World Kidney Day 2020: Plant-based nutrition offers hope for both prevention and treatment of kidney disease

By Dr Anis Ta’eed MBBS, FRACP

Maintaining healthy kidneys is often overlooked in the fight against chronic diseases.  Yet, chronic kidney disease (CKD) currently affects approximately one in ten adults worldwide and its burden is increasing. By 2040, it is projected to become the fifth most common cause of years of life lost globally. [1]

 

Without appropriate treatment strategies, CKD progresses to end-stage kidney failure requiring dialysis or transplantation to sustain the individual’s life.In high-income countries like Australia, the cost of dialysis and transplantation on the health care budget is immense, while in low-income countries most people with kidney failure have inadequate, if any, access to such lifesaving treatments. 

 

For these reasons, World Kidney Day this year focuses on the importance of preventative interventions to avert the (a) onset and (b) progression of kidney disease. [1] As a nephrologist, I would argue there is nothing more powerful than optimal plant-based nutrition to help achieve these goals. 

 

Primary prevention of CKD: averting the onset of CKD

 

The two most common causes of CKD are diabetes and high blood pressure (hypertension), which are together responsible for up to two-thirds of cases. Each of these diseases causes chronic damage to the blood vessels and internal structures of the kidney over time. In fact, up to 30% of people with diabetes will develop CKD within 20 years of their diagnosis. [2] In order to prevent CKD, we must therefore first address these two chronic diseases. 

 

“The most common causes of chronic kidney disease are type 2 diabetes and high blood pressure.”

 

Fortunately, there is now established evidence that dietary change is a powerful strategy to treat both diabetes and hypertension, as it addresses their root cause: the highly processed, energy dense, nutrient-poor standard Western diet. Research shows that shifting to a more whole food, plant-based diet can not only prevent but even reverse these conditions. 

 

Type 2 diabetes

 

Looking at type 2 diabetes first, a recent meta-analysis of 9 prospective studies found a healthy plant-based pattern of eating reduced the risk of developing type 2 diabetes by 30%. [3]. This is almost certainly an underestimate of the true reduction because the studies analysed adjusted for body weight (BMI), which is a mediator of dietary effect. Several controlled trials have also demonstrated reversal of established diabetes with dietary change alone. One such trial compared an unrestricted low-fat fully plant-based diet to a control group on a calorie restricted American Diabetic Association diet. [4] After 22 weeks, a larger proportion of the low-fat plant-based group were able to reduce their glycaemic therapy (43% vs. 26%). In addition, hemoglobin A1c decreased 0.96% in the plant-based group compared to 0.56% in the control. Given the starting mean A1c of 8.0%, this reduction represents substantial improvement in their disease.

 

Hypertension

 

Several dietary factors also impact blood pressure and rates of hypertension. Specifically, low sodium, high potassium (e.g. plant intake), low alcohol and weight loss all substantially reduce blood pressure [5], and the combination has been demonstrated in controlled trials to be very effective. [6] For example, amongst those with a systolic blood pressure >150 mmHg, the low-salt DASH diet (rich in fruits, vegetables and whole-grains) compared to a high-salt standard American diet had a mean reduction in systolic blood pressure of 20.8 mmHg. [7] This is more effective than any single drug therapy, without the harmful side effects. 

 

Further benefits

 

Moving beyond the prevention and treatment of diabetes and hypertension there is even further evidence that a healthy diet helps to prevent CKD. Observational studies have shown a diet encouraging the consumption of plants is inversely associated with the development of CKD [8] and the initiation of dialysis [9], despite statistical adjustment for diabetes, obesity and hypertension. I have explored some of the specific mechanisms through which a plant-based diet improves kidney health further below. 

 

Secondary prevention: slowing CKD progression

 

Diet is critical in the management of all CKD, irrespective of whether the disease is due to diabetes and hypertension, or other conditions such as auto-immune diseases, polycystic kidneys or malformations from birth. In all cases, a standard Western diet contributes significantly to chronic kidney damage and therefore plays a major role in the progressive worsening of kidney function and the development of end-stage kidney failure. 

 

“In all cases, a standard Western diet contributes significantly to chronic kidney damage.” 

