Disclosed are a novel therapeutic agent and a novel prophylactic agent for atherosclerosis, a blood cholesterol level-lowering agent, and a functional food or a food for specified health uses effective for the inhibition and/or prevention of aging of blood vessels or inflammation in blood vessels. Specifically disclosed are an inhibitor of the progression of atherosclerosis, a prophylactic agent for atherosclerosis, a blood cholesterol level-lowering agent, and a functional food and a food for specified health uses both effective for the inhibition and/or prevention of aging of blood vessels or inflammation in blood vessels, each of which comprises, as an active ingredient, a hydrolysis product of a collagen comprising at least one collagen tripeptide Gly-X-Y [wherein Gly-X-Y represents an amino acid sequence and X and Y independently represent an amino acid residue other than Gly].
