The high potassium foods diet has been shown to reduce strokes, osteoporosis and kidney stones. Multiple population based studies have shown these effects. But for the favorable effects to be attributed to the potassium to sodium ratio, there has to be an extensive body of work in the basic sciences showing why this would be the factor leading to improved health, and not something else going on at the same time. In other words, there has to be a framework into which all the basic science findings, and all the clinical studies, and all the population based studies, fit without contradicting each other.
In some recent posts we have discussed large population studies showing how Finland and Japan saw dramatic reduction in strokes from an increase in the potassium to sodium ratio in their diet. But over several decades there could be other changes in their societies that were the true cause of these improvements. Basic science studies confirm that it is the potassium to sodium ratio.
To Find Tables With The Potassium Content In Food
If you want to skip the science and just find a list of high potassium foods or tables with the potassium content of various foods, you can click the “Links to Food Potassium Tables” tab above to find posts with tables. The posts are listed by major food group, such as fruit juices, vegetables, or fish. Click on the link to the table that would have the food you are interested in.
Basic Science At The Cell Level
To justify the claim that it was the potassium to sodium ratio in the diet requires a large underpinning of basic science to support the claim. We previously discussed the basic cellular actions of potassium and sodium on the cell membrane in a prior post.
By affecting the electrical charge of the cell membrane, potassium and sodium influence how the cell membrane works. Nerves and muscles function by changes in the cell membrane charge. Changes in cell membrane charge also influence hormone secretion. A change in the ratio of potassium to sodium causes a change in the ,and thus affects how the cell membrane works. This basic cell biology is well enough established that it is in medical school textbooks on physiology.
Moving up from the cell is how potassium and sodium affect tissues and organs. In addition to the direct effect that we discuss later in this article, these two ions affect tissues and organs by influencing multiple hormones, both endocrine and paracrine. One of the most elegant models is how these ions affect blood pressure.
The Two Basic Kinds Of High Blood Pressure
It is important to understand that there are two kinds of blood pressure increases. One is a quick temporary rise, and the other is a long term rise. The very quick elevation of blood pressure occurs with sudden stimuli, such as a “flight or fright” response. This is brought on by a different mechanism than a long term elevation of blood pressure. The quick one goes away in several minutes if the stimulus goes away, and is consistent with good health. The long term elevation remains until there are major changes in the body.
We won't discuss the quick elevation, since it is normal and not something that leads to disease. The long term elevation, however, is symptomatic of a true problem. This is the type elevation labeled hypertension, and is a serious health problem. It arises from the actions of the endocrine hormones renin, angiotensin and aldosterone.
Two Elegant Models
A great deal of work was done on understanding how these hormones work. Much of this work was done in the classic molecular approach giving us many pieces of the puzzle of hypertension. However, three researchers used a different approach, called a systems approach. With this approach they were able to put the pieces of the puzzle together into a beautiful, well-fitting model.
The first researcher was Dr. Arthur Guyton. By using an engineering approach to model and simulate all the factors influencing blood pressure, Dr. Guyton (1) was able to show that constriction of the resistance blood vessels only had a short term rise in blood pressure. This was the “flight or fright” type of elevation. To have a long term rise in blood pressure, there had to be a change in the way the kidneys responded to blood pressure.
The kidneys respond to blood pressure by regulating blood volume. They do this by controlling how much sodium they pull back out of the urine. A certain amount of water must accompany the sodium.
If the blood volume flowing through the kidneys is too great the kidney cells will excrete sodium and the water that must accompany it. If the blood volume is too little, kidney cells pull back sodium and water into the blood. Sodium then passes from the blood into the fluid that sits around all our cells. And from there it passes into the cell. This sodium and water causes problems in all three locations.
The Model That Puts It All Together
Dr. Guyton's associates, Dr. Young and Dr. Hall, used this same systems approach with computer simulations to study the interactions of various hormones and the kidneys (2). This work showed how potassium and sodium interact with renin, angiotensin and aldosterone, the three main hormones affecting hypertension. From experiments they performed, these doctors and their associates derived a mathematical model. After coming up with this theoretical model, they tested the model with further experiments.
The model showed that aldosterone secretion is determined by two main influences. Angiotensin (which also causes the blood vessels to constrict) and potassium concentration in the blood stream are the two main influences. Aldosterone in turn determines how potassium is excreted by the kidney, and how it is distributed throughout the body. The potassium concentration also affects the kidney's ability to filter the blood. A higher rate of filtration causes an increase in sodium excretion, and a lowering of blood pressure.
Dr. Young did not just look at potassium concentration in the blood, but also looked at potassium intake, that is, the potassium in the diet. The model predicted multiple changes in renin, angiotensin and aldosterone, and the actions of these hormones with different potassium levels.
The Golden Ratio – Potassium To Sodium
Even more exciting, the model could predict that a potassium to sodium ratio above 5 would almost never lead to an imbalance of sodium and potassium in the body. And when the ratio was below 0.6 it almost always leads to an imbalance. This imbalance inevitably resulted in hypertension.
Later studies (3) by Dr. Young showed many of the secondary effects from this imbalance, all of which are present in hypertension. They include such changes as increased free radical formation in blood vessel cells, proliferation of vascular smooth muscle, and an increased tendency to form blockages in the arteries. These kinds of changes are found in vascular disease, cardiac disease, and strokes.
As science has continued to discover more and more about hypertension, the findings continue to confirm these two elegant models.
1. Circulation: overall regulation. Guyton AC, Coleman TG, Granger HJ. Annu Rev Physiol. 1972;34:13-46.
2. Analysis of long-term potassium regulation. Young DB. Endocr Rev. 1985 Winter;6(1):24-44.
3. Potassium's cardiovascular protective mechanisms. Young DB, Lin H, McCabe RD. Am J Physiol. 1995 Apr;268(4 Pt 2):R825-37.