My three-year-old son doesn't like food. He doesn't seem to have any particular food preferences or favorites. He only eats small amounts of various foods and generally dislikes eating. How can I ensure he gets a healthy diet without undernutrition? Currently, he usually drinks a glass of milk daily, sometimes two, but he refuses to eat rice or other foods. What essential foods do you recommend for a three-year-old to ensure his health and nutrition?