I'd suggest Glycine but if you are not allowed sugar for medical reasons, consult a doctor first. Glycine like many chemicals play many parts in the body and combine with other chemicals, like other amino acids. Its one of the ingredients of creatine, now creatine gets broken down into creatinine which is a gram positive and gram negative anti bacterial, and bacteria in the brain & body can also affect personality so there may be other factors at play contributing to your mood. If you want to study this, then you should know the answer to your question!