Yes, a BCom graduate can go for a nutritionist course. A BCom (Bachelor of Commerce) doesn't directly qualify someone as a nutritionist, but it doesn't preclude them from pursuing further education in nutrition. Many nutrition courses are open to graduates from various backgrounds, as long as they meet the entry requirements. These requirements will vary depending on the specific institution and course. Some programs might prefer applicants with a science background, but others are open to those with different undergraduate degrees.
A BCom graduate might need to take some prerequisite courses to fulfill any science requirements before being accepted into a nutrition program. It's essential to check the specific admission requirements of the nutrition courses they are interested in.