It is well-known that foods high in potassium help to keep blood pressure in normal range.
High blood pressure (or hypertension) is a silent killer. Worldwide, it affects an estimated 1 billion people. Approximately 75 million of these live in the United States - totaling around 1 in 3 people.
Studies over recent years have clearly demonstrated that eating a diet high in salt (and therefore sodium), such as the standard Western diet, can lead to hypertension.
This most recent review, published in American Journal of Physiology - Endocrinology and Metabolism, shows that high sodium intake is not the only important dietary factor; potassium also has a vital role to play.
The importance of potassium
Potassium, an electrolyte, is necessary for nerves to transport messages and for muscles to contract. It keeps the heart beating and helps to ship nutrients into cells and remove cellular waste. Potassium also assists in the maintenance of healthy bones and reduces the risk of kidney stones.
The author of the current review, Alicia McDonough, Ph.D., professor of cell and neurobiology at the Keck School of Medicine at the University of Southern California, sums up her findings: "Decreasing sodium intake is a well-established way to lower blood pressure, but evidence suggests that increasing dietary potassium may have an equally important effect on hypertension."
- tuna and salmon
- fat-free milk
- macadamia nuts and almonds
Her review explores the links between potassium, sodium, and the sodium-potassium ratio, delving into a range of studies in the field and drawing conclusions about potassium's benefits.
The investigation included interventional and population studies, as well as research into the molecular mechanisms involved.
McDonough found a number of population studies demonstrating that higher dietary potassium, as rated by urinary excretion or dietary recall, was generally associated with lower blood pressure, regardless of the level of sodium intake.
Other studies looking specifically at potassium supplements gave similar findings.
Beyond population studies, McDonough looked at sodium-potassium research in rodent models to help explain the potential mechanisms behind this interaction. It seems that the body uses sodium to keep a check on potassium blood levels.
"When dietary potassium is high, kidneys excrete more salt and water, which increases potassium excretion. Eating a high potassium diet is like taking a diuretic."
Alicia McDonough, Ph.D.
Her conclusion, in a nutshell, is that potassium is vital for keeping blood pressure within a normal range. Sodium is still a key player, but simply reducing salt intake alone may not be enough to control hypertension.
McDonough explains that raising potassium levels in the diet will require a conscious effort. As humans evolved, they ate a great deal of fruits, vegetables, roots, beans, and grains, all of which provide an ample supply of potassium. However, sodium was less easy to come by and, therefore, we evolved to crave salt. Our natural desire for salt has since been satisfied by the food industry, who mix more than we require into processed foods.
At the same time, potassium levels in our diets have steadily dropped as we move away from fresh fruit and vegetables.
As McDonough says: "If you eat a typical Western diet, your sodium intake is high, and your potassium intake is low. This significantly increases your chances of developing high blood pressure."
How much potassium should we consume?
The authors of the paper explain that, because our bodies evolved to deal with a low sodium, high potassium diet, "consuming a surfeit of dietary potassium" is a "good strategy."
According to a 2004 Institute of Medicine report, adults are advised to consume at least 4.7 grams of potassium each day in order to lower blood pressure. This level of consumption, they say, will diminish the effects of salt and reduce kidney stones risk, as well as bone loss.
McDonough recommends that potassium content be added to food labels to help the public to make better-informed decisions about their potassium consumption.
Because the review takes into account a range of studies, the findings are compelling. Further research will, no doubt, draw a clearer picture of how sodium and potassium interact to keep blood pressure at healthy levels. However, the findings of the paper make familiar conclusions, as the authors write: "Medical communities, [former] First Lady Michelle Obama, and common sense tell us to eat more fruits and vegetables and to get regular exercise to optimize our health."