(1) The six nutrients in human body include sugar, oil, protein, vitamins, water and inorganic salts. Rice mainly contains sugar, fried chicken legs mainly contain oil and protein, scrambled eggs mainly contain protein, oil and inorganic salts, and tofu soup mainly contains protein, water and inorganic salts, which is deficient in vitamins. Vitamins mainly exist in vegetables and fruits.

(2) Under the catalysis of enzymes, glucose is slowly oxidized into carbon dioxide and water, and at the same time, energy is released for body activities to maintain a constant body temperature.

(3) Calcium iodate [Ca(IO3)2] contains three elements: calcium, oxygen and iodine, among which iodine is a trace element.

Therefore, the answer is: (1) vitamins; Tomatoes (only write the names of vegetables or fruits); (2) water and carbon dioxide; (3) iodine.