Science - December 9, 2004

Even more reason to eat your greens

Nearly all studies indicate that a high intake of meat drastically increases the chance of intestinal cancer. Researchers at WCFS and the research institute NIZO in Ede have now discovered that green leafy vegetables completely reverse the damaging effect of meat. They have reported their findings in the journal Carcinogenesis.

Those who eat a lot of red meat, such as pork and beef, or processed meat, such as Spam or salami have a greater chance of developing intestinal cancer. In Western societies, where meat still forms the main focus of warm meals, intestinal cancer is one of the most common forms of cancer.
It is not known how meat causes intestinal cancer. A popular theory seeks the cause in the substances that arise when meat is fried, heterocyclic amines. However, these compounds are now regarded as less likely to be the cause since researchers have discovered that the compounds are found in higher concentrations in fried chicken than in fried beef. WCFS is currently studying another suspicious substance in red meat: the organic iron compound haem.
The researchers gave rats a diet similar to that of an average westerner. A control group got food that contained no haem. The researchers discovered that the gut contents of rats that had received haem damaged the gut wall, which resulted in the cells of the gut wall dividing more often. The chance of mutant gut cells arising is probably higher, and therefore also the chance of cancer developing.
When the researchers repeated the experiments with food that had spinach added to it, the effect disappeared completely. Spinach was not an accidental choice. Epidemiological studies have shown that a high consumption of green vegetables, and especially leafy vegetables, reduces the chance of cancer. The active substance is probably the green, or chlorophyll, which the Wageningeners discovered when they substituted pure chlorophyll for the spinach and obtained the same results.
How the greens work became clear when the researchers analysed the faeces of their animal subjects. The researchers found more unchanged haem in the pellets of the rats that had eaten haem and greens, than in the pellets of rats that had only eaten haem and no greens. It appears that greens prevent the organic iron from being converted into another substance, and this is the other, as yet unknown, substance that damages the cells of the gut wall. Attempts to uncover the structure of the substance have failed so far, which has been named the ‘haem factor’.
The researchers expect that the relation between haem, greens and intestinal cancer will also hold for humans. They note however that their rats generally ate more leafy vegetables than most humans consume. If the animals had been humans they would have eaten almost a pound of spinach a day. The researchers are now planning experiments with less chlorophyll. / WK