Study archive · page 4

In a network meta-analysis of 13 trials with 181 participants, caffeine, sodium bicarbonate and their combination each produced small performance improvements over placebo, but combining them showed no clear advantage over either supplement alone despite larger metabolic responses such as a bigger rise in blood lactate.

⚠What it shows: A fair answer to the stacking question, but a small one: results pooled from 13 trials totalling just 181 people, and responses may differ with training status. Each supplement's benefit was small to begin with, so the margins here are fine.Review · Metabolites

Pooled results from seven crossover trials in 103 people found acute caffeine gave a small boost to overall CrossFit performance (Hedges' g 0.13) and raised blood lactate; neither the relative dose nor training status significantly changed the effect.

⚠What it shows: A real but small edge: results pooled from seven small crossover trials covering 103 people, only 13 of them women. That thin, mostly male evidence base means the true size of the benefit could still shift.Meta-analysis · Nutrients

CoQ10 supplementation showed no robust benefit for athletes across 24 pooled studies: VO2max was unchanged, and blood pressure, muscle damage markers and inflammation did not shift either. The only favourable signal, on the oxidative stress marker malondialdehyde, appeared in a secondary analysis and was described by the authors as fragile.

⚠What it shows: A fairly convincing null: results pooled from 24 studies in 613 trained people showed no effect on aerobic capacity, muscle damage or inflammation. Nearly all the studies had quality concerns and small numbers, so a niche benefit under extreme training stress cannot be completely excluded.Review · 3 Biotech

In a meta-analysis of six randomised trials covering 262 adults with diagnosed anxiety or stress-related disorders, exercise reduced anxiety symptoms significantly more than usual treatment or control conditions, with a moderate effect size.

⚠What it shows: Encouraging but built on a small base: results pooled from six trials covering 262 adults with diagnosed anxiety or stress-related disorders. The average benefit was moderate, but with so few trials the true size remains uncertain.Meta-analysis · Psychiatry Res

Pooled results from 12 studies covering 393 regular cannabis users found that cannabis cues triggered moderate craving reactions overall, and that brain-wave responses to the cues were large while self-reported craving and heart rate responses were far weaker.

⚠What it shows: Solid as summaries go: results pooled from 12 studies of 393 regular users, mostly teens and young adults, with no sign that negative findings were buried. The physical measures disagreed with each other a lot, so treat the striking brain-wave figure as a rough size rather than a precise one.Meta-analysis · Addiction

Exercise appears to reshape the brain's working memory circuits in two distinct ways: pooled imaging data from 11 studies found training programmes increased cerebellum activity and quietened the thalamus, while long-term exercisers showed an entirely different, non-overlapping pattern of brain activation.

⚠What it shows: Treat this as an early map rather than settled science: it pools brain scans from only 11 studies and 403 people, and the short-term and long-term patterns did not overlap, so how one becomes the other is anyone's guess.Review · Brain Sci

In cohort studies comparing 7195 isotretinoin users in Canada and 340 in the UK against acne patients on oral antibiotics, isotretinoin was not associated with increased risk of depression, psychosis, suicide or attempted suicide; relative risks were around 1.0.

⚠What it shows: Reassuring rather than final: researchers followed acne patients in two large health databases rather than testing the drug in a trial, comparing 7195 isotretinoin users in Canada and 340 in the UK against antibiotic users. Rare or small effects cannot be completely ruled out this way.Meta-analysis · Arch Dermatol

Oral probiotics made only a slight difference to acne after 4 weeks, but by 12 weeks they had reduced severity grading and cut total lesion counts by an average of 10.4 versus control, in pooled results from randomised trials covering 623 patients.

⚠What it shows: Encouraging but thin: the results pool 9 trials with 623 people in total, and the improvement in severity scores only just scraped past chance, so larger trials could still shrink or erase the effect.Meta-analysis · Clin Exp Dermatol

Across 11 randomised trials with 686 participants, vitamin D supplementation reduced the severity of atopic dermatitis in children and adults compared with control groups.

