Which supplement works better to reduce frequency of the common cold: l-cystine or l-theanine?

Ratings at a Glance

Supplement	Effectiveness Rating	Confidence Rating
L-Cystine
L-Theanine

Effectiveness Rating: L-Cystine vs L-Theanine

The effectiveness rating is a measure of the supplements' ability to reduce frequency of the common cold. This rating answers the question of whether or not a supplement does what it claims. Both l-cystine and l-theanine have good (but not great) evidence showing they may be able to reduce frequency of the common cold. Both supplements should provide some positive results.

Confidence Rating: L-Cystine vs L-Theanine

Another factor to take into account when comparing supplements is the confidence rating. This rating is a measure of how valid each supplement's effectiveness rating is. Remember, the confidence rating is a measure of how much you can trust the effectiveness rating. This rating is based on how many studies are included in the database on a supplement's claims. Ideally, you want a high effectiveness AND confidence rating.

Both l-cystine and l-theanine have low confidence ratings. This means neither supplement has an adequate amount of research to back up this claim. A low confidence rating questions the validity of the effectiveness rating.