Vegan Diets And Kidney Health: What's The Connection?

A vegetarian diet is a popular alternative to the casual diet and is considered healthy, positively affecting cardiovascular health. Chronic Kidney Disease (CKD) is a leading cause of death for 1.5% of the global population. The objective of this systematic review was to investigate the potential impact of a vegetarian diet on kidney function in CKD patients.

The investigation was performed using the PRISMA 2020 Checklist and PRISMA 2020 flow diagram. The search terms included: ‘vegetarian diet’ AND ‘nephropathy’, ‘eGFR’, ‘albuminuria’, ‘chronic kidney disease’. Four RCTs with a total of 346 participants were included in the presented systematic review. Two largest RCTs reported an increase in eGFR following a change to a vegetarian diet. Another two found no significant differences between the experimental and control groups, also these trials were associated with a high risk of bias in terms of missing data outcome and the randomization process.

The findings collected in this systematic review suggest that a vegetarian diet improves renal filtration function in CKD patients. Therefore, it seems essential to conduct further research involving the impact of the diet on the progression of CKD.

Vegetarian diets can meet the higher protein needs of a dialysis patient. Plant protein sources have been shown to decrease protein in the urine (proteinuria), slow the decline of glomerular filtration rate (GFR) and kidney blood flow, result in less kidney tissue damage when compared to animal proteins, reduce kidney cyst growth, and improve lipid (blood fat) profile of the blood.

While people in the earlier stages of kidney disease are generally told to limit protein intake, dialysis patients require more protein because of protein loss during dialysis and increased body needs. It is more difficult for vegetarian dialysis patients to consume enough protein and keep potassium and phosphorus controlled without using a protein supplement—this is especially true for those who are vegans, because no eggs or milk products are consumed.

The benefits of a plant-based diet for kidney health

Kidney disease, or CKD (chronic kidney disease), is any process that damages the kidneys, the body's filter and regulator for blood and urine content. When the kidneys are impaired, there can be a dangerous buildup of water, sodium, and toxins in the blood, and not enough in the urine. In some cases, there may be too much protein or blood in the urine. Severe cases of kidney disease may require a kidney transplant or long-term dialysis.

Plant-based diets are beneficial for kidney health as they can help manage weight, blood pressure, and diabetes. Studies have shown that eating whole grains, nuts, fruits, and vegetables is one of the most important ways to keep kidneys healthy. A plant-based diet can also help prevent and slow the progression of chronic kidney disease by lowering blood pressure and reducing blood phosphate levels.

• Improved kidney function: A plant-based diet can help improve kidney filtration function and slow the progression of CKD.
• Reduced risk of kidney disease: Plant-based diets can help lower the chance of getting kidney disease in the first place.
• Improved weight management: Plant-based foods tend to have fewer calories than animal-based foods, which can help with weight management.
• Lower blood pressure and cholesterol: A plant-based diet can help reduce blood pressure and "bad" cholesterol, which are risk factors for heart disease.
• Lower risk of diabetes: Plant-based diets can help improve insulin sensitivity and lower blood sugar levels, reducing the risk of diabetes.
• Improved antioxidant levels: Plant-based foods are rich in antioxidants, which protect cells from damage and can help reduce inflammation.
• Reduced acid load: Eating less animal-based foods can lower the acid load on the kidneys, reducing stress on these organs.
• Lower phosphorus absorption: Plant-based diets can help bind phosphorus, reducing the risk of phosphorus buildup in the blood, which can cause harm to bones and blood vessels.
• Reduced protein in the urine: Plant-based diets have been associated with reduced protein in the urine, which is a sign of improved kidney function.

One potential pitfall of a plant-based diet for people with kidney disease is the risk of high potassium levels, as plant foods can be rich in potassium. However, this can be managed by avoiding or limiting certain foods, such as dried fruit, plant-based juices, and sauces. It is also important to have your blood checked regularly to monitor potassium levels.

Additionally, people with kidney disease may need to pay close attention to their protein intake, as it can be more challenging to consume enough protein on a plant-based diet. This is especially true for those on dialysis, who have higher protein requirements. Working with a dietitian can help ensure that you are getting enough protein and other necessary nutrients while following a plant-based diet.

The impact of a vegetarian diet on chronic kidney disease

Chronic Kidney Disease (CKD) is a leading cause of death worldwide, with approximately 15% of the adult population in the United States affected. CKD patients have a 57% higher chance of cardiovascular mortality and a 7% higher risk of stroke for every 10 mL/min/1.73 m² decrease in GFR.

Vegetarian and vegan diets have become increasingly popular worldwide. A vegetarian diet is most commonly associated with a lacto-ovo vegetarian diet, which includes fruits, vegetables, dairy products, eggs, and honey. A pescetarian diet includes fish, while a vegan diet only allows fruits and vegetables.

