Nutrients in Peanut Skins 花生皮的營養

Peanuts are a common snack food for Americans. Peanuts are composed of a thick, outer shell and, when cracked open, have a nut or seed encased by a thin, papery skin. The shell and skin are often thrown out, as the nut is the tasty portion of the product. However, the skin has beneficial properties. Peanut skin extract is now a product that consumers can buy, but some peanut lovers eat the skin as part of the treat, and some peanut butters actually use the skin when producing the item.
 

Resveratrol

Resveratrol is produced naturally by the peanut plant and is high in the skin. It is a phytoalexin, which is an antimicrobial substance produced by plants to act as a toxin to attack organisms that pose a threat during growth. High doses of resveratrol have been shown to lower blood sugar significantly, notes the USDA. It may also fight cancer, have beneficial heart effects and, possibly, extend life. Resveratrol may have anti-aging effects, which is now a current research topic, explains the USDA.

• Peanut Oil

Peanut skins are up to 17 percent oil. The oil is mainly composed of long-chain, fatty acids, including behenic acid and lignoceric acid. Behenic acid is often a component of moisturizers and conditioners, used for its smoothing properties. A recent study conducted by North Carolina A&T State University notes that peanut skin oil is not widely used yet by all cosmetic companies, but has promising effects once laboratory extraction procedures are perfected.

Dietary Fiber

Peanut skins are also a good source of dietary fiber. Fiber is the part of the plant that is indigestible. It is broken down into soluble and insoluble fiber. Soluble fiber is fermented in the digestive tract and can help lower total cholesterol. Insoluble fiber adds bulk to food and aids in digestion. Peanut skins are a good source of both types of fiber.

Polyphenols

Polyphenols are components found in plants that provide antioxidant properties. They are found in peanut skins and nuts. Antioxidants have anti-inflammatory effects and help overall health by fighting free radicals that cause oxidation of cells. According to the United States Department of Agriculture (USDA), polyphenols may reduce the risk of cancer and cardiovascular disease. They can also have anti-aging effects and positive effects on arthritis.

http://www.livestrong.com/article/98722-nutrients-peanut-skins/

.....Yet these skins are high in phenolic compounds, meaning they have antioxidant properties. Studies on antioxidants suggest they may protect against oxidative stress, which has been implicated in a number of diseases and cancers in humans.

http://medicalxpress.com/news/2012-11-peanut-skins-boosts-nutrition.html

 

But there seem to be benefits from eating peanut skins as well. Not only are they high in fiber, but they contain reservatrol, the same antioxidant that red wine is famous for, which is also an antimicrobial, and which in lab tests has been shown to lower blood sugar and may be an important weapon in the fight against cancer.

A more recent study in 2009 showed that roasting peanuts with their skin on actually increased the amount of antioxidants in peanuts.

http://www.seriouseats.com/2011/10/whats-up-with-peanut-skins.html

Peanut skins, currently considered a waste product of industrial peanut processing, had remarkably high antioxidant capacities across all roast conditions.

These antioxidant increases upon roasting were attributed to greater concentrations of phenolic compounds and/or "browning" reaction products.

http://www.ars.usda.gov/is/pr/2009/091208.htm

 

Bioactives

Research has identified numerous compounds in peanuts and in their skins that may have added health benefits beyond basic nutrition. Peanuts have been touted as a functional food with numerous functional components. These bioactive components have been recognized for having disease preventative properties and some are antioxidants while other are thought to promote longevity. Packaged together with vitamins, minerals, and healthy fats, protein, and fiber, peanuts are a complex plant food that promotes health with each bite. Simply put, peanuts are bioactive food in a shell.

Arginine
If you want to get your blood moving, add more arginine to your diet. Peanuts can certainly help boost your levels as they have the highest level among foods. Arginine is an amino acid that is a precursor to nitric oxide. Nitric oxide helps to keep your arteries relaxed, improving blood flow. It is also known to improve healing time in tissues in your body.

