Ultra-processed foods and cancer

This story was all over the news today:

“Ultra-processed foods may be linked to cancer, says study”The Guardian, 15^th Feb. 2018

The news comes from a French study that looked into whether cancer was associated with highly processed foods. As usual, the question is whether the actual results of the study warrant the hysteria currently playing out in the media? (Spoiler: the answer to that is almost always an emphatic NO!)First things first; this is an excellent study, with well carried out data collection and good analysis of the results. The authors looked at 104,980 people, and asked them to fill out a daily survey about their diet. Using that data they compared cancer rates to the people’s self-reported diets.The study found that high consumption of “ultra-processed foods” was associated with a 12% increased risk of cancer. In men, no one cancer type was specifically increased, in older women the foods were associated with an 11% increase in breast cancer.These studies are notoriously difficult to interpret, mainly because, aside from their diet, there are numerous differences between people. In this study for example, the participants who consumed a higher amount of ultra-processed foods were more likely to be smokers, and less likely to be physically active.Clearly, what people eat is only part of a larger lifestyle. People who eat healthily tend to be healthier in other areas of their lives, so it is very difficult to say that a specific dietary choice is actually causing cancer. The authors of this study tried to correct for things like this, but that is extremely difficult to do, something that was acknowledged by the authors in their paper.It is also worth saying that the definition of “ultra-processed” is a hard one to pin down. The definition used in this study was based on a food classification system called NOVA, but this is still not very clearly defined, which means it is difficult to draw any practical conclusions from it. Unfortunately, in the media the term is wielded to mean anything that isn’t “natural”, despite this being wrong. For example, according to the classification used in this study, gluten-free artisanal bread is ultra-processed, as are vegan health shakes, and organic protein bars.While this is a solid piece of research, the public reaction to it is likely to be misplaced. Unfortunately, it is likely to play into the “clean eating” fad, which is largely nonsense. It is now clear that the fashion for “clean eating” has legitimised eating disorders, and may in fact be doing far more harm than good.However, as global consumption of processed food increases, it is very important that we understand their impact on health. This research clearly warrants more study, but these findings alone cannot offer practical advice to consumers. As always, if you have a varied diet and get a bit of exercise, there isn’t much to worry about! 

Milk and Parkinson's

As the population has been getting older, there has been increased attention paid to neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. These are diseases that cause a progressive loss of mental function (dementia), or problems with movement, such as tremors. The causes of these diseases are still relatively unknown, so there is a lot of public interest in studies that look at this. This week a paper was published that suggests there may be a link between high consumption of low fat dairy (particularly milk), and Parkinson’s. This was picked up by numerous media outlets, with predictable headlines.

Do you eat 'low-fat' branded food? Parkinson’s disease could be triggered by THISThe Express, 12/06/17

It has been known for a few years that there may be a link between dairy consumption and Parkinson’s. However, this link has always been weak and controversial, so the benefits of drinking milk have far outweighed the potential harm. This week’s study took this further by analysing this link in a huge number of patients, far more than have ever been studied before.So what have they found? Well firstly, there’s no need to give up drinking milk. The study did NOT find that low fat milk causes Parkinson’s. That’s not to say the headlines were entirely wrong, but the study was not designed to find whether milk causes Parkinson’s. It was designed to see whether people who drank lots of low fat milk were more prone to the disease. This is a subtle distinction, but an important one. I have written about this in the past (correlation vs causation), but it is worth repeating. Just because two things are happening together, doesn’t mean that one is causing the other. On top of that, milk is full of nutrients, so cutting it out or the diet may have unintended consequences.This study was a big one, including nearly 130,000 people. Of those 1,036 people developed Parkinson’s over the course of the study. When they looked at how much milk these people drank compared to the rest, they found that there was no difference. However, if they specifically looked at the consumption of low fat milk, they found that people who drank 3 or more glasses per day were more likely to develop Parkinson’s. The association wasn’t very strong, with the general population having a 0.8% chance of getting the disease, and those who drink lots of  low fat milk having a 1% chance. It’s a small difference, but with an aging population, this could mean significantly more people with the disease.The authors of the paper are careful to emphasise that they are not showing that milk causes Parkinson’s. They make several alternative suggestions themselves, including the possibility that Parkinson’s itself affects dietary behaviour, causing people to drink more milk. However, it must be considered a possibility that low fat milk is increasing the rate of Parkinson’s.So is it advisable to limit your milk consumption? At present, the answer to that is no. Milk contains nutrients we need, including calcium and potassium, and has significantly less sugar than other drinks. Per glass (240ml), it has 2.6 teaspoons of sugar, compared to 5.2 teaspoons in orange juice, and 6.4 in Coca-Cola. Additionally, those at risk drank 3 or more glasses per day, which is quite a lot.In short, there is no need to start drinking black tea and putting water on your cereal. Paranoid people might want to limit their consumption to less than a litre a day, but I won’t be changing my habits on the back of this evidence!

