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Originally published October 20 2013

Quercetin protects against cadmium-induced oxidative toxicity

by David Gutierrez, staff writer

(NaturalNews) The common antioxidant quercetin may counter the toxic effects of cadmium on the body, according to a study conducted by researchers from Zhejiang University in China and published in the journal Anatomical Record in 2010.

Cadmium is a highly dangerous and widespread heavy metal that has been linked to cancer, impaired brain function and development and damage to organs including the lungs, kidneys and bones. According to a groundbreaking study by Arizona State University researchers that was published in the journal Biological Trace Element Research earlier this year, high blood levels of cadmium are one of the single strongest factors linked to the severity of autism symptoms.

The Centers for Disease Control and Prevention (CDC) lists cadmium as number seven among the 275 most hazardous substances.

Antioxidant prevents cell death

The Chinese study focused on one specific toxic effect of cadmium: the damage it does to sperm cells. The researchers orally administered 4 mg/kg of body weight of cadmium chloride to male mice. After two weeks, the scientists were able to observe that damage to sperm cells occurred early in spermatogenesis. This damage was caused by decreased levels of the testicular antioxidant glutathione (GSH) and activity levels of the testicular antioxidants superoxide dismutase (SOD) and GSH peroxidase (GSH-Px), as well as increased lipid peroxidation and hydrogen peroxide production in the testes. The researchers also observed that cadmium led to higher levels of sperm cell death (apoptosis) by increasing the expression of the proteins BAX and caspase-3 while decreasing expression of the protein Bcl-xl.

Supplementing the mice's diets with the antioxidant quercetin at a dose of 75 mg/kg body weight led to significant decrease in sperm cell death. Quercetin supplementation suppressed both lipid peroxidation and hydrogen peroxide production in the testes while also leading to significant decreases in levels of GSH and activity levels of SOD and GSH-Px. Finally, quercetin protected sperm cells from apoptosis by increasing the expression of Bcl-xl and decreasing the expression of BAX and caspase-3. This suggests that the antioxidant and anti-apoptotic properties of quercetin can help protect sperm cells from cadmium-induced damage.

Onions and apples

Quercetin is an antioxidant in the flavonol family and is found in onions, apples, tea and wine. In addition to preventing sperm cells from cadmium damage, quercetin has also been linked to a number of other health benefits.

Particularly notable was a study conducted by researchers at the Institute of Food Research and published in the journal Atheroscleroisis in 2008, which addresses concerns that, while quercetin has been shown to be highly effective in laboratory experiments on cell lines, the antioxidant quickly breaks down in the stomach and intestines when ingested as part of the diet. Quercetin skeptics had suggested that, because of this quick breakdown, quercetin naturally consumed in foods such as apples would have little or no health benefit.

The 2008 study showed, however, that both quercetin and the metabolites produced when it breaks down in the digestive system act as anti-inflammatories on the cells of human blood vessels. This suggests that dietary quercetin would indeed have the heart and blood pressure-promoting health benefits that had been observed in laboratory studies.

Another study, published in the American Journal of Epidemiology, found that a high dietary intake of flavanols decreases the risk of pancreatic cancer by 25 percent in non-smokers and by more than 50 percent in smokers. When the researchers examined dietary intake of quercetin in isolation, rather than intake of flavanols in general, they still found a reduction in the risk of pancreatic cancer.

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