Providing materials that promote ammonia metabolism in the body and materials that have an excellent effect of improving ammonia metabolism and are effective in improving endurance and anti-fatigue. An ammonia metabolism promoter containing catechins as an active ingredient. A preventive or ameliorating agent for hyperammonemia, hepatic encephalopathy or chronic fatigue syndrome, which comprises catechins as an active ingredient. Ammonia metabolism promoters, endurance improvers and anti-fatigue agents containing catechins, citrulline and arginine as active ingredients.体内のアンモニア代謝を促進する素材、および優れたアンモニア代謝改善作用を有し、持久力向上および抗疲労に有効な素材の提供。カテキン類を有効成分とするアンモニア代謝促進剤。カテキン類を有効成分とする高アンモニア血症、肝性脳症もしくは慢性疲労症候群の予防もしくは改善剤。カテキン類、シトルリンおよびアルギニンを有効成分とするアンモニア代謝促進剤、持久力向上剤および抗疲労剤。
