Review links potassium to reduced blood pressure

by Jeff Gelski
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GENEVA – Increasing intake of potassium led to a reduction in blood pressure in people with hypertension and had no adverse effect on blood lipid concentrations, catecholamine concentrations or renal function in adults, according to results of a systematic review and meta-analyses published on-line April 5 in the British Medical Journal. Catecholamines play a role in the body’s physiological response to stress.

Researchers from the World Health Organization, the Norwich Medical School in the United Kingdom and Imperial College London examined 22 randomized controlled trials that involved 1,606 people and 11 cohort studies that included 127,038 people.

Higher intake of potassium, which is found in such foods as bananas, baked beans and granola, was associated with a 24% lower risk of stroke. Evidence was found of reduced systolic blood pressure and reduced diastolic blood pressure. The results suggest increased potassium intake potentially is beneficial to most people without impaired renal handling of potassium for the prevention and control of elevated blood pressure and stroke.

The Institute of Medicine in 2004 set an adequate intake for potassium at 120 mmol (4.7 grams) per day for all adults. The I.O.M. at that time did not set an upper limit because it found no evidence of chronic excess intakes of potassium in apparently healthy people. The Dietary Guidelines for Americans 2010 also recommends adults consume at least 4.7 grams of potassium per day.

In many countries, however, average potassium intake is below 70-80 mmol per day, according to the review in the British Medical Journal. The researchers found no evidence of countries reporting an average population consumption of potassium of 120 mmol per day.

The researchers found a higher potassium intake of 90-120 mmol per day reduced blood pressure and was associated with a lower risk of incident stroke. Intake above 120 mmol per day did not seem to have any additional benefit.

Potassium chloride often is used in place of salt (sodium chloride) to reduce sodium in processed food products. The review in the British Medical Journal addressed sodium and potassium. It said consuming 90 mmol or more of potassium per day and reducing sodium intake to less than 2,000 mg per day would lead to a sodium:potassium ratio of about 1:1, a ratio considered beneficial for health.

According to the review, potassium had the most benefit in reducing blood pressure in individuals who consumed more than 4,000 mg of sodium per day. The review also found a statistically significant decrease in blood pressure with increased potassium when sodium intake was between 2,000 mg to 4,000 mg per day.

“Therefore, increased potassium can continue to be beneficial in terms of blood pressure even as individuals and populations decrease their sodium intake,” the researchers said.

According to the National Kidney Foundation, New York, too high of a potassium level in blood may cause an irregular heartbeat or heart attack. Healthy kidneys keep the right amount of potassium in the body, but people with kidneys that are not healthy may need to limit certain foods that may increase the level of potassium in the blood to a dangerous level, according to the National Kidney Foundation.

According to the review in the British Medical Journal, intervention trials have included potassium consumption as high as 400 mmol per day from food for several weeks and 115 mmol per day for up to a year without any reported adverse effects. Some isolated cases of acute toxicity from “extremely high” potassium intake in supplement form have been reported, according to the review.

“Because of the safety of consumption of increased potassium from food, our objectives did not include testing a potential upper limit of intake,” the researchers said.

The review did not include studies in babies that were being breastfed or studies in patients with acute disease conditions such as HIV positive status, heart failure or renal failure.

“Therefore, the results should not be interpreted to include those age groups or acutely ill patients, especially those with impaired renal function and defective renal potassium handling,” the researchers said.

Funding for the review came from various sources, including W.H.O. funds, the Kidney Evaluation Association Japan, and the governments of Japan and the Republic of Korea.
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