Study archive · page 12

A systematic review of nine randomised placebo-controlled trials found that beetroot supplementation may improve oxidative metabolism and muscle force production in combat sports athletes, though the effects appear to depend on the population, intake duration, muscle group and exercise type.

⚠What it shows: Promising but thin: a sweep of all the studies turned up just nine trials, most testing a one-off dose, with almost no data in women. Treat this as a maybe rather than a proven edge.Systematic review · Nutrients

Pooled across 17 randomised trials, L-arginine supplementation produced only a borderline reduction in triglycerides of 6.03 mg/dl and had no significant effect on LDL cholesterol, total cholesterol, HDL cholesterol or the inflammatory markers CRP and TNFα.

⚠What it shows: Trust the null here: results pooled from 17 trials showed nothing beyond a small triglyceride dip that only just reached significance, so any everyday benefit is likely trivial.Meta-analysis · Pharmacol Res

In a pooled analysis of 33 randomised trials, both EPA and DHA lowered triglycerides, but EPA also reduced total and LDL cholesterol while DHA raised total cholesterol, LDL and HDL. DHA also increased insulin levels compared with EPA.

⚠What it shows: One of the bigger pooled datasets on this question, drawing on 33 trials of purified EPA or DHA, though the trials disagreed on the size of each shift and what the opposing cholesterol changes mean for health is not settled.Meta-analysis · Clin Nutr

In pooled trials of older adults, probiotic supplementation improved handgrip strength by 2.50 kg and gait speed by 0.10 m/s, but only the walking speed gain held up when the researchers stress-tested the numbers.

⚠What it shows: Promising but thin: only 8 trials made the review and just 4 fed the pooled analysis, and when the least robust data were removed the grip strength benefit vanished. Treat the walking speed gain as the sturdiest finding here, not the headline strength number.Meta-analysis · Nutr Rev

In a network meta-analysis of 25 trials with 1,096 adults, of which 16 entered the comparison network, aerobic training lowered 24-hour systolic ambulatory blood pressure by 4.77 mmHg and high-intensity interval training by 6.86 mmHg, with a smaller 2.25 mmHg reduction after resistance training. Ranking put HIIT first and resistance training last, but no exercise mode was statistically better than another, and there were too few trials to assess combined or isometric training.

⚠What it shows: Solid on direction, weak on the ranking: results pooled from 25 trials in 1,096 adults, and only 16 of those fed the head-to-head network. No mode came out statistically ahead of any other, and there were too few trials to judge combined or isometric training at all.Meta-analysis · J Hypertens

In people already diagnosed with coronary heart disease, keeping up physical activity was associated with 36% lower all-cause mortality and closer Mediterranean diet adherence with 26% lower, in a review pooling data on at least 260,354 patients.

⚠What it shows: Persuasive but mostly from following patients rather than assigning them lifestyles: the pool covered 34 data sources and at least 260,354 people with heart disease, only six of them trials where people were assigned at random. Healthy habits tend to travel together, so part of the benefit may come from elsewhere.Meta-analysis · Nutrients

Pooled results from 15 randomised trials show aerobic exercise improved flow-mediated dilation, a measure of how well blood vessels widen, by an average of 2.23 units in people with high or borderline high blood pressure. Moderate or vigorous intensity sustained for at least 12 weeks worked best.

⚠What it shows: The direction is trustworthy, the size less so: results pooled from 15 trials in people with raised or borderline blood pressure, but the studies disagreed with each other a lot, so the exact improvement is uncertain.Meta-analysis · J Hypertens

In a sweep of 105 randomised trials covering 6805 adults with raised blood pressure, improved diet cut systolic pressure by 5.0 mmHg and aerobic exercise by 4.6 mmHg, with alcohol restriction, salt restriction and fish oil also producing reliable drops. Potassium, magnesium and calcium supplements showed no robust effect.

⚠What it shows: About as solid as lifestyle evidence gets: 105 trials with 6805 adults assigned at random, each running at least 8 weeks. The sweep dates from 2006, so supplement trials published since are not counted.Meta-analysis · J Hypertens

In a meta-analysis of 26 randomised trials, resistance training lowered systolic blood pressure by 4.13 mmHg and diastolic by 2.03 mmHg in adults with type 2 diabetes compared with usual care, with larger drops in programmes lasting over 12 weeks; resting heart rate and aerobic capacity also improved modestly.

