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American Journal of Kidney Diseases

Nutrition and Kidney Health: Processing Emerging Evidence About Foods

Published:September 21, 2022DOI:https://doi.org/10.1053/j.ajkd.2022.06.002
      Related Article, p. 589
      When caring for patients with chronic kidney disease (CKD), nutrition is a key consideration for the overall management of high blood pressure, blood glucose, fluid retention, and cardiovascular disease risk.
      • Ikizler T.A.
      • Burrowes J.D.
      • Byham-Gray L.D.
      • et al.
      KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update.
      Adherence to nutrition recommendations is challenging for individuals with CKD because the guidance is complex and there is a marked difference between what is recommended and what is typically consumed. Notably, the typical diet in the United States is characterized by ultraprocessed, calorically dense foods, and it is higher than recommended in saturated fat, sodium, and added sugar, and lower than recommended in vegetables, fruits, and whole grains.
      Although most foods in the global food supply undergo some processing to ensure safety, there are concerns about foods that are ultraprocessed given evidence of associations with poor diet quality
      • Louzada M.L.
      • Baraldi L.G.
      • Steele E.M.
      • et al.
      Consumption of ultra-processed foods and obesity in Brazilian adolescents and adults.
      ; high intake of total energy, added sugars, and sodium; and low intake of fruits, vegetables, and fiber.
      • Moubarac J.C.
      • Batal M.
      • Louzada M.L.
      • Martinez Steele E.
      • Monteiro C.A.
      Consumption of ultra-processed foods predicts diet quality in Canada.
      • Rauber F.
      • da Costa Louzada M.L.
      • Steele E.M.
      • Millett C.
      • Monteiro C.A.
      • Levy R.B.
      Ultra-processed food consumption and chronic non-communicable diseases-related dietary nutrient profile in the UK (2008-2014).
      • Poti J.M.
      • Mendez M.A.
      • Ng S.W.
      • Popkin B.M.
      Is the degree of food processing and convenience linked with the nutritional quality of foods purchased by US households?.
      There are also documented associations with certain diet-related cancers,
      • Elizabeth L.
      • Machado P.
      • Zinöcker M.
      • Baker P.
      • Lawrence M.
      Ultra-processed foods and health outcomes: a narrative review.
      cardiovascular diseases,
      • Elizabeth L.
      • Machado P.
      • Zinöcker M.
      • Baker P.
      • Lawrence M.
      Ultra-processed foods and health outcomes: a narrative review.
      all-cause mortality,
      • Schnabel L.
      • Kesse-Guyot E.
      • Allès B.
      • et al.
      Association between ultraprocessed food consumption and risk of mortality among middle-aged adults in France.
      obesity,
      • Mendonça R.D.
      • Pimenta A.M.
      • Gea A.
      • et al.
      Ultraprocessed food consumption and risk of overweight and obesity: the University of Navarra Follow-Up (SUN) cohort study.
      hypertension,
      • Mendonça R.D.
      • Lopes A.C.
      • Pimenta A.M.
      • Gea A.
      • Martinez-Gonzalez M.A.
      • Bes-Rastrollo M.
      Ultra-processed food consumption and the incidence of hypertension in a Mediterranean cohort: the Seguimiento Universidad de Navarra Project.
      and diabetes.
      • Elizabeth L.
      • Machado P.
      • Zinöcker M.
      • Baker P.
      • Lawrence M.
      Ultra-processed foods and health outcomes: a narrative review.
      However, little is known about the impacts of ultraprocessed foods on kidney health.
      In this issue of AJKD, Du et al
      • Du S.
      • Kim H.
      • Crews D.C.
      • White K.
      • Rebholz C M.
      Association between ultraprocessed food consumption and risk of incident CKD: a prospective cohort study.
      describe the association between intake of ultraprocessed foods and incident CKD. The authors define ultraprocessed foods as “industrially processed foods and drink products that contain little to no intact foods [that] mostly comprise ingredients extracted from foods and contain nonculinary substances and artificial additives to enhance the shelf life and palatability.” Intake of ultraprocessed foods was assessed by self-report via food frequency questionnaire. Incident CKD was defined as estimated glomerular filtration rate <60 mL/min/1.73 m2 accompanied by ≥25% decline therein, CKD-related hospitalization or death, or incident kidney replacement therapy. Du et al report that after adjusting for potential confounding by participant demographic characteristics, lifestyle factors, and health behaviors there was a greater risk of developing CKD for those participants in the highest quartile of consumption of ultraprocessed foods compared to those in the lowest quartile. Further, the risk of CKD appeared to be linear. Notably, the analyses also suggest that switching from eating ultraprocessed food to minimally processed food was associated with lower risk of CKD.
      The analytic approach by Du et al has several strengths, including the use of data from the Atherosclerosis Risk in Communities (ARIC) study, which is a large, biracial epidemiologic cohort with high-quality dietary data assessment.
      • Du S.
      • Kim H.
      • Crews D.C.
      • White K.
      • Rebholz C M.
      Association between ultraprocessed food consumption and risk of incident CKD: a prospective cohort study.
      As such, although the assessment of diet by self-report has its limitations, there can be confidence in the estimates of ultraprocessed foods. The use of the ARIC cohort study also allowed the study of an apparently healthy population who were free of CKD at the time of dietary assessment. This aspect is important because once individuals develop CKD it cannot be reversed, its management is complex, and patients are asked to make many dietary adjustments. Additionally, in later stages of CKD caution is advised for potassium-rich foods, often fruits and vegetables, that were previously recommended as part of healthy diets to reduce disease risk factors (Table 1). Thus, these findings by Du et al regarding a modifiable dietary factor can support efforts for the primary prevention of CKD.
      Table 1Summary of Guidance for Select Dietary Patterns in Individuals with CKD or CKD Risk Factors
      Dietary PatternCharacteristicsGuidance
      • Arnett D.K.
      • Blumenthal R.S.
      • Albert M.A.
      • et al.
      2019 AHA/ACC Guideline on the Primary Prevention of Cardiovascular Disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
      ,
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      for CKD Risk Factors (BP, Diabetes, Obesity)
      Guidance for CKD
      • Ikizler T.A.
      • Burrowes J.D.
      • Byham-Gray L.D.
      • et al.
      KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update.
      ,
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Typical US dietUltraprocessed, calorically dense

