4 Kidney-Friendly Spring Superfoods

 Fruits & Vegetables

by Linda Ulerich, RD, LD

With spring upon us, it is time to think about all the wonderful fruits and vegetables that are coming back into season. Lots of fruits and vegetables are labeled as "superfoods" but what does this actually mean?

While there is no medical or scientific definition of the term "superfood," most consider it to be a food that has an unusually high amount of antioxidants, vitamins or other nutrients. Often these foods are beneficial to our health and many foods fall in this category, whether they've officially been labeled as "superfoods" or not.

Remember that a healthy diet is one that contains a variety of foods, including plant-based foods, such as fruits, vegetables, whole grains, nuts and seeds and low-fat animal protein sources.

The two leading causes of kidney disease are diabetes and high blood pressure, but when these conditions are controlled, kidney disease can often be prevented or slowed down. Making healthy food choices and controlling sugar, fat, and sodium intake can make a big difference in managing the risk factors for kidney disease and protecting the kidneys.

Foods such as dried beans, salmon, and nuts and seeds are nutrient-rich and considered to be superfoods due to their nutrient content. These are typically available year-round, and their high nutrient content can be due to the high level of minerals, omega-3 fatty acids, protein sources, or antioxidants. Some fruits and vegetables that "peak" in spring, or are typically in season this time of year, are considered kidney-friendly* superfoods. Let's see why certain foods make the list:

  1. Blueberries are rich in vitamins C and K, in manganese, and antioxidants. They are a good source of soluble fiber and only 80 calories per cup. They are plentiful in the spring. Tasty fresh, blueberries can easily be frozen for later use and freezing blueberries does not damage the antioxidants they contain. Blueberries also have a low glycemic index (GI), which means they have a lower impact on blood sugars levels once digested. The GI for blueberries is around 50 per serving and other "superfood" berries such as blackberries, raspberries and strawberries have a GI of 30-40—making them all great choices for those wanting to control blood sugars.
  2. Kiwifruit**, also known as Chinese gooseberries, is considered a superfood because it is high in vitamin C, potassium, fiber, antioxidants and serotonin levels. A study involving kiwifruit consumption showed improved sleep onset, duration, and efficiency in adults with self-reported sleep disturbances, indicating that the antioxidants and serotonin in kiwifruit may be beneficial in the treatment of sleep disorders.1 A half cup of kiwifruit contains 52 calories and a low GI of 7.
  3. Kale and other dark leafy greens such as Swiss chard, collards, and spinach are also considered superfoods as they are all rich in vitamins A, C, K, fiber and calcium. Kale contains only 33 calories in 1 cup (raw) and has a very low GI of 3. Kale is considered to have an edge over the other dark greens because it has one of the highest ORAC ratings. ORAC stands for oxygen radical absorbance capacity, which measures foods' ability to scavenge free radicals. Free radicals are unstable molecules in our body that are known to cause cellular damage. Free radical damage is believed to play a role in certain diseases or disorders such as cardiovascular disease, asthma, Alzheimer's disease, and macular degeneration. Studies have also indicated that kale may be one of the best foods to fight urinary tract infections due to its high pro-vitamin A content.2
  4. Broccoli** is a cruciferous vegetable and is considered a superfood because it is a good source of vitamin C, A, and K, calcium, potassium and folate, as well as fiber, beta-carotene and other antioxidants. Two antioxidants in particular, indole-3-carbinol and sulforaphane may have a role in reducing some forms of cancer.3 The National Cancer Institute has clinical trials underway to determine if indole-3-carbinol is a possible cancer preventive agent.4 One cup of raw broccoli has 30 calories with 6 grams of carbohydrate giving it a low GI of only 3. Many other cruciferous vegetables are also considered superfoods, including cauliflower, Brussels sprouts, cabbage and bok choy.

For those needing to limit sodium in their diet, it's important to know that all fruits and vegetables are naturally low in sodium. The advantage of eating fresh fruits and vegetables is that we get all the nutrients and fiber, and none of the sugar or salt that can be added to frozen and canned varieties. If you're shopping in the canned or frozen food section, be sure to read product labels to see what may have been added to the products you're considering.

*This article is meant to offer general health information. Before you make changes to your daily diet, consult with your doctor, dietitian or other healthcare practitioner to ensure your diet meets your nutritional and overall needs.

**Broccoli and kiwifruit are considered high potassium food choices and should be limited by people on dialysis and those with a dietary potassium restriction.

Citations

  1. http://apjcn.nhri.org.tw/server/APJCN/20/2/169.pdf
  2. http://web.b.ebscohost.com/ehost/pdfviewer/pdfviewer?vid=2&sid=82fd0610-b5dc-4702-a7d8-722f516dadc3%40sessionmgr110&hid=110
  3. Balk JL. Indole-3-carbinol for cancer prevention. Altern Med Alert 2000; 3:105-7.
  4. http://www.cancer.gov/drugdictionary?cdrid=38058