I talk a lot about cancer. I write about it for this magazine, I talk about it a lot on my podcast (Skeptics with a K), and from time to time I give talks at Skeptics in the Pub groups to explain what cancer is, how we treat it with real science and medicine, and finally, why people believe in alternative cancer treatments that aren’t evidence-based.
There are a few questions I can usually guarantee will come up during the Q&A, one of which is around the idea that cancer often has an environmental cause – someone will reliably ask me is cancer sometimes preventable, and if that is the case, what can I recommend doing to avoid cancer.
This is not a simple question to answer.
Firstly, cancer while cancer can be caused by environmental factors, it is not only caused by environmental factors. It can also be caused by heritable genetic factors. In adult cancers this typically means you’ve inherited a predisposition to a particular cancer, like changes in the BRCA gene which increases your risk of breast cancer. Inheriting those genetic changes does not mean you’re guaranteed to get cancer, but it increases the likelihood that you will develop cancer in your lifetime.
In some cases, you might be able to do something to change your risk levels – such as a complete double mastectomy to remove all breast tissue, if you are carrying certain BRCA mutations. But it many cases you are unlikely to know which genetic mutations you carry, and even if you do know, there’s not much you can do to reduce your risk, beyond reducing the environmental factors which might exacerbate your risk. For example, if you know you’re genetically predisposed to colorectal cancer, then you might reduce your exposure to certain foods, or you might undertake more regular screening.
Secondly, cancer is a disease of living. The longer you live, the more likely you are to get cancer. While this is partially to do with lifetime exposure to environmental factors that can increase your risk of cancer, it’s also just the nature of living. If each cell replication has a certain percentage risk of leading to a genetic mutation, then the more cell replications, the more genetic mutations you will acquire. And if each genetic mutation has a certain percentage risk of being cancer causing, then the more genetic mutations you acquire, the more likely you are to acquire a cancer-causing mutation.
These are things we have little to no control over. However, the thing we do have control over, to some extent, is our environment. We know that exposure to some environmental factors increases our risk of acquiring a genetic mutation. The examples I usually give – partly because we’re so clear on the connection – are alcohol, sunshine and smoking tobacco.
Cutting out smoking is a no-brainer. It absolutely causes cancer, and it is the biggest cause of one of the most common cancers. Smoking causes over 70% of all lung cancers, and lung cancer is the third most common cancer in the UK.
But when it comes to other environmental factors, my aim is to work towards risk management, rather than complete risk avoidance. That means trying to be reasonably aware of risk factors, without taking it to the extreme in a way that might have a detrimental effect on your mental health, and it means weighing up the risks and benefits of activities, to reduce your risk where appropriate for you personally.
For example, sun exposure is a risk factor for skin cancer, and some forms of skin cancer are very metastatic and can be quite deadly, so reducing sun exposure is a reasonable risk management approach. But being outdoors has a lot of health benefits, and sun exposure is the best vitamin D source. So how do we balance the risk/benefits? We know sun beds are particularly high risk, so for me they are not an option. We also know that experiencing sunburn is higher risk – so we can take sunburn prevention steps, like wearing high factor SPF, and avoiding sun exposure during the sunniest parts of sunny days.
Ultimately, for people to take a risk management approach, they need to be reasonably well informed on what the risks are and how serious those risks are, and that is where governmental guidance can come into play.
There are lots of different types of guidance that look at lots of different areas but in the past weeks we’ve seen changes in the US’s Dietary Guidelines which were first introduced in 1980. These changes included some changes to dietary guidelines for alcohol consumption which were discussed by Dr. Mehmet Oz, the administrator of the Centers for Medicare & Medicaid Services in a news briefing. “In the best-case scenario,” he said, “I don’t think you should drink alcohol”.
The updated guidelines say that people should “Consume less alcohol for better overall health.” And that “People who should completely avoid alcohol include pregnant women, people who are recovering from alcohol use disorder or are unable to control the amount they drink, and people taking medications or with medical conditions that can interact with alcohol.”
This sounds quite good and balanced: reduce your alcohol intake, and in the best-case scenario don’t drink alcohol at all. This is advice I would give, and it is the advice of the WHO, who say there is no safe level of alcohol consumption.
We know that alcohol consumption increases the risk of certain cancers, and we know that it can lead to or contribute other health problems. When we’re discussing potential health benefits of consuming certain alcoholic beverages like red wine, the studies are often not about the alcohol, but about other ingredients in those drinks; they involve an ingredient that is not unique to alcoholic beverages; and they’re not actually measuring the intake of alcoholic drinks, but the specific ingredient in different forms in the lab. Resveratrol is the canonical example – any positive health benefits it might have are not limited to consuming it in red wine, and the quantities of red wine you’d need to consume to experience any resveratrol effects would mean that any positive would be vastly outweighed by the negatives of the increased alcohol consumption.
So, while I enjoy alcohol, and I am happy on a personal level to consume alcohol at a low-to-moderate level, I also know that I am increasing my risk of health problems, including cancer. And while I try to bring balance by maintaining a broadly healthy diet and incorporating other health promoting things like exercise, I know that the healthiest option would be to remove alcohol from my diet entirely. But autonomy is about making personal choices, and I get to choose which risks I take – as long as I am accurately aware of the consequences.
