Foods rich in vitamin C may lower the risk for some cancers, including those of the mouth, esophagus, stomach, and breast. Long-term use of supplemental vitamin C may protect against cataracts. Helps make collagen, a connective tissue that knits together wounds and supports blood vessel walls. Helps make the neurotransmitters serotonin and norepinephrine Acts as an antioxidant, neutralizing unstable molecules that can damage cells. Bolsters the immune system.