and early 2000s, with no new eligible trials in the past decade, and that long-term efficacy is not established [2]. Patients on modafinil still averaged well below normal wakefulness on the lab test [3].
Sleepiness in sleep apnea despite CPAP
Shown to reduce residual sleepiness in sleep apnea, about 2 to 3 points on the Epworth scale, with about three times the adverse events of placebo.
Compared with placebo, on top of CPAP [3][4][5]
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- Modafinil or armodafinil improved Epworth Sleepiness Scale scores by 2.2 points (95% CI 1.5 to 2.9) and Maintenance of Wakefulness Test times by 3 minutes (95% CI 2.1 to 3.8) over placebo. Adverse events tripled and withdrawals for adverse events doubled, with no rise in hospitalizations or deaths [4]. A second meta-analysis found Epworth scores lower by 2.96 points with modafinil (95% CI 2.19 to 3.73) and 2.63 with armodafinil (95% CI 1.85 to 3.40) [5]. In the 12-week label trial, 61% on modafinil 200 mg and 68% on 400 mg were rated improved against 37% on placebo [3].
- Population
- 1,466 patients in 10 trials of at least 2 weeks [4]; 723 patients in 11 modafinil trials and 1,009 in 5 armodafinil trials [5]; 327 adults with sleep apnea, 80% fully using CPAP [3].
- Sources
- [3], [4], [5]
- Caveats
- The European Medicines Agency removed this indication in 2011 over an unfavorable balance of benefit and risk, which the first review sought to re-examine [4]. The drug treats sleepiness, not the airway obstruction [3].
Sleepiness in shift work disorder
Shown to reduce sleepiness on night shifts in people diagnosed with shift work disorder, about 1 point on a 10-point scale. No trials tested shift workers without the disorder.
Compared with placebo [6][7][8]
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- Armodafinil taken before the night shift lowered Karolinska Sleepiness Scale scores by 0.99 points (95% CI 0.67 to 1.32, range 1 to 10) and sped simple reaction time by 50 milliseconds at 3 months. Modafinil lowered the same score by 0.90 points (95% CI 0.35 to 1.45) [7]. In the pivotal 3-month trial, modafinil 200 mg lengthened nighttime time to fall asleep by 1.7 minutes against 0.3 on placebo, and 74% against 36% were rated clinically improved [8]. The armodafinil label reports the same kind of trial results for 150 mg [6].
- Population
- 2 armodafinil trials with 572 participants and 1 modafinil trial with 183, within a Cochrane review of 15 trials and 718 shift workers [7]; 209 patients with shift work disorder [8].
- Sources
- [6], [7], [8]
- Caveats
- The trial authors noted that treated patients remained very sleepy at night [8]. The Cochrane review found no trials in shift workers without a diagnosed disorder, and rated the evidence moderate quality [7].
Alertness and performance during sleep deprivation
Shown to keep sleep-deprived healthy people awake and to hold memory and executive function better than placebo, though repeated doses did not prevent decline over longer deprivation.
Compared with placebo [12]
The numbers and sources
- Effect
- In sleep-deprived individuals, modafinil maintained wakefulness, memory and executive function to a significantly greater degree than placebo. Over longer sleep deprivation, repeated doses did not prevent cognitive performance from deteriorating, while wakefulness was maintained and people possibly became overconfident about their own performance [12].
- Population
- Healthy adults in single- or double-blind randomized trials [12].
- Sources
- [12]
- Caveats
- One meta-analysis, and the abstract does not give pooled effect sizes or head counts [12].
Depression, as an add-on
Shown to improve depression scores and remission modestly when added to standard treatment, in unipolar and bipolar depression, an off-label use.
Compared with placebo added to standard treatment [15][16]
The numbers and sources
- Effect
- Added to first-line treatment, modafinil improved overall depression scores (point estimate -0.35, 95% CI -0.61 to -0.10) and remission (OR 1.61, 95% CI 1.04 to 2.49), with a positive effect on fatigue and adverse events no different from placebo [15]. In bipolar depression, added modafinil or armodafinil raised response (RR 1.18, 95% CI 1.01 to 1.37) and remission (RR 1.38, 95% CI 1.10 to 1.73), with no rise in mood switching or suicide attempts [16].
- Population
- 910 adults with major depressive disorder or bipolar depression in 6 trials [15]; 795 on drug and 792 on placebo in 5 bipolar depression trials, 4 of them of armodafinil [16].
