Vitamin B complex (B1, B2, B3, B5, B6, B7, B9, B12): Supports metabolism, helps energy production and protects nervous system health. Although vitamin B complex has many beneficial effects for the body, it can be harmful when taken in excessive amounts. Here are the benefits and harms of vitamins B1, B2, B3, B5, B6, B7, B9 and B12 in the B vitamin complex: Benefits: B1 (Thiamine): Contributes to energy production, protects nervous system health and supports carbohydrate metabolism. B2 (Riboflavin): Helps energy production, has antioxidant effects and supports skin health. B3 (Niacin): It can lower cholesterol levels, contributes to energy production and maintains nervous system health. B5 (Pantothenic acid): Aids energy production, can help cope with stress, and supports skin health. B6 (Pyridoxine): Supports protein metabolism, protects nervous system health and strengthens the immune system. B7 (Biotin): Supports hair, skin and nail health, regulates carbohydrate metabolism and contributes to energy production. B9 (Folic Acid): Contributes to DNA synthesis, supports the healthy development of the baby during pregnancy and can reduce the risk of anemia. B12 (Cobalamin): Supports the formation of red blood cells, protects the health of the nervous system and helps energy production. Harms: Some B vitamins (such as B6 and B12) can cause nerve damage and toxicity when taken in excessive amounts. In some people, B vitamins can cause allergic reactions and side effects such as skin rash, itching, or redness. Some B vitamins (e.g. B3) can cause liver damage when taken in high doses. It is thought that some B vitamins (e.g. B9 - folic acid) may increase the risk of cancer when taken in excess. Therefore, it is important to get the amount your body needs through a balanced diet rather than taking excessive amounts of B vitamin complex supplements. It is best to take B vitamin complexes in appropriate amounts in consultation with a nutritionist. Additionally, people with B vitamin deficiency may need to take supplements, but a specialist should be consulted on this matter.