What is salt sensitive hypertension? What is the effect of dietary salt restriction on BP?
Salt resistance/sensitivity refers specifically to the effect of dietary sodium chloride (salt) intake on BP. Increased dietary salt intake promotes an early and uniform expansion of extracellular fluid volume and increased cardiac output. To compensate for these hemodynamic changes and to maintain constant BP with high sodium intake, peripheral vascular resistance falls and is associated with an increase in production of nitric oxide. Among those who are salt sensitive, the decline in peripheral vascular resistance and the increase in nitric oxide are impaired or absent in salt sensitivity, promoting an increase in BP in these individuals.
Salt-sensitive hypertension has variable definitions, but is conventionally defined as an increase in systolic BP of ≥10 mm Hg in response to 6 g of dietary salt loading. Salt-sensitive hypertension is most prevalent in African Americans, the obese, the elderly, those with high pulse pressure (i.e., ≥70), and those with CKD. Among those with a salt-rich diet, changing to a sodium-restricted diet has consistently lowered BP. This salt-restricted diet is particularly useful in people with resistant hypertension. It also enhances of the antihypertensive effects of diuretics, ACE inhibitors, and ARBs. Current guidelines recommend diets containing no more than 100 mEq of sodium (2.3 g) per day, a target below the 3.4 g consumed by most Americans.