- Sources
- [15], [16]
- Caveats
- Few trials. Both reviews included bipolar trials, so they overlap. Not an FDA-approved use.
Long COVID
Limited evidence: fatigue, brain fog, sleep and pain improved from baseline in uncontrolled studies of long COVID. No randomized trials were found.
The numbers and sources
- Effect
- A 2026 systematic review screened 397 records and found no randomized trials. In 4 pre-post studies (155 people) at 1 to 6 mg a day, fatigue (Hedges' g -0.74, 95% CI -1.11 to -0.37), brain fog (g -0.53), sleep (g -0.60), pain (g -0.93) and daily function (g -0.93) improved from baseline [12].
- Population
- 155 people with long COVID in the US and Ireland in uncontrolled studies [12].
- Sources
- [12]
- Caveats
- The review rated certainty as low, and its studies had no control group [12]. No peer-reviewed randomized trial was located.
Fatigue in neurological conditions
Mixed results: one review found less fatigue in multiple sclerosis, and an earlier review found benefit only after brain injury and not in multiple sclerosis or Parkinson's.
Compared with placebo [13][14]
The numbers and sources
- Effect
- Across 10 trials, modafinil lowered fatigue after traumatic brain injury (MD -0.82, 95% CI -1.54 to -0.11) and sleepiness in Parkinson's disease (MD -2.45 on the Epworth scale), but fatigue did not differ from placebo in pooled Parkinson's or multiple sclerosis studies [13]. A later review of 7 studies in multiple sclerosis found lower Modified Fatigue Impact Scale scores (MD -4.42, 95% CI -8.01 to -0.84) and more adverse events (RR 1.30) [14].
- Population
- 535 patients with Parkinson's disease, multiple sclerosis, brain injury or post-polio syndrome in 10 trials [13]; 7 controlled studies in multiple sclerosis [14].
- Sources
- [13], [14]
- Caveats
- Most trials were small [13]. The two reviews disagree on multiple sclerosis, and neither studied fatigue in people without a diagnosed condition.
Symptoms and quality of life in subclinical hypothyroidism
Not shown to improve quality of life or thyroid symptoms in adults with subclinical hypothyroidism, including those 65 or older, though it brought TSH into range.
The numbers and sources
- Effect
- Thyroid hormone lowered mean TSH into the reference range (0.5 to 3.7 mIU/L against 4.6 to 14.7 on placebo) but did not change general quality of life (SMD -0.11, 95% CI -0.25 to 0.03) or thyroid-related symptoms (SMD 0.01, 95% CI -0.12 to 0.14) [1]. In adults aged 65 or older, the change in Hypothyroid Symptoms score at 1 year was 0.2 on both levothyroxine and placebo (difference 0.0, 95% CI -2.0 to 2.1). Tiredness scores did not differ (difference 0.4, 95% CI -2.1 to 2.9), and no secondary outcome improved [2].
- Population
- 21 RCTs with 2,192 nonpregnant adults, 3 to 18 months [1]; 737 adults with mean age 74.4 and TSH 4.60 to 19.99 mIU/L [2].
- Sources
- [1], [2]
- Caveats
- Most participants had mildly raised TSH. [1] rated the evidence moderate to high quality. [2] was funded by the European Union FP7 and others.
Energy and mitochondrial function in healthy people
Not studied in people. In human cells in the lab, methylene blue raised mitochondrial complex IV by 30% and oxygen use by 37 to 70%.
No study in people. This rests on lab studies, how it acts in the body.
The numbers and sources
- Effect
- In cultured human fibroblasts, nanomolar methylene blue increased mitochondrial complex IV by 30%, raised cellular oxygen consumption by 37 to 70% and increased heme synthesis. The authors propose this comes from methylene blue cycling between its oxidized and reduced forms inside mitochondria [8].
- Population
- Human IMR90 fibroblasts and HepG2 liver cells in culture, and rat liver mitochondria [8].
- Sources
- [8]
- Caveats
- Cell culture only. No trial was located that measured energy, fatigue or mitochondrial function in healthy people taking methylene blue.
Supplements
Attention and alertness under sleep loss
Shown to improve attention, reaction time and driving lane control in sleep-deprived adults, compared with sleep loss without caffeine.
