Acute Kidney Injury (AKI) is a sudden decrease in kidney function that can occur in critically ill individuals, sometimes superimposed on Chronic Kidney Disease (CKD). AKI can lead to significant health complications and increased risk of mortality. Nutrition plays a crucial role in managing AKI, helping to offset metabolic complications and improve patient outcomes. This article provides a comprehensive guide to dietary guidelines for AKI, incorporating recommendations from leading health organizations and experts in the field.
Understanding Acute Kidney Injury (AKI)
AKI is characterized by a rapid decline in kidney function, often determined by changes in serum creatinine and urine volume. While changes in serum creatinine are also monitored in CKD, the timeframe for these changes is significantly different in AKI, with a more acute and dramatic shift in kidney function. The onset of AKI triggers metabolic changes, leading to hypermetabolism and hypercatabolism, affecting various systems in the body.
General Principles of a Renal Diet
People with compromised kidney function must adhere to a renal or kidney diet to cut down on the amount of waste in their blood. Wastes in the blood come from food and liquids that are consumed. When kidney function is compromised, the kidneys cannot filter or remove waste properly. If waste is left in the blood, it can negatively affect a patient’s electrolyte levels. A renal diet is one that is low in sodium, phosphorous, and protein. A renal diet also emphasizes the importance of consuming high-quality protein and usually limiting fluids. Some patients may also need to limit potassium and calcium.
The DASH Diet: A Foundation for Kidney Health
The Dietary Approaches to Stop Hypertension (DASH) Diet is often recommended for individuals with kidney disease. This diet emphasizes fruits, vegetables, whole grains, and low-fat dairy products. The DASH Diet is endorsed by the National Kidney Foundation, The National Heart, Lung and Blood Institute, The American Heart Association, the Dietary Guidelines for Americans, and the USDA MyPyramid.
Key Components of the DASH Diet
The DASH Diet is rich in:
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- Fruits
- Vegetables
- Low-fat dairy products
- Whole grains
- Fish
- Poultry
- Beans
- Seeds
- Nuts
It is low in:
- Salt and sodium
- Added sugars and sweets
- Fat
- Red meats
Who Should Follow the DASH Diet?
The DASH diet is a recognized treatment for hypertension, heart disease, and kidney disease and can slow the progression of heart and kidney disease. If you already have chronic kidney disease, you should speak with your doctor and dietitian before starting any new diets as you may have special restrictions to consider. The DASH diet should not be used by people on dialysis. Individuals on dialysis have special dietary needs that should be discussed with a registered dietitian.
Example DASH Diet (2,000 Calorie)
| Food Group | Daily Servings | Serving Size |
|---|---|---|
| Grains | 6-8 | 1 Slice bread, 1 oz dry cereal, ½ cup cooked rice, pasta, or cereal |
| Vegetables | 4-5 | 1 cup raw leafy vegetable, ½ cup cut-up raw or cooked vegetable, ½ cup vegetable juice |
| Fruits | 4-5 | 1 medium fruit, ¼ cup dried fruit, ½ cup fresh, frozen, or canned fruit, ½ cup fruit juice |
| Fat-free or low-fat milk products | 2-3 | 1 cup milk or yogurt, 1 ½ oz cheese |
| Lean meats, poultry, and fish | 6 or less | 1 oz cooked meats, poultry, or fish, 1 egg |
| Nuts, seeds, and legumes | 4-5 per week | 1/3 cup or 1 ½ oz nuts, 2 Tbsp peanut butter, 2 Tbsp or ½ oz seeds, ½ cup cooked legumes (dry beans and peas) |
| Fats and oils | 2-3 | 1 tsp soft margarine, 1 tsp vegetable oil, 1 Tbsp mayonnaise, 2 Tbsp salad dressing |
| Sweets and added sugars | 5 or less/week | 1 Tbsp sugar, 1 Tbsp jelly or jam, ½ cup sorbet, gelatin, 1 cup lemonade |
- Whole grains are recommended for most grain servings as a good source of fiber and nutrients.
- Serving sizes vary between ½ cup and 1 ¼ cups, depending on cereal type.
Key Nutrients to Manage in AKI
Sodium
Sodium is a mineral found in most natural foods and is one of the body’s three major electrolytes (along with potassium and chloride). Electrolytes control the fluids going in and out of the body’s tissues and cells. Too much sodium can be harmful for people with kidney disease because their kidneys cannot adequately eliminate excess sodium and fluid from the body.
Recommendations for Sodium Intake
- Read Food Labels: Always check food labels for sodium content.
- Limit Processed Foods: Avoid packaged foods, frozen dinners, canned soups, and fast foods, which often contain added salt.
- Use Herbs and Spices: Use herbs and spices for flavor while cooking instead of adding salt.
- Fresh or Frozen Vegetables: Choose fresh or frozen vegetables over canned ones. If using canned vegetables, drain and rinse them to remove extra salt.
Potassium
Potassium is a mineral found in many foods and is essential for keeping the heartbeat regular and muscles working correctly. When the kidneys fail, they can no longer remove excess potassium, leading to a buildup in the body.
Recommendations for Potassium Intake
- Monitor Potassium Levels: Regularly monitor potassium levels through blood tests.
- Limit High-Potassium Foods: Depending on individual needs, limit high-potassium foods such as bananas, oranges, cantaloupe, dried fruits, winter squash, and salt substitutes.
- Choose Low-Potassium Foods: Opt for low-potassium options like apples, peaches, carrots, green beans, white bread, and white rice.
- Be Mindful of Elevated Blood Sugars: Elevated blood sugars can increase potassium levels.
Phosphorus
Phosphorus is a mineral critical in bone maintenance and development. Normal working kidneys remove extra phosphorus in the blood. When kidney function is compromised, the kidneys no longer remove excess phosphorus, leading to high levels that can weaken bones.
