Collard greens are a nutritious leafy green vegetable that have long been a staple of Southern American cuisine. They are packed with vitamins, minerals and fiber. However, for people with kidney disease, certain foods like collard greens may need to be limited in the diet. This article provides an overview of collard greens, their nutrient content and if and how they can be included in a kidney-friendly diet.
What Are Collard Greens?
Collard greens are a cruciferous vegetable in the same family as kale, broccoli and Brussels sprouts. They have dark green, loosely layered leaves with a slightly bitter taste. Collard greens are a staple vegetable in soul food and Southern U.S. cuisine, often cooked low and slow with smoked meats.
However, collard greens are growing in popularity across the country as people recognize their stellar nutritional benefits. They can be sautéed, braised, stewed, grilled or even eaten raw in salads. Popular collard green dishes include collard greens with bacon, braised collard greens, and collard green slaw.
Nutrient Profile of Collard Greens
Collard greens are one of the most nutrient-dense foods you can eat. A 1 cup serving (190g) of chopped collard greens contains 1:
|Nutrient||Amount||% Daily Value*|
|Vitamin A||448 mcg||50%|
|Vitamin C||52 mg||60%|
|Vitamin K||547 mcg||454%|
*Percent Daily Values are based on a 2,000 calorie diet.
As you can see, collard greens are packed with important vitamins and minerals like vitamins A, C and K, calcium, iron and potassium. They are one of the best sources of vitamin K, providing over 450% of the daily recommended value in just one cup.
They also contain a hefty dose of fiber, with 7.6 grams per serving. Fiber supports digestion and heart health. It also helps feed the healthy bacteria in your gut microbiome.
Additionally, collard greens contain beneficial plant compounds like anthocyanins, quercetin and sulforaphane that have antioxidant and anti-inflammatory effects in the body 2.
Benefits of Collard Greens
Regularly eating collard greens and other leafy green vegetables has been linked to many health benefits:
* Improve digestive health – The fiber content in collard greens acts as a prebiotic to support the growth of probiotics in the gut. Their magnesium and potassium help relieve constipation.
* Support heart health – Collard greens contain potassium and vitamin K which help reduce blood pressure and prevent calcification of arteries.
* Reduce inflammation – The antioxidants in collard greens buffet free radicals that can trigger widespread inflammation in the body.
* Lower cholesterol – The fiber and bile acid-binding properties of collard greens have been shown to reduce LDL (bad) and total cholesterol.
* Support bone health – The calcium, magnesium and vitamin K in collard greens promotes bone growth and reduces the risk of fractures.
* Aid blood clotting – The high vitamin K content helps activate proteins involved in blood clotting.
* Provide antioxidant protection – Collard greens are packed with antioxidants that protect cells against oxidative damage.
* May lower cancer risk – Studies show the antioxidants and anti-inflammatory compounds in collard greens may reduce the risk of certain cancers.
Clearly, adding collard greens to your diet provides a major health boost. But can kidney patients also reap these benefits from collard greens? Let’s find out.
Kidney Disease and Diet
For people with chronic kidney disease (CKD), diet can have a major impact on kidney function and overall health. In CKD, damaged kidneys are unable to properly filter waste products and excess fluid from the blood.
This can cause a build up of waste products in the bloodstream, resulting in symptoms like nausea, loss of appetite, fatigue and itchiness. Over time, untreated kidney disease can lead to complications like anemia, bone disease and heart disease.
That’s why people with kidney disease may need to follow special diets like the kidney diet or renal diet recommended by their doctor or dietitian. The goals of the kidney diet are typically to 3:
* Limit phosphorus intake – Healthy kidneys remove excess phosphorus from the blood. In kidney disease, blood phosphorus levels can become too high, pulling calcium from the bones.
* Limit potassium intake – Excess potassium can also build up when kidneys are not working properly. High blood potassium can cause dangerous heart arrhythmias.
* Limit sodium intake – For people with high blood pressure or fluid retention, sodium intake needs to be moderated to reduce blood pressure and fluid overload.
* Manage protein intake – Getting adequate protein is important for health but not overdoing it, as waste products from protein metabolism must be filtered out by the kidneys.
* Limit fluids – For individuals with fluid retention, excess fluids in the diet can burden the kidneys.
With all these dietary restrictions, kidney patients may wonder if they can include healthy, nutritious foods like collard greens in their diets. Let’s look at some guidelines around eating collard greens with kidney disease.
Can You Eat Collard Greens on a Kidney Diet?
The answer is generally yes – collard greens can be part of a kidney-friendly diet in moderation. Here are some tips for including collard greens if you have kidney disease:
– Focus on the potassium content. Collard greens contain 218 mg potassium per 1 cup serving. For comparison, 1 cup kale has 299 mg potassium and 1 cup spinach has 839 mg. So collard greens have relatively low to moderate potassium compared to other leafy greens. Work with your renal dietitian to determine the right potassium limits for you.
– Watch your phosphorus intake. Cooked collard greens have 60 mg phosphorus per cup. While not extremely high in phosphorus, this mineral can add up over the course of a day for kidney patients. Try balancing intake of higher phosphorus greens like collard greens with lower phosphorus vegetables.
