Function: Antioxidant, immunity, collagen formation, bone development, cancer prevention and treatment, gum health, hormone and amino acid synthesis, adrenal gland hormones, wound healing

Sources: Citrus fruits, tomatoes, green peppers, dark-green leafy vegetables, broccoli, cantaloupe, strawberries, brussels sprouts, potatoes, asparagus

Optimal Intake: 500-1,500 mg

Deficiency Signs: Scurvy (rare in North America), signs of which include bleeding gums, poor wound healing, joint tenderness and swelling, recurrent infections, and profuse bruising

Toxicity: The first symptom of too much vitamin C is generally diarrhea, which disappears when the dosage is reduced.