Does Nutella cause cancer?

On a recent cycling trip in Canada, I ate an obscene amount of Nutella. It works as a great lunch, and dipping fresh bread in it is a delicious snack. When you are exercising all day every day, a tasty, spreadable, dippable energy source like this is extremely useful. Don’t get me wrong, it is a very unhealthy food, but despite this, I’m a fan.Which is why I was surprised this week to see Ferrero (the makers of Nutella) defending their product against claims that it causes cancer. A quick internet search revealed the problem. As the Tech Times put it: “Nutella Can Cause Cancer, Study Warns”. The Huffington Post ran with: “Stores Are Pulling Nutella After Report Links It To Cancer”, while the Daily Mail asked “Could Nutella give you CANCER?”. So what is this all about, and should you stop eating Nutella?As I’m sure you can guess, the simple answer is no, there is currently little evidence to suggest that you need to avoid Nutella. This panic was based on a study released by the European Food Safety Authority (EFSA) last year which suggested that when palm oil is refined at above 200°C, it releases something called glycidyl fatty acid esters (GE). Previous work has shown that at high levels this chemical can cause cancer in rats. Ferraro do indeed use palm oil in Nutella, so people have made an assumption that it therefore contains GE. However, Ferrero have clearly stated that they do not process their palm oil at 200°C, so no GE is produced in the process. Case closed.But for the sake of argument, lets pretend they do refine their palm oil at 200°C. Would the hypothetical amount of GE in Nutella be a cause for concern? In the EFSA report they quote the levels of GE that cause tumours in 25% of rats (10.2 mg/kg/day in case you are interested). Now obviously we would want to play it safe, and wouldn’t want to consume anywhere near that amount. So for argument’s sake, lets see how much Nutella we would need to eat to get 1/10,000^th of that amount (thanks to this article for calculating the numbers). It turns out that the average adult would need to eat nearly 100g of the stuff every day to reach 1/10,000^th of the amount that gives rats cancer. That’s over two jars a week, and if you are eating that much Nutella, then cancer is the least of your problems. The same amount of Nutella (800g) contains over 450g of sugar, which is double what your TOTAL sugar intake should be for a week.Simply put, concerns about cancer are a terrible reason to stop eating Nutella. Their use of palm oil has many other problems associated with it, including the devastating environmental impact, but that is another argument. As always, this is a case of poor journalism. The study itself didn’t mention Nutella, and was just focused on the GE. Some simple fact checking would have shown that Nutella does not process their palm oil in a way that produces GE, but there is nothing like a food scare to attract clicks.

Correlation vs Causation

The following headline caught my eye recently:

“Migraines could be caused by gut bacteria, study suggests”The Guardian – 18/10/16

To anybody who suffers from migraines, this is very interesting; at the moment, we really don’t understand what causes them. If a study has figured this out, then we may be able to help the estimated 15% of the population who are sufferers.This report is based on a paper published this week, titled:

“Migraines Are Correlated with Higher Levels of Nitrate-, Nitrite-, and Nitric Oxide-Reducing Oral Microbes in the American Gut Project Cohort”mSystems – 2016

The eagle eyed among you may have spotted the problem with this already. The Guardian has switched the word “correlated” for the word “caused”, so immediately you can see why the headline is wrong. Unfortunately the research did not show that gut bacteria cause migraines. What it did show was that people who suffer from migraines are more likely to have slightly different bacteria in their mouths than people who don’t. While this might lead you to think that there is a link, you cannot conclude this from the data. The difference between the two is easiest to explain in an example.The sales of ice-cream (A) correlates with the number of shark attacks (B). This could mean one of a number of things:

1. That A causes B.

Sharks are attacking more because people are buying more ice-cream.