The numbers and sources
- Effect
- Across 45 publications in sleep-deprived or sleep-restricted people, caffeine improved attention response time (g 0.86), attention accuracy (g 0.68, 95% CI 0.48 to 0.88), executive function (g 0.35, 95% CI 0.15 to 0.55), reaction time (g 1.11, 95% CI 0.75 to 1.47) and driving lane control (g 1.67, 95% CI 1.32 to 2.02) [7]. In 7 placebo-controlled trials in military personnel under sleep loss, caffeine improved vigilance and response performance (SMD 0.73, 95% CI 0.50 to 0.96), complex cognitive performance (0.54, 95% CI 0.16 to 0.93) and military task performance (0.45, 95% CI 0.19 to 0.71) [8].
- Population
- Sleep-deprived or restricted adults, 327 effect estimates [7]. Military personnel in 7 randomized trials [8].
- Sources
- [3], [7], [8]
- Caveats
- The pooled effects are against a sleep-deprived baseline, not a rested one. The abstract's confidence interval for attention response time (0.53 to 0.83) does not contain its point estimate (0.86), which suggests a typo in the source.
Fatigue
Shown to reduce fatigue in iron-deficient adults without anemia. In one trial, only women with ferritin at or below 50 µg/L improved.
The numbers and sources
- Effect
- In iron-deficient adults without anemia, iron reduced self-reported fatigue (SMD -0.38, 95% CI -0.52 to -0.23, I² 0%, 4 trials, 714 participants) [3]. In 144 non-anemic women with unexplained fatigue, 80 mg a day of elemental iron for 4 weeks lowered fatigue by 29% versus 13% on placebo (difference 0.95 points on a 10-point scale, 95% CI 0.32 to 1.62). Only women with ferritin at or below 50 µg/L improved [4]. A 2025 meta-analysis of non-anemic participants found less fatigue in RCTs (d 0.34), and no effect when participants without iron deficiency were analyzed alone [5].
- Population
- Iron-deficient non-anemic adults [3]; Swiss women aged 18 to 55 in primary care [4]; 1,408 participants in 18 studies, 1,176 of them menstruating adults and 204 aged 5 to 17 [5].
- Sources
- [3], [4], [5]
- Caveats
- Fatigue is self-reported. Reference [4] is one of the trials pooled in [3], and the two reviews may share other trials [3][5]. The 2025 abstract does not give confidence intervals [5].
Fatigue
Shown to reduce fatigue modestly in adults with fatigue, including chronic illness, across few small trials.
The numbers and sources
- Effect
- In 4 RCTs pooled, ginseng reduced fatigue (SMD 0.34, 95% CI 0.16 to 0.52) [3]. A systematic review of 10 studies of Asian and American ginseng in people with fatigue found modest evidence of benefit and a low risk of adverse events [4].
- Population
- Adults with fatigue, including chronic illness [3][4].
- Sources
- [3], [4]
- Caveats
- The meta-analysis authors judged the evidence insufficient because trials were few and small [3].
Energy and fatigue in healthy people
Small trials found a B complex lengthened time to exhaustion in 32 young adults, and a B, C and mineral product raised self-rated stamina in working men.
The numbers and sources
- Effect
- In a double-blind crossover trial, 28 days of a B1, B2, B6 and B12 product (Ex PLUS) raised running time to exhaustion 1.26-fold over placebo (p < 0.05) and lowered blood lactate and ammonia during and after exercise [10]. In 198 employed men given a B complex with vitamin C and minerals or placebo for 28 days, the supplement group rated themselves higher for physical stamina across assessments, and for concentration, mental stamina and alertness after a working day at some time points [11].
- Population
- 32 healthy adults aged 20 to 30, half women [10]. 198 men aged 30 to 55 in full-time work [11].
- Sources
- [10], [11]
- Caveats
- Two small trials of branded products. The second product also held vitamin C and minerals, so the B vitamins' share cannot be separated [11]. Ratings were self-reported, and effects in [11] appeared at some time points and not others.
Energy and immunity
One trial found a fruit and vegetable juice powder cut days with moderate or severe cold symptoms by 20% in hospital staff. No trial measuring energy was located.
The numbers and sources
- Effect
- In 529 healthcare workers given encapsulated fruit and vegetable juice powder (Juice Plus+) or placebo daily for 8 months, days with moderate or severe cold symptoms over 6 months averaged 7.6 against 9.5 (p = 0.023). Total days with any cold symptom did not differ, 29.4 against 30.7 (p = 0.616) [11].
