Plant-based diets

Goals of nutritional intervention in CKD and dialysis

Nutritional goals

• Promote optimal nutritional status, growth and development
• Control the biochemical and metabolic consequences associated with CKD
• Prepare children with ESKD for kidney transplant readiness and candidacy

Medical nutrition therapy in pediatric vs adult dialysis patients

• Growth
• Bone development
• Meeting developmental milestones
• Establishing initial relationships with food and nurturing that relationship through chronic illness
• Supporting autonomy with feeding
• Advocating liberalization when clinically feasible

Barriers to achieving optimal growth and nutritional status

• Malnutrition
  • Poor appetite
  • Malabsorption
  • Changes in acid-base balance (e.g., metabolic acidosis)
• Gastrointestinal disturbances
  • Reflux
  • Delayed gastric emptying (gastroparesis)
  • Emesis
  • Early satiety
  • Constipation
  • Diarrhea
• Metabolic bone and mineral abnormalities
• Hormonal abnormalities
  • Chronic growth deficits, especially linear growth (stunting)
• Psychosocial issues
  • Difficulty concentrating
  • Decreased ability to learn new knowledge (e.g., diet education)
  • Negative self-image (e.g., feeling different from other kids)
  • Relationship and behavioral problems
• Developmental issues
  • Delayed language and motor skill development
  • Oral aversion

Current paradigm

Classic renal diet for patients on dialysis

• High protein
  • ↑ intake of animal protein
• Low potassium
  • ↓ intake of fruits, vegetables, beans, lentils, nuts, and seeds
• Low phosphorus
  • ↑ intake of refined grains
  • ↓ intake of whole grains
• Low sodium
  • ↑ intake of blander tasting foods
• Fluid restriction, in needed
  • ↓ water intake
  • ↓ intake of fruits and vegetables with higher water content
  • ↑ risk of constipation
• Restrictions typically made preemptively or in response to clinical or laboratory findings
• Fruit and vegetable intake typically lower across the CKD spectrum and unnecessary restriction may risk vitamin and mineral insufficiencies
• Adherence burdensome, leading to overall poor adherence and can compromise the overall quality of the diet and be detrimental to one’s health
• Individual nutrient modifications often results in complex nutritional messages that are confusing, inconsistent and constraining
  • Conflicting priorities, often result in poor compliance
  • Lack of autonomy
• Restriction of dietary phosphorus intake was associated with poorer nutritional status and higher mortality in adult patients on HD, suggesting that constraining phosphorus intake resulted in unintended restrictions in beneficial macronutrients
• Limited evidence to support efficacy of single nutrient restriction

Plant-based diets

• No single definition of a plant-based diet
• In general, can be defined as: a dietary pattern that focuses on maximizing the consumption of whole, plant foods such as fruits ,vegetables, legumes, whole grains, nuts and seeds
• Plant-based eaters aim to minimize the intake of animal-based foods (meats, eggs, seafood, poultry, dairy), heavily processed, and refined foods (pastries, soda)
• Not necessarily focusing on “vegan” or “vegetarian,” but rather on increasing plant-based food intake

General adult population

• Commonly studied plant-based dietary patterns:
  • Dietary approaches to stop hypertension (DASH) diet
  • Mediterranean diet
  • Vegetarian diet
• Observational studies suggest that plant-based dietary patterns may be superior to single-nutrient interventions due to the cumulative effects of multiple nutrients consumed through the diet
  • High intake of fruits, vegetables, fish and omega-3 fatty acids, legumes, whole grains, and nuts
  • Naturally lower in sodium red meat, saturated fat, and phosphate additives
  • Naturally higher in fiber
• Plant-based diets have longstanding associations with reduced cardiovascular incidence and mortality in non-CKD adult populations
• Some evidence of a negative association between vegetarian diets and prevalence of CKD, proposing possible protective factors
• Some evidence of ↓ production of uremic toxins, inflammatory status, and oxidative stress among individuals following a plant-based diet

Adult CKD (non-dialysis) population

• Heavily researched
• Plant-based diets associated with ↓ kidney-related mortality, ↓ cardiovascular disease risk, ↓ systemic inflammation, ↓ microalbuminuria, and slower progression to ESRD
• Plant-based diet also limits the bioavailability of dietary phosphorus compared to higher animal protein diets, thereby ↓ absorption due to the presence of phytate
  • ↓ % of plant-based phosphorus is absorbed relative to animal-based phosphorus
• ↑ intake of dietary acid load (associated with ↑ meat and cheese intake and ↓ fruit and vegetable intake) is associated with significantly ↑ risk of progressing to ESRD
• ↑ intake of fruit and vegetables in associated with ↓ blood pressure, improved metabolic acidosis, and slowed eGFR compared with control patients
  • Alkali-rich foods include, but not limited to:
    • Apples, apricots, oranges, peaches, pears, raisings, strawberries, carrots, cauliflower, eggplant, lettuce, potatoes, spinach, tomatoes
• Gut dysbiosis is a major contributor to build-up of uremic toxins in patients with low GFR
• Low dietary fiber intake associated with ↑ concentrations of inflammatory markers, myocardial hypertrophy, arterial stiffness, and a ↑ risk of CV events and death
• ↑ fiber intake associated with reduced uremic toxin (Indoxyl sulphate), improved lipid profile, oxidative status, and ↓ systemic inflammation
• More studies on the long-term safety and efficacy of ↑ fruit/vegetable intake needed before a plant-based diet can become routinely recommended