2. That B causes A.

People are buying more ice-cream because of all the stark attacks.

3. That something else causes both A and B.

In good weather people go swimming more, and also buy more ice-cream.

4. That it is just coincidence that A and B are happening together.

Unlikely in this case, but actually extremely common, as I describe below.It is very, very easy to find correlations between random things. Take this fact, for example: the divorce rate in Maine is correlated with the consumption of margarine (see image below). This obviously does not mean that margarine causes divorces.Or the fact that the number of people who drown by falling in pools each year is correlated with the number of films that Nicholas Cage has been in that year. While it is tempting to suggest that Nicholas Cage films are so bad they are causing people to fall into pools, it seems a bit of an extreme reaction to his awful acting.These kinds of spurious correlations are everywhere if you look for them. There is a very good website (here) that mines data to find new ones, including the two examples I have used above. While these correlations are usually obviously nonsense, sometimes a correlation makes instinctive sense, and it is easy to believe that one thing is causing another, without actually having any evidence that it is true. This unfortunately can cause serious damage.As the rate of vaccination has increased over the last few decades, we have seen an explosion in the number of diagnoses of autism, which has led some people to claim that vaccines cause autism. It is an understandable assumption. The symptoms of autism appear at around the same stage as vaccination, so you can see why some parents jump to that conclusion. However, it has been clearly shown that there is no link between the two. In fact, the increase in the rate of autism is largely down to increased awareness and reporting, and not actually a result of more kids being autistic. Unfortunately however, the belief that these correlated events (autism onset and vaccination) are linked has led to a decrease in vaccination rates, and many preventable illnesses and deaths*.This problem of mixing up correlation and causation is common in the media, and an easy trap to fall into. Certainly correlation sometimes does mean causation, but without additional evidence we simply cannot say that it does. Correlation studies are common in science, and are an important research tool, particularly for informing future studies. Unfortunately, these are sometimes over-interpreted, and lead to things being linked without cause.The migraine study that I started this blog post with shows a correlation, but not causation. However, other studies have shown that chemicals that these bacteria produce can indeed cause headaches. While neither study is conclusive, it suggests that it may be worth following up these findings in further studies, which is exactly what the researchers recommend. Unfortunately, that wouldn’t make such a good headline. *It is worth pointing out that a certain percentage of people will get these illnesses, regardless of vaccinations. The numbers on the linked website above include these cases, so it is very difficult to know how many are directly due to decreased vaccination. It is clear though that the numbers have been increasing with decreasing vaccination rates, but if this blog post has taught you anything, it is that we cannot say that one has definitely caused the other. However, when combined with other available evidence, we can be very sure of that assertion. 

Hot drinks and cancer

You may have seen a frankly terrifying headline this week:

“Hot drinks probably cause cancer, warns World Health Organisation”Telegraph, 15th June 2016