Vegetarians and vegans have lower levels of common risk factors, such as BMI, fasting glucose, LDL-cholesterol, and triglycerides, compared to meat-eaters. Meta-analyses show that total cholesterol and LDL-cholesterol levels can be reduced by up to 35% with a vegetarian diet. Vegetarians also have lower blood pressure, with a decrease of 9.1 mmHg in systolic BP and 5.8 mmHg in diastolic BP compared to non-vegetarians.

The impact of a vegetarian diet on CKD

A vegetarian diet may improve renal filtration function in CKD patients and delay its progression. However, only a small number of studies have been conducted on this topic, and more research is needed.

A review of four RCTs with a total of 346 participants found that two of the largest RCTs reported an increase in eGFR following a change to a vegetarian diet. The other two studies found no significant differences between the experimental and control groups, but these trials were associated with a high risk of bias.

A vegetarian diet can be beneficial for phosphorus homeostasis, as plant-based protein sources significantly decrease fibroblast growth factor 23 (FGF23) levels and serum phosphorus levels. Vegetarian diets are also associated with lower systolic pressure, which may have protective effects for the kidneys and the heart. Additionally, plant-based diets have anti-inflammatory effects, reducing oxidative stress and protecting against renal injury.

Other benefits of a vegetarian diet for CKD patients

• Lower proteinuria and serum urea: A vegetarian diet was found to reduce urinary albumin excretion and serum urea concentration.
• Improved lipid profile: Plant-based diets can improve the blood fat profile.
• Gut microbiome diversity: Vegetarian diets provide a diversity of gut microbes, preventing dysbiosis and low-grade inflammation.
• Anti-inflammatory effects: Vegetarian diets are rich in antioxidative vitamins like vitamin C, E, and beta-carotene, leading to lower concentrations of uric acid and hsCRP.
• Quality of life: A vegetarian diet positively affects various aspects of quality of life, including physical, social, environmental, and psychological domains.

Limitations and considerations

• Protein intake: While people with earlier stages of kidney disease are generally advised to limit protein intake, dialysis patients require more protein due to protein loss during dialysis and increased body needs. It can be challenging for vegetarian dialysis patients to consume enough protein while controlling potassium and phosphorus levels without using supplements.
• Sodium, phosphorus, and potassium restriction: Vegetarians with CKD will need to limit certain foods high in sodium, phosphorus, and potassium based on their kidney function and lab results, just like other CKD patients.
• Iron, calcium, zinc, vitamin D, and B12: These nutrients should not be a concern for vegetarians on dialysis, as the prescribed renal vitamin typically includes vitamin B12 and zinc, and dialysis patients are regularly evaluated and prescribed calcium, vitamin D, and intravenous iron as needed.

A vegetarian diet may improve renal filtration function in CKD patients and delay its progression. However, more research is needed, including studies with larger groups and improved homogeneity. CKD patients considering a vegetarian diet should consult a dietitian to avoid potential nutritional deficiencies and ensure adequate protein intake.

The risks of a vegan diet for kidney patients

A vegan diet, when not carefully planned, may pose certain risks for kidney patients. While a vegan diet can be beneficial for kidney health, it is important to be aware of potential challenges to ensure optimal nutrition and health.

Risk of Malnutrition

One of the main concerns for kidney patients on a vegan diet is the risk of malnutrition. The dialysis process can result in the loss of essential proteins, leading to weakness, low energy, loss of muscle mass, and overall poor health. To mitigate this risk, it is crucial to include sufficient protein-rich foods in the diet. While a vegan diet eliminates animal-based proteins, plant-based sources such as legumes, nuts, and grains can provide adequate protein. However, careful planning is necessary to ensure sufficient protein intake.

Limited Food Choices

Following a vegan diet with kidney disease may require limiting certain foods that are typically included in a vegan diet. For example, patients may need to restrict their intake of fruits, vegetables, and whole grains to control potassium and phosphorus levels. This can reduce the variety of food options available to vegans, making it more challenging to meet nutritional needs.

High Potassium and Phosphorus Levels

Fruits, vegetables, and whole grains, which are staples of a vegan diet, tend to be rich in potassium and phosphorus. While these minerals are essential for health, high levels can be dangerous for kidney patients. Potassium helps maintain healthy nerve and muscle function, but when kidneys are impaired, excess potassium can build up in the blood, leading to heart problems. Phosphorus, if not adequately managed, can accumulate in the blood and cause harm to bones and blood vessels. Therefore, kidney patients on a vegan diet must carefully monitor their intake of these minerals.

