Does not work
Tested properly, and it did not hold up.
Most of this site is somewhere in the middle, because most of the science is. These 24 claims, across 19 supplements, are the exceptions in one direction: enough good studies exist to answer the question, and the answer is no.
Ranked by how often people look them up
- Moringa for cholesterolThe biggest review covered 9 trials.
- Milk thistle for blood sugarThe biggest review covered 6 trials.
- Zinc for immunity and coldsThe biggest review covered 34 trials.
- Collagen for skin, hair and nailsThe biggest review covered 23 trials.
- Selenium for cancer preventionThe biggest review covered 5 trials.
- Omega-3 for heartThe biggest review covered 86 trials.
- Vitamin B12 for heartThe biggest review covered 15 trials.
- Vitamin B12 for memory and focusThe biggest review covered 16 trials.
- Vitamin B12 for moodThe biggest review covered 16 trials.
- Ginkgo biloba for memory and focusThe biggest review covered 13 trials.
- Ginkgo biloba for tinnitusThe biggest review covered 12 trials.
- L-lysine for cold soresThe biggest review covered 32 trials.
- Vitamin C for preventing coldsThe biggest review covered 29 trials.
- Vitamin K2 for cholesterolTested in 108 people.
- Vitamin K2 for inflammationTested in 375 people.
- L-arginine for heartThe biggest review covered 13 trials.
- L-arginine for weight and body fatThe biggest review covered 8 trials.
- Vitamin D for boneThe biggest review covered 11 trials.
- L-citrulline for enduranceThe biggest review covered 9 trials.
- L-tyrosine for enduranceThe biggest review covered 8 trials.
- Iodine for memory and focusThe biggest review covered 2 trials.
- Tribulus terrestris for testosterone and libidoThe biggest review covered 10 trials.
- Green tea extract for cancer preventionThe biggest review covered 11 trials.
- Calcium for boneThe biggest review covered 69 trials.
What a hollow capsule is, and is not
Hollow is the hardest state to earn on this site. It is not the same as a ghost, which means nobody has looked. Hollow means people looked properly, and the answer came back no.
It is also narrower than it sounds. Every entry above is one claim, not the whole supplement. Zinc not shortening a cold says nothing about zinc for anything else, and a supplement can be hollow for one thing and solid for another. Each name links to the supplement, where every claim we scored for it is listed.
The line under each name is the strongest evidence behind that verdict, and it is not the same size everywhere. Some of these rest on a review of dozens of trials, others on a few hundred people. A short line is not a weaker verdict on its own, but it is worth clicking through before you act on it.
And a verdict is only as good as the studies under it. We weigh how a study was built, not how well it was run, which we set out in full on how we score. The opposite page is never tested together, the combinations no trial has looked at.