5. B Vitamins The B vitamins, which include B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12, play numerous roles in energy production, metabolic processes, and nerve function. A deficiency in B vitamins can lead to lethargy, poor appetite, and neurological issues.