Low Sodium, High Potassium Diet And Kidneys

A high potassium sodium ratio in the diet has been shown to have many advantages. This has been especially shown for lowering blood pressure. However there are concerns about too high of a ratio, especially a concern about having too little salt in the diet. There have been medical articles written suggesting caution about going too low with sodium intake. These studies have been based mostly on patients who are ill and have cardiac problems. They probably do not apply to healthy people. There is no question that there are groups of people who can have an extremely low sodium intake and avoid hypertension.

The Yanomami

Yanomami Woman & Child
Yanomami Woman and Child

The Yanomami Indians of the Amazon have a diet that has almost no salt, is high in potassium, and is high in alkaline foods. They have virtually no hypertension. Their urinary potassium sodium ratio is over 150 to 1. And their urine is very low in chloride, which is a sign of alkaline urine.

However there are many differences between the Yanomami and modern mankind. It would not be possible to live a modern life and to live as the Yanomami. What is responsible for their ability to live on such a low sodium diet?

Potassium Sodium Ratio Control In The Kidney

One of the main considerations in balancing potassium and sodium in the body has been how the kidney controls sodium and potassium excretion. The major mechanism that has been studied is the sodium-potassium-ATPase pump in kidney cells. This cellular pump allows potassium and sodium to be excreted by exchanging potassium and sodium.

It does this through the pump's interaction with two ion channels in kidney cells, the ENaC channel and ROMK channel. This mechanism can only allow a ratio of 0.67 potassium to be excreted for every sodium reabsorbed. So the question is how so much potassium can be eliminated by the kidney without an exchange for sodium. How can the kidney excrete 150 potassiums for every sodium it excretes?

A Recent Study

A recent study (1) helps to explain this. BK channels are potassium channels in the cell. In the kidney these channels secrete potassium into the urine. The majority of them are located in the intercalated cells (IC) of the distal nephron. It is also known that the BK channels secrete potassium independent of sodium, and independent of aldosterone. This is in contrast to the aldosterone stimulated ROMK channels which are involved in the ATPase exchange of sodium for potassium in the distal nephron.

The intercalated cells (IC) are kidney cells that have very few sodium-potassium-ATPase pumps. The IC are the main location where potassium is excreted into the urine. This study used knockout mice (with no BK channels in IC) and wild type mice (with normal channels) to determine the role of the BK channels. They put these mice on different diets. Then they studied the blood and urine, as well as doing microscopic studies on the intercalated cells (IC), to determine the effect on the BK channels.

The Diets

The control diet they used was regular mouse chow with a potassium to sodium ratio of 3.2. This is higher than the ratio of the typical Western diet.

The experimental diets had even higher potassium sodium ratios. The potassium sodium ratio for the normal sodium, high potassium diet was 26.5. For the low sodium, high potassium diet the ratio was 848. This ratio is much higher than any modern diet.

The researchers also varied the experimental diet to achieve a urine that would be acid or alkaline. To achieve a more alkaline urine, the researchers substituted bicarbonate and citrate (a bicarbonate precursor commonly found in food) for chloride in the diet.

What Happened In The Kidney?

They found an increase in the number of BK channels in the intercalated cells when the diet had a high potassium and high alkaline content. And they found that there was no buildup of potassium in the blood on the high potassium, high alkaline diet, even when the diet was the low sodium diet.

When the diet was high in potassium and also high in chloride the urine was acid. In this condition, there was an increase in BK channels, but the channels did not function. When the urine was acid, there was a high buildup of potassium in the blood.

The researchers also found that with the high potassium, high alkaline diet that there was more loss of potassium in the sweat and in the colon. BK channels are not just in kidney cells, but also are present in sweat cells and colon cells.

How Does This Study Apply To Me?

This study explains how the Yanomami can avoid a high buildup of potassium in their blood while on a diet with a high potassium sodium ratio. The food that they eat is high in potassium, and also is high in alkaline precursors so that they have a very alkaline urine. This combination is very conducive to a low blood pressure.

So to get a blood pressure like the Yanomami, you do not need to move to the Amazon jungle and live primitively. Just change your diet to a low sodium, high potassium, alkaline diet.
1. Bicarbonate promotes BK-a/ß4-mediated K excretion in the renal distal nephron. Cornelius RJ, Wen D, Hatcher LI, Sansom SC. Am J Physiol Renal Physiol. 2012 Dec 1;303(11):F1563-71. doi: 10.1152/ajprenal.00490.2012. Epub 2012 Sep 19.