Children with cancer often have deficiencies in important vitamins and minerals. A study found that almost all children with cancer had at least one micronutrient deficiency, with many having multiple deficiencies. Common deficiencies included vitamin C, vitamin D, zinc, and vitamin A. Surprisingly, the children's dietary intake did not seem to affect their deficiency status. More research is needed to understand why these deficiencies occur and how they can be treated in children with cancer.