- Population
- 529 hospital staff in Berlin aged 18 to 65, mostly nurses, 80% women [11].
- Sources
- [11]
- Caveats
- One trial of one encapsulated fruit and vegetable product, not a greens drink powder. Symptoms were self-reported in diaries, and the effect was limited to more severe symptom days [11]. No trial of AG1 or other greens blends measured energy, fatigue or infections.
Mood, energy and quality of life
One trial found better mood, energy and quality of life than placebo over 12 weeks in Peruvian adults at low and high altitude.
The numbers and sources
- Effect
- In 175 adults living at low and high altitude, 3 g a day of red or black maca extract for 12 weeks improved mood, energy, health-related quality of life and chronic mountain sickness scores compared with placebo. Black maca lowered blood glucose [7].
- Population
- Adults in Peru at low and high altitude [7].
- Sources
- [7]
- Caveats
- One trial of spray-dried extracts.
Stress and fatigue
Limited evidence: a review of Soviet-era research reports clinical trials in asthenia and stress protection in animals, without figures in its summary.
The numbers and sources
- Effect
- A review of research from the former USSR reports that animal studies found Schisandra protected against a broad range of stressors, including heat, cold, immobilization and low air pressure, and that numerous clinical trials reported benefit in asthenia, neurosis and astheno-depressive states. In healthy people it altered nitric oxide and cortisol levels in blood and saliva [7].
- Population
- Animal studies and clinical trials in the former USSR, reviewed [7].
- Sources
- [7]
- Caveats
- A narrative review, largely of older Russian-language studies. Its abstract gives no trial sizes, comparison groups or effect sizes [7]. No recent placebo-controlled trial of Schisandra alone for stress or fatigue was located.
Energy and endurance
Limited evidence: a review of Soviet-era studies reports more endurance and working capacity in healthy people and in animals, without figures in its summary.
The numbers and sources
- Effect
- The same review reports that Schisandra increased physical working capacity in animal studies, and in healthy people increased endurance, accuracy of movement, mental performance and working capacity [7]. In a 12-week trial in postmenopausal women, resting lactate, a fatigue-related marker, changed differently on Schisandra than on placebo [2].
- Population
- Animal studies and studies in healthy people in the former USSR, reviewed [7]. 45 postmenopausal women [2].
- Sources
- [7], [2]
- Caveats
- A narrative review of older studies, with no trial sizes or effect sizes in its abstract [7]. The lactate result was one measure among several in a small trial, and endurance itself was not tested [2].
Fatigue
Limited evidence: 2 trials in people with depression found no difference in fatigue from control.
The numbers and sources
- Effect
- In 2 trials in people with depression, fatigue did not differ from control (SMD -0.33, 95% CI -1.38 to 0.72, I² 89%) [20].
- Population
- Patients with depression, alone or with multiple sclerosis, breast cancer or polycystic ovary syndrome [20].
- Sources
- [20]
- Caveats
- Two trials with high heterogeneity. No review of fatigue in healthy people was located.
Energy and fatigue
Limited evidence: only one trial measured fatigue in people with normal B12, too few to pool.
The numbers and sources
Metabolism, energy and weight loss
Not studied in people. Iodine is needed to make thyroid hormone, but in mice low iodine shrank fat stores, and in people high intakes went with more underactive thyroid.
No study in people. This rests on how it acts in the body, animal studies.
The numbers and sources
- Effect
- Iodine is an essential part of the thyroid hormones thyroxine and triiodothyronine, and both too little and too much can cause hypothyroidism or hyperthyroidism [13]. In mice kept on a low-iodine diet, T4 fell and TSH rose, fat made up about 2.3 times more of the energy burned, and fat depots were about 60% smaller than on a normal diet, while oxygen use and activity did not change [14]. In a Chinese cohort, subclinical hypothyroidism developed more often in regions with more than adequate or excessive iodine intake than where intake was mildly deficient [7].
- Population
- A review [13]. C57BL/6 male mice [14]. 3,018 people in three regions of China [7].
- Sources
- [13], [14], [7]
- Caveats
- No trial measured weight, energy or metabolic rate in people given iodine. The mouse result runs opposite to the weight loss claim and does not show what supplements do in people [14].
