Red meat, mobile phones, plastic bottles, chemical sweeteners, power lines, coffee … All things have been attributed to cancer. If you are confused, you are not alone. The problem is not a lack of information. Rather, on the contrary: there is so much information that it is sometimes extremely difficult to distinguish myth from fact. What is the most reliable way to determine that you are at risk?
Red meat, mobile phones, plastic bottles, chemical sweeteners, power lines, coffee … What has not been attributed to cancer? Don't worry if you get confused, you are not alone. The problem is not a lack of information. Rather, on the contrary: we were bombarded with such a stream of information - and disinformation! - that it is sometimes extremely difficult to distinguish a myth from a fact.
It is still necessary to understand, because cancer concerns each of us. Even if you have not had cancer yourself, you probably know someone who has had cancer. In the UK, the lifetime chance of contracting cancer is one in two. According to statistics, cancer is the second most common cause of death after cardiovascular disease. Every sixth inhabitant of the Earth dies of cancer.
Cancer is a whole group of diseases, the mechanisms of its occurrence are numerous and complex, but we can fully reduce the risk if only we can determine its causes. It's not easy, and even among the experts there is disagreement. And yet, in recent years, we have made great strides on this issue thanks to a huge amount of research concerning both environmental factors and hereditary predisposition. So what do we know about the causes of cancer - and what we don’t know? And if we are faced with conflicting information - how to properly assess the risks?
Last year's poll clearly showed how confused public opinion is on this issue. In a survey of 1,330 Britons, researchers from University College London and the University of Leeds found that more than a third of respondents attributed carcinogenic properties to chemical sweeteners, genetically modified foods, plastic bottles and mobile phones. Over 40% believe cancer is stressful - although this link remains unproven. Even more alarming, only 60% are aware of the carcinogenicity of sunburn. And only 30% are aware of the strong relationship of cancer with the human papillomavirus (HPV).
Many observers were stunned by these results - and in vain. In the case of cancer, the gap between public opinion and scientific discovery has long roots. Take the aspartame debate, for example. Over the past half century, heated debates have not abated around this sweetener - and the degree of conviction of the general public in its carcinogenicity is constantly fluctuating. There are many articles on the Internet claiming that aspartame causes brain cancer. And yet, there is no convincing evidence that it can cause uncontrolled mutations at the cellular level - and this feature is considered the hallmark of all cancer - there is no. The same goes for antiperspirants, fluoridated water, power lines, smart meters, cleaning products, and more.
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A third of people mistakenly believe plastic bottles cause cancer
And yet the obvious conclusion that we are overly gullible or even ignorant would be wrong. In fact, public opinion is not always unfounded. The notion that cancer can cause injury has long been dismissed by oncologists, including researchers from University College London and the University of Leeds, but a study published in 2017 acknowledged that the connection was indeed possible. In addition, there is no consensus on whether certain products are carcinogenic or not. Take coffee, for example. Last year, a California court banned the sale of coffee without a "cancer warning" in the state because it contains acrylamide. It is classified as a "probable carcinogen" by the World Health Organization (WHO), although there is no clear evidence that it increases the risk of any type of cancer. So,Due to the presence of this substance in food baked or fried, whether in oil or over an open fire, it is recommended not to overuse chips, toast, and the like. However, whether there is enough of it in your morning cup of coffee to be considered a carcinogen is an open question. At this stage, we don't have enough scientific evidence to say for sure.
Even where there is sufficient research, the conclusions can be interpreted in different ways. This is due to the fact that both approaches to research on carcinogens have their drawbacks. Laboratory studies on animals or their cellular material are more accurate, but their results are not always applicable to humans. Human studies are more difficult to interpret due to the large number of confounding factors that distort the results. Hence the disagreement in the medical environment - what is carcinogenic and what is not. So, the unanimous conclusion is that there is no direct link between e-cigarettes or red meat and cancer, but studies that have appeared over the past couple of years claim that there is. Other studies point to the "bad luck" factor altogether. This obscure term implies that cancer can be caused by unknown causes,which we are not able to influence.
All this confusion creates the misconception that the likelihood of getting cancer is unaffected
In addition, there is a material interest in oncological research - therefore, some skepticism is completely justified. After all, the tobacco industry has been trying to hide the link between smoking and lung cancer - for decades. There is also such a point that academic research is often financed by big business, and this leads to a conflict of interest. For example, the chief physician of the Sloan-Kettering Memorial Cancer Center in New York, one of the leading in the world, resigned due to accusations that he did not inform the public about corporate sources of funding for a number of studies from major journals.
Selfish interest
Corporate funding undermines the credibility of research. One recent work concluded that randomized clinical trials are three times more likely to produce results when large businesses are involved. In addition, research backed by industry tends to be published faster - and thus more likely to influence the theory and practice of cancer treatment.
On the other hand, one has only to suspect selfish interests, as horror stories appear. For example, in July 2018, The Observer reported that the mobile phone industry had successfully lobbied to keep the link between phones and brain cancer silent, but studies have shown there is no such link.
In addition, the involvement of large businesses can influence the risk assessment. Last August, a US court ordered Monsanto, the fertilizer giant, to pay $ 289 million to landowner Dwayne Johnson, who had cancer. The court ruled that Johnson's cancer was caused by a herbicide produced by the company, although the scientific basis for this decision is lame. The judge reduced the amount of payments, but Johnson was still paid 78 million.
