Researchers have found that chlorophyll in green vegetables can help protect against modest carcinogen exposure levels commonly found in the environment. The negative aspect is that the chlorophyll increases the number of tumors at very high carcinogen exposure levels.
Beyond confirming the value of chlorophyll, the study at Oregon State University raises serious questions about whether traditional lab studies done with mice and high levels of toxic exposure are providing accurate answers to what is a real health risk, what isn't, and what dietary or pharmaceutical approaches are useful.
The findings were done using 12,360 rainbow trout as laboratory models, instead of more common laboratory mice. Rodent studies are much more expensive, forcing the use of fewer specimens and higher carcinogen exposures.
"There's considerable evidence in epidemiologic and other clinical studies with humans that chlorophyll and its derivative, chlorophyllin, can protect against cancer," said Tammie McQuistan, a research assistant working with George Bailey, a professor emeritus in the Linus Pauling Institute at OSU.
"This study, like others before it, found that chlorophyll can reduce tumors, up to a point," McQuistan said.
"But at very high doses of the same carcinogen, chlorophyll actually made the problem worse. This questions the value of an approach often used in studying cancer-causing compounds," she stated.
In one part of the study, trout were exposed to fairly moderate levels of a known carcinogen, but also given chlorophyll. This reduced their number of liver tumors by 29-64 percent, and stomach tumors by 24-45 percent.
But in another part of the study, using much higher and unrealistic doses of the same carcinogen, the use of chlorophyll caused a significant increase in the number of tumors.
In other words, traditional research with small numbers of animals fed very high doses of a carcinogen might conclude that chlorophyll has the potential to increase human cancer risk. This study, and other evidence and trials, concludes just the opposite.
t also found that the protective mechanism of chlorophyll is fairly simple - it just binds with and sequesters carcinogens within the gastrointestinal tract until they are eliminated from the body. At the lower carcinogen doses and cancer rates relevant to humans, chlorophyll was strongly protective.
"The central assumption of such experiments is that intervention effects at high carcinogen dose will apply equally at lower carcinogen doses," the researchers wrote in their report.
"Contrary to the usual assumption, the outcomes in the major target organ were strikingly dependent on carcinogen dose.
"Results derived at high carcinogen doses and high tumour responses may be irrelevant for human intervention," they concluded.
The study was published in the journal Food and Chemical Toxicology.