Vitamins and minerals – zinc and vitamin C were high on the list, and some herbs.
The brown-eyed redheads have slower reflexes and should consider getting more Vitamin X (or whatever it is).
For example, if the system (conspiracy theorists will call it "The System") determines that people like me are happier and healthier with more thiamine in their system, that will come up in my custom vitamin formulation, which also includes whatever nutrients I didn't get enough of that day.
But just as I would trust my doctor or nutritionist to create a custom vitamin formula for me based on all my medical records and health conditions, I would be a million times more comfortable letting the system do it based on every bite I swallow, every bit of my genetic code, and every byte of data about the billion people to which it has access.
Or, we gravitate toward anecdotes like, "I take my vitamin C every day and haven't had a cold in year."