Which supplement works better to improve running performance: beetroot juice or tryptophan?

Ratings at a Glance

Supplement	Effectiveness Rating	Confidence Rating
Beetroot Juice
Tryptophan

Effectiveness Rating: Beetroot Juice vs Tryptophan

The effectiveness rating is a measure of the supplements' ability to improve running performance. This rating answers the question of whether or not a supplement does what it claims. Both beetroot juice and tryptophan have good (but not great) evidence showing they may be able to improve running performance. Both supplements should provide some positive results.

Confidence Rating: Beetroot Juice vs Tryptophan

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.

Beetroot Juice's confidence rating is higher than tryptophan's. This means beetroot juice's effectiveness rating from above is more valid. This does not necessarily mean that beetroot juice works better, it simply means the evidence (included in this database) backing up beetroot juice is more established.