Scientific Opinion on the substantiation of health claims related to gamma-linolenic acid and maintenance of joints (ID 494, 637, 1774, 2098), weight maintenance following weight loss (ID 496), maintenance of peripheral blood flow (ID 638), maintenance of normal blood pressure (ID 1771), maintenance of normal blood cholesterol concentrations (ID 1771) and maintenance of bone (ID 1774) pursuant to Article 13(1) of Regulation (EC) No 1924/2006