Eating potassium-rich foods like sweet potatoes, avocados, spinach, beans, bananas – and even coffee – could be key to lowering blood pressure, according to Dr Alicia McDonough, 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 1bn people worldwide. The World Health Organisation estimates that hypertension is responsible for at least 51% of deaths due to stroke and 45% 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 that 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 benefit.
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% 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.
Abstract
The World Health Organization ranks hypertension the leading global risk factor for disease, specifically, cardiovascular disease. Blood pressure (BP) is higher in Westernized populations consuming Na+-rich processed foods than in isolated societies consuming K+-rich natural foods. Evidence suggests that lowering dietary Na+ is particularly beneficial in hypertensive individuals who consume a high-Na+ diet. Nonetheless, numerous population studies demonstrate a relationship between higher dietary K+, estimated from urinary excretion or dietary recall, and lower BP, regardless of Na+ intake. Interventional studies with K+ supplementation suggest that it provides a direct benefit; K+ may also be a marker for other beneficial components of a “natural” diet. Recent studies in rodent models indicate mechanisms for the K+ benefit: the distal tubule Na+-Cl− cotransporter (NCC) controls Na+ delivery downstream to the collecting duct, where Na+ reabsorbed by epithelial Na+ channels drives K+ secretion and excretion through K+ channels in the same region. High dietary K+ provokes a decrease in NCC activity to drive more K+ secretion (and Na+ excretion, analogous to the actions of a thiazide diuretic) whether Na+ intake is high or low; low dietary K+ provokes an increase in NCC activity and Na+ retention, also independent of dietary Na+. Together, the findings suggest that public health efforts directed toward increasing consumption of K+-rich natural foods would reduce BP and, thus, cardiovascular and kidney disease.
Authors
Alicia A McDonough, Luciana C Veiras, Claire A Guevara, Donna L Ralph
[link url="https://www.sciencedaily.com/releases/2017/04/170405130950.htm"]University of Southern California material[/link]
[link url="http://ajpendo.physiology.org/content/312/4/E348"]American Journal of Physiology: Endocrinology and Metabolism abstract[/link]