      Higher than recommended in saturated fat, sodium, added sugar

      Lower than recommended in vegetables, fruits, whole grains

      Lower than recommended in vitamin D, calcium, dietary fiber, and potassium
      Recommends limiting
      • Arnett D.K.
      • Blumenthal R.S.
      • Albert M.A.
      • et al.
      2019 AHA/ACC Guideline on the Primary Prevention of Cardiovascular Disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
      ,
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Recommends limiting
      • Ikizler T.A.
      • Burrowes J.D.
      • Byham-Gray L.D.
      • et al.
      KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update.
      ,
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Healthy (eg, Mediterranean, DASH-style) dietEmphasizes vegetables; fruits; whole grains; lower-fat dairy; healthy dairy alternatives; healthy animal protein foods including lean meats, poultry, and eggs; seafood; beans, peas, and lentils; nuts, seeds, and soy products; and healthy oils

      Limits foods and beverages high in added sugars, saturated fat, and sodium
      Recommends choosing
      • Arnett D.K.
      • Blumenthal R.S.
      • Albert M.A.
      • et al.
      2019 AHA/ACC Guideline on the Primary Prevention of Cardiovascular Disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
      ,
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Recommends exercising caution and individualization
      • Ikizler T.A.
      • Burrowes J.D.
      • Byham-Gray L.D.
      • et al.
      KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update.
      ,
      • Evert A.B.
      • Boucher J.L.
      • Cypress M.
      • et al.
      Nutrition therapy recommendations for the management of adults with diabetes.
      Healthy (eg, vegetarian, plant-forward) dietMinimally processed

