Salt Restriction

Have we been getting it wrong?

Low-salt labels on food packages and restaurant menus act as a constant reminder to lower our salt intake because salt is “bad for our health”.  

If, like me, you’re suffering from high blood pressure, this is particularly poignant, as your GP is likely to advise you to restrict your salt intake to less than 1 teaspoon a day.

There have indeed been some studies that show that salt restriction can lower blood pressure. But, as I know personally, it’s really hard to maintain, and the average person like me, only gets a benefit of 1-2 percent blood pressure reduction, and there aren’t any studies to show that this culinary punishment actually reduces heart disease and strokes in the long term. 

So, has salt been unfairly demonised? And is it really the salt in our diet or the lack of potassium that’s causing the problem?

Photo by Jason Tuinstra

A new study in the highly rated scientific journal JCI, prompted me to revisit this subject. 

The DASH diet (Dietary Approach to Stop Hypertension), which – as the name suggests – is specifically designed for people with high blood pressure, focuses on eating vegetables, fruit and whole grains. If you’re eating this way, you’re naturally getting a good amount of potassium.  

Following the DASH diet has been shown to lower blood pressure, as has potassium supplementation or replacement of salt with potassium mixes. Some recent meta-analyses of 21 trials of salt substitutes have suggested that increasing potassium to your diet has a three fold bigger health impact on blood pressure and heart disease than just reducing salt alone, and this seems to work for both supplements and changes to your vegetable intake.

But why aren’t we going all out on recommending potassium instead of salt restriction? 

One reason is that as usual, policy makers don’t like to change nutrition advice and the other is that  until now, the mechanism by which potassium affects blood pressure has been largely unknown. 

This new study addressed this question. The researchers discovered, using really sophisticated mouse model studies and lab techniques, that potassium works through a receptor called NCC (sodium chloride co-transporter) to change blood pressure levels by altering the amount of salt that’s retained by the body.