High salt intake can increase catecholamines and blood pressure in certain contexts

Background

The previous article talked about the calcium-excreting effects of high salt intake which can be problematic for people on low-calcium diets. Another potential problem are the context specific effects of salt on catecholamine and blood pressure.

Relevant studies

Study 1: 20 healthy men consumed three diets with varying salt content

• Low salt: 0.6-6.1g salt/day
• Normal salt: 6.1-10.5g salt/day
• High salt: 10.6-15g salt/day (Normal salt diet + 9x0.5g salt capsules)

They looked at norepinephrine, epinephrine and renin. Renin decreased with increasing salt intake. In regard to norepinephrine and epinephrine, they found that the low salt diet caused the highest levels that was significantly lowered on the normal salt diet. However, the high salt diet lead to a signficant increase in norepinephrine and a trend of increased epinephrine levels.

Study 2: 10 healthy controls and 20 patients with hypertension consumed diets with varying salt intake

• Low salt: 0.6g salt/day  
• Medium salt: 5.9g salt/day
• High salt: 11.7g salt/day

They then looked at effects on blood pressure an various stress hormones. They found that a higher salt had no blood pressure increasing effect in healthy individuals but lead to a significantly increased BP in previously hypertensive subjects. From these subjects, they identified 12 salt sensitive and 8 salt resistant people. In all subjects a lowering of aldosterone and renin was seen. In controls and salt-resistant hypertensives, norepinephrine and epinephrine decreased also with increasing salt intake. However in salt sensitive hypertensive patients, norepinephrine increased on the high salt diet.

 

 

Conclusions

The results underline the general anti-stress effects of salt, especially on the renin-aldosterone system. However, they also indicate that at very high salt intakes and/or in salt-sensitive people, increasing salt could have detrimental effects. Besides causing calcium loss (1), salt can worsen hypertension and increased plasma catecholamines in susceptible people. These mechanisms could explain the increased rates of cardiovascular death in people with salt intakes higher than 15 grams/day compared to moderate salt intakes between 8 and 15 grams per day (2).