I think Lisa's advice is great! Health will likely offer a lot of classes that provide beneficial education for someone pursuing nutrition. Another thing to consider would be a complementary field in an area that interests you. I'm an RD currently working in community nutrition and there's a lot of benefit to having an agricultural/horticulture background, especially if you're interested in working in urban food, farmer's markets, or with the extension service in your state. I think food science, kinesiology, and even hospitality if you're interested in the food service side of things, would be great choices as well.
If you are wanting to become an RD you'll need to obtain your degree from an ACEND-accredited program and complete a dietetic internship. Something else to consider is that starting in 2024 anyone wanting to take the exam to become an RD will be required to have their Masters Degree.