Nutrition is an evolving science. And like all sciences, discoveries bring about changes in recommendations. So it’s important to keep reading and researching, even when you finish the course.
You will find that not all experts agree about nutritional recommendations. Official guidelines are likely to vary from cutting edge discoveries. This is normal.
Enjoy exploring this fascinating subject. There are many resources on the internet and in local libraries. Always remember when you are researching something to check the quality of your resources. For example, do they have any scientific references or is this just a non-expert’s blog? Any commercial resource is likely to contain some bias.