Table 2. The Cochrane Central Register of Controlled Trials (CENTRAL).

This table was created by one of the authors of this article.

No.	Search	Result
#1	"collagen" OR "hydrolyzed collagen"	10287
#2	oral supplementation	10778
#3	"skin rejuvenation" OR "skin aging"	1422
#4	hydration skin	1410
#5	elasticity skin	1001
#6	#1 AND #2 AND #3 AND #4 AND #5	32
Total: 32