Vitamin B1 plays a key role in the breakdown of carbohydrates from food to make energy. It supports healthy functioning of the heart, muscles and nerves and also acts as an antioxidant, protecting the body from the degenerative effects of ageing, alcohol consumption and smoking. Vitamin B1 is required for the production of acetylcholine, a neurotransmitter that helps concentration. Vitamin B1is also useful in helping to protect the body from insect bites. Signs of vitamin B1 deficiency: Persistent tiredness, irritability, constipation, loss of appetite and forgetfulness.