Onions! Ok where to start -- white onions, yellow onions, red onions, vidalia onions, sweet onions, shallots.. so many flavors PACKED WITH NUTRIENTS that do everything from helping keep our hearts healthy and lowering the risk of cancer to easing the pain associated with arthritis and preventing the common cold.
Background
Onions, after tomatoes, are the second most cultivated vegetable with a worldwide production of about 64.5 million tons. Onion bulb is rich in flavonoids, especially flavonols such as quercetin, isorhamnetin and kaempferol. From the approximately 20 detectable flavonols in onion species, quercetin-3,4-O-diglucoside and quercetin-4-O-monoglucoside are the main flavonols. These two make up to 80–85% of the total flavonoid content.
Health Benefits
Not only are they abundant in flavanols these babes are rich in vitamin B6, vitamin C, manganese, molybdenum (essential in preserving tooth enamel), potassium, phosphorous, and copper.
Flavonoids can act as antimutagens/promutagens and antioxidants/pro-oxidants, depending on the levels consumed as well as the physiological conditions in the body. Biological activities accredited to quercetin include its antiviral, anti-inflammatory, antioxidant, psychostimulant activity, antiproliferative, antimicrobial properties and mitochondrial biogenesis. Due to absorption differences in conjugated forms, the bioavailability of quercetin varies in foods. These biological properties are the basis for potential benefits to overall health and protection against various diseases, such as osteoporosis, certain forms of cancer and pulmonary and cardiovascular diseases.
Onions are also particularly important in the diet of diabetics because they are rich in chromium, a trace mineral that helps cells respond to insulin. Moreover, refined sugar depletes the body’s chromium levels, so onions are an excellent source of chromium replacement for anyone who consumes refined sugar.
Onions also help to reduce blood pressure and cholesterol and strengthen bone health. They have anti-inflammatory benefits, reducing symptoms related to inflammatory conditions such as asthma, arthritis, and respiratory congestion. Some studies have noted that onions lessen the adverse effects of colds and flus.
Antioxidant Mechanism of Active Component Quercetin
Quercetin exerts its antioxidant activity by scavenging reactive oxygen species (ROS) and preventing ROS formation with chelating transition metal ions, such as iron and copper. Hydrogen peroxide is a non-radical ROS produced in living cells as a result of cellular metabolism. Hydrogen peroxide can react with metal ions (copper and iron) and form hydroxyl radicals. These radicals can disrupt macromolecules in cells and cause inevitable damage. Hydrogen Peroxide must be degraded for the cells to survive. Quercetin can function as an antioxidant on cells stressed by hydrogen peroxide. In a study, human hepatoma cell line HepG2 cells were used to explain the detoxification mechanism of quercetin against H2O2. Quercetin blocks reactive oxygen species by Fenton reaction. The chelation with metal ions such as copper to form hydroxyl radicals. Quercetin becomes oxidized, less harmful but reactive, and then oxidized form of quercetin interacts with thiol compounds (Gluthione) and goes back to the stable form.
Metabolism
Onions are also particularly important in the diet of diabetics because they are rich in chromium, a trace mineral that helps cells respond to insulin. Moreover, refined sugar depletes the body’s chromium levels, so onions are an excellent source of chromium replacement for anyone who consumes refined sugar.
Studies have shown that there is unpredictability in the favored pathways among individuals, which may be due to differences in gut microflora populations. The quercetin glucosides in onions are more readily absorbed than those found in tea and the rutinosides found in apples. Quercetin derivatives and any remaining unmetabolized quercetin are released into the circulation via the hepatic portal vein. Quercetin may be absorbed systemically from the gastrointestinal tract via the lymph. In the liver, quercetin and its derivatives are further subjected to conjugation, resulting in the formation of sulfate or glucuronide. The metabolic conversions involve a complex combination of deglycosylation, glucuronidation, sulfation, methylation and possibly deglucuronidation. Intermolecular bonds between albumin and quercetin conjugates are formed. Quercetin is eliminated slowly from the body being circulated as a quercetin-albumin complex.
REAP THE REWARDS! Go on with yo bad self and saute, simmer, grill, roast (their magical superpowers can stand the heat), or pickle & pop em raw if your tastebuds can handle it. We recommend buying strong onions. They’re best for inhibiting all the bad stuff. The more pungent the taste, the better!