Difficulty in Meeting Protein Requirements

Meeting protein requirements can be challenging for kidney patients on a vegan diet. Animal-based proteins are typically complete proteins, providing all the essential amino acids needed by the body. Plant-based proteins, on the other hand, tend to be incomplete, lacking in certain amino acids. To ensure adequate protein intake, kidney patients following a vegan diet must carefully combine different plant-based sources to obtain all the essential amino acids. This can be a complex task and may require guidance from a dietitian.

Risk of Vitamin Deficiency

Vitamin deficiency is another potential concern for kidney patients on a vegan diet. Vitamins such as B12, which is primarily found in animal-based foods, may be lacking in a vegan diet. Deficiency in this vitamin can lead to anemia and neurological issues. Fortified plant-based foods and supplements can help address this issue, but careful attention is required to ensure adequate intake.

In conclusion, while a vegan diet can offer benefits for kidney patients, it is important to be aware of these potential risks. Working closely with a healthcare team and a registered dietitian is crucial to ensure that the diet is properly planned and tailored to the patient's specific needs.

How to adapt a vegetarian diet for kidney patients

A vegetarian diet can be safe and beneficial for kidney disease patients with careful planning. Here are some key considerations and guidelines to adapt a vegetarian diet for kidney patients:

• Protein Management: Kidney patients need to monitor their protein intake to prevent wastes from building up in the blood. Vegetarian sources of protein include seitan (wheat gluten), tofu, tempeh, nuts and nut butters, eggs and egg substitutes, and meat analogues (soy burgers, veggie hot dogs, etc.).
• Sodium Restriction: Some vegetarian foods can be high in sodium, especially processed and commercially-produced plant proteins. Limit the use of frozen meals, canned soup, dried soups, miso, packaged vegetable broths, processed cheese, salted nuts, salty sauces, and snacks.
• Potassium Management: Routine blood testing is necessary to monitor potassium levels. If levels are high, limit fruit and vegetable servings to five per day. Choose fruits and vegetables with lower potassium content. Soybeans, textured vegetable protein, soy nuts, and soy flour are also high in potassium.
• Phosphorus Restriction: Dairy products, dark colas, and processed foods can be high in phosphorus. Limit soy yogurt, rice milk, and soy milk to one serving per day. Whole grains are a better source of phosphorus than white breads and grains due to the presence of phytates, which reduce phosphorus absorption.
• Vitamins and Minerals: Consult a doctor or dietitian to determine if vitamin and mineral supplements are necessary. Most people with kidney disease will require a water-soluble vitamin without fat-soluble vitamins or minerals.
• Calorie Monitoring: Ensure you are consuming enough calories by including calorie supplements when needed.
• Dialysis Considerations: For those on dialysis, a lower potassium dialysate may be suggested to control potassium levels.

It is important to work closely with a doctor and dietitian to adapt a vegetarian diet to the specific needs of kidney patients. This may include adjusting the diet as needed for acceptable urea clearances and providing renal education materials.

The best vegetarian foods for kidney patients

Vegetarian diets can be safe and beneficial for kidney disease patients with careful planning. Here are some of the best vegetarian foods for kidney patients:

• Whole grains: Whole grains such as whole grain pasta, brown rice, barley, quinoa, millet, couscous, and amaranth are excellent sources of fibre and healthy nutrients. They can help fill out your diet and provide essential vitamins and minerals.
• Fruits and vegetables: These are an important part of a kidney-friendly diet as they are rich in antioxidants, which help protect your cells from damage. However, some fruits and vegetables are high in potassium, so it is important to monitor your intake. Selecting lower-potassium options and limiting your intake to five servings per day can help keep your potassium levels in check.
• Legumes: Beans, peas, and lentils are good sources of plant-based protein. However, they are also high in potassium and phosphorus, so it is important to include them in your diet in moderation and consult with a dietitian to determine the appropriate amount for your specific needs.
• Unsalted nuts: Nuts are a great source of protein and healthy fats for vegetarians. However, they can be high in sodium and phosphorus, so it is important to choose unsalted varieties and consume them in moderation.
• Soy products: Tofu, tempeh, and soy milk are excellent sources of protein for vegetarians. They are versatile and can be used in a variety of dishes. However, it is important to check the product labels to monitor your intake of sodium, potassium, and phosphorus.
• Eggs: Eggs are a good source of protein and can be included in a kidney-friendly vegetarian diet. They are also a complete protein, meaning they provide all the essential amino acids your body needs.
• Dairy products: While dairy products like milk and cheese can be a good source of protein, they should be consumed in moderation due to their high phosphorus content. Non-dairy alternatives like rice milk and soy milk can be good substitutes, but be sure to choose unsweetened varieties to avoid added sugar.

It is important to work with a dietitian or healthcare professional to determine the specific needs of your body and create a meal plan that works for you. They can help you monitor your nutrient intake and make adjustments as needed to ensure you are getting the proper nutrition while managing your kidney disease.

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