A 5-year randomized controlled trial found that dietary acid reduction through increased fruit and vegetable intake or sodium bicarbonate supplementation may slow kidney function decline and reduce cardiovascular disease risk in patients with primary hypertension and macroalbuminuria.
In the study, published in The American Journal of Medicine, researchers examined the effects of dietary interventions on hypertension outcomes. They randomly assigned 153 patients with primary hypertension, normal kidney function (estimated glomerular filtration rate ≥ 90 mL/min/1.73m2), and macroalbuminuria (urine albumin-to-creatinine ratio > 200 mg/g) to one of three groups: increased fruits and vegetables, oral sodium bicarbonate supplementation, or usual care. All of the participants received standard pharmacologic therapy, including angiotensin-converting enzyme inhibitors and statins.
The study was conducted at Texas Tech University Health Sciences Center from 1996 to 2011. Participants were identified through a clinic system feature prompting urine albumin-to-creatinine ratio measurement in all patients with hypertension. Among 29,241 patients screened, 1.5% (n = 440) of them met the initial criteria of macroalbuminuria, normal estimated glomerular filtration rate, and no cardiovascular disease.
Study population characteristics included a mean age of 48.84 ± 6.6 years, 51% female, and a racial/ethnic composition of 47.1% Black, 23.5% Hispanic, and 29.4% non-Hispanic White. At baseline, mean systolic blood pressure was 157.5 ± 8.7 mmHg, and mean Potential Renal Acid Load was 61.7 ± 10.3.
Interventions:
- Fruits and vegetables group: 2 to 4 cups daily of base-producing fruits and vegetables, including apples, apricots, oranges, peaches, pears, raisins, strawberries, carrots, cauliflower, eggplant, lettuce, potatoes, spinach, tomatoes, and zucchini
- Sodium bicarbonate supplementation group: 0.4 mmol/kg body weight/day of oral sodium bicarbonate (average of 4 to 5 650-mg tablets daily in 2 divided doses)
- Usual care group: Standard medical care.
Among the key findings were:
- Slower kidney function decline: Both intervention groups showed slower estimated glomerular filtration rate decline compared with usual care (fruits and vegetables: –1.08 mL/min/1.73m2/year, sodium bicarbonate supplementation: –1.17 mL/min/1.73m2/year, usual care: –1.94 mL/min/1.73m2/year, P < .001 for both interventions vs usual care).
- Reduced albuminuria progression: Urine albumin-to-creatinine ratio increased less in both intervention groups compared with usual care (P < .001 for both).
- Greater blood pressure reduction: The fruits and vegetables group achieved lower systolic blood pressure compared with the sodium bicarbonate supplementation and usual care groups (P < .001).
- Improved cardiovascular risk markers: The fruits and vegetables group showed greater reductions in low-density lipoprotein (LDL) cholesterol, Lp(a) cholesterol, and body mass index (BMI) compared with sodium bicarbonate supplementation and usual care groups (P < .001 for all comparisons). Specifically, LDL cholesterol reduction became significant by year 2 (P < .001), Lp(a) cholesterol by year 1 (P < .001), and BMI by year 2 (P = .002).
- Lower medication requirements: Patients in the fruits and vegetables group required lower doses of enalapril, diltiazem, and atorvastatin compared with usual care (P < .001, P = .002, and P = .001, respectively). Additionally, the fruits and vegetables group had lower median doses of hydrochlorthiazide compared with the sodium bicarbonate supplementation group (P = .013).
Outcomes were assessed annually, including estimated glomerular filtration rate, urine albumin-to-creatinine ratio, blood pressure, lipid profiles, and plasma acid-base parameters. Plasma acid-base parameters showed significant increases in total carbon dioxide, bicarbonate, and partial pressure of carbon dioxide in both intervention groups compared with usual care by year 2 (P < .001 for all).
The fruits and vegetables group demonstrated a significant decrease in Potential Renal Acid Load every year after baseline (P < .001), while the sodium bicarbonate supplementation and usual care groups showed no significant changes (P > .354).
Attrition rates were reported, with 47 participants in both the fruits and vegetables and sodium bicarbonate supplementation groups, and 44 to 45 in the usual care group completing the 5-year follow-up.
Statistical analysis used mixed linear regressions with random person intercepts to accommodate missing data cause by attrition. The study was powered to detect a 25% difference in estimated glomerular filtration rate decline rate among groups with 80% power and 0.05 significance level.
This comprehensive study highlighted the importance of routine albuminuria screening in hypertensive patients to identify underlying chronic kidney disease and cardiovascular risk. The findings supported incorporating dietary interventions, particularly increased fruit and vegetable intake, as an approach to managing hypertension and reducing associated kidney and cardiovascular complications.
The researchers suggested considering fruits and vegetables as part of the primary treatment strategy for hypertension, with pharmacologic therapy adjusted as needed, rather than solely as an adjunctive measure. Future studies are needed to determine if patients with less severe albuminuria show similar responses to dietary acid reduction.
The authors declared having no competing interests.