 

Protein: the plant advantage

 

One of the most important dietary factors for kidney health is protein intake. From animal studies it has been known for decades that a diet high in protein increases the workload for the kidneys (hyperfiltration). [10] Initially the kidney compensates well, but this extra stress has serious long-term consequences, ultimately resulting in progressive damage. Human studies support this animal research. Observational studies demonstrate a clear linear relationship between protein intake and risk of progression to kidney failure. [11] Furthermore, controlled trials show a low protein diet results in a slower decline in kidney function over time compared to a high protein diet. [12,13,14] 

 

Unfortunately, the standard Western diet typically is very high in animal product derived protein, with average intakes close to two-times the recommended daily requirements (0.6-0.8g per kg of body weight per day). [15] Not only is protein intake on a whole food plant-based diet naturally lower (whilst remaining sufficient), but the proteins also come directly from plant origins. This is important because at least some animal proteins appear to be more detrimental to the kidney than plant proteins. [10] In fact, one study found that replacing just one daily serve of red meat with soy and/or other legumes could reduce the risk of reaching end-stage kidney disease by 50%. [16]

 

“Animal proteins appear to be more detrimental to the kidney than plant proteins”

 

Dietary acid: the facts

 

Another important aspect of dietary effects on kidney function is acidosis. Every piece of food we eat is made up of acid and base pre-cursors that affect the acid-base balance in our blood. Animal-derived and refined foods are generally net acid-producing, whilst fruits, vegetables and legumes are net alkali-producing. In CKD, the kidney’s ability to maintain normal acid-base balance in the blood becomes impaired and acidosis can develop. Chronic acidosis is not only associated with a loss of bone mass, impaired heart function and increased risk of death, but also contributes to worsening kidney function. [17] It is therefore unsurprising that high dietary acid load (i.e. high consumption of animal foods) has been shown to significantly increase the risk of kidney failure [18] and markers of kidney disease progression. [19] 

 

Tertiary prevention: preventing CKD complications

 

Lastly, in addition to slowing kidney function decline, a whole food plant-based diet addresses many complications seen in advanced kidney disease such as:

 

Cardiovascular disease:

It is a sad fact that for people with CKD the risk of dying from cardiovascular disease is 20 times greater than the risk of requiring dialysis or transplantation. Plant-based diets are associated with a significantly lower risk of cardiovascular disease in both observational studies [20] and controlled trials. [21,22] A meta-analysis of 6 cohort studies of people with CKD found those eating a healthy dietary pattern (higher intake of plants) was associated with a 27% reduction in overall death. [23]

 

High phosphate levels:

In kidney disease phosphate can build up in the blood and cause harm to bones and blood vessels, leading to an increased risk of death. Whole plant foods help combat this as they contain phytates that bind to dietary phosphate, thereby significantly reducing its gut absorption compared to highly processed and animal foods. [24] 

 

Uremic toxins:

 

Numerous organic solutes, which are normally removed from the blood by the kidney, accumulate in CKD and contribute to various symptoms, heart disease and risk of death. Due to changes in gut bacteria, two of the most well studied toxins, indoxyl sulfate and p-crestyl sulfate, have been found to be approximately 60% lower in vegetarians compared to omnivores. [25] 


 

Summary

 

If we, as a global society, are to successfully manage the worldwide rising levels of CKD we will need to focus on holistic preventative strategies. Plant-based nutrition is not only an effective tool for primary prevention of kidney disease onset, but it can also play a powerful role in both secondary and tertiary prevention due to its ability to slow disease progression and avert severe complications. This World Kidney Day, I encourage everyone to raise awareness of both kidney disease and this underutilised approach to reduce its increasing impact on society. 

 

 

ENDS

 

About the author 

 

Dr Anis Ta’eed is a qualified general physician and nephrologist from

Melbourne. Anis was initially directed to a whole food plant-based (WFPB) diet in adolescence by his grandfather, a psychiatrist with a keen interest in the role of nutrition in disease prevention. He also saw the powerful effects of lifestyle change first-hand after his father was able to reverse his diabetes completely by following a WFPB diet. As a junior doctor, Anis systematically reviewed the medical literature and immediately began his own personal transition. Now as a nephrologist, he is passionate about the benefits of a WFPB diet specifically for kidney health as well as for overall chronic disease management, and advocates for this approach to eating with colleagues and patients alike. 

 

Dr Ta’eed has been a member of Doctors For Nutrition since attending the charity’s inaugural Nutrition in Healthcare conference in February 2019, and has since become one of the charity’s valued expert volunteers, contributing particularly to medical content, including its online topic summary on chronic kidney disease.



 

References:

  1. worldkidneyday.org/2020-campaign/2020-wkd-theme/

  2. kidney.org.au/your-kidneys/support/kidney-disease

  3. Qian F, Liu G, Hu F et al. Association between plant-based dietary patterns and risk of type 2 diabetes. JAMA Intern Med 2019 Jul 22. doi: 10.1001/jamainternmed.2019.2195 

  4. Barnard ND, Cohen J, Jenkins DJ et al. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care. 2006 Aug;29(8):1777-83.