⚠What it shows: A credible pooled result: 26 trials where adults with type 2 diabetes were assigned at random to resistance training or usual care. The trials disagreed with each other on blood pressure and few reported results for women, so the exact size of the drop is uncertain.Meta-analysis · Diabetes Res Clin Pract

A meta-analysis of 29 randomised trials in 1329 adults found progressive resistance training lowered total cholesterol by 2.7%, LDL cholesterol by 4.6% and triglycerides by 6.4%, but did not meaningfully change HDL cholesterol.

⚠What it shows: Solid but modest: results pooled from 29 trials in which 1329 men and women were assigned at random to lift or not. The improvements are real yet small, and the underlying trials all date from before 2008.Meta-analysis · Prev Med

Pooled results from 31 randomised trials in 2779 overweight or obese adults show exercise training improved mental health, eased depression, lifted mood, trimmed waist circumference by an average of 2.77 cm and added 1.16 kg of lean body mass, alongside gains in several quality of life domains.

⚠What it shows: Solid footing: results pooled from 31 trials covering 2779 overweight or obese adults, so the direction of these effects is trustworthy. Some psychological, body composition and quality of life measures did not budge, and the authors say the long-term picture still needs confirming.Meta-analysis · Biol Res Nurs

Across 14 randomised trials in middle-aged and older women, nutrition-only strategies had a limited but positive effect on muscle mass, strength and function: six trials showed benefits from protein, vitamin D, vitamin D with magnesium or fish oil, while eight showed no effect at all.

⚠What it shows: A fair reading of a thin field: a sweep of all the trials in middle-aged and older women found just 14, and they disagreed on what to supplement, how much and for how long. That means no single nutrition strategy comes out clearly on top, and exercise appeared to shape the results in several studies.Systematic review · Calcif Tissue Int

Across randomised trials, regularly eating pigmented rice was linked with fasting glucose lower by 1.60 mg/dL, body weight lower by 0.23 kg and diastolic blood pressure lower by 1.39 mmHg, while cholesterol, triglycerides, BMI and systolic pressure did not move.

⚠What it shows: Treat as a lead, not a verdict: each pooled outcome rested on 5 or fewer trials and at most 349 people, and the studies differed in rice type, duration and who took part. The improvements are also small enough to question how much they matter day to day.Systematic review · Curr Nutr Rep

Pooled results from 33 trials found probiotic yogurt barely outperformed conventional yogurt: a small rise in faecal acetate and in interleukin-10, no significant difference in C-reactive protein or oxidative stress markers, and the reviewers rate the certainty of the evidence as very low.

⚠What it shows: Take the nulls seriously but not as final: results pooled from 33 trials found little daylight between the two yogurts, and the reviewers themselves rate the certainty as very low. The studies disagreed with each other and their design changed some results, so a real difference could still be hiding.Meta-analysis · J Nutr Biochem

In a pooled analysis of three randomised trials with 922 adults, once-weekly semaglutide produced significantly greater reductions in body weight, HbA1c and fasting plasma glucose than once-daily liraglutide, while rates of severe and gastrointestinal side effects were comparable between the two drugs.

⚠What it shows: Credible but slim: only three head-to-head trials with 922 people could be pooled, so the exact size of semaglutide's advantage is still a rough estimate.Meta-analysis · Clin Transl Sci

A systematic review of 31 studies found minimal evidence that prescribed exercise makes healthy adults move less during the rest of the day: 100% of randomised trials reported no reduction in non-exercise activity or energy expenditure.

⚠What it shows: Reassuringly consistent: a sweep of all the studies on this found 31 relevant papers, and every trial where people were assigned at random showed no drop in day-to-day movement outside workouts. The authors note few studies were purpose-built to test this with gold-standard measurement, so small effects could still have slipped through.Systematic review · Clin Obes

In a meta-analysis of 36 randomised trials, GLP-1 receptor agonists reduced lean body mass by 1.51 kg on average and SGLT2 inhibitors by 1.04 kg, with lean mass accounting for 28% of the total weight lost on these drugs.

