l carnitine an SirenLabs® L-Carnitine Elite Burn Creatine & Acetyl-L-Carnitine Energy Plus,

An early cross-sectional study of 101 fertile and infertile men found that L-carnitine concentrations in semen were positively correlated with the number of sperm, the percentage of motile sperm, and the percentage of normal appearing sperm in the sample (110), suggesting that L-carnitine may play an important role in male fertility

This is backed up by another study on brain function, which found that creatine is most likely to exert an influence in situations whereby cognitive processes are stressed. A review suggested that creatine supplementation might also help the brain recover from trauma and shows promise for combating age-related cognitive decline

In IBD, acetyl-L-carnitine improves immune tolerance by decreasing the ratio of Th17 cells and macrophages.[ref] Inborn errors of metabolism: Genetic mutations and carnitine Genetic mutations in the genes involved in the carnitine shuttle can cause inborn errors of metabolism for long-chain fatty acids

However, as mentioned above, the data is mixed