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Myth checker: popular supplement claims, checked

Each answer below comes from one finding we have re-checked against the abstracts of its studies: the grade, what the studies found, and the studies themselves on PubMed. Some claims hold up, some don’t, and some are mixed, and we say which.

Answers checked against the abstracts on 7 November 2026No buy links

Claims

  • Does fish oil keep your memory sharp as you get older?

    No clear effectVery limited evidenceRe-checked 8 November 20261 trial · 1,525 people

    Not in the trial linked here. In a 3-year trial of 1,525 people aged 70 and over with memory complaints, omega-3 capsules made no difference to how much their memory and thinking declined compared with placebo.

  • Does L-carnitine improve endurance?

    No clear effectVery limited evidenceRe-checked 8 November 20264 small trials · 56 people

    Mostly no. Three of the four small trials linked here found no change in endurance; the fourth, in five rugby players, found they cycled longer before exhaustion. A 2021 review found no gain in moderate exercise either, but some in short, hard efforts.

  • Does valerian help you sleep?

    Improved a littleLimited evidenceRe-checked 8 November 20261 trial · 100 people

    One trial says it may. Women after menopause who had insomnia reported better sleep quality on valerian extract than on placebo over 4 weeks. One trial is limited evidence.

  • Does ginger ease period pain?

    Improved a littleLimited evidenceRe-checked 8 November 20261 trial · 150 people

    In one trial, about as much as two common painkillers. Students with period pain who took ginger had pain relief similar to those who took ibuprofen or mefenamic acid. There was no placebo group, so the trial can't show how much was the ginger itself.

  • Does vitamin B6 help PMS?

    Improved a littleLimited evidenceRe-checked 8 November 20266 studies, including a review of 9 trials · 940 women in the review

    Probably a little, but the trials are weak. A review of 9 trials with 940 women found more improvement in premenstrual symptoms on B6 than on placebo, though most of the trials were of low quality. The single trials linked here disagree with each other.

  • Does beetroot juice improve exercise performance?

    Improved a littleModerate evidenceRe-checked 8 November 20264 reviews of trials

    A little, in some kinds of exercise. Reviews of many trials found a small gain, mostly in tests to exhaustion and in people who aren't trained athletes. Time trials and trained athletes showed little or no gain.

  • Does baking soda improve sprint and race performance?

    Improved a littleLimited evidenceRe-checked 8 November 202610 small trials

    Sometimes, a little. Baking soda is sodium bicarbonate. Of the 10 small trials linked here, 6 found faster times or more power in races or repeated sprints, and 4 found no difference.

  • Does beta-alanine improve exercise performance?

    Improved a littleLimited evidenceRe-checked 8 November 20261 review of 18 trials and 1 trial

    A little, for all-out efforts lasting 30 seconds to 10 minutes. A review of 18 trials in trained young men found a small gain; a trial of 5-second sprints found none.

  • Does glucosamine help knee pain?

    MixedModerate evidenceRe-checked 8 November 202611 studies, including a review of 20 trials

    The trials disagree. Trials of one prescription form of glucosamine sulfate (the Rotta preparation) mostly found less pain. Trials of other forms, and the better-run trials, mostly found it no better than placebo, including a trial of 1,583 people.

  • Does fish oil ease anxiety?

    Improved a littleLimited evidenceRe-checked 8 November 20261 trial · 68 people

    One trial found a modest effect. Medical students who took omega-3 fish oil for 12 weeks reported 20% fewer anxiety symptoms than those on placebo.

  • Does whey protein curb hunger?

    Improved a littleLimited evidenceRe-checked 8 November 20261 review of 8 trial reports

    A little, over the longer term. In the 3 longer-term reports in a review of 8, appetite fell slightly; in short tests, whey was no better than carbohydrate.

  • Does psyllium fiber help you feel full?

    Improved a littleLimited evidenceRe-checked 8 November 20263 small studies · 45 people

    For a few hours, a little. In two of three small, short studies, psyllium raised fullness or lowered hunger after a meal. In the third, people ate more at a snack after it than after wheat bran, and no breakfast changed how much they ate over the whole day.

Being re-checked

We get asked these often. Their findings are still being re-checked against the studies, so they have no answer or grade here yet.

How we check a claim

  • We pick claims people really ask about, and only claims about how the body works, not about curing a disease.
  • Each claim is matched to one finding on our site: a supplement, an outcome and a grade. A claim is answered only once that finding has been re-checked: every linked study was confirmed on PubMed and read against the finding’s grade, direction and study count.
  • We then read each study’s abstract ourselves and wrote the answer from it. Every quote is copied from an abstract, and every number in an answer appears in one.
  • Before publishing, we checked each answer against recent reviews. Where the wider research disagreed with the finding on our site, we left the claim out and asked for the finding to be re-checked.
  • If a finding is changed or opened again for checking, its answer here is hidden and marked “Being re-checked”, with no grade, until we check it again.
  • Grades run from A (strong) to D (very limited). How we grade.
  • Nothing here links to a product, whatever the answer.

For education only, not medical advice. Talk to a qualified clinician before starting any supplement.

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