This claim says that taking lots of vitamin C, echinacea, garlic, or vitamin D doesn't actually help you get better from a cold, according to real studies done on people.
Evidence from Studies
Supporting (3)
Community contributions welcome
Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of stratified aggregate data
This study looked at vitamin D for preventing colds and found it doesn't work well, which supports part of the claim, but it didn't test the other vitamins or herbs mentioned.
Vitamin C for preventing and treating the common cold.
This study looked at whether taking lots of vitamin C helps with colds and found it doesn't really work for most people. It supports part of the claim about vitamin C but doesn't test the other things like echinacea or garlic.
Megadose vitamin C in treatment of the common cold: a randomised controlled trial
This study looked at high-dose vitamin C and found it didn't help with colds, which matches part of the claim. But it didn't test the other things like echinacea or garlic, so we can't say for sure about those.
Contradicting (3)
Community contributions welcome
Vitamin C reduces the severity of common colds: a meta-analysis
This study shows that high-dose vitamin C does help reduce cold severity, which goes against the claim that it doesn't work, but it doesn't say anything about the other things like echinacea or garlic.
Vitamin C for preventing and treating the common cold.
This study only looks at vitamin C, not the other things mentioned, and it shows vitamin C doesn't prevent colds for most people but might help a little in reducing how long or bad a cold is if taken regularly.
The study looked at some of the same things as the claim but found that echinacea, vitamin C, and vitamin D can help with colds in some cases, which goes against the claim that they have no effect. It also didn't study garlic at all.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.