⚠What it shows: One of the better-tested supplement findings: results pooled from 11 trials in 686 children and adults all point the same broad way, though the trials differed somewhat from each other and the authors still want larger, longer studies before calling it settled.Meta-analysis · Nutrients

Micronised progesterone shortened the time it took to fall asleep in pooled trial data, mostly from postmenopausal women, but did not significantly improve total sleep time or sleep efficiency. Self-reported sleep improved in most trials.

⚠What it shows: Promising but thin: only 9 trials totalling 388 people, almost all postmenopausal women, and the trials disagreed with each other. Several also gave oestrogen at the same time, which muddies what the progesterone alone achieved.Meta-analysis · J Clin Endocrinol Metab

A systematic review of 32 human studies found caffeine consistently suppresses the slow-wave brain activity that marks deep sleep and increases faster, more wake-like brain activity, producing lighter sleep even when conventional sleep-stage measures barely change.

⚠What it shows: A solid picture from a sweep of all the studies on this, 32 in total, but the studies disagreed with each other too much to pool into one number, so the findings were summarised in words. How big the effect is for you depends on dose, timing, how habitually you use caffeine, your age and your genetics.Systematic review · Nutrients

Pooled results from 50 randomised trials covering 4,379 adults aged 65 and over show supervised exercise modestly lowers C-reactive protein and raises the anti-inflammatory marker IL-10, while effects on other inflammatory signals such as IL-6 and TNF-α were inconsistent.

⚠What it shows: About as solid as this topic gets, though modest in size: results pooled from 50 trials in 4,379 people aged 65 and over pointed the same way for C-reactive protein. Many of the underlying studies had quality problems, so the true size of the benefit is uncertain.Study · Gerontologist

In a meta-analysis of 10 prospective studies, unfit people had twice the risk of dying from any cause regardless of body mass index, while overweight and obese people who were fit had mortality risks similar to normal-weight fit people.

⚠What it shows: Strong for a pattern, weaker for cause: it pools 10 studies that measured fitness objectively and then followed people over time to see who died, so fit people may still differ in other healthy ways the analysis could not fully account for.Meta-analysis · Prog Cardiovasc Dis

In pooled trials of people with osteoarthritis and rheumatoid arthritis, mostly women, low-load resistance training with blood flow restriction produced similar gains in muscle strength, muscle mass and functionality to moderate and high-intensity training, and outperformed low-load training without restriction on knee extension strength.

⚠What it shows: Promising but thin: only five trials made the cut, mostly in women with arthritis, and the strength results varied somewhat between studies. Enough to call the approach promising, not enough to call it proven.Systematic review · PLoS One

Pooling 4 randomised trials in 263 office workers with chronic low back pain, exercise interventions may reduce pain in the short term; the certainty of the evidence was rated very low and no trial measured work productivity.

⚠What it shows: A weak signal, not a verdict: only 4 trials with 263 office workers could be pooled, the reviewers rated the pain evidence very low certainty, and not one study measured whether people actually functioned better at work.Study · J Occup Health

Pooled trial data in postpartum women found abdominal exercises reduced the separation between the rectus muscles below the belly button more than abdominal binding or no intervention, but not above it, and neither approach clearly improved disability or pelvic floor scores.

⚠What it shows: Reasonably solid for the lower-belly result: results pooled from 13 trials in postpartum women, though the trials used differing definitions and measures, which muddies comparisons. The gap above the navel did not clearly respond to anything tested, and disability and pelvic floor scores did not clearly improve either.Meta-analysis · Physiother Res Int

In a meta-analysis of 18 randomised trials, Tai Chi was associated with reductions in systolic and diastolic blood pressure, LDL cholesterol, triglycerides and total cholesterol in women aged 45 and over, with no clear effect on HDL cholesterol or fasting glucose.

