Diet or Additional Supplement to Increase Potassium Intake: An Adaptive Clinical Trial

High blood pressure is the leading cause of cardiovascular disease worldwide, including in Canada. The prevalence of high blood pressure is steadily rising, with growing and ageing population. Many medicines are available to decrease blood pressures successfully, as well as many non-medical options, such as dietary changes and exercise. There is a marked preference amongst patients, reiterated in a recent Hypertension Canada report, for more research into methods for controlling blood pressure without medicines or to reduce the burden of taking many pills to control high blood pressure. Indeed, effective options do exist, especially with diet, specifically decreasing sodium and increasing potassium in diet. Both these recommendations are also made by organizations worldwide including the World Health Organization as well as Hypertension Canada. Though a lot of focus has been on sodium intake in the public health outreach, even the potassium intake in diet remains woefully low amongst adult Canadians. Excellent data exist in the published research reporting that increasing potassium intake, either as diet or even as supplements, reduces blood pressure and reduces risk of cardiovascular outcomes such as stroke. The advice most often provided is to 'eat more fruits and vegetables' which does not get translated into concrete change.

The Investigators propose to do a clinical trial in two stages (as an adaptive trial design). In the first stage, participants with high blood pressure and proven low potassium intake (measured on the basis of collecting urine for 24 hours) will get individually tailored dietary advice, reinforced by weekly supportive phone/email support. If at 4 weeks, there has not been a desired increase in potassium intake, the patients will be prescribed an additional potassium supplement. Testing at 4 weeks will be conducted again to confirm the efficacy of the potassium supplement. Final measurements will be planned at 52 weeks to observe and measure the persistence of the effect of diet or additional supplement. Concurrent measurements of sodium intake, blood pressure, participant satisfaction, safety measures will also be done.

The results of the study would help determine the most effective method of increasing potassium intake, thus reducing blood pressure, need for blood pressure lowering medicines, at the same time potentially increasing participant satisfaction. The current guidelines recommend changes in diet (not supplement) to increase potassium intake, hence the two stage design will only add supplements if the most rigorous dietary advice does not work. The Investigators have received letters of support from the World Hypertension League and Hypertension Canada in support of the research design and for dissemination and implementation of the findings.