TL;DR – Are you athletic and play sports, or work a hard labor job? Start with a base of 2500mg, adjusting by 480mg-600mg upwards per hour of heavy sweating. Are you an average person with a desk job that doesn’t sweat? 2300mg per day and below is probably a good starting point.
After having a a bit of a wake-up call from MyFitnessPal, I decided to do a bit of research on sodium intake. As it turns out, newer studies are a bit in conflict with older studies, but generally have common sense information. The CDC generally recommends 2300mg per day as an upper limit, but more modern studies suggest the opposite – lower sodium might be the cause of heart issues for those that under eat sodium, while those who extremely overeat sodium also suffer from heart related conditions. They mention that the results look like a “J” curve, showing that 1500mg and below exhibit extreme issues along with people in the 4000mg+ range. However, this is for the average adult, do what does it mean for us who lift often or are generally athletic?
One study which states that, “People working in moderately hot conditions for 10 hrs on average will lose between 4.8 and 6 g of sodium,” which translates to .48g – .6g per hour, or 480-600mg. So, take into account the conditions of your workout and how much you sweat and adjust accordingly. I workout in Southern California and leave legitimate puddles of sweat on the ground after a single set of heavy deadlifts, so chances are I’m on the upper end of that spectrum. If you work a hard labor job, this increases even more.
So for athletes, it probably varies day to day in the end. I, for one, need to cut back a bit because I was averaging 4000-5000mg per day, even on rest days which is unnecessary. It’s probably a good idea to take 2500 as a baseline and work around there in order to find a balance depending on your own personal sweat bank.