Restricting sodium intake is most likely to help you if your blood pressure goes up when you are under emotional stress. Congestive heart failure, like angina, is especially likely to be relieved by sodium restriction if it is worse under stress. One of the reasons sodium restriction relieves angina is that it stimulates the kidneys to remove excess epinephrine (adrenaline) from circulation.
Research by the team Friberg, Meredith, Jennings, Lambert, Fazio, and Esler at the Baker Medical Research Institute in Australia found that the low-sodium diets begin to influence the kidneys’ handling of the “overflow” of epinephrine when consumption of sodium is about 2400 mg per day, about the level that doctors recommend. Their studies found that the same effect was found when consumption of sodium was as little as 300 mg per day, a more severe restriction in sodium than any doctor or nutritionist ever recommends. In either case, the rate at which the kidneys remove stress hormones from the bloodstream approximately doubled.
The important thing about the effect of sodium restriction on the kidneys’ ability to remove stress hormones from circulation is that while it reduces the amount of the hormones, it does not injure the heart’s ability to respond to them. Even if you are on a low-sodium diet, your heart will still beat faster when you are under intense stress, as in the instance when you need to bolt out the door as your house catches fire. But your heart is not under the constant stimulation of excessive stress hormones if you just cut out the salt.