Published in Food Research International, a team from Poland investigated the anti-cancer properties of onion skin when incorporated into white bread after previous work established fortification increased the antioxidant value.
“Onion skin supplementation of bread has not yet been directly considered in terms of its effects on cancer cell properties, nor was the impact of the interactions between onion skin and bread components on their bioavailability and biological activity estimated,” the researchers wrote.
“…Due to the localization of gastric cancers and their predominantly dietary etiology, bread supplementation with onion skin may be especially efficient in the prevention of these tumors.”
The team previously demonstrated chemopreventive potential in broccoli sprout-supplemented bread against gastric cancer and quinoa leaves for prostate cancer.
Findings on onion skin-supplemented bread showed the wheat bread matrix optimized the antioxidant profile of onion skins, and vice versa.
“Our data suggest that onion skin-supplementation elevates bioactivity of wheat bread, including antioxidant potential, and onion skin phenolics that interfere with the cellular traits crucial for gastric cancer promotion and progression,” the researchers wrote.
In vitro findings showed an increase in the inhibitory effect of wheat bread extracts on gastric cancer cell proliferation and motility. Supplementation inhibited superoxide dismutase (SOD) and activated catalase (CAT) – enzymes considered biomarkers of chemoprevention.
These effects were found at extract concentrations that were physiologically relevant – ca. 150 g of bread for 75 kg of body mass.
“Our current observations confirm pro-healthy potential of onion skin phenolic compounds.”
Complex interactions… further research required
However, while findings were promising the researchers said interactions between onion skin, wheat bread and gastrointestinal processing remained complex and had to be better understood.
“…The bioactivity of phenolic compounds and potentially beneficial effects of wheat bread fortification with onion skin may be regulated by subtle interactions between onion skin and bread phenolic compounds, and food matrix. They are modulated by gastrointestinal processing,” they explained.
These interactions – between single polyphenolic compounds, combinations and flavonoids with the bread matrix, they said, deserved further research efforts.
Source: Food Research International
Published online ahead of print, doi: 10.1016/j.foodres.2015.02.008
“Onion skin – Raw material for the production of supplement that enhances the health-beneficial properties of wheat bread”
Authors: U. Gawlik-Dziki et al.