With lupus, the immune system attacks healthy cells anywhere in the body. When lupus attacks the kidneys, it’s called lupus nephritis. The kidneys are the body’s primary filtration system, so your diet directly impacts your renal (kidney) health. Your kidneys are responsible for regulating the electrolytes in your bloodstream, processing protein, and removing toxins.

People with lupus nephritis need to be particularly mindful of what they eat and drink to avoid additional kidney damage and other complications. The severity of your condition will determine how strict you must be with nutrition.

The five tips below are based on the top two types of foods to eat more of and three food items to avoid if you’re living with lupus nephritis. You’ll also find recommendations on other dietary considerations when managing life with the condition.

Learning which foods to eat and which ones to avoid with lupus nephritis may seem overwhelming at first. But with the support of your nephrologist, a registered dietitian nutritionist, or another expert who specializes in kidney health, you’ll be well on your way to understanding the best diet for your needs.

1. Increase Healthy Fats

Having impaired kidney function may seem to limit the variety of foods you can eat. Adding heart-healthy unsaturated fats to your meals and snacks is a good way to keep your calories up and maintain a healthy weight. In particular, anti-inflammatory omega-3 fatty acids are beneficial for autoimmune diseases because they promote healthy immune function. You can get omega-3s from plant sources, such as nuts and seeds, and from animal sources, including sardines, salmon, and other fatty fish.

Researchers have found that flaxseed offers protective effects against lupus nephritis. For example, it can delay the spillage of protein into the urine (called proteinuria), and it can preserve the glomerular filtration rate, which is a key indicator of kidney disease. Flaxseeds can be added to granola, cereal, yogurt, baked goods, or smoothies. The fiber in flaxseeds can make them difficult to digest, so you can grind them up to release their maximum benefits.

Here are some food combinations you could try to boost your intake of healthy fats:

• Almond, cashew, or peanut butter on toast or apple slices
• Canned or smoked salmon in place of tuna salad or cold cuts
• Chia seeds mixed into yogurt or oatmeal
• Guacamole on crackers or sandwiches
• Hemp hearts on salads
• Olive oil and vinegar for salad dressing
• Walnuts in baked goods

2. Choose Low-Potassium Fruits and Vegetables

Fruits and vegetables are essential for good health. Many fruits and vegetables contain the nutrient potassium, which helps to keep cell fluid at the right level. Unfortunately, too much potassium can be dangerous if your kidneys aren’t functioning at full capacity. Choosing lower-potassium options will give you vitamins, minerals, antioxidants, and dietary fiber while protecting your kidneys.

Examples of lower-potassium fruits and fruit-based foods (with less than 150 milligrams per half cup) include:

• Applesauce
• Blueberries
• Cranberries
• Eggplant
• Pineapple
• Watermelon

Vegetables that aren’t too high in potassium include:

• Cucumbers
• Endive
• Onions
• Raw cabbage

Spacing your intake throughout the day will give your kidneys more time to process potassium from food, so your blood levels are less likely to spike suddenly. It’s important to keep in mind that whole grains, beans, and legumes also contain potassium, so you should be mindful of your total potassium intake from multiple sources.

Healthy fat sources such as avocados and nuts are high in potassium, so talk to your doctor about your specific potassium restrictions to determine the right serving sizes for you.

3. Reduce Sodium in Your Diet

Sodium can cause high blood pressure and put added strain on your kidneys. Moderating how much sodium you consume is one of the most important dietary changes to protect kidney function.

Here are some ways to cut back on sodium:

• Avoid pickled foods. Pickles, olives, and other preserved foods are typically very high in sodium.
• Cook fresh meats or choose plant-based proteins. Cold cuts, hot dogs, sausage, bacon, and jerky tend to be high in salt that’s added during processing.
• Experiment with salt-free flavors. Use fresh herbs, peppers, lemon juice, garlic, onion, or vinegar to bring flavor without sodium.
• Read food labels. When purchasing condiments, frozen meals, or snack foods, always check the label to compare how much sodium is in different brands.
• Watch out for canned items. Rinsing canned foods with water will help cut down on the sodium content. Look for sodium-free canned goods, such as beans or soups. Frozen vegetables are a sodium-free alternative to some canned vegetables.

