Vitamin/ˈvaɪtəmɪn/ Definition 1 of 2Pro Tip 1/3Food Source Vitamins come from what we eat, not just tablets. Most are crucial for bodily functions. Carrots are a good source of vitamin A. Pro Tip 2/3Health Essential Your body needs vitamins to work properly, and they prevent many health issues. Vitamins help maintain good eyesight and strong bones. Pro Tip 3/3Deficiency Diseases Not having enough vitamins can lead to diseases, some preventable with a balanced diet. A lack of vitamin C can cause scurvy.