Chronic Kidney Disease

Key Points

• Aims: The aim of this study was to investigate the associations of plant-based diets with the risks of chronic kidney disease (CKD) progression and all-cause mortality in individuals with CKD. 
  
  
• Study Design: This was a prospective cohort study including 2,539 participants aged 21 to 74 years with mild-to-moderate CKD. Participants attended annual in-person visits and completed a telephone interview every 6 months. Also, dietary intakes were self-reported using the National Cancer Institute’s Diet History Questionnaire.
  
  
• Diet Quality: Healthy plant foods included whole grains, fruits, vegetables, nuts, legumes, and tea/ coffee. Unhealthy plant foods included fruit juices, sugar-sweetened beverages, refined grains, potatoes, and sweets and desserts. Animal foods included animal fats, dairy, eggs, fish/seafood, meat (poultry and red meat), and miscellaneous animal foods.
  
  
• Results: A 10-point higher score for the unhealthy plant-based diet index was associated with a 14% higher risk of CKD progression (HR, 1.14 [95% CI, 1.03-1.25) and all-cause mortality (HR, 1.11 [95% CI, 1.00-1.23). During a median follow-up of 12 years the mortality rate was lowest for those with the highest adherence to the overall plant-based diet index (HR, 0.74 [95% CI, 0.62-0.88], P trend < 0.001).
  
  
• Limitations: Diets were self-reported which is subject to measurement error.

Conclusion

Patients with CKD can reduce CKD progression and all-cause mortality risk by adhering to a whole food, plant-based diet. They should avoid unhealthy plant foods such as those high in saturated fats and refined grains.

Key Points

• Aims: The aim of this systematic review and meta-analysis were to evaluate the effect protein types (animal or plant) have on inflammation markers (CRP, IL-6, TNF-α) among adults with varying stages of CKD.
  
  
• Eligibility: Studies were eligible if they were a clinical control trial, included humans, participants were >18 years of age, the intervention included plant and/or animal protein, included the amount and/or frequency that participants consumed these proteins and primary outcomes included inflammation markers such as CRP, IL-6, and/or TNF-α. Ten studies were identified and included in analyses.
  
  
• Results: Among participants who were not on dialysis, there was a decreasing trend in CRP levels when consuming plant proteins compared to animal proteins. In dialysis patients, there was a significant decrease in CRP levels favoring unspecified proteins (Hedges’ g = 2.11; 95% CI 1.12, 3.11; p < 0.001). Also, there was a decreasing trend in inflammation markers–CRP, IL-6, and TNF-α when comparing plant proteins to animal proteins.
  
  
• Quality Risk and Bias Assessment: Non-randomized control trials were included which may introduce low to moderate risk of bias.
  
  
• Limitations: A limited number of studies were included because of narrow eligibility criteria. Also, the ability to compare studies was reduced because of high heterogeneity in study design, sample size, and outcome measures.

Conclusion

This meta-analysis showed that compared to plant proteins, animal proteins increase CRP levels and thereby inflammation. Regardless of what stage the CKD patient was in, plant proteins showed a decrease in inflammation markers. Educating CKD patients is vital for them to make positive nutrition decisions which can increase their eGFR and slow the progression of kidney disease.

Key Points

• Aims: The aim of this systematic review was to explore the impact of a vegetarian diet on kidney function in patients with CKD.
  
  
• Eligibility: Studies were included if participants had CKD, if the intervention included a plant-based diet, including subgroups of a vegetarian and vegan diet, the study groups were compared to a control group - the omnivore (standard) diet and if the final outcomes compared the initial estimated glomerular filtration rate (eGFR) and final eGFR at the end of the study. Four randomized controlled trials (RCT) with a total of 346 participants were included.
  
  
• Results: The two largest RCTs observed benefits of a vegetarian diet with an increase in eGFR (P=0.01, P=0.01). No significant differences were observed between experimental (plant-based) groups and control groups in the other two RCTs, but they also exhibited a high risk of bias due to missing data or the randomization process.
  
  
• Quality Assessment and Risk of Bias: The risk of bias was low in all domains of the Risk of Bias 2 tool.
  
  
• Limitations: Only articles written in English were included which may introduce language bias. The limited sample of included articles may also limit generalizability. Heterogeneity in study design, eligibility criteria and outcome measures among included studies may have also limited available comparisons.

Conclusion

A plant-based diet may be beneficial for renal filtration function in patients with CKD and potentially delay disease progression. However, only a small number of studies were eligible for this review so results should be interpreted with caution.

Future Directions

Based on the findings from this topical review, researchers may consider the following suggestions for future research.

Study Duration: Studies with >6-month follow-up should be conducted to investigate the long-term implications of plant-based diets on CKD outcomes.

Population Diversity: As with most nutrition research, predominantly mid-aged Caucasian females make up the majority of sample sizes. Studies should prioritize racial and gender differences across outcomes related to the effects of plant-based diets on CKD.

Effect of Protein Type: Randomized controlled trials should be conducted to compare the effect of protein type on inflammation markers among people with CKD.

Type of Plant Foods: Future research should determine if differences exist between the effects of whole plant foods (i.e., fruits, vegetables, grains) and processed plant foods (i.e., soy or pea protein-based foods) on CKD outcomes.