  5. Appel L. The effects of dietary factors on blood pressure. Cardiol Clin 2017; 35:197-212

  6. Yokoyama Y, Nishimura K, Barnard ND et al. Vegetarian diets and blood pressure: a meta-analysis. JAMA Intern Med. 2014 Apr;174(4):577-87.

  7. Juraschek SP, Miller ER, Weaver CM, Appel LJ. Effects of Sodium Reduction and the DASH Diet in Relation to Baseline Blood Pressure. J Am Coll Cardiol. 2017 December 12; 70(23): 2841–2848

  8. Kim H, Caulfield LE, Garcia-Larsen V et al. Plant-Based Diets and Incident CKD and Kidney Function. Clin J Am Soc Nephrol. 2019; 14:682-691

  9. Smyth A, Griffin M, Yusuf S et al. Diet and Major Renal Outcomes: A Prospective Cohort Study. The NIH-AARP Diet and Health Study. J Ren Nutr. 2016 Sep;26(5):288-98

  10. Kontessis P, Jones S, Dodds R et al. Renal, metabolic and hormonal responses to ingestion of animal and vegetable proteins. Kidney Int. 1990 Jul;38(1):136-44.

  11. Metzger M, Lun Yuan W, Haymann J et al. Association of a low-protein diet with slower progression of CKD. Kidney Int Rep 2018; 3: 105-114

  12. Levey AS, Greene T, Beck GJ et al. Dietary protein restriction and the progression of chronic renal disease: what have all of the results of the MDRD study shown? Modification of Diet in Renal Disease Study group. J Am Soc Nephrol. 1999 Nov;10(11):2426-39.

  13. Nezu U, Kamiyama H, Kondo Y et al. Effect of low-protein diet on kidney function in diabetic nephropathy: meta-analysis of randomised controlled trials. BMJ Open. 2013 May 28;3(5)

  14. Hanh D, Hodson EM, Fouque D. Low protein diets for non-diabetic adults with chronic kidney disease. Cochrane Database Syst Rev. 2018 Oct 4;10:CD001892

  15. Munro HN et al. (1987) Protein nutriture of a group of free-living elderly. Am J Clin Nutr 46: 586–592

  16. Lew QJ, Jafar TH, Koh HW et al. Red Meat Intake and Risk of ESRD. J Am Soc Nephrol. 2017 Jan;28(1):304-312

  17. Dobre M, Yang W, Chen J et al. Association of serum bicarbonate with risk of renal and cardiovascular outcomes in CKD: a report from the Chronic Renal Insufficiency Cohort (CRIC) study. Am J Kidney Dis. 2013 Oct;62(4):670-8

  18. Banerjee T, Crews DC, Wesson DE et al. High dietary acid load predicts ESRD among adults with CKD. J Am Soc Nephrol 2015; 26:1693-1700

  19. Goraya N, Simoni J, Jo CH, Wesson DE. A comparison of treating metabolic acidosis in CKD stage 4 hypertensive kidney disease with fruits and vegetables or sodium bicarbonate. Clin J Am Soc Nephrol. 2013 Mar;8(3):371-81

  20. Kim H, Caulfield LE, Garcia-Larsen V, Steffen LM, Coresh J, Rebholz CM. Plant-Based Diets Are Associated With a Lower Risk of Incident Cardiovascular Disease, Cardiovascular Disease Mortality, and All-Cause Mortality in a General Population of Middle-Aged Adults. J Am Heart Assoc. 2019;8(16):e012865. 

  21. Ornish D1, Scherwitz LW, Billings JH et al. Intensive lifestyle changes for reversal of coronary heart disease. JAMA. 1998 Dec 16;280(23):2001-7

  22. de Lorgeril M1, Salen P, Martin JL et al. Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation. 1999 Feb 16;99(6):779-85.

  23. Kelly JT, Palmer SC, Wai NS et al. Healthy Dietary Patterns and Risk of Mortality and ESRD in CKD: A Meta-Analysis of Cohort Studies. Clin J Am Soc Nephrol 2017; 12:272-279

  24. Kalantar-Zadeh K, Gutekunst L, Mehrotra R et al. Understanding sources of dietary phosphorus in the treatment of patients with chronic kidney disease. Clin J Am Soc Nephrol. 2010 Mar;5(3):519-30

  25. Patel KP, Luo FJ, Plummer NS et al. The production of p-cresol sulfate and indoxyl sulfate in vegetarians versus omnivores. Clin J Am Soc Nephrol. 2012 Jun;7(6):982-8

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