I would like to start a discussion on the exact interpretation of RDI’s.
I have encountered two different ways to calculate the amount of a substance. I will illustrate this with an example: potassium.
Most people agree that the RDI of potassium is 3,5 gram.
- One way to get there is to add 3,5 gram of potassium salt (KaCl), and call it a day.
- The other way is to take the percentage of mass of potassium into account when calculating how much potassium you need: Potassium is 39 gram per mol, Chloride is 35,5, so the percentage of potassium in KaCl is 39/(39+35,5) = 52%. This would mean adding slightly less than 7 gram om potassium salt to soylent.
I have observed that some people around here use the second method. Some use the first, but it is less common.
In the case of sulphur, Rob said in one of his posts that after his sulphur deficiency he added 2 gram of MSM per day. This number has spread it’s way througout the community, until one day I saw someone point out that to get 2 gram of sulphur, you need to add 5,7 gram MSM, because MSM is only 32/91 = 35% sulphur. Something has gone clearly wrong here!
That’s not the worst thing: my multivit uses the first method exclusively. For the mineral Iodide, whose RDI is 0,15 mg, it contains 0,15 mg potassium iodide, which is only 127/(127+39) = 77% iodide.
I have searched for the actual way the RDI is determined/measured, and have come up empty handed. I have found sources for either method, and the wikipedia article on RDI heavily references a physical book I don’t have acces to.
Does anyone have any trustworthy source regarding all this?
Is my multivit falling short?