Fruits and vegetables’ latest superpower? Lowering blood pressure

Dietary potassium linked with lower blood pressure


University of Southern California – Health Sciences


A new
study links increased dietary potassium with lower blood pressure.


Eating potassium-rich
foods like sweet potatoes, avocados, spinach, beans, bananas — and even coffee
— could be key to lowering blood pressure, according to Alicia McDonough, PhD,
professor of cell and neurobiology at the Keck School of Medicine of the
University of Southern California (USC).

“Decreasing sodium
intake is a well-established way to lower blood pressure,” McDonough says,
“but evidence suggests that increasing dietary potassium may have an
equally important effect on hypertension.”

Hypertension is a global
health issue that affects more than one billion people worldwide. The World
Health Organization estimates that hypertension is responsible for at least 51
percent of deaths due to stroke and 45 percent of deaths due to heart disease.

McDonough explored the
link between blood pressure and dietary sodium, potassium and the
sodium-potassium ratio in a review article published in the April 2017 issue of
the American Journal of Physiology — Endocrinology and Metabolism. The
review looked at population, interventional and molecular mechanism studies
that investigated the effects of dietary sodium and potassium on hypertension.

McDonough’s review found
several population studies demonstrating that higher dietary potassium
(estimated from urinary excretion or dietary recall) was associated with lower
blood pressure, regardless of sodium intake. Interventional studies with
potassium supplementation also suggested that potassium provides a direct

McDonough reviewed recent
studies in rodent models, from her own lab and others, to illustrate the
mechanisms for potassium benefit. These studies indicated that the body does a
balancing act that uses sodium to maintain close control of potassium levels in
the blood, which is critical to normal heart, nerve and muscle function.

“When dietary
potassium is high, kidneys excrete more salt and water, which increases
potassium excretion,” McDonough says. “Eating a high potassium diet
is like taking a diuretic.”

Increasing dietary
potassium will take a conscious effort, however. McDonough explains that our
early ancestors ate primitive diets that were high in fruits, roots,
vegetables, beans and grains (all higher in potassium) and very low in sodium.
As a result, humans evolved to crave sodium — but not potassium. Modern diets,
however, have changed drastically since then: processed food companies add salt
to satisfy our cravings, and processed foods are usually low in potassium.

“If you eat a
typical Western diet,” McDonough says, “your sodium intake is high
and your potassium intake is low. This significantly increases your chances of
developing high blood pressure.” When dietary potassium is low, the
balancing act uses sodium retention to hold onto the limited potassium, which
is like eating a higher sodium diet, she says.

But how much dietary
potassium should we consume? A 2004 Institute of Medicine report recommends
that adults consume at least 4.7 grams of potassium per day to lower blood
pressure, blunt the effects of dietary sodium and reduce the risks of kidney
stones and bone loss, McDonough says. Eating ¾ cup of black beans, for example,
will help you achieve almost 50 percent of your daily potassium goal.

McDonough recommends
developing public policies to increase intake of dietary potassium from
plant-based sources. She also advocates adding potassium content to nutrition
labels to help raise consumers’ awareness of economical sources of potassium.

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Materials provided by University of Southern California –
Health Sciences
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Journal Reference:

1.    Alicia A. McDonough,
Luciana C. Veiras, Claire A. Guevara, Donna L. Ralph. Cardiovascular
benefits associated with higher dietary K vs. lower dietary Na evidence from
population and mechanistic studies
. American Journal of Physiology –
Endocrinology And Metabolism
, 2017; 312 (4): E348 DOI: 10.1152/ajpendo.00453.2016