⚠What it shows: Encouraging but shaky: it pools 18 trials in women aged 45 and over, and the studies disagreed with each other enough that the size of the benefit may not repeat in every group or setting.Systematic review · Front Cardiovasc Med

A pooled analysis of 75 trials in 1,206 athletes found protein supplements improved endurance and strength compared with no supplement, but every statistically significant benefit came from trials where the protein group also took in more total energy. The gains may reflect extra calories rather than protein itself.

⚠What it shows: Take the benefits with a pinch of salt: results pooled from 75 trials in 1,206 athletes, but every significant win came from studies where the supplement group also consumed more energy overall. Extra calories, not protein itself, may explain the edge.Meta-analysis · J Int Soc Sports Nutr

A sweep of 36 human trials found plant foods such as tart cherry, pomegranate, beetroot and berry juices often reduced perceived muscle soreness in the 24 to 72 hours after exercise, but showed no consistent benefit for muscle function, subsequent performance or blood markers, and no specific product, dose or timing could be recommended.

⚠What it shows: Take the big picture, not any single juice: a sweep of 36 human trials in active people found soreness relief in several of them, but products, doses and designs varied so much the authors could not pool the numbers or back any one option. Benefits beyond soreness did not hold up consistently.Systematic review · Nutrients

In 1169 Spanish adults followed for a mean of 21.5 years, each 10 bpm rise in resting heart rate was associated with about 15% higher risk of dying from any cause; the link was clearest in people carrying exactly three cardiovascular risk factors and was not statistically significant in those with fewer or more.

⚠What it shows: Treat this as a flag, not a cause: researchers followed 1169 Spanish adults for over two decades rather than testing anything, so a faster pulse may simply travel alongside other problems. The link was only clear in the group with exactly three risk factors, and that subgroup pattern could partly reflect chance.Study · J Clin Med

Across 45 randomised trials, GLP-1 receptor agonists were associated with a modest rise in thyroid disorders overall, but no significant increase in any single condition, including thyroid cancer, hyperthyroidism, hypothyroidism, thyroiditis, thyroid mass or goitre.

⚠What it shows: Reassuring on the specifics but not fully settled: results pooled from 45 trials found no significant rise in thyroid cancer or any single thyroid condition. These diseases are rare, so even trials this size can miss small risks, and the modest rise in thyroid problems as a combined category keeps the question open.Meta-analysis · Front Endocrinol (Lausanne)

Adding Lactobacillus probiotics to standard Helicobacter pylori eradication therapy was linked to a 10% relative increase in treatment success and a 30% relative drop in side effects across 32 randomised trials of 4,010 patients. The eradication benefit appeared only with triple therapy regimens, and the side effect reduction only in adults.

⚠What it shows: Solid as pooled evidence goes: results pooled from 32 trials in 4,010 people pointed the same way for both success and side effects. The eradication boost showed up only alongside triple therapy, so it may not help with other antibiotic regimens.Meta-analysis · Eur J Clin Pharmacol

An analysis pooling 26 randomised trials in 11,897 healthy adults and children found all four flu antivirals assessed were associated with shorter symptoms, with zanamivir linked to the fastest relief and baloxavir to the lowest risk of complications and side effects. Oseltamivir at 75 mg was the exception on tolerability, associated with more nausea and vomiting.

⚠What it shows: A strong basis for comparing the drugs against each other: results pooled from 26 trials in 11,897 otherwise healthy adults and children. It ranks the pills rather than telling you whether any is worth taking for a mild bout, and the complications finding rests on moderate quality evidence.Meta-analysis · JAMA Netw Open

Genetic evidence from 23,868 men with prostate cancer and 23,051 controls suggests alcohol is unlikely to affect whether men develop the disease. Variants in alcohol-metabolising genes were, however, linked to prostate cancer mortality, hinting that drinking may influence how the disease progresses.

⚠What it shows: Indirect but hard to confound: instead of asking men what they drink, it used inherited gene variants that change how the body handles alcohol, pooling results from 25 studies of 23,868 men with prostate cancer and 23,051 without. The progression signal rests on a handful of variants, so it needs confirming before anyone treats it as settled.Meta-analysis · Int J Cancer