Ever since the 1930s, when a provocative study found a high-salt diet worsened asthma symptoms in children, researchers have speculated that our national appetite for salt is one reason asthma leaves more and more of us breathless. Thanks to recent work by Tim Mickleborough, Ph.D., a physiologist at Indiana University’s Department of Kinesiology, we’re closer to knowing how.
Mickleborough and his colleagues started with 24 young men and women with exercise-induced asthma. Twelve were put on a low-salt diet that allowed them no more than 3,750 mg of salt per day (that’s 1,600 mg sodium, salt being 40 percent sodium). The other 12 were put on a high-salt diet: they ate the same foods as the first group plus a daily capsule containing 10,000 mg of extra salt. The low-salt group were given placebo capsules. (Government guidelines recommend no more than 2,300 mg of sodium per day—about 1 teaspoon salt.)