Nutrient looks good. I completed Sports, Exercise and Health Science (SEHS) doing the IB and seem to have covered most of these listed:
"At the completion of this course, students will have knowledge of basic human nutrition, nutrient requirements, nutrient content of foods and the broad role of nutrition in maintaining optimal health."
Obviously the content will have some difference, but I think I have a decent foundation to build on. It seems the HSC doesn't have a Sports Science equivalent, except PDHPE which is apparently much easier than the IB SEHS course (according to my HSC friends).
On top of that, we had a number of "options" that we could choose to study, and our school had a heavy emphasis on nutrition, digestion and absorption, energy balance and nutritional strategies. I had a young substitute teacher once who was studying Sports Science in University, and he said that the content we were learning in IB SEHS was mostly the same as First Year University Sports Science.
So if that's the case, I may pick up Nutrition in the First Trimester and see how I go, and if it gets too difficult or overwhelming, I'll drop it by closing date.