Hoffman & Stuempfle 2015, sodium intake during an ultramarathon

Study of runners in a 161 km ultramarathon in the heat. Total sodium intake (food plus supplements) was unrelated to outcomes: intake rates were similar between those who became hyponatraemic and those who did not, those who cramped and those who did not, and those with and without nausea. The authors concluded that exercise-associated muscle cramping, dehydration, hyponatraemia and nausea over efforts up to 30 hours in the heat are not explained by total sodium intake. Direct field evidence against sodium supplementation as a fix for these problems.