Should salt intake be cut down to prevent primary hypertension?

The role of salt in hypertension

Epidemiological data indicate a weak but significant positive correlation between the level of salt intake and blood pressure. It is unclear how this relationship is mediated but some studies indicate that heredity for hypertension is associated with an increased sensitivity to salt. Decrease of the salt intake decreases blood pressure in established hypertension and should be used as a therapeutic adjuvant in mild uncomplicated hypertension much more often than is now the case. Increased salt intake in young subjects with or without heredity for hypertension does not seem to increase the blood pressure during a 4-12 week load. Increased salt intake in middle-aged men, on the other hand, seem to induce a blood pressure increase irrespective of the presence or absence of a positive family history. The sensitivity to a high salt intake might thus be associated with aging. Increase of the salt intake from the normal level seems to induce an increase in sympathetic nervous activity. The interplay between the level of salt intake and sympathetic nervous activity should be studied in more detail.

Dietary sodium reduction for hypertension prevention and treatment

Nutritional-nonpharmacological approaches for the treatment and prevention of hypertension are of great interest. Sodium reduction is one of the primary methods recommended for these purposes. The general public is interested in the reduction of dietary sodium intake and has responded with a decrease in table salt use, the purchase of lowered sodium food products, and the use of food labels to help guide food purchases. Countervailing trends in the use of convenience foods and dining out increase the difficulty for individuals to lower sodium intake. Clinical trials that have used sodium reduction alone or in combination with other lifestyle therapies have demonstrated the feasibility of reducing dietary sodium intake from 30% to 50% for up to 4 years, in a variety of populations. Trials that used lifestyle and weight loss interventions have also achieved significant reductions in body weight and alcohol consumption and increases in physical activity. A variety of studies indicate that long-term sodium reduction is feasible and that it is acceptable to patients. No negative consequences of these interventions have been observed, and in some cases improvement in the intake of other nutrients has occurred. Nonpharmacological interventions have resulted in hypertension control in significant proportions of the trial populations. These studies demonstrate that the foregoing types of interventions can significantly contribute to hypertension treatment and prevention.

Salt and blood pressure in Belgium

Blood pressure, pulse rate, body weight, and height were measured on two occasions in the inhabitants of a random 10% sample of households in a Belgian village. Twenty-four-hour urinary excretion of creatinine, sodium, and potassium was also determined. In subjects over the age of 19 there was a significant correlation for both systolic and diastolic pressure with age and body weight and, in women, also with pulse rate. After adjusting for these three variables, the systolic blood pressure in men was negatively correlated with the daily urinary potassium excretion, and the diastolic blood pressure in women negatively with the urinary sodium: creatinine ratio. The present data, obtained within one society, do not support a role for dietary sodium in the distribution of blood pressure within this population. Comparison of the present results with data from other countries does not refute the salt-genetic hypothesis but suggests also that a high potassium intake may lower blood pressure.