Adrenal fatigue
Not studied in people for adrenal fatigue. Licorice slows the body's inactivation of cortisol, and a systematic review found no evidence adrenal fatigue is a medical condition.
No study in people. This rests on how it acts in the body.
The numbers and sources
- Effect
- In 7 healthy volunteers given licorice, sodium retention came with a change in cortisol metabolism showing that licorice blocks 11-beta-hydroxysteroid dehydrogenase, the enzyme that converts cortisol to inactive cortisone in the kidney [14]. A systematic review of 58 studies of cortisol and fatigue found no substantiation that adrenal fatigue is an actual medical condition [15].
- Population
- 7 healthy volunteers in a mechanism study [14]. 58 studies of cortisol and fatigue [15].
- Sources
- [14], [15]
- Caveats
- The enzyme effect is what raises blood pressure and lowers potassium (see Risks), and it does not show that licorice changes fatigue. No trial of licorice for fatigue or adrenal symptoms was located.
Energy, fatigue and well-being
Not studied in people. In rodents, raising NAD often improved metabolic, mitochondrial and physical function measures, with results varying by model.
No study in people. This rests on animal studies.
The numbers and sources
- Effect
- A 2026 systematic review of 80 rodent studies found that raising NAD was frequently associated with improvements in metabolic, mitochondrial, inflammatory and functional outcomes, though effects varied across models and endpoints. It found no outcome trial of IV or intramuscular NAD for wellness in people [6].
- Population
- Rodents in 80 studies of NAD-related compounds given by mouth or by injection [6].
- Sources
- [6]
- Caveats
- Rodent results do not show how people feel after an infusion. The rodent studies covered NAD-related compounds in general, not infused NAD alone. No trial measured energy, fatigue or well-being after IV NAD [6].
Therapies
Fatigue in healthy adults, high-dose vitamin C drip
One trial of 141 office workers found a 10 g vitamin C drip lowered current fatigue for a day more than saline, and usual fatigue did not differ.
Compared with an infusion of normal saline only [3]
The numbers and sources
- Effect
- Fatigue right now, on a 0 to 10 scale, fell from 5.64 to 5.10 at 2 hours and 4.97 at 1 day with vitamin C, and went from 5.54 to 5.31 and 5.66 with saline (p = 0.004). Usual fatigue (p = 0.870) and worst fatigue (p = 0.202) over the previous 24 hours did not differ. The effect appeared in people with low baseline vitamin C levels (p = 0.004) and not in those with high levels (p = 0.206) [3].
- Population
- 141 healthy office workers aged 20 to 49 in Korea, 70 given vitamin C and 71 saline, followed for one day [3].
- Sources
- [3]
- Caveats
- One trial measuring one day. At one day the two groups' changes differed by about 0.8 points on the 10-point scale. Hospital trials of intravenous vitamin C in sepsis and other critical illness are covered on the vitamin C page.
Practices
Alertness, noradrenaline and dopamine
Small studies found plasma noradrenaline rose 530% and dopamine 250% during an hour in 14°C water, and people reported feeling more alert after a 5-minute immersion.
The numbers and sources
- Effect
- During 1-hour head-out immersion at 14°C, plasma noradrenaline rose by 530% and dopamine by 250%, with adrenaline unchanged. Immersion at 20°C or 32°C did not produce these rises [16]. After a 5-minute cold bath, 33 adults reported feeling more active, alert and attentive [19].
- Population
- A group of young men, number not given in the abstract [16]. 33 adults [19].
- Sources
- [16], [19]
- Caveats
- Hormones were measured in blood during a 1-hour immersion, far longer than a typical plunge, and blood levels are not brain levels. Neither study had a control group for the self-reported feelings. No trial measured attention or cognitive performance.
Chronic fatigue syndrome
Limited evidence: perceived fatigue fell after 4 weeks of Waon therapy in 10 inpatients with chronic fatigue syndrome, in a study with no control group.
The numbers and sources
- Effect
- Perceived fatigue on a numerical scale decreased significantly after 4 weeks, with no significant reduction at 2 weeks. Negative mood and performance status improved. Pain and vigor did not change significantly [28]. A 2009 review rated the evidence for chronic fatigue syndrome as weak, from a single study [14].
- Population
- 10 consecutive inpatients, treated once a day, 5 days a week for 4 weeks [28].
