Tatar is dangerous

: Cancer Viruses in Beef: Raw and Dangerous

Statistically speaking, those who eat a lot of red and processed meat have an increased risk of colon cancer. The connection has been known for some time, and studies have only recently confirmed it again. To date, however, it is not clear what exactly is the trigger.

Carcinogenic substances are suspected, which are formed from ingredients of the meat, especially when searing and grilling. In the case of salami, sausages or ham, conversion products of the nitrite curing salt used as a preservative are possible.

Cancer researcher Harald zur Hausen sees another possible trigger that also has to do with the method of preparation: Viruses in beef that has not been heated above 60 degrees Celsius - i.e. in steak that has not been cooked through, in carpaccio or air-dried specialties such as B├╝ndnerfleisch. They could be involved in the development of cancer in the human intestinal tract.

Nobel Prize for a bold idea

The man has experience with bold hypotheses. In the 1970s, he suggested that cervical cancer could be caused by viruses. Most scientists at the time thought that was absurd. But zur Hausen's research group actually found certain types of human papillomavirus (HPV) in cells of cervical cancer and developed a vaccine against it. For his discovery, zur Hausen received the 2008 Nobel Prize in Medicine.

Today it is considered certain that other viruses can also cause cancer or at least participate in its development (see box). So why not colon cancer too?

Harald zur Hausen, who is now 77 years old, still working at the German Cancer Research Center in Heidelberg, has systematically looked for possible connections between eating habits and the frequency with which colon cancer occurs. Carcinomas of the colon and rectum, as the technical term is used, are the second most common cancer in women and the third most common in men, but they are very unevenly distributed across the globe.

There is a high risk of illness where people eat a lot of beef, for example in North America, Argentina, Uruguay, New Zealand, Russia and Europe. The risk is relatively low in China, with its traditional preference for pork, as well as in Arab and African countries, where sheep and goats are more likely to be on the table.

The lowest colorectal cancer rate in the world is found in India. There is generally little meat eaten there and the consumption of beef is taboo for the majority of the population for religious reasons. Investigations in Japan and Korea provided particularly interesting findings, where colon cancer used to be comparatively rare. However, from 1975 onwards, the rate in Japan doubled within twenty years. South Korea saw a similarly dramatic increase from the mid-1990s.

Possible explanations: Before that, imports of beef, pork and dairy products had increased in the two countries. Shabu-shabu was fashionable in both Japan and Korea, a type of fondue chinoise in which strips of beef are briefly dipped in boiling broth so that they are still red inside. In Korea, raw ground beef is also popular, served with spicy sauces and an egg yolk. Mongolia, from which the tartar originally comes, has a low colon cancer rate; there, however, the minced meat also comes from the yak, not from domestic cattle.

From this data, published in the International Journal of Cancer, zur Hausen found that the carcinogenic substances in grilled food cannot be the sole trigger. Because these also arise when white meat such as poultry or fish is fried, deep-fried or smoked at high temperatures. And even where lamb and goat meat is predominantly on the menu, it often comes off the grill or is seared before braising. It is therefore tempting, writes the HPV discoverer in the specialist article, to speculate that viruses are involved in the development of cancer that are specifically found in raw and slightly heated beef.

Another indication is the fact that in northern India, of all places, the risk of colon cancer is increased where a type of B├╝ndnerfleisch is part of the diet: "In the eyes of a virologist, air drying is the best way to preserve viruses in a way that they can survive," says zur Hausen.

So far only candidates

We are now looking for a small virus that can withstand temperatures of up to 60 degrees Celsius, nestles in both cattle and humans, but does not multiply in human cells, but reprograms them to become cancer cells.

Zur Hausen has already found a few candidates who fit this profile. In order to prove his hypothesis, he would have to show that certain sections of this genetic material can stimulate human cells to proliferate in an uncontrolled manner. At the same time, he would have to detect the same sections in cancer cells. It's all just speculation for now. If the proof is successful, should the researchers actually be able to detect a cattle-specific pathogen that is involved in the development of colon cancer, meat producers and lovers of medium-cooked steaks would only hope that science will also find a vaccine against it. However, this can take time.