Can multivitamins increase risk of providing cancer cells with micro and macro nutrients, in large doses?

Unknown! Great question! studies give conflicting results. Some chemotherapy works by inhibiting folate (folic acid) used by cancer cells, so high doses of folate (folic acid) aren't good for cancer patients. High doses of vitamin c inhibit some cancers growing in a dish, but also inhibit chemotherapy effects in patients with cancer. I advise getting nutrients from food and avoiding any high-dose supplementation.