⚠What it shows: About as solid as this evidence gets: results pooled from 36 trials comparing these drugs with placebo or other treatments, with consistent findings across sexes, conditions and measurement methods. Most participants had obesity or diabetes, and whether the lean tissue lost translates into weaker strength or function was not measured.Meta-analysis · Diabetes Metab Res Rev

A systematic review of 15 randomised trials covering 4656 people found exercise, alone or inside multi-part programmes, was the only intervention with consistent evidence for improving intrinsic capacity and quality of life, the functional measures behind healthspan. Supplements and calorie restriction had too little evidence to judge.

⚠What it shows: Encouraging but early: a sweep of all the trials on this found only 15 worth including, 4656 people in total, and the programmes varied so widely that only exercise appeared often enough to judge. For supplements and calorie restriction the evidence was simply too thin.Systematic review · J Gerontol A Biol Sci Med Sci

A meta-analysis of 17 trials with 2,344 sedentary older adults found programmes grounded in behaviour-change theory cut sitting time and added 8.43 minutes of moderate-to-vigorous activity and 867.30 steps a day, with small knock-on improvements in BMI, blood sugar control and systolic blood pressure. Diastolic pressure unexpectedly rose slightly.

⚠What it shows: The behaviour change is believable, the health payoff barely registers: pooled from 17 trials in which 2,344 older adults were assigned at random, and the small unexplained rise in diastolic pressure needs following up.Meta-analysis · BMC Geriatr

In people with metabolic syndrome, synbiotic supplements reduced insulin, triglycerides, total and LDL cholesterol, systolic blood pressure and waist circumference, and cut body weight by 4.3 kg on average across pooled trials. Fasting glucose, BMI, diastolic blood pressure and C-reactive protein did not change significantly.

⚠What it shows: Encouraging but resting on just five trials with 1049 people, all with metabolic syndrome, and the trials often disagreed on how large the benefits were, so the exact numbers deserve caution.Meta-analysis · Pharmacol Res

An umbrella review of 17 meta-analyses, covering 156 randomised trials of probiotics in adults, found that the beneficial associations with cognitive health outcomes are supported by moderate to high quality evidence, though the best strains, doses and durations remain unclear.

⚠What it shows: Stronger than the usual supplement story: a sweep of 17 pooled analyses covering 156 trials rated many probiotic and cognition links as moderate or high quality evidence. The underlying trials were small, 37 to 409 people, and ran from under a week to 28 weeks, so which strains and doses actually work is still an open question.Systematic review · Nutr Rev

Pooling 19 randomised trials in 1,826 women across 13 drug-free approaches, foot reflexology ranked as the most effective for new mothers' sleep quality in the first 3 months after birth, while cognitive behavioural therapy for insomnia ranked best from 4 to 12 months.

⚠What it shows: Promising rather than final: results pooled from 19 trials in 1,826 mothers, but few of the options were ever tested against each other directly, so the rankings rest on indirect comparisons. Whether foot reflexology truly beats the rest needs head-to-head trials.Meta-analysis · J Clin Sleep Med

In a review pooling 145 studies from China, every 10 µg/m³ of long-term PM2.5 exposure was associated with 15.1% higher cardiovascular mortality and 21.0% higher lung cancer mortality, with short-term pollution spikes also linked to more deaths and illness.

⚠What it shows: Strong and consistent, but built from following populations rather than testing exposures on anyone, so pollution cannot be proven to be the direct cause. The 145 pooled studies all come from China, where other risks of city living travel with dirty air and are hard to fully separate.Meta-analysis · J Environ Sci (China)

Across 13 randomised trials in 691 women with PCOS, vitamin D supplementation reduced fasting blood glucose, insulin, triglycerides, total cholesterol, VLDL cholesterol and LDL cholesterol, with no significant effect on HDL cholesterol.

⚠What it shows: Fairly trustworthy: results pooled from 13 trials in 691 women with PCOS, and the authors' checks suggested enough people had been studied to back the main findings. The best dose and whether the benefits last are still unknown.Meta-analysis · BMC Endocr Disord