      Exclusive of or limited in meats

      Emphasizes vegetables, fruits
      Recommends choosing
      • Arnett D.K.
      • Blumenthal R.S.
      • Albert M.A.
      • et al.
      2019 AHA/ACC Guideline on the Primary Prevention of Cardiovascular Disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.
      Recommends exercising caution
      • Ikizler T.A.
      • Burrowes J.D.
      • Byham-Gray L.D.
      • et al.
      KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update.
      Abbreviations: BP, blood pressure; CKD, chronic kidney disease.
      As with all nutrition epidemiologic studies, this analysis has some inherent limitations. First, it is difficult to account for residual confounding by unmeasured or imprecisely measured factors related to both ultraprocessed food consumption and CKD. These analyses also force us to guess about the mechanisms that underlie the observed associations with CKD risk factors and ultimately the kidneys. The processing of foods may include salting, sugaring, baking, frying, deep frying, smoking, pickling, curing, canning, addition of various chemicals (preservatives, synthetic vitamins, minerals, and cosmetic additives), and use of complex packaging.
      • Louzada M.L.
      • Baraldi L.G.
      • Steele E.M.
      • et al.
      Consumption of ultra-processed foods and obesity in Brazilian adolescents and adults.
      Ultraprocessed foods also have a higher glycemic load and lower satiety, likely because processing the food alters the properties and introduces additives that may reduce gut-brain satiety signaling.
      • Fardet A.
      Minimally processed foods are more satiating and less hyperglycemic than ultra-processed foods: a preliminary study with 98 ready-to-eat foods.
      Mechanisms of action may include alteration of the food matrix such that what reaches the distal gut feeds the microbiome differently than minimally processed foods
      • Snelson M.
      • Tan S.M.
      • Clarke R.E.
      • et al.
      Processed foods drive intestinal barrier permeability and microvascular diseases.
      ; effects seen in animal models such as increased inflammation, uremic toxins, and advanced glycation end products (AGEs)
      • Snelson M.
      • Tan S.M.
      • Clarke R.E.
      • et al.
      Processed foods drive intestinal barrier permeability and microvascular diseases.
      ; or serving as a proxy for diet quality because ultraprocessed foods displace other healthy foods.
      • Louzada M.L.
      • Baraldi L.G.
      • Steele E.M.
      • et al.
      Consumption of ultra-processed foods and obesity in Brazilian adolescents and adults.
      The clinical and public health relevance of the work of Du et al is high. In clinical practice, providers need tools to effectively and efficiently assess diet and counsel patients, especially those at risk of developing CKD. One option is to use a tool that incorporates the “5A” framework into nephrology and primary care clinics.
      • Vadiveloo M.
      • Lichtenstein A.H.
      • Anderson C.
      • et al.
      Rapid diet assessment screening tools for cardiovascular disease risk reduction across healthcare settings: a scientific statement from the American Heart Association.
      This framework suggests clinicians assess the risk behavior, advise change, agree on an action plan, assist with treatment, and arrange follow-up. In patients at risk for CKD and with CKD, a full diet history should be taken and, importantly, social determinants of health should be discussed. Furthermore, to do this work effectively, providers should be resourced with electronic health records that track and report dietary practices, consumption of healthy and processed foods, patient behaviors, and patient-reported outcomes.
      • Vadiveloo M.
      • Lichtenstein A.H.
      • Anderson C.
      • et al.
      Rapid diet assessment screening tools for cardiovascular disease risk reduction across healthcare settings: a scientific statement from the American Heart Association.
      The action plan should be designed with the patient, it should be culturally sensitive, and it should ensure that patients who have economic concerns or who live in food deserts are connected with resources necessary for positive dietary change. Given the widespread availability and use of ultraprocessed foods, nephrologists and primary care physicians would benefit from taking a team approach including registered dieticians and other accredited nutrition providers, health care providers, social workers, and community health workers. But this approach should also be patient-centered, with consideration for patient burden.
      Healthy dietary patterns are a cornerstone for prevention of CKD and other chronic diseases. Globally, improper diets make the biggest contribution to the burden of disease. In the United States, the Dietary Guidelines for Americans provide recommendations for the population aged 2 years and older and emphasize healthy dietary patterns that include fresh, minimally processed whole foods. KDOQI has used a rather limited body of evidence to put forward guidelines for those with CKD.
      • Ikizler T.A.
      • Burrowes J.D.
      • Byham-Gray L.D.
      • et al.
      KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update.
      Over the last decade, there has been growth in the evidence base for diet and CKD, with a shift in focus to diet quality and dietary patterns.
      • Rebholz C.M.
      • Crews D.C.
      • Grams M.E.
      • et al.
      DASH (Dietary Approaches to Stop Hypertension) diet and risk of subsequent kidney disease.
      ,
      • Bach K.E.
      • Kelly J.T.
      • Palmer S.C.
      • Khalesi S.
      • Strippoli G.F.M.
      • Campbell K.L.
      Healthy dietary patterns and incidence of CKD: a meta-analysis of cohort studies.
      This shift has important implications for patients with CKD because it acknowledges that foods are not eaten in isolation; rather, they are consumed in combinations. Although intake of individual nutrients such as sodium, potassium, phosphorus, and protein must be clinically monitored for patient safety, this monitoring should be accompanied by diet counseling that is patient-centered, practical, and feasible and that optimizes adherence to a pattern that is delicious and nutritious. Once chronic kidney damage occurs it is irreversible, making risk factor modification critical. As we process the findings from Du et al, we see a clear call to make the healthy diet choice the default choice in order to positively and sustainably impact kidney health.

      Article Information

      Authors’ Full Names and Academic Degrees

      Cheryl A. M. Anderson, PhD, MPH, MS, and Titilayo Ilori, MD, MS.

      Support

      None.

      Financial Disclosure

      The authors declare that they have no relevant financial interests.

      Peer Review

      Received May 23, 2022, in response to an invitation from the journal. Accepted June 23, 2022, after editorial review by an Associate Editor and a Deputy Editor.

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