June 27, 2011 | 5
Even if you adore red meat, you’ll put off your big juicy steak by hearing what Harald zur Hausen has to say about it. At the 61st Lindau meeting, the Nobel laureate spoke about his current hypothesis about why beef causes colorectal cancer. He thinks it might contain a nasty pathogen that infects us that then 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.
Right: Harald zur Hausen at Lindau, photo: Christine Ottery
Zur Hausen reached this hypothesis by eliminating possible carcinogenic factors and searching for correlations. First, he looking 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 degrees Celsuis 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. At the moment, 21 per cent of cancers are known to stem from infections, including Hepatitis B, 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 Taiwan 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.
He 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, below. As for beef, I’ll be having mine well done in the future.
About the author: Christine Ottery is a freelance science writer who writes on for the Guardian, TheEcologist.co.uk, SciDev.net and Wired magazine. She recently graduated from a MA Science Journalism at City University London, U.K. She blogs at Open Minds and Parachutes and tweets at @christineottery.
The views expressed are those of the author and are not necessarily those of Scientific American.