All in all, it's no surprise that many are confused. There is a misconception that the likelihood of contracting cancer cannot be reduced in any way. As the WHO notes: "About a third of cancer deaths are attributed to five major behavioral and nutritional risk factors: high body mass index, inadequate intake of fruits and vegetables, lack of physical activity, and tobacco and alcohol use."
Tobacco smoking is the largest risk factor, accounting for 22% of cancer deaths worldwide. WHO also highlights exposure to sunlight and other forms of radiation, and notes that in low- and middle-income countries, up to a quarter of cancer cases are caused by infections such as hepatitis and HPV.
It should be recognized that researchers have identified a number of proven carcinogens (see section “High and Low Risk”), whose effects cannot always be avoided or minimized. Another challenge is that there is still a long way to go to determine the full picture of risk factors. A recent study showed that it is possible to establish the cause of cancer in only four out of ten cases - and, as a rule, it is smoking and being overweight. Another study rated the level of uncertainty even higher. Scientists have concluded that two-thirds of cancers are the result of "random mutations" - errors in DNA replication - which are currently impossible to predict.
The risk is high and not very
If so much money and energy is invested in cancer research, why are we still so ignorant? Well, actually, cancer is very different from most diseases. First, it can develop gradually, which makes it difficult to accurately determine its cause - in contrast to the same malaria or cholera. Second, there is no clear causal relationship. It happens that people smoke all their lives - and safely do without lung cancer. So to assume that there is a single culprit is oversimplification. In fact, uncontrolled cell division - and cancer is characterized by it - can be caused by a whole range of environmental factors.
In addition, we still have a lot to learn about the genetic nature of cancer. True, biologists have made great strides in identifying individual mutations. For example, we have found that hybrid genes - that is, genes that are composed of two genes, originally from different chromosomes - are often associated with some cancers of the blood and skin. We also know that a gene called TP53 suppresses the development of tumors. In general, this gene mutates most often in cancer. However, the full range of its functions remains unsolved. We still don't know exactly how many genes are in the human genome, not to mention how they are in a relationship, and what changes must occur to cause cancer.
Another equally complex area of undoubted interest is the microbiome - the microbes that live inside the body and on its surface. Each of us has hundreds of species of bacteria coexisting in the gut, and a deficiency in some or the presence of others can predispose to cancer. For example, helicobacter pylori bacteria are considered to be one of the causes of stomach cancer. In addition, our microflora is influenced by diet, hygiene and the environment. However, we still know very little about the interaction of these factors with the genome and microbiome - or how exactly these bacteria contribute to the development of cancer or, conversely, reduce its risk.
All this complicates the task of finding out the cause of cancer. But there is also a constructive view of the problem. Cancer has accompanied humanity throughout evolution. Thanks to this, we are no longer powerless in front of him, because our immune system has developed a number of mechanisms and has learned to partially block the disease. One of them is the aforementioned TP53 gene. Its product is a protein that stops the proliferation of cancer cells. Another such mechanism is the arrest or "arrest" of the cell cycle, which prevents the mutated cells from completing their intended life cycle. Paul Ewald and Holly Swain Ewald of the University of Louisville, Kentucky, called these mechanisms "barriers." When you are not sure about the carcinogenicity of a particular product or occupation, it makes sense to consider whether they can weaken these barriers.“An evolutionary perspective allows us to draw reasonable, albeit speculative, conclusions even in the absence of concrete evidence,” explains Paul Ewald.
Evolutionary perspective
This approach helps explain why cancer is so common in the modern world. One of the reasons is that people have begun to live longer, and this increases the likelihood that failures in DNA replication will sooner or later lead to cancer. In addition, it is possible that our behavior does not correspond to our evolution. An example of a so-called evolutionary inconsistency is not breastfeeding. So children are deprived of complex sugars, but they nourish the intestinal microflora and carry out "fine tuning" of the immune system. In general, as living standards rise, children are less likely to be exposed to pathogens - which prepare the immune system to fight disease later in life. Mel Greaves from the Cancer Research Institute in London came to the conclusion thatthat it is here that one should look for the cause of acute lymphoblastic leukemia, an extremely common childhood disease.
Thus, by embracing the modern lifestyle, we, perhaps unwittingly, are breaking down the barriers that block cancer. If so, then, from an evolutionary perspective, it will help researchers focus on risk factors - and as a result, it will be possible to determine for sure which foods and which lifestyle should be avoided. But the problem remains multifaceted. Paul Ewald warns: it is not individual causal relationships that need to be considered, but a set of factors. Greaves notes that Western lifestyles have changed so rapidly and so dramatically - and by the way, they continue to change - that identifying the factors that cause cancer will be difficult.
The good news is that we may already have all the information we have. Each year, large, expensive studies are conducted in an attempt to determine whether a particular substance or behavior is causing cancer. Sifting through a mountain of data is much more difficult if you don't know what you are looking for. But evolutionary thinking will help steer the scientific spotlight in the right direction.
It may never be possible to identify every single factor underlying cancer in a particular person - but we are quite capable of making informed decisions to avoid risks. Therefore, when you come across the next horror story, ask yourself: are these statements supported by specific data, whether material interest is involved in the study, and, most importantly, whether the conclusions are consistent with human evolution.
Jonathan Goodman - Fellow of King's College London and PhD student at the University of Cambridge (UK)