Regarding vitamin D, I would add that the only way to make sure your vitamin D level is sufficient is to get tested. Relying on the DRI alone will leave some people insufficient. I expect that many Soylent users will be insufficient and maybe deficient in vitamin D, not because of any failing on Soylent's part, but because this is already true for a random selection of the non-Soylent-using population. Dark-skinned individuals, obese individuals, and people with very little sun exposure (or living at a high latitude) are more likely to be deficient.

Practically speaking, this means: during your next annual physical, make sure your doctor tests your vitamin D along with your other bloodwork. The correct test is called 25(OH)D. Your insurance should cover it. (I am making an assumption about how privileged most HNers are.) Aim for a blood level of 30-40 ng/mL. <20 ng/mL is deficient, >=30 is sufficient, while >40 is probably pushing it, i.e. observational studies suggest that mortality starts to increase slightly around that point. A level greater than 50 ng/mL is almost certainly excessive, though still not close to toxicity. Some people argue for supplementing enough vitamin D to achieve higher blood levels (>40 ng/mL), but IMO the evidence doesn't support doing this and it might be harmful.