Following on from the last post on random mutations causing most cancers, H/T Rose for news of the lifestyle medics rapidly striking back. Dr Emma Smith, Cancer Research UK’s senior cancer information officer, writes:
Yes, sometimes developing cancer is just bad lack – but that doesn’t mean you should keep smoking
The front pages today have given a good airing to research that says developing cancer can be simply down to bad luck. This isn’t actually new. It’s well established that certain gene faults can trigger some types of the disease. But – as the researchers themselves point out – we know that there are also other factors at play.
Cancer is caused by damage to our DNA. Environmental factors like UV rays and lifestyle habits such as inhaling cancer-causing chemicals in tobacco, can damage our DNA – as can the process of ageing. The damage builds up over time and if a cell becomes too badly damaged it can start to multiply out of control – leading to cancer.
This misrepresents the new theory, which is not that inherited gene faults can trigger cancer (which isn’t a new idea), but that random mutations of genes in dividing cells can also trigger cancers. You might start out with good genes, but end up with faulty ones. And because it’s a random process, it’s just bad luck if you end up with cancer.
The good news is that four out of 10 cases of cancer can be prevented by making small lifestyle changes. So it’s absolutely vital to look at ways to help stop the disease developing in the first place.
I don’t think the new research said that 4 out of 10 cancers could be prevented by small lifestyle changes:
Scientists looked at the number of cell divisions of 31 types of bodily tissue and compared them with the overall incidence of cancer in the population of America.
They found that the more cell mutations occurred, the higher the rate of cancer, suggesting that it was the number of random errors in replication that was driving tumours rather than outside environmental forces.
For example the cells of the pancreas regenerate far more quickly than those of the pelvis, which is why pancreatic cancer is far more common than pelvic cancer.
However some cancers such as lung and skin cancer had higher rates than their mutations should predict, suggesting that genetics or lifestyle factors had increased the risk.
Lead researcher Professor Bert Vogelstein, said: “Cancer-free longevity in people exposed to cancer-causing agents, such as tobacco, is often attributed to their ‘good genes,’ but the truth is that most of them simply had good luck.
“Our study shows, in general, that a change in the number of stem cell divisions in a tissue type is highly correlated with a change in the incidence of cancer in that same tissue.
“We found that the types of cancer that had higher risk than predicted by the number of stem cell divisions were precisely the ones you’d expect, including lung cancer, which is linked to smoking; skin cancer, linked to sun exposure; and forms of cancers associated with hereditary syndromes.”
So there was a strong correlation of cancer with the number of cell divisions in various tissues. If the incidence of lung and skin cancer was higher than predicted, they suggested that this might be due to genetics or lifestyle. They didn’t say which.
The only question is: how much higher was the incidence of lung and skin cancer above that predicted? If it was 10% higher, and this was definitely due to lifestyle factors, then at most you could improve your chances of not getting cancer by 10% if you made the necessary lifestyle changes.
And giving up smoking isn’t a “small lifestyle change”, anyway. It’s a very large one. Particularly if it results in a gut bacteria catastrophe, and weight gain:
Weight gain after quitting smoking not caused by overeating
“The average smoker gains up to 5kg in the year after smoking and until now, experts have put the weight gain down to nervous nibbles or comfort eating to deal with stress.
But researchers at Zurich University Hospital believe that when we quit smoking the real cause of weight gain could be the bacteria in our intestines.
After quitting, researchers found gut flora in smokers became much more like an obese person’s.
Over nine weeks, the researchers studied faecal samples from 20 volunteers –– five non-smokers, five smokers and 10 people who quit one week into the study.
They found people who had recently quit have more Proteobacteria and Bacteroidetes bacteria, which helps the body store fat instead of excreting it.
Over the nine-week study, the quitters gained an average of 2.2 kg, but said they had not changed their food and drink consumption.
“Under the same living conditions, they gained weight after the cessation of smoking, and they showed a change in the microbiota,” said study leader Professor Gerhard Rogler said.
But the lifestyle zealots – who are really just puritanical moralists – won’t abandon interfering in people’s lifestyles easily. It is, after all, their raison d’être.