Just “Google” there are plenty of articles.
BTW: Are you sure you were speaking to a nutritionist?
https://healthfoodmadeeasy.com/oats-groats-whats-the-difference/
excerpt below
Whole Oat Groats
Oat Groats (say that fast a few times!) are the starting point. This is the harvested “as-is” product. Whole oat groats are widely used as animal feed, but not so easily found for human consumption. Some health food stores carry them and you can find them on-line.
Whole oat groats can be cooked or steamed, but because they’re a bigger grain than rice or even whole wheat kernels, take much longer to cook. It can take up to an hour, although a pressure cooker will shorten the cooking time. Because they are “as-is”, they have the highest nutritional value of all forms of oats. They are digested very slowly, which reduces the glycemic load and makes them quite filling.
