Here is a little summary of what he's saying: The only things we really know about nutrition are related to diets that cause obvious problems quickly. Ie, we know vitamin-c is needed because it causes scurvy. What we know now and are learning is that there are possibly thousands of other interactions and nutrients needed for diet that are more subtle. We do not yet have a complete model for this, and probably won't for a few more decades. Therefore, anything made now will be insufficient because we know our current model is flawed.