A compound present in saliva - along with common proteins in blood and muscle - may protect human cells from DNA-damaging plant chemicals, according to a study.

Dangerous plant chemicals called pyrogallol-like polyphenols (PLPs) are found in tea, coffee and liquid smoke flavouring.

"The presence of natural defence in our body could help explain why PLPs are not crippling cells and causing illness as would be expected from their toxic punch and widespread use," said lead author Scott Kern from Johns Hopkins University's Kimmel cancer centre, US.

Kern and his colleagues demonstrated that PLPs found in everyday foods and flavourings could do significant damage by breaking strands of DNA.

In their research, they found that the impact of the toxins was very strong - in some cases producing 20 times the damage of chemotherapy drugs delivered to cancer patients.

"If these chemicals are so widespread and they damage DNA to such a high degree, we thought there must be defence mechanisms that protect us on a daily basis from plants we choose to eat," Kern suggested.

An enzyme in saliva called alpha-amylase, the blood protein albumin and the muscle protein myoglobin all protected cells from DNA breakage by tea, coffee and isolated PLPs.

"Do people who eat the same PLP-containing diet day after day develop a natural cellular protection to the toxins?

"What does not kill us makes us stronger may be right in this case," Kern said in a paper reported online in the journal Food and Chemical Toxicology.

(Agencies)

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