– Moderate portion sizes. Stick to 1/2 to 1 cup serving sizes of collard greens and be mindful of how they fit into your total nutritional needs for the day. Larger portions may provide too much potassium, phosphorus or other minerals.
– Cook properly. Boiling collard greens can reduce the potassium and phosphorus content. Discard the cooking water which will contain some of the leached minerals. Steaming and sautéing also retain less minerals than eating collard greens raw.
– Manage with medications. Your doctor may adjust doses of potassium-lowering medications like kayexalate or sodium polystyrene sulfonate to help maintain safe blood potassium levels if your diet includes higher potassium foods like collard greens.
– Work with a renal dietitian. Get individualized nutrition advice from a specialist who can help you create meal plans that include collard greens and other produce you enjoy in kidney-friendly portions. This helps ensure you get important nutrients while avoiding any dietary extremes.
With the right preparation methods and portion sizes, collard greens can be incorporated into many kidney diets. Always check with your healthcare providers about specific recommendations for your individual dietary needs.
Nutrient Substitutions for Collard Greens
If collard greens need to be limited or avoided in your diet, don’t worry – you have options. Here are some nutrient-dense substitutes for collard greens that may work better for your kidney diet:
|Fiber||Green beans, summer squash, egg whites, berries|
|Vitamin A||Carrots, butternut squash, red bell peppers|
|Vitamin C||Broccoli, cauliflower, strawberries, oranges|
|Vitamin K||Brussels sprouts, parsley, cucumbers, asparagus|
|Calcium||Almond milk, calcium-set tofu, navy beans|
|Iron||White beans, lentils, spinach, pumpkin seeds|
|Magnesium||Edamame, banana, halibut, brown rice|
These foods can provide vitamins, minerals and other nutrients similar to collard greens but are lower in potassium, phosphorus and other compounds that need to be limited in kidney diets. Work with your dietitian to come up with more alternatives to create nutritious, varied and delicious kidney-friendly meals.
Kidney-Friendly Ways to Cook Collard Greens
If you can include collard greens in your diet, here are some healthy ways to prepare them:
– Sautéed Collards – Thinly slice collards and sauté with olive oil, garlic, onions and seasonings. Finish with a squirt of lemon juice.
– Braised Collards – Simmer chopped collards in low-sodium vegetable or chicken broth until tender and season with pepper or red pepper flakes.
– Steamed Collards – Steam over boiling water until bright green and just tender then toss with lemon-pepper seasoning.
– Collard Rolls – Blanch collard leaves then fill with hummus, roasted vegetables or other filling. Roll up burrito-style.
– Massaged Kale Salad – Massage sliced collards with lemon juice and olive oil then stir in other veggies, nuts and seeds for a salad.
– Roasted Collards – Toss chopped collards with a little oil then roast in oven until crispy. Sprinkle with parmesan cheese if desired.
Sticking to simple preparations with limited added sodium is best for kidney diets. Play with different seasonings like garlic, onions, vinegar, spices and herbs to keep collard greens flavorful.
Should Kidney Patients Take Collard Green Supplements?
Collard greens can also be taken in supplement form, like capsules made from collard green powder or extracts. However, these should be used cautiously in kidney disease.
The concentrated nutrients in collard green supplements can provide excessive amounts of potassium, vitamin K, vitamin C and other compounds that need to be limited in kidney diets. For example, a typical collard greens supplement may contain:
– 800-1200 mcg vitamin K (up to 100 times more than 1 cup raw collard greens)
– 100-200 mg vitamin C (4-8 times more than 1 cup raw collard greens)
– 200-400 mg potassium (double that of 1 cup raw collard greens)
These high levels make collard greens supplements generally unsuitable for people with kidney failure or on dialysis. Excessive intake of certain nutrients like potassium through supplements can be dangerous for kidney patients.
Always talk to your nephrologist before taking any new supplements, including collard green supplements. They can review the product to see if it may be safe in limited amounts for your individual condition. But for most people with impaired kidney function, getting nutrients from real, whole collard greens is the better option.
The Role of Collard Greens in a Kidney Diet
To sum up, collard greens can be part of a healthy diet for many people with kidney disease when consumed in moderation. Sauteeing, braising, steaming or boiling collard greens can reduce mineral content to appropriate levels. Pay attention to overall daily potassium, phosphorus and fluid intake when incorporating collards.
Work closely with your healthcare team to personalize your diet and find the right balance of nutritious produce like collard greens. With smart preparation methods and portion control, collard greens can provide vitamins, minerals and health benefits without straining your kidneys.
1. U.S. Food Data Central. Collards, cooked, boiled, drained, without salt. https://fdc.nal.usda.gov/fdc-app.html#/food-details/169918/nutrients
2. Leighton, F et al. The Impact of the Flavonoid-Rich Foods on Cardiovascular Diseases. _Current Medicinal Chemistry_. 2018. https://pubmed.ncbi.nlm.nih.gov/29580576/
3. The National Kidney Foundation. Potassium and Your CKD Diet. https://www.kidney.org/atoz/content/potassium