- Sources
- [28], [14]
- Caveats
- Ten inpatients and no control group.
Quality of life in type 2 diabetes
Limited evidence: quality of life, stress and fatigue scores improved after 3 months of infrared sauna in people with type 2 diabetes, in a study with no control group.
The numbers and sources
- Effect
- After 20-minute sessions 3 times a week for 3 months, physical health, general health and social functioning scores on the SF-36v2 improved, as did visual analogue scores for stress and fatigue [29].
- Population
- Patients with type 2 diabetes at one rural Canadian health center [29].
- Sources
- [29]
- Caveats
- No control group. The abstract gives no participant count, no effect sizes and no blood sugar results.
Fatigue in multiple sclerosis
Limited evidence: fatigue and functional status scores improved after a series of sessions in 48 people with multiple sclerosis, in a study with no untreated group.
The numbers and sources
- Effect
- After a series of daily sessions at -110°C or lower, functional status and the feeling of fatigue improved in both a low-fatigue and a high-fatigue group, with larger changes in the high-fatigue group [23].
- Population
- Two groups of 24 people with multiple sclerosis, matched for age and sex [23].
- Sources
- [23]
- Caveats
- Both groups received cryotherapy, so there is no comparison with no treatment.
Long COVID
Mixed results: a 40-session sham-controlled trial found better cognition, energy and sleep scores in long COVID, and a 10-session trial found no difference from sham.
The numbers and sources
- Effect
- In 73 patients with symptoms at least 3 months after infection, 40 daily sessions improved global cognitive function (d = 0.495, p = 0.038), attention, executive function, energy (d = 0.522), sleep, psychiatric symptoms and pain interference compared with sham [12]. In 80 patients, 10 sessions at 2.4 bar over 6 weeks did not differ from sham at 13 weeks in physical functioning (difference 0.63, 95% CI -7.04 to 8.29) or role limitations due to physical health (difference 2.35, 95% CI -5.95 to 10.66). Both groups improved [13].
- Population
- 73 adults, 37 treated and 36 sham [12]. 80 previously healthy adults aged 18 to 60, 40 per group [13].
- Sources
- [12], [13]
- Caveats
- The trials differ fourfold in the number of sessions and in their outcome measures. Outcomes in the positive trial were assessed 1 to 3 weeks after the last session [12].
Oral health, energy and immunity
Not studied in people. Social media videos credit mouth taping with better sleep and oral health, and with more energy and immunity.
No study in people. This rests on what users report.
The numbers and sources
- Effect
- A review of TikTok videos about mouth taping found the most common proposed advantages were improved sleep and oral health. The same review reports claims of increased energy, immunity and dental health, and found few of them had been evaluated [5].
- Population
- The first 50 TikTok videos meeting the review's criteria [5].
- Sources
- [5]
- Caveats
- Claims in videos are not measurements. No study located tested mouth taping for oral health, dental health, energy or immunity.
Daily life
Alertness and fatigue after a nap
Shown to raise vigilance and alertness and to reduce felt fatigue after a nap, in three meta-analyses of nap studies.
Compared with control conditions the abstract does not describe [1]; a no-nap control condition, and the same people before the nap [2]; a no-nap condition in randomized trials [3]
The numbers and sources
- Effect
- Naps improved vigilance (Cohen's d 0.610, 95% CI 0.291 to 0.929) [1]. Alertness improved after a nap (effect size 0.29, 95% CI 0.10 to 0.48), with better results for naps before 1 p.m. [2]. Perceived fatigue fell after a nap following a normal night (SMD -0.76, 95% CI -1.24 to -0.28), and benefits were also seen after partial sleep deprivation [3].
- Population
- 60 samples from 54 studies [1]. 381 working-age adults in 11 studies [2]. 291 young males in 22 randomized trials [3].
- Sources
- [1], [2], [3]
- Caveats
- Most studies were in laboratories, short and small. Fatigue was self-rated, and heterogeneity was high (I² 89.5%) [3].
Bright light, naps and other measures for sleepiness on shift
Mixed results: in a Cochrane review, bright light at night lowered sleepiness slightly in two studies, while naps, exercise and sleep education gave inconclusive results.
