A simple fruit-cereal intervention shows promising cardiorenal signals in CKD patients

A simple fruit-cereal intervention shows promising cardiorenal signals in CKD patients

A small Japanese study suggests that a low-salt oat-based cereal breakfast may improve blood pressure, lipid risk markers and gut health indicators in people with moderate chronic kidney disease, while highlighting the need for larger controlled trials.

In a recent study published inGroceriesResearchers examined the effects of fruit muesli (FGR) intake on patients with chronic kidney disease.

Chronic kidney disease and cardiovascular risk

CKD is a significant global health problem affecting approximately 843.6 million people worldwide and is associated with increasing mortality rates. It is predicted to be the fifth leading cause of years of life lost worldwide by 2040. Lifestyle-related diseases, including diabetes, obesity and hypertension, are important risk factors for CKD. CVD also worsens life prognosis, similar to CKD, and the two diseases often occur simultaneously.

The incidence of cardiovascular disease increases with the progression of CKD, with cardiovascular disease being the leading cause of death in CKD patients. Dietary interventions, including Mediterranean, whole grain, and low-protein diets, have been reported to reduce the risk of chronic kidney disease. Fruit muesli is a grain food made primarily from oats and contains about 0.24g of salt per 50g serving, making it a low-sodium option compared to typical Western or Japanese dishes.

Nutritional properties of oats and muesli

The main ingredient in granola, oats, contains beta-glucan, a water-soluble fiber that is thought to lower low-density lipoprotein cholesterol (LDL-C) and blood sugar levels. Previously, in a before-and-after observational study, the authors found that FGR intake reduced salt intake and blood pressure (BP) and improved the intestinal environment in hemodialysis patients. They hypothesized that taking FGR could lead to similar improvements in patients with chronic kidney disease.

Study design and participant selection

In the present study, researchers examined the effectiveness and safety of FGR consumption in patients with moderate chronic kidney disease. Patients aged 20 years or older with stable disease status and an estimated glomerular filtration rate of 15–89 ml/min were recruited at a university hospital in Japan. Individuals with active inflammation, reduced nutritional status, malignancies, or steroid therapy were excluded.

Measurements, intervention and data collection

Blood and urine samples were collected during outpatient visits. Clinical chemistry tests and a complete blood count were performed. Blood pressure was measured non-invasively and average home blood pressure was calculated over the previous week. Urine testing was performed using automated analyzers and nutritional status was assessed using the Geriatric Nutritional Risk Index. Patients also completed questionnaires about bowel movements.

Changes in stool form and frequency were assessed using the Bristol Stool Form Scale. The intervention replaced participants' usual breakfast with 50 g of FGR at least five days per week for two months. Tanaka's formula was used to estimate daily salt intake from spot urine samples. After the intervention, laboratory tests, questionnaires, and blood pressure measurements were repeated.

Clinical and biochemical results

25 people took part in the study, 24 of whom were included in the final analysis. Participants had an average age of 66.8 years, were predominantly male (83 percent), and primarily had CKD stages G3a to G3b, with stage G3 accounting for approximately 71 percent. Diabetic nephropathy was present in 87 percent of patients.

Systolic blood pressure decreased significantly from 128.9 mmHg at baseline to 124.3 mmHg after the procedure, while diastolic blood pressure showed a nonsignificant reduction. No adverse events were reported.

No changes in hepatic, renal or hematopoietic function were observed, including serum creatinine and estimated glomerular filtration rate. LDL-C and the ratio of LDL-C to high-density lipoprotein cholesterol (HDL-C) decreased significantly, while HDL-C and triglycerides remained unchanged. Glycated hemoglobin, glucose metabolism and electrolyte levels also remained unchanged. Ferritin levels decreased significantly, but the clinical relevance remains unclear.

Urinary albumin, sodium, chloride, potassium and albumin-creatinine ratio showed no significant changes. Estimated daily salt intake increased from 8.4 g/day to 9.2 g/day, a result that the authors believe may reflect limitations of the estimate based on spot urine. Urinary N-acetyl-beta-D-glucosaminidase, a marker of renal tubular damage, decreased significantly. Improvements in stool frequency and stool quality were also observed.

Interpretation, limitations and implications

Overall, two months of fruit cereal consumption was associated with reductions in urinary markers of tubular damage, lower systolic blood pressure, and improvements in lipid and gut health markers in patients with moderate chronic kidney disease. These results suggest potential cardiovascular and renal benefits but should be considered hypothesis-generating.

Key limitations include the single-arm, open-label design, lack of a control group, small sample size, short intervention duration, and lack of dietary records. The exclusive recruitment of Japanese participants and the involvement of a food manufacturer in the research program may further limit generalizability. Larger, longer-term studies in diverse populations are needed.

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