A small Japanese study suggests that a low-salt, oat-based granola breakfast could improve blood pressure, lipid risk markers and indicators of gut health in people with moderate chronic kidney disease, while highlighting the need for larger-scale controlled trials.
Study: Consumption of fruit granola may contribute to a reduction in the risk of cardiovascular disease in patients with stage G2-4 chronic kidney disease. Image credit: Katarzyna Hurova/Shutterstock
In a recent study published in foodsresearchers studied the effects of consuming fruit granola (FGR) on patients with MRC.
Chronic kidney disease and cardiovascular risk
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MRC It is a significant global health problem, affecting approximately 843.6 million people worldwide, and associated with increasing mortality rates. By 2040, it is expected to become the fifth leading cause of years of life lost worldwide. Lifestyle conditions, including diabetes, obesity, and hypertension, are major risk factors for CKD. MCV also worsens life prognosis, similar to CKD, and the two conditions often coexist.
The incidence of cardiovascular disease increases with the progression of CKD, with cardiovascular disease being the leading cause of mortality in patients with CKD. Dietary interventions, including Mediterranean, whole-grain, low-protein diets, have been reported to reduce the risk of chronic kidney disease. Fruit granola is a grain food primarily made from oats and contains approximately 0.24 g of salt per 50 g serving, making it a low sodium option compared to typical Western or Japanese meals.
Nutritional properties of oats and granola
Granola’s main ingredient, oats, contains beta-glucan, a water-soluble dietary fiber that reduces low-density lipoprotein cholesterol (LDL-C) and blood sugar. Previously, the authors noted that FGR consumption reduced salt intake and blood pressure (PA) and improved the intestinal environment in hemodialysis patients in a before-after observational study. They hypothesized that FGR consumption could lead to similar improvements in CKD patients.
Study design and participant selection
In the present study, researchers investigated the effectiveness and safety of FGR consumption in patients with moderate CKD. Patients aged 20 years or older with a stable disease state and an estimated glomerular filtration rate of 15 to 89 ml/min were recruited from a university hospital in Japan. Individuals with active inflammation, reduced nutritional status, malignancy, or corticosteroid therapy were excluded.
Measurements, intervention and data collection
Blood and urine samples were collected during outpatient visits. Clinical chemistry tests and complete blood count were performed. Blood pressure was measured non-invasively and the average home blood pressure over the previous week was calculated. Urinalysis was performed using automated analyzers and nutritional status was assessed using the Geriatric Nutritional Risk Index. Patients also completed questionnaires regarding bowel movements.
Changes in stool shape and frequency were assessed using the Bristol Stool Shape Scale. The intervention replaced participants’ usual breakfast with 50 g of FGR at least five days a week for two months. The Tanaka formula was used to estimate daily salt intake from spot urine samples. Laboratory tests, questionnaires and blood pressure measurements were repeated after the intervention.
Clinical and biochemical results
The study involved 25 people, 24 of whom were included in the final analysis. Participants had a mean age of 66.8 years, were predominantly male (83 percent), and had predominantly CKD stages G3a to G3b, with stage G3 accounting for approximately 71 percent. Diabetic nephropathy was present in 87 percent of patients.
Systolic BP decreased significantly from 128.9 mmHg at baseline to 124.3 mmHg post-intervention, while diastolic BP showed a non-significant reduction. No adverse events were reported.
No changes were observed in hepatic, renal, or hematopoietic function, including serum creatinine and estimated glomerular filtration rate. LDL-C and LDL-C in high-density lipoprotein cholesterol (HDL-C) decreased significantly, while HDL-C and triglycerides remained unchanged. Glycated hemoglobin, glucose metabolism, and electrolyte levels were also unchanged. Ferritin levels decreased significantly, although 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 finding the authors say may reflect the limitations of the urine-based point estimate. Urinary N-acetyl-beta-D-glucosaminidase, a marker of renal tubular damage, was significantly decreased. Improvements in stool frequency and stool quality were also observed.
Interpretation, limitations and implications
Overall, two months of fruit granola consumption was associated with reductions in urinary markers of tubular damage, lower systolic blood pressure, and improvements in lipid- and gut-related health markers in patients with moderate CKD. These results suggest potential cardiovascular and renal benefits, but should be considered hypothesis generating.
Key limitations include the single-group open design, lack of a control group, small sample size, short duration of the intervention, and lack of dietary records. Exclusive recruitment of Japanese participants and involvement of a food manufacturer in the research program may further limit generalizability. Larger, longer-term studies in diverse populations are needed.
