Regulation 4 ProhibitionsI1 Scotland Subject to regulation 5, no person shall– (a) add tryptophan to food; (b) sell, or offer for sale, food containing tryptophan; or (c) expose for sale food containing tryptophan. Annotations Commencement I1 Reg. 4 in force at 11.11.2005, see reg. 1(1) ← Regulation 3 Regulation 4 Regulation 5 →