Compared with normal light [2]; control conditions the review abstract does not describe, for naps and other measures [2]
The numbers and sources
- Effect
- Bright light during the night shift lowered sleepiness by 0.83 points on the Stanford Sleepiness Scale (95% CI -1.3 to -0.36, very low-quality evidence). Another trial found no difference on another scale, and bright light during day shifts did not reduce sleepiness. A single nap opportunity changed reaction time by 11.87 ms, not significant. Exercise and sleep education showed promise without enough data to judge [2].
- Population
- 556 shift workers who also work nights, in 17 randomized trials [2].
- Sources
- [2]
- Caveats
- Most comparisons gave low to very low-quality evidence and studies were too varied to pool [2].
Food and drink
Focus and alertness
One trial found caffeinated coffee helped people take in new information and offset fatigue against decaffeinated coffee, with no change in working memory or mood.
Compared with decaffeinated coffee [12]; people drinking no coffee [13]
The numbers and sources
- Effect
- In 144 volunteers, caffeinated coffee had no effect on initial mood or working memory, improved encoding of new information and counteracted fatigue that built up over the test session, against decaffeinated coffee. It raised blood pressure and pulse [12]. In adults 60 or older, those drinking 266.4 to 495 g of coffee a day had lower odds of a low processing speed score (OR 0.56, 95% CI 0.35 to 0.89) than non-drinkers. Decaffeinated coffee was not linked to any cognitive score [13].
- Population
- 144 volunteers, 72 men and 72 women, mean age 21, on one morning [12]. 2,513 US adults aged 60 or older, surveyed once [13].
- Sources
- [12], [13]
- Caveats
- One small single-morning trial, and a survey measured at one time point that cannot show cause. Trials of caffeine on attention are on the caffeine page.
Alertness and mental performance
A systematic review found the caffeine dose in a typical energy drink can improve mental performance, with little evidence that taurine, ginseng or other added ingredients contribute.
Compared with caffeine alone or placebo, in the studies reviewed [5]
The numbers and sources
- Effect
- A typical 235 ml energy drink provides 40 to 250 mg of caffeine, doses that improve cognitive performance and, at the higher levels, physical performance. Across 32 articles, apart from weak evidence for glucose and guarana extract, there was an overwhelming lack of evidence that ingredients other than caffeine enhance physical or cognitive performance [5].
- Population
- 32 articles testing energy drink ingredients alone or with caffeine [5].
- Sources
- [5]
- Caveats
- A systematic review without pooled numbers. Pooled trials of caffeine and attention are on the caffeine page.
Mood and energy, the sugar rush
Not shown to lift mood at any point after eating it, in a meta-analysis of 31 studies. Fatigue was higher and alertness lower in the first hour.
Compared with placebo [5]
The numbers and sources
- Effect
- Across 176 effect sizes, carbohydrate had no positive effect on any aspect of mood at any time after eating. In the first hour, it was linked to more fatigue and less alertness than placebo [5].
- Population
- 1,259 participants in 31 studies [5].
- Sources
- [5]
- Caveats
- The review covered carbohydrate in general, mostly sugars, taken in single doses. It does not test daily eating patterns.
Diets
Energy
One uncontrolled study in fibromyalgia found 7 of 8 health survey scores improved on a mostly raw vegetarian diet, all but bodily pain. No study in healthy people.
Compared with before the diet, in the same people [7]
The numbers and sources
- Effect
- In people with fibromyalgia on a mostly raw vegetarian diet of fruits, salads, carrot juice, tubers, grains, nuts, seeds and a barley grass product, the fibromyalgia impact score fell 46%, from 51 to 28. Seven of the 8 SF-36 health survey subscales improved significantly, bodily pain being the exception [7].
- Population
- 30 adults with fibromyalgia enrolled, 20 analyzed at 2 or 4 months [7].
- Sources
- [7]
- Caveats
- No control group, and a third of participants were not in the main analysis. The abstract does not give the change on the SF-36 vitality scale on its own. People with fibromyalgia, not healthy people seeking more energy [7].
Lab markers
Fatigue in adults with low ferritin and no anemia
Shown in trials: iron given to adults with low ferritin and no anemia reduced self-rated fatigue, with no change in measured physical capacity.