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Recommendations for Phosphorus Intake
- Avoid Processed Foods: Avoid packaged foods that contain added phosphorus. Look for additives with "PHOS" in the ingredients list.
- Limit High-Phosphorus Foods: Reduce intake of dairy products, organ meats, colas, deli meats, and processed foods with phosphate additives.
Protein
Protein is necessary for building muscle, repairing tissue, and fighting infection. The proper consumption of protein is tricky for Chronic Kidney Disease patients as the amount differs with each stage of disease.
Recommendations for Protein Intake
- High-Quality Protein: Emphasize high-quality protein sources.
- Individualized Protein Needs: The amount of protein needed varies with each stage of kidney disease.
- Plant-Based Protein: Plant-based proteins like beans and nuts are easier on the kidneys than animal proteins.
- Avoid Unnecessary Supplements: Avoid very large amounts of protein, especially in the form of unnecessary supplements.
Fluids
Fluid needs can vary depending on the patient. When estimating these goals, account for serum sodium, hyper- or hypovolemia, urine output, and kidney function.
Recommendations for Fluid Intake
- Individualized Fluid Allowance: A patient’s fluid allowance is calculated on an individual basis, depending on urine output and dialysis settings.
- Monitor Fluid Intake: Carefully monitor fluid intake to avoid fluid buildup, which can lead to swelling and stress on the heart and lungs.
- Limit Fluids: Limit fluids based on urine output and fluid build-up, including beverages, soups, gelatin, frozen desserts, and ice.
- Tips to Manage Thirst: Chew gum, rinse your mouth with water and spit it out, suck on a piece of ice, mints, or sugar-free hard candy.
Calories
Calories are like fuel. If you don’t eat enough, your body will take protein from the muscles for energy. It’s important to make sure you get the right number of calories. If you don’t, you may get weak and damage your kidneys.
Recommendations for Calorie Intake
- Adequate Calorie Intake: Ensure adequate calorie intake to prevent the body from using protein from muscles for energy.
- Healthy Weight: Maintain a healthy weight to avoid burdening the kidneys.
- Weight Loss: If overweight, some weight loss may be helpful under the guidance of a dietitian.
Additional Dietary Considerations
Vitamins and Minerals
Kidney patients may need to limit some foods. If so, you may need to take special vitamin or mineral supplements, but only if a dietitian or healthcare provider tells you to. Some vitamins or mineral supplements may be harmful to people with kidney disease.
Recommendations for Vitamins and Minerals Intake
- Special Supplements: Take special vitamin or mineral supplements only if recommended by a dietitian or healthcare provider.
- Avoid Over-the-Counter Supplements: Check with your healthcare provider before taking any medications you can buy without a prescription.
- Kidney-Specific Supplements: Consider a special supplement made for people with kidney disease or specific supplements like vitamin D, folic acid, or iron.
- Avoid Herbal Supplements: Avoid taking herbal supplements.
Considerations for Diabetes
If you have diabetes, you need to control your blood sugar to prevent more damage to your kidneys.
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Recommendations for Diabetes
- Control Blood Sugar: Control blood sugar to prevent further kidney damage.
- Consult a Dietitian: Work with a dietitian to create an eating plan that helps control blood sugar while limiting sodium, phosphorus, potassium, and fluids.
- Diabetes Educator: Consider consulting a diabetes educator for better management of diabetes.
Portion Control
Good portion control or watching how much you eat is important in a kidney-friendly eating plan, because you may need to limit how much of certain things you eat and drink.
Tips for Portion Control
- Read Nutrition Labels: Learn the serving size and nutrient content.
- Measure Portions: Use nutrition facts lists to measure the right portions for foods without nutrition labels.
- Eat Slowly: Eat slowly and stop when full.
- Avoid Distractions: Avoid eating while watching TV or driving.
Working with a Dietitian
Meeting with a dietitian is a service covered by Medicare and may also be covered by other types of insurance. You may need to call your insurance provider to see if your plan covers meeting with a dietitian.
Benefits of Consulting a Dietitian
- Tailored Nutrition Plan: Create a tailored nutrition plan based on individual preferences and needs.
- Medical Nutrition Therapy (MNT): Receive medical nutrition therapy, an approach to treat kidney disease through a tailored nutrition plan.
- Overcome Eating Challenges: Get help overcoming eating challenges and adjusting to dietary changes.
Nutrition Support in AKI
Experts suggest that nutrition support can have a significant impact on AKI. Using nutrition to offset the multiple metabolic complications associated with this kidney injury can help to improve patient outcomes.
Protein Needs in AKI
Protein catabolism largely drives an individual’s need for this nutrient. Inflammation makes it difficult for the patient to reach a positive protein balance and evidence suggests aiming for a neutral nitrogen balance may be more reasonable.
Energy Needs in AKI
While indirect calorimetry is the preferred method for measuring energy needs in this patient population, this option is not always available to the RDN.
Fat Needs in AKI
Recommendations for percentage of total calories from fat with AKI are not all that different from estimates in a critically ill patient. As mentioned, changes in cholesterol and triglycerides may occur as part of the metabolic response to AKI.
Lifestyle and Home Remedies
During your recovery from acute kidney injury, a special diet can help support your kidneys and limit the work they must do.
General Recommendations
- Choose Foods Lower in Potassium: These include apples, peaches, carrots, green beans and white bread and white rice.
- Don't Eat Foods with Added Salt: This includes many packaged foods, such as frozen dinners, canned soups and fast foods.
- Limit Phosphorus: Phosphorus is a mineral found in foods, such as dark-colored sodas, milk, oatmeal and bran cereals.