Pediatric CKD and dialysis populations

• Limited research in these populations
• Evaluated using CKiD data in 2021 by Shah, et al, but due to the limited variability of plant-based intake among the cohort they were unable to establish an association between plant-based protein intake and CKD progression or electrolyte abnormalities
• Some available research on estimating the potential renal acid load (PRAL) and acid base status in pediatric CKD patients

General pediatric population

• Plant-based diets deemed safe by the Academy of Nutrition and Dietetics and

Phosphorus

• Multicenter, pragmatic, parallel-arm open-label RCT of a standard vs modified low phosphorus diet in adult HD patients [PMID 33163715]
  • Patients assigned to:
    • Modified diet = some pulses and nuts, increased use of whole grains, and increased focus on avoidance of phosphorus additives
    • Standard diet = restrictions pulses, nuts, whole grains and other high phosphorus foods
  • Results:
    • Both diets well tolerated
    • No significant difference in change in serum phosphate levels despite ↑ intake of phytate-bound dietary phosphorus in the modified diet group
    • Dietary fiber intake significantly higher, as was % of patients reporting ↑ number of bowel movements while following the modified diet
    • No significant difference in the change in serum potassium or in reported protein intake between the two groups
    • More patients reported modified diet was “very difficult” to follow
• Crossover trial of 9 patients randomized to alternate between animal protein heavy diet and plant protein heavy diet resulted in significantly lower phosphorus levels after plant protein heavy diet compared to animal protein heavy diet, despite similar phosphorus content

Potassium

• Lack of discernible relationship between dietary potassium intake and pre-dialysis serum potassium concentrations in adult HD patients
  • Only about 2% of pre-dialysis potassium fluctuations attributable to dietary intake
• Observational study of non-vegetarian vs vegetarian adults on HD showed no statistically significant difference between serum potassium levels between either group
  • Serum phosphorus was found to be significantly lower among the vegetarian group vs the non-vegetarian group (p <0.05)
• Serum potassium concentrations reflect a complex interaction of numerous intrinsic factors including:
  • Nervous/endocrine signals (e.g., epinephrine, aldosterone, insulin), prolonged fasting
  • Hyperosmolality
  • Tissue breakdown
  • Intracellular/extracellular chemical concentrations (e.g., acid-base balance)
  • Circadian rhythms
  • Organ system functionality
  • Environmental exposures (e.g., diet and modifications)
  • Stooling patterns
    • Bowel potassium excretion is ↑ in CKD
      • Due to ↑ secretion into the bowel rather than ↓ absorption
    • Can excrete up to 3 g/day in stool

Renal diet paradigm shift

• Shifting from single nutrition focus → dietary patterns + portion modifications (if needed)
• Dietary patterns consider the cumulative effect of synergy between the combinations of foods and nutrition with less focus on classifying foods as “good” or “bad”
• More focus on quality and diversity of the diet, particularly with liberalization of plant-based foods when able

Key takeaways

• Adopting a whole food, plant-based diet approach that shifts focus onto foods (e.g., whole grains, fruits, vegetables, etc.) rather than single nutrients shows considerable promise in reaching overall health goals
• There is potential for long-term health benefits observed in the adult CKD populations
• May help manage metabolic acidosis and gut dysbiosis
• Promotes a more diversified dietary pattern
• Less stress on “good” and “bad” foods that have the potential to initiate disordered eating/negative relationships with food and nutrition
• The potential for higher risk of
  hyperkalemia
  among some patients on dialysis remains valid, thus emphasizing the importance of individualized, medical nutrition therapy counseling is necessary to avoid depriving patients of the potential effects of a plant-based diet
• Plants with lower potassium content provide choice for those who need to limit their potassium intake more conservatively
• More observational studies and RCTs needed before universally recommending strict, plant-based diets in the pediatric and adult dialysis populations

Role of pediatric kidney practitioners

• When there is room for liberalization, allow it!
• Modify portion sizes and frequency of intake, if needed, to still allow favorite healthy foods
• Advocate for inclusion of healthy food choices (whole grains, fruit, vegetables, legumes, nuts)
  • Create individualized nutrition therapy
    • No patient should ever be treated the exact same. Every patient is unique and responds differently to interventions
    • Closely monitor lab trends and tailor nutrition therapy recommendations accordingly to promote a more diverse intake
• Our universal goal is to strive to meet the DRI for all micronutrients, as permissible, to support optimal growth
• Utilize phosphorus binders with meals and/or snacks to help diversify diet
  • Use of phosphorus binders in adult dialysis patients was associated with a 14% risk reduction in mortality
  • Use of phosphorus binders may allow more relaxed dietary phosphorus restrictions leading to better nutritional intake and improved long-term survival
• Help our patients establish healthy relationships with food to prevent negative connotations with nutrition and to set them up for success before and after a future kidney transplant