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Beef bug to blame for bowel cancer?

Adore red meat? You may be put off that next juicy rump by hearing what Harald zur Hausen has to say about it. At the 61st Lindau* meeting this week, the Nobel laureate spoke on his current hypothesis about why beef causes colorectal cancer: it might contain a nasty pathogen that causes the disease but the source hasn’t been discovered yet.

Colorectal cancer has a high incidence among men and women worldwide, and cases are increasing. Researchers blame this on the ‘Westernisation’ of lifestyles, including eating more red meat, in economically transitioning countries, such as China.

Zur Hausen reached this hypothesis by eliminating possible carcinogenic factors and searching for correlations. First, he looked at the way that food was cooked, and found that it seems implausible to blame the cooking processes for beef-related cancer when eating white meat or fish cooked the same way is safe.

He also looked at countries that have high and low incidences of bowel cancer, and found that in countries where red meat is eaten, but predominantly not beef (ie mutton or goat), incidences are still relatively low compared to North America, Europe and Australia, where the incidence is high.

Lastly, zur Hausen considered that beef is often served ‘rare’, and that this could affect the ability of viruses to survive cooking. He said that papillomavirus, polyvirus and single strand DNA viruses can endure a roasting at 80 C for 30 minutes. Much beef is cooked more lightly than this. And zur Hausen’s hypothesis may explain the rise in bowel cancer cases in Japan, where the staple protein is traditionally fish, rather than beef.

Zur Husen says that if we can find an infection that causes colorectal cancer, then 35 per cent of the world’s cancer cases could be traced back to an infection. Currently, 21 percent of cancer types are known to be probably caused by pathogens – including Hepatitis B (increases incidence of liver cancer), Helicobacter, Schistosoma.

And, of course, zur Hausen won his Nobel prize in 2008 by proving that high-risk HPV virus causes cervical cancer. The cancer of the cervix is the second most frequent cancer in women with 530 000 cases a year, globally – and 86 per cent of these cases are in developing countries.

The first vaccine to prevent cancer was the Hepatitis B vaccine, developed in 1984. But the vaccine everyone’s talking about is the HPV vaccine, which can protect close to 100 per cent of previously non-exposed women, and likewise prevents the infection of cervical precursor lesions. Zur Hausen said that high risk HPV can be completely eliminated if all girls are vaccinated before reaching sexual maturity – and the vaccination of boys will close the circle of infection.

Harald zur HausenHe said that we should look for more infections that cause cancer. Could all cancers be linked to an infection? You can watch zur Hausen’s lecture in full, by clicking on this link. As for beef, perhaps it’s wise to have it well done in the future.

* The Nobel Laureate Meeting at Lindau is a scientific conference held yearly in Lindau, Germany, inviting Nobel prize winners to present to and interact with top young researchers from all over the world.

Source: Scientific American

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