KaleRaw kale is a good source of vitamin C. However, cooking kale will lower the vitamin C content. CollardsCollards are a good source of vitamin C, vitamin A, calcium, and fiber. Add to salads and sandwiches: Heat kills some vitamin C. Enjoy vegetables raw in salads and sandwiches to get the most vitamin C.Heat kills some vitamin C. Enjoy vegetables raw in salads and sandwiches to get the most vitamin C. Blend into smoothies: Add leafy greens like kale and collard greens to smoothies. They provide vitamin C, as well as vitamin A, vitamin K, folate, calcium, and fiber. They provide vitamin C, as well as vitamin A, vitamin K, folate, calcium, and fiber.