Some Nutra products apply to pretty much everyone, while some will only appeal to a niche audience. The best way to learn about the market is to research each product type and create a list of its appeal across demographics, primarily age and gender.
If you are not sure how your audience will evolve, use a mix of broad and narrow affiliate offers, to understand which performs best. And as you get a better idea of your audience, focus on products that will suit them, and your pocket of course.