By Jody Paglia Tanzman, RD,LDN,CLC
When you’re chopping up fruits and vegetables for juices and smoothies, it seems as if half of the produce goes in the garbage in the form of rinds, peels and skins. Well guess what, you might have been throwing away some valuable nutrients! Rich in health-protective phytochemicals and antioxidants, the outer layers of fruits and vegetables are often more nutritious than the food they protect. Ever wondered if you could do something with them? Read on below for some common foods you might want to add to your diet.
(Please note that all produce must be washed thoroughly before being eaten, and to minimize exposure to pesticides and other harmful chemicals, organic produce is recommended when eating raw skins and peels).
There are over 60 different types of flavonoids in citrus, plant compounds that are known to exhibit antioxidant properties in humans. Many of these flavonoids have their highest concentrations within the peel. Naringin is a flavonoid found in grapefruit and grapefruit peel, mandarin peel and lemon peel (though not the fruit). Studies have shown that naringin is a powerful antioxidant, so powerful that it may reduce radiation-induced damage to the cells of the body. (Note that naringin can also increase the effects of certain drugs; you should consult with your doctor if you regularly consume these foods). Hesperidin, another flavonoid, is found in the white inner layer of lemons, limes, grapefruit and oranges, and has been shown to inhibit bone loss and decrease serum and liver lipids in postmenopausal mice.
Citrus peels also contain an aromatic compound called d-limonene, basically the essential oil that gives the fruit its distinctive smell. This compound has a well-established reputation for chemopreventive activity against many types of cancer, especially colorectal and breast cancer. Limonene is also used in the treatment gastroesophageal reflux disease (GERD) due to its ability to neutralize gastric acid. In addition, limonene is a solvent of cholesterol and can help dissolve gallstones that contain cholesterol.
Gram for gram, citrus peels also contain higher levels of many minerals and vitamins such as vitamin C and dietary fiber than the fruit. For example, 1 tablespoon of lemon peel contains double the amount of vitamin C and triple the amount of fiber than 1 wedge of lemon without the peel, according to the USDA database.
Though citrus peels may be considered by some people to be bitter tasting, in some populations, such as the American Southwest, citrus peel consumption is rather common. How to use those peels? Juice them! Though many people peel their fruit before juicing, a good powered juicer will be able to handle the peel of citrus fruits. Joe himself juices his citrus with their peel on. You can also zest or grate the peel to infuse the essence of citrus within smoothies and baked goods. Grated peel or finely chopped peel also adds a bright flavoring in savory dishes and sauces.
I love watching my son eat watermelon. He’ll hungrily gobble up all of the juicy pink fruit, but the moment he gets to the tart white rind, his mouth twists into what can only be called a grimace. Yes, the white rind is tart, but by throwing away the rind, not only are you discarding about 40% of the fresh weight of the watermelon, you are losing a potent source of citrulline. Citrulline is an amino acid that is converted to arginine in the body. Arginine increases blood flow, decreasing blood pressure and improving overall cardiovascular health. Arginine may also have an anti-diabetic effect. Dietary arginine supplementation has been shown to decrease blood sugars in diabetic rats, and a 2011 research study published in Food Science & Biotechnology found that mice supplemented with an extract of watermelon rind had both increased insulin levels and decreased blood glucose levels.
Watermelon rind is also lower in sugar content than the flesh, and higher in potassium and dietary fiber (that’s a lot of useable garbage!). Instead of throwing the white rind away, when you cut up the watermelon flesh leave some of the white rind attached. You can juice the watermelon this way, or add it to smoothies. If you find the result a little bitter, the addition of sweet fruits and/or spices such as fresh ginger will offset the bitterness. Pickled watermelon rind is also a classic Southern alternative to pickles.
Strange as it may sound, in some parts of the world eating a mango with its skin on is the norm. Perhaps those cultures know that the mango skin contains a significant amount of antioxidants and healthful compounds that are only found in small amounts in the mango pulp. Mangiferin is a phytochemical found in large amounts in the skin. A powerful antioxidant, mangiferin has been found to have anti-inflammatory and anti-tumor properties in numerous research studies. Mangiferin may be especially effective as a protectant against skin cancer and this UV-protectant ability is valued in the cosmetics industry.
Mangoes can be eaten raw with their skin on, though some people may not like the texture or find the taste to be bitter. If you find that to be the case, cut up the mango with its skin and blend in a high powered blender, mixing with other fruits and vegetables. Choose some of the thinner skinned varieties and make sure the fruit is ripe, as that is when the skin is at its thinnest. Like the watermelon rind, mango skin can be pickled. Mango skin can also be sun or oven dried to make a crunchy chip.
While mango skin is edible, please note that it can cause an allergic reaction in some people. Known as “mango itch” in Hawaii, the sap of the mango tree and mango skin contain urushiol, the same compound responsible for the itchy skin rash seen in poison ivy and poison oak. People who are sensitive to poison ivy and oak may also be sensitive to the urushiol in mangoes and should avoid eating the skin.
This denotes the papery skin beneath the shell that surrounds the peanut. This skin is discarded in peanut manufacturing due to the high fatty oil content that can turn rancid and limit shelf life. Most peanut butters are made with blanched peanuts where the skin is discarded, which is quite a shame, as the skin contains high amounts of antioxidants. In fact, according to a 2005 study, peanut skin contains double the amount of total antioxidants than the highly touted green tea.
One of these antioxidants is resveratrol, which is also found in the skins of red grapes. Resveratrol promotes cardiovascular health by inhibiting the formation of blood clots and reducing inflammation (preventing atherosclerosis). Though also thought to defend the body against cancer through its assistance in cancer cell death, among other things, resveratrol might be best known for its defense against aging.
The easiest way to incorporate peanut skins into your diet is to buy roasted peanuts in their shell. Break open the shell and consume both peanut and skin. Some health food stores may also have unskinned peanuts available to grind for peanut butter.
This refers to the hard, dark green part of the leek at the top that I must admit I have always thrown away in favor of the white and light green parts (No it’s not a peel, but it’s something we typically throw away and shouldn’t!). I was always told that the dark green parts weren’t edible. Boy, was I wrong. Not only are the leaves edible, but according to several studies, the leaves have stronger antioxidant properties than the rest of the leek. Kaempferol is found in large quantities in the leek leaves. Like resveratrol, kaempferol has been shown to inhibit arterial plaque formation and prevent oxidative damage to our cells. Kaempferol is also chemopreventive, inhibiting the formation of cancer cells within the body.
While the green leaves are thicker than the shaft of the leek, they only need a little time to cook. The secret is to slice them fairly thinly, in rounds or strips. Braise them in a little stock, or sauté them in a little oil over medium heat until lightly browned and use as a garnish. Chop them up and add them to your vegetables when making stocks. If you blanch them first (to make them malleable), you can also use the leaves to roll with tofu, fish or other protein, infusing it with a mild oniony flavor.
Now you won’t be throwing away so much wonderful produce when you’re juicing and cooking in the kitchen!