I am concerned about the high level of iron in official soylent recipe (last I checked it was ~18mg). That’s probably sufficient for the average woman, but I’m a man, and that’s too much iron for me. WebMD recommends 8mg for the typical man.
It’s possible I may have hemochromatosis, as one of my parents has it, so I tend to be especially concerned about avoiding stuff fortified with iron.
Perhaps the iron (and other vitamins/minerals as well?) could be added in separately as a powder or solution? This would allow both men and women to get the proper amount, and would also satisfy the needs of people with a special condition like anemia or hemochromatosis.