Restaurant meals and takeout food usually have more sodium than you’d add when cooking for yourself. Check menus ahead of time to see if there are any low-sodium options, or ask your server if your food can be prepared with minimal salt.

4. Ask Your Doctor About Reducing Meat and Dairy

Your doctor may advise that you cut back on protein from meat and dairy products to minimize strain on your kidneys. Depending on the status of your kidney function, you may not need to cut out these foods completely. However, choosing smaller portions will let you enjoy your favorite dishes and get essential amino acids while doing less kidney damage. If you do need to minimize or cut out animal products and red meat, you should be able to find plant-based alternatives at your supermarket.

5. Balance Intake of High-Potassium Fruits and Vegetables

High-potassium fruits and vegetables can be tricky to handle for impaired kidneys. People with lupus nephritis should be aware of which plant-based foods are highest in potassium so they can balance their intake with other foods.

High-potassium fruits (more than 250 mg per half cup) include:

• Avocados
• Bananas
• Cantaloupe
• Dates
• Nectarines
• Oranges
• Prunes
• Pumpkin
• Tomatoes and tomato juice

High-potassium vegetables include:

• Artichokes
• Beets and beet greens
• Brussels sprouts
• Parsnips
• Potatoes
• Spinach
• Sweet potatoes

Although bananas are a popular food for snacks or breakfast, people with lupus nephritis should use caution when eating them. Since bananas are a high-potassium fruit, you’d be better off choosing apples, citrus fruits, or berries instead. If your doctor says bananas are OK, have a few slices or half a banana at a time rather than eating an entire banana in one sitting.

Cooked veggies and fruit juices are more concentrated in potassium than fresh fruits or veggies. For example, cooked leafy greens such as spinach have a lot more potassium per cup than the same portion of fresh. Ask your renal dietitian about cooking methods (such as boiling and discarding the cooking water) to extract some potassium.

Sometimes doctors put people with kidney issues on a potassium binder. This is a special type of medication that will reduce the load of potassium your body absorbs from food. You can ask your doctor if potassium binders are a good option for you and how they will affect your dietary choices.

Additional Guidelines

People with lupus nephritis may need to consider other dietary recommendations, including monitoring phosphate intake and restricting fluid intake.

Monitoring Phosphate Intake

Different amounts of the mineral phosphorus are found in various foods and beverages. Phosphorus is necessary for strong bones and teeth and other functions of the body. However, too much phosphorus can build up in the blood if the kidneys aren’t functioning properly. High phosphorus levels can weaken bones and cause high blood pressure, among other problems.

Phosphorus occurs naturally in some foods. It’s also added to many packaged foods and beverages as a preservative. Lunch meat, frozen meals, and some sodas have added phosphorus.

Your doctor may advise you to take a phosphate binder or to restrict your intake of phosphorus depending on your kidney function.

Restricting Fluid

Normally, drinking plenty of water is helpful for the kidneys. However, having lupus nephritis may mean that your body takes longer to filter out water. If you’re required to restrict fluids, you can cope with dry mouth by chewing gum, sucking on hard candy, or rinsing your mouth with water.

Ask for Help

If you’re confused about what to eat, don’t hesitate to reach out for help from your health care team. In addition to helping you understand lupus nephritis treatments, they can help you understand lifestyle behaviors that can support your health. Adjusting to a new way of eating takes time, so be patient with yourself as you focus on progress, not perfection.

Talk With Others Who Understand

MyLupusTeam is the social network for people with lupus and their loved ones. On MyLupusTeam, more than 218,000 members come together to ask questions, give advice, and share their stories with others who understand life with lupus. More than 14,000 members have lupus nephritis.

Have you had to make changes to your diet because of lupus nephritis? What challenges have you experienced, and what works well for you? Share your thoughts in the comments below, or start a conversation by posting on MyLupusTeam.