Resveratrol In attempts to stay youthful, some have sought wine and grapes, but also peanuts, because they all contain a compound thought to increase endurance and contribute to longevity. This compound is resveratrol. Resveratrol is known as a bioactive compound that reduces cardiovascular disease and cancer risk. It has antioxdant properties and also reduces inflammation. All parts of the peanut contain resveratrol from the roots to the skins and even the shell (Chen, 2002; Francisco, 2008).

Many plants naturally produce resveratrol when they are under attack by pathogens such as bacteria. These attacks are a form of stress to the plant and studies are now showing that by stressing peanuts in various ways, the resveratrol content can be increased (Rudolf, 2005).

If you are wondering how much resveratrol is in peanuts, the southern style boiled peanuts have the most, even more than red wine and red grape juice on a part per million basis (Sanders, 2000). Peanut butter is not too far behind grape juice, with about three times more resveratrol than roasted peanuts with skins (Sobolev, 1999; Ibern-Gomez, 2000).

Phytosterols
You may have noticed that there are certain brands of margarine that have blended in phytosterols (or plant sterols) to the mix. This is because these compounds have been found to lower your chlolesterol. Well, a handful of peanuts can naturally offer phytosterols contributing to this same benefit.

Peanuts, peanut butter, peanut flour, and peanut oil are all filled with phytosterols that block the absorption of cholesterol from your diet. And emerging evidence is showing that they also decrease inflammation and reduce the growth of various cancers (Woyengo, 2009). In one study, researchers at the State University of New York at Buffalo found a reduction of prostate tumor growth by over 40 percent and almost a 50 percent reduction in the occurrence of spreading to other parts of the body (Awad, 2000).

The main phytosterols in peanuts include beta-sitosterol, campesterol, and stigmasterol, but new research has found that there are even more phytosterols in peanuts than was thought. In addition to the healthy fats, protein, and fiber in peanuts, phytosterols may also be contributing to the decreased risk of heart disease that has been shown in population groups who eat a small amount of peanuts daily (Awad, 2001).

Phenolic Acids
Phenolic acids have been shown to have antioxidant function and a protective role against oxidative damage diseases like coronary heart disease, stroke, and various cancers. Roasted peanuts have levels comparable to other common foods like green tea and red wine, but when the skins are kept on, levels surpass those in berries (Francisco, 2009).

New research clearly shows that peanuts and their skins are exceptional sources of functional compounds, including phenolic acids (Francisco, 2008; 2009). If you look closely at your spoonful of peanut butter, you will notice small speckles. These speckles are ground peanut skins. Spreading peanut butter on your morning toast not only satisfies your taste buds, but also brings unique benefits to our health.

Flavonoids
Flavonoids are in all parts of the peanut plant. They act as a natural pesticide and some provide potent odors or bitter flavors as a defense system, while others are antimicrobial. In foods, flavonoids are responsible for color, taste, and protection of vitamins, enzymes, and fat oxidation.

A high intake of flavonoids is thought to be protective against heart disease and cancer by various mechanisms. They may also play a role in circulation after soon after we eat. There is no recommendation for flavonoids, but research is emerging as to how these bioactive compounds are benefiting health. Peanuts and peanut butter are considered a major food source of flavonoids and contain same types found in green and black tea, apples, red wine, and soybeans (Francisco, 2008).

Antioxidant Capacity
The numerous bioactive components in peanuts contribute to their antioxidant capacity. Compared to well-known foods like green tea and red wine, peanuts have higher antioxidant capacity (Halvorsen, 2006). When peanuts are consumed with their skins, their antioxidant capacity doubles. And roasting can at times actually increase this capacity as well (Craft, 2010). Roasted peanuts with skins, for example, have higher antioxidant capacity than blueberries (Francisco, 2008). When you eat a handful of cocktail peanuts, you can be assured that your body is taking in a myriad of unique compounds to help in disease prevention.

http://www.peanut-institute.org/health-and-nutrition/protective-nutrients/bioactives.asp