This perhaps isn’t common knowledge, but the RDA was derived from taking the top median population scaled by health, and figuring out what their nutrient intake was. From there our “typical healthy people nutrient values” were born.
We are feeding ourselves by aggregate data, and it seems to more or less work - no one has died by following the RDA conservatively. However, I have seen different strategies towards making a Soylent recipe that would be more or less justified depending on how the RDA is interpreted. Some people, like myself and I think Rob at one point, have thought about treating the RDA as an elemental, or “real” target - inferred by the fact that you can figure out the elemental content of a salt, e.g. potassium chloride, and then count each mole as being 52.455% potassium and 47.55% chloride.
Most recipes I have seen do not treat their ingredients with this much resolution. In a matter of fact, many nutritional labels do not do this either. Nutritional labels equivocate the RDA fulfillment with the weight of the salt instead of the elemental weight. This can be palpably untrue, as you might see from the above statistic.
Based off of its derivation, does the RDA encapsulate bioavailability/stochiometry information and risk? Or do we have to know more about the survey method? I’m thinking what’s missing in our analysis is how they figured out the nutritional content of the diet in the first place. Measuring it from food includes bioavailability in the target, meaning that we assume typical bioavailabilities and salts when creating our recipe; measuring it by some other means, e.g. in the blood or urine, loses the bioavailability information. This becomes more important when we find that bioavailability varies highly within a given nutrient complex.
By wanting to increase precision we also increase the complexity of the approach, which increases risk by human error and risk from the inferential bias. Due to the success of Soylent, what we are doing is adequate, so nothing really has to change if we don’t want it to. Nevertheless by exploring this question we either become better at meeting our nutritional needs, or we find that our bioavailability doesn’t matter or worse can lead to dangerous results if we don’t understand it well but attempt to.