Assessing the consequences
Awareness of the consequences can be challenging, because research is not always clear cut, and the ways we talk about risk can be influenced by all sorts of factors. In the same moment that the US Dietary Guidelines were updated, media coverage also included headlines like “Alcohol causes cancer, and less than 1 drink can increase your risk − a cancer biologist explains how” from The Conversation, “Even one drink a day raises mouth cancer risk by 50%, study warns” from The Independent and “Just one alcoholic drink a day spikes mouth cancer risk by 50 per cent, concerning new research reveals” from The Daily Mail.
The Daily Mail explained
Drinking even a small amount of alcohol can increase your chances of developing mouth cancer by 50 per cent, according to a new study.
The research, published in BMJ Global Health, found that having just 9g of alcohol a day—which is just slightly over a standard alcohol unit—can make the likelihood of being diagnosed with the potentially fatal disease soar.
According to the Mouth Cancer Foundation, 10,825 people in the UK were diagnosed with the disease last year, and it was responsible for 3,637 deaths, more than cervical and testicular cancer combined.
So far, so scary. However, crucially, we are conflating cancers here. The study itself was looking at buccal mucosa cancer: cancer of the insides of the cheeks or lips, which makes up around 10% of mouth cancer cases. So, that immediately cuts those 10,825 people per year in the UK down to roughly 1,083.
This study is genuinely a really important piece of work, because the work was conducted in India, which is one of the areas where mouth cancer is particularly prevalent – though that is thought to be related not just to alcohol consumption, but to the high use of chewing tobacco in this region. Guidance in the UK already points to smoking, chewing tobacco and alcohol intake as risk factors for mouth cancer, and this research showed new evidence that combining chewing tobacco with alcohol intake compounds the risk, with 62% of the cases in the study attributed to this combination.
This is especially important research because we know mouth cancers are increasing, and we’re seeing an increase in the use of things like snus, the oral tobacco pouches which are held under the lip, tongue, or in the cheek. Yet the media focused on the alcohol factors from the study, omitting the contributing role of tobacco entirely from their headlines. We don’t even know if these data can even be extrapolated from India to the UK or other areas, since there are a whole range of other cultural factors which might influence this finding.
For example – the authors restricted the analysis to men, because pretty much 0% of women reported any alcohol intake. This is a suspiciously low level of alcohol consumption, which might be explained by the fact that the study is based on self-reported data, which means it has a level of unreliability. It seems unlikely that among the Indian women surveyed, none of them consumed alcohol; it seems more likely that they failed to accurately report what alcohol they consumed, because of cultural expectations and stigmas.
Scaremongering articles are never the way to highlight this sort of research, and while a 50% increase in risk of buccal mucosa cancer with 9g daily alcohol consumption per day is a significant finding, we should also be asking what a 50% increase actually means in terms of numbers. Unfortunately, I couldn’t find any data to tell me the specific prevalence of this type of mouth cancer in the UK, but bear in mind-that a scary-sounding increase of 50% might mean raising your risk from two in a million to three in a million. The absolute figures matter, if we’re going to accurately assess what risks we are comfortable taking.
Ultimately, we do know that alcohol consumption increases the risk of seven types of cancer: mouth, upper throat, larynx, oesophagus, breast, liver and bowel. This is because alcohol can both damage cells and prevent repair to damaged cells. Which is why those new US Dietary Guidelines are particularly strange. According to The New York Times, the previous set of US Dietary Guidelines which were issued in 2020 explicitly stated that even moderate drinking may increase the risk of cancer and some forms of cardiovascular disease as well as the overall risk of dying. This has been removed from the current guidance. Since the guidelines were first introduced in 1980, they have included specific guidance on the amount of alcohol that constitutes a reasonable limit with a suggestion to limit to one or two standard alcoholic drinks per day. Or more specifically no more than one alcoholic drink per day for women and no more than two alcoholic drink per day for men. This guidance has also been removed from the new guidelines.
And if we look at those guidelines again, we can see where this might be an issue, because the guidelines now say: “Consume less alcohol for better overall health”. But what does ‘less’ mean? For some it might mean cutting from eight drinks per day down to seven – a decrease, sure, but one that’s not really going to reduce your health risks in a meaningful way.
You may be tempted to think this is fine, because everyone already knows that alcohol consumption is risky. However, a study from the MD Anderson Cancer Center in Texas published late last year found that 53% of Americans don’t know that alcohol consumption increases your risk of cancer. Some − around 1% − even believe that drinking alcohol reduces your risk of cancer − presumably with a tip of the hat to those red wine drinking resveratrol rats. So removing these comments from the guidelines has potentially significant implications.
But what of Dr Oz? At least he told you that you should drink no alcohol at all, right? Well, yes, he did say that… but he also said that alcohol also provides “an excuse to bond and socialize, and there’s probably nothing healthier than having a good time with friends in a safe way.” And that in certain regions in Greece, Italy and Japan, where people live longer, they drink “very judiciously and usually in a celebratory fashion”.
So, do we think people take away from that, that alcohol has health implications? Or do we think that people will assume the social benefits of alcohol outweigh the risks? After all, he told us that “in the best-case scenario” we shouldn’t drink alcohol, and looking around the world, do we feel we are in the best-case scenario?
I’m going to leave the last word on this to the chief executive of the Alcohol Policy Alliance, one Mike Marshall (not to be confused with the editor of The Skeptic), who explained that as far as his group was concerned, omitting any mention the link with cancer is “a win for Big Alcohol”.
