According to a study published in the journal Science, oral administration of type II collagen decreases symptoms of rheumatoid arthritis. The authors conducted a randomized, double-blind trial involving 60 patients with severe, active rheumatoid arthritis. A decrease in the number of swollen joints and tender joints occurred in subjects fed with chicken type II collagen for 3 months, but not in those that received a placebo. Four patients in the collagen group had complete remission of the disease. No side effects were evident.
^Trentham, D.; Dynesius-Trentham, R.; Orav, J.; Combitchi, D.; Lorenzo, C.; Sewell, K.; Hafler, D. & Weiner, H. (1993). "Effects of Oral Administration of Type II Collagen on Rheumatoid Arthritis". Science261 (5119): 1727–1730. doi:10.1126/science.8378772.