Research Award Recipients

SAFE-VEG: A Randomized, Repeated N-of-1 Crossover Trial to Assess the Safety of Liberalizing Fruit and Vegetable Intake in Adults on Hemodialysis

Co-applicant(s): Lara Maleyeff, Remi Goupil, Valérie Jomphe

Lay Abstract

Background: People receiving hemodialysis can have high blood potassium (hyperkalemia). This can be dangerous, causing heart rhythm problems or even sudden death. Because of this risk, many are told to avoid potassium-rich foods, especially fruits and vegetables. At our center, people on dialysis eat under two servings per day, well below the recommended seven. Fruits and vegetables are essential for health. In the general population, diets rich in them reduce heart disease and help people live longer. People on dialysis already face high heart risk, yet are advised to avoid foods that might protect it. Restrictions are based on caution and lab tests, not real-world trials. No controlled study has tested whether more fruits and vegetables raise blood potassium to unsafe levels in this population. This gap matters. If modest amounts are safe, people could enjoy a more balanced diet that supports heart health.

Purpose: SAFE-VEG will test whether giving people on dialysis 15–20 mmol/day of potassium from fruits and vegetables (about six extra servings) raises blood potassium compared with their usual diet. A small rise is expected and usually safe. We aim to rule out larger increases (=0.4 mmol/L) that could raise heart risk. We will detect smaller changes but focus on preventing bigger, harmful jumps.

Method: SAFE-VEG is a repeated “N-of-1” crossover trial: each person tries both conditions (usual diet and extra fruits and vegetables) in short periods, serving as their own control. This gives precise results with fewer people and limits time on a potentially risky diet. Who can join? Adults on thrice-weekly in-center dialysis who do not already eat many fruits and vegetables and have no recent high potassium. What happens? Participants are randomly assigned to four weekly phases:

• Fruit and vegetable phase: 4 days of daily bags with six servings (15–20 mmol potassium).

• Control phase: 4 days with no study-provided foods, usual diet only.

Each phase is followed by a 3-day washout (no study food) so potassium levels reset.

Safety checks: Blood potassium is measured at every dialysis session (12 times per person). If levels are too high (=6.0 mmol/L once, or =5.6 mmol/L twice in the same week), the person stops the study. Dialysate potassium and binders cannot be changed during participation.

Other measures: We also track blood pressure, weight gain between sessions, and side effects. An independent biostatistician reviews de-identified results at checkpoints (after 16, 20, 24, 28, and 32 participants). The trial can stop early for clear harm or convincing safety.

Anticipated Outcomes: We expect six extra servings per day will not raise potassium to dangerous levels. This test will give reliable data on whether strict potassium restrictions are needed. If the rise is small, people may enjoy more variety, fiber, and nutrients without fear. If not, it confirms the need for restriction.

Patient Engagement: Patient-inclusive priority setting has repeatedly flagged nutrition and dietary restrictions as key issues in dialysis. SAFE-VEG addresses this by testing whether a modest increase in fruits and vegetables can be done safely. Our patient-partner reviewed the plan to ensure the bags are acceptable and not too burdensome. She will advise throughout and help co-write the plain-language results.

Relevance to Patients/Community: SAFE-VEG tackles a question that affects the daily lives of almost everyone on dialysis. For decades, people have been told to restrict fruits and vegetables, often at the cost of dietary enjoyment and long-term health. By testing this directly, SAFE-VEG could shift practice and ease the burden of dietary restrictions.

• If safe: People on dialysis could meet Canada’s Food Guide recommendations (around 7 or more servings per day) instead of the very low intakes reported today. This would improve diet quality, variety, and quality of life.

• If harmful: Care teams will know the caution is justified and can focus on other safe ways to improve diet. Either way, the study empowers people and provides evidence to guide advice.

Conclusion: SAFE-VEG is the first controlled trial to test whether people on dialysis can safely eat more fruits and vegetables. With a careful, patient-centered design and strict safety checks, the study will provide urgently needed answers.