The numbers and sources
- Effect
- In a meta-analysis of randomized trials in iron-deficient adults without anemia, iron supplementation reduced self-reported fatigue (standardized mean difference -0.38, 95% CI -0.52 to -0.23, 4 trials, 714 participants). Maximal oxygen consumption did not differ (SMD 0.11, 95% CI -0.15 to 0.37, 9 trials, 235 participants), nor did timed exercise tests [7]. In one of the larger trials, in women with unexplained fatigue and ferritin below 50 ng/mL, the fatigue score fell 47.7% with iron and 28.8% with placebo (difference -18.9%, 95% CI -34.5 to -3.2), with no effect on quality of life, depression or anxiety [8].
- Population
- 1,170 adults in 18 trials [7]. 198 menstruating women aged 18 to 53 with hemoglobin above 12.0 g/dL, treated for 12 weeks [8].
- Sources
- [7], [8]
- Caveats
- Fatigue was self-rated, and the larger trial was observer-blinded with closed labels, not fully double-blind [8]. Trials defined iron deficiency by different ferritin cut points.
Sexual function, vitality and walking in a trial that raised testosterone in older men
One trial found raising low testosterone in men 65 and older improved sexual function moderately, with no benefit for vitality or walking distance.
The numbers and sources
- Effect
- In 790 men aged 65 or older with testosterone below 275 ng/dL and symptoms, testosterone gel for 1 year raised levels to the mid-normal range for men aged 19 to 40. Sexual activity increased (P below 0.001), as did sexual desire and erectile function. The share of men gaining at least 50 meters in the 6-minute walk did not differ significantly in the Physical Function Trial, and was 20.5% against 12.6% when men from all three trials were pooled. There was no significant benefit for vitality, and mood and depressive symptoms were slightly better [21].
- Population
- 790 men aged 65 or older, mean of two testosterone results below 275 ng/dL, treated for 1 year [21].
- Sources
- [21]
- Caveats
- One trial of 1 year. The authors state that it enrolled too few men to draw conclusions about the risks of treatment [21].
Symptoms and quality of life in trials that lowered a mildly raised TSH
Not shown to improve quality of life or thyroid symptoms when levothyroxine lowered TSH into range in 21 trials of adults with subclinical hypothyroidism.
The numbers and sources
- Effect
- In a trial of 737 adults aged 65 and older with TSH of 4.60 to 19.99 mIU/L, levothyroxine left TSH at 3.63 mIU/L at 1 year against 5.48 on placebo. The Hypothyroid Symptoms score did not differ (between-group difference 0.0, 95% CI -2.0 to 2.1), nor did the Tiredness score (0.4, -2.1 to 2.9) [24]. Across 21 trials, thyroid hormone brought mean TSH to 0.5 to 3.7 mIU/L against 4.6 to 14.7 mIU/L on placebo, with no benefit for general quality of life (standardized mean difference -0.11, 95% CI -0.25 to 0.03) or thyroid-related symptoms (0.01, -0.12 to 0.14) [25]. A guideline panel that reviewed the same trials issued a strong recommendation against thyroid hormones for adults with subclinical hypothyroidism, and stated that it does not apply to women trying to become pregnant or to people with TSH above 20 mIU/L [26].
- Population
- 737 adults, mean age 74.4, mean baseline TSH 6.40 mIU/L [24]. 2,192 nonpregnant adults in 21 randomized trials lasting 3 to 18 months [25].
- Sources
- [24], [25], [26]
- Caveats
- A marker that tracks an outcome is not always one whose correction changes it. The pooled trials lasted 3 to 18 months. The guideline panel judged effects on cardiovascular events and deaths to be uncertain, measured in one trial with few events [26].
Symptoms in trials that added T3 to thyroxine for hypothyroidism
Not shown to change pain, mood, fatigue, quality of life, weight or cholesterol when T3 was added to thyroxine in 11 trials of adults with hypothyroidism.
The numbers and sources
- Effect
- A meta-analysis of 11 randomized trials found no difference between combined T4 and T3 treatment and T4 alone for bodily pain (standardized mean difference 0.00, 95% CI -0.34 to 0.35), depression (0.07, -0.20 to 0.34), anxiety (0.00, -0.12 to 0.11), fatigue (-0.12, -0.33 to 0.09) or quality of life (0.03, -0.09 to 0.15). Body weight and blood lipids did not differ, and adverse events did not differ between regimens [10].
- Population
- 1,216 adults with clinical hypothyroidism in 11 randomized trials [10].
- Sources
- [10]
- Caveats
- The trials compared treatments in people already treated for hypothyroidism, and the abstract does not report the free T3 levels reached. Searches ran to September 2005 [10].