Almost every news source carried this story, and the headlines were universally similar to the one above. This story comes from a report by the WHO, which looked at the association between coffee and mate (a South American herbal tea) and various forms of cancer. In short, they found that there was no association between coffee or mate and cancer, but that the temperature of the beverage may be linked to oesophageal cancer. This, of course, is nothing to worry about. The report classifies hot drinks as “probably carcinogenic to humans”, group 2A in their classification. Other items in this category are the act of frying food, working as a hairdresser or barber, red meat, and working night shifts. This categorisation tells us about the hazard of hot drinks, but not about the risk.The words "hazard" and "risk" are regularly used interchangable, so the distinction between them is one that is lost on most people. Hazard is whether something can happen or not. Risk is the likelihood that it will happen. There is a hazard of crashing when you are driving with your eyes open or with your eyes closed. However, the risk is quite different in each of these cases. This report tells us about the cancer hazard of hot drinks, but nothing about the cancer risk, so the fact that hot drinks are on this list isn’t very informative.So what do we know about the risk of hot drinks. Firstly, this applies to drinks consumed at 65°C or above. So if you put milk in your tea or coffee, then you’re ok. Even if you don’t, oesophageal cancer isn’t very common, so even a big increase in risk wouldn’t translate into many more cases (see below for an explanation of this). If you want to do something to decrease your already small chance of getting oesophageal cancer, then consider stopping smoking, stopping drinking, eating more fruit and veg or losing excess bodyweight, all of which are known risk factors.The system of classification used by the WHO is unfortunately ripe for misinterpretation. It is almost impossible to prove a negative, so proving something definitely doesn’t cause cancer is difficult. The WHO has now classified 1,051 different things for their likelyhood of causing cancer. Of those, they have only rated a single one as “probably doesn’t cause cancer”. (For those who are interested, that one thing is Caprolactam, a compound used in the production of nylon).Nearly half of the rest fall into the “not classifiable” category because we just don’t have enough evidence to say either way. This may be because the evidence is inconclusive, or because studies have never been done. In reality, if the WHO analysed whether swivel chairs caused cancer, they would fall into this category rather than the "probably don't cause cancer"one, because we have never needed to study it.So by the WHO system, we can't say that the following don't cause cancer: chlorinated drinking water, caffeine, mobile phones, fluorescent lighting, hair colouring products, magnets or tea. They are in the “not classifiable” category. However, aloe vera, pickled vegetables and dry cleaning are all classified as “possibly cause cancer”. As you can see, this classification causes more confusion in the general public than anything else.When you understand the difference between hazard and risk it becomes far easier to interpret the constant health scare stories in the media. “Mobile phones may cause cancer” is a terrifying headline, until it is put into this context. The increased understanding of risk is a vital tool in the rational toolbox. And because large parts of the media don’t seem to possess this, it is one that we can get a lot of use out of! Absolute risk v relative riskI mentioned above that even a large increase in risk of oesophageal cancer doesn’t mean many extra cases. To understand this you have to understand the difference between relative risk and absolute risk.Have a look at the diagram below. In both situations you have a 100% increase in relative risk. However, in one case this means your absolute risk goes from 1% to 2%. In the other  it goes from 35% to 70%.To to bring it back to hot drinks, imagine a crazy situation where they give us a 50% increase in risk for oesophageal cancer. (Just to be clear, there is not a 50% increased risk with hot drinks, I made that number up as an example of a large increase.)The rate of oesophageal cancer is around 15 cases per 100,000 people, so your risk of getting it is 0.015%. A 50% increase in risk means that the rate would rise from 15 to 22.5 cases per 100,000. In this case your risk has now gone from 0.015% to 0.0225%, an increase of 0.0075%.You can see how an enormous increase in your relative risk (50%) can mean only a tiny increase in your absolute risk (0.0075%). So when you hear someone say that x increases your risk of cancer, your first question should be “but what is the risk of me getting that cancer in the first place?”. Once you know that you will have a far better idea whether the rest of the claim needs to be listened to.

Trust in science

As with every other week, the last 10 days has brought a slew of tabloid stories, linking various things with causing or curing cancer:GOOD: antacids, Chinese herbal remedy, berries and tea, anthrax, frying foodBAD: being tall, tonsils, artificial football pitches, The RAF, oral sexAs always, these stories are largely nonsense, suitable only for the bin. Unfortunately, they are reported credulously and are widely read, and this saturation of health-related articles has several negative consequences.The constant bombardment of people with often-contradictory health information can drown out real health advice, making people think that eating some nuts can offset the effects of a terrible lifestyle for example. There is an enormous industry based on the peddling of cancer-preventing foods and supplements, often with a thin veneer of scientific respectability, and thanks to tabloid reporting, a much wider reach than should be allowed. It’s infuriating.However, the most insidious problem with poor media portrayal of science is the gradual erosion of trust in science. This may not seem like a significant issue, but it may be the most important. The rejection of vaccines, denial of climate change and resistance to genetic modification of foods, for example, are all rooted in science denial.This is an issue with many causes. Both political and religious beliefs play a major role in our view of the evidence, as does self-interest, meaning that arguments are often politicised or financially motivated. When Andrew Wakefield, for example, “found” a link between vaccines and autism, he personally profited from people not using the MMR.The driving force behind denialist movements are often organisations that stand to gain from the confusion (climate change denial has largely been funded by groups that will suffer most from restrictions on fossil fuels). There has been a deliberate drive to manufacture controversy in many areas, most famously by the tobacco industry, whose tactic was not to win the debate, but to “foster and perpetuate the illusion of controversy in order to muddy the waters around scientific findings that threaten the industry”. A leaked memo to George W Bush on climate change tactics from 2002 suggested that although the scientific debate was closing, it was important “to continue to make the lack of scientific certainty a primary issue in the debate”. Media organisations are often complicit in this, and there are many examples of the deliberate undermining of the scientific process, most notably by Fox News in the US.That being said however, the large majority of people who subscribe to denialist views are people who have no such motivation. These people appear to have a basic mistrust of science, and are swayed by the anti-science rhetoric. It is easy to understand why parents hesitated to vaccinate after the initial reports of a link to autism, but despite this link being definitively shown to be false, vaccination rates in large parts of the world are still suffering. Be it the left-wing embracing of alternative medicine, the right-wing support of climate change denial or religious creationism, the anti-science movement is a pervasive one, largely based on the mistrust of science.There are several roots of this mistrust. An obvious one is that science can undermine deeply held beliefs. When this happens, people are likely to reject the evidence, rather than give up their belief. In fact, when challenged on such a belief, people are more likely to strengthen their belief rather than the other way around (known as the “backfire effect”). This needn’t be a religious belief, and is something that has been observed in many areas of life, such as the belief in superstition or alternative medicine. If science continuously challenges these beliefs, then people stop believing in the science.It is also the case that a misunderstanding of what science actually is also contributes to this issue. Many people see science as an “institution”, something that is telling us what to do. The reality is that it is a process. This misunderstanding of science makes it much easier for people to rationalise the rejection of valid conclusions, regardless of the strength of the evidence. The power of anecdotal evidence is a classic example of this: “my father smoked 20 a day, and he lived ‘til he was 90”. This view of science as an “institution” also feeds into an anti-establishment mentality that can also result in science denial. This is the same mentality that is behind the belief in grand conspiracies.And this brings me back to the tabloids. If you are told every day that random things are making you sick, or are essential to health, it is likely that you will become desensitised to them. It is easy for people to reject science-based advice, because tabloid reporting makes science appear far more confused than it actually is. The reporting of preliminary findings, or of badly carried out science, leads to a confused picture of our current understanding. Scientists are constantly studying and learning, working towards the truth. Bad science and incorrect results are inevitable in science, but it is a self-correcting process that gradually works to show what is real and what is not.Our entire civilisation is based on scientific innovation and progress. While that progress cannot be halted, it can be slowed by the mistrust of the public in the scientific process. That can only be a bad thing.

Gluten-free diets

The last few years have brought an increased awareness of the presence of gluten in our diets. In line with this, the Daily Mail recently ran an article headlined “Could going gluten-free boost your brain power? Landmark study reveals diet 'reduces fatigue and increases energy levels'”.The article in question was published on the Mail Online. In it they report on a study that links a gluten-free diet to decreased fatigue, flatulence and bloating. There is so much wrong with the piece it’s difficult to know where to begin, so I’ll start with the most concerning issue: that the study was funded by Genius Gluten Free Foods.That’s right, this “Landmark” study was funded by the very people who will benefit most from its result. This fact alone throws up big red flags, but reading further brings up some other major issues.The study has not been published, neither online or in a peer-reviewed journal. I contacted the University of Aberdeen, The Rowett Institute and authors of the study, to try to get my hands on the data (or the press release the journalist was working from), but to no avail. From the article in the Daily Mail, I can say that the study itself had fewer than 100 people in it, far too small a sample size to say anything concrete unless the study used extremely stringent criteria (which it did not).Furthermore, the article itself points out that the participants ate a healthier diet while on the study, making it entirely possible (and likely) that the effects seen were not as a result of the gluten-free diet, but as a result of eating better in general.I could go on all day, but I’ll leave it at that. The article is clearly rubbish, but it does highlight the recent popularity of gluten-free diets however, and this is a topic about which there is a lot of controversy.Removing gluten from the diet has become big business. According to the BBC, 29% of American adults (70 million people) say they are trying to cut back on gluten. This results in a gluten-free market in the US of almost $9 billion. Here in the UK, sales of gluten-free foods were around £184 million in 2014, which shows just how common it has become.It is safe to say that there are certainly people who do benefit hugely from a gluten-free diet. These are people with coeliac disease, an autoimmune disorder that results a decrease in the ability of the intestine to absorb the nutrients it needs. It is thought that around 1% of the population have some level of coeliac disease, so it is a relatively common disorder. Additionally, most of that 1% are undiagnosed, so it is certain that a gluten-free diet can improve the symptoms of some people.Another group that may benefit from the diet are those with non-coeliac gluten sensitivity, but this is controversial, as it has not yet been shown that gluten sensitivity actually exists. The most definitive study into this (in 2013) showed that gluten was not causing the symptoms of the patients in their study. They laid the blame at the door of a group of carbohydrates known as FODMAPs (which are partially eliminated in a gluten-free diet). Other research has blamed ATIs, plant proteins that are common in grains. Regardless, diet clearly influences the symptoms in these people.With the caveat in mind that going gluten-free will help some people, it must be pointed out that the large majority of people trying to reduce the gluten in their diets have no need to. Studies have shown that at least two-thirds of people who claim they have non-coeliac gluten sensitivity cannot tell if they have been exposed to gluten or not. The design of that study also makes us confident that this is an underestimation. The same study showed that symptoms often got worse if the subjects thought they were eating gluten, suggesting that the nocebo effect plays a large role in their symptoms (I’ve previously written about the nocebo effect here. Put simply, it is an ill effect caused by the suggestion or belief that something is harmful).“Gluten-free” is a fad diet, albeit an extremely popular one. Gluten is widely perceived to be unhealthy, a contention for which there is little evidence. Celebrities (Gwyneth Paltrow, Miley Cyrus) and sport stars (Novak Djokovic) have further propagated this myth, leading to the boom in sales we have seen recently.The problem is that there are risks attached. It is known that some foods that are free from gluten are actually less healthy than the original variety because they may contain more fat or sugar and thus more calories. In order to attain the same texture and consistancy, starches and binding agents are often added. It has also been shown that avoiding wheat products can lead to deficiencies in nutrients such as folate.The majority of people who are gluten-free do it because they are under the impression that it is better for you. In reality, they are spending more money on products for no real benefit, and feeding an industry that encourages people to unnecessarily buy more expensive foods. Eating more fruit and vegetables is a much wiser investment.As I’ve already pointed out, there are people who benefit from a gluten-free diet. However, that is not the case for the majority. I’ll leave the final word to Dr. Ruth Kava, who is a Senior Nutrition Fellow at the American Council on Science and Health. She commented that “The bottom line is that if you don’t really need to go gluten-free, don’t bother. And to determine if you do, consult a gastroenterologist, not a celebrity diet guru.” Well said.

Confused by what you read in the papers?

There are constantly contradictory science news articles in the papers, particularly surrounding our health. Aspirin, milk, breast-feeding, money, sex and pizza have all been reported in the main stream press to both cause and prevent cancer (amongst many other things; this website is well worth a read!).Take, for example, statins. This week it was reported that they can reduce complications after surgery. This may confuse you; didn't the same papers warn us this year that statin use may be killing hundreds? Although, don't statins cure prostate cancer? And make women angry?Statins are the most commonly prescribed drugs in the UK. They are used to lower cholesterol levels, and as such help prevent cardiovascular disease. Sir Roger Boyle, the government’s former National Director for Coronary Heart Disease, claims that statins save 9,000 lives a year in the UK alone (I have been unable to find a source for this claim however, so cannot guarantee its accuracy).However, while it is well established that they are effective in high-risk groups, the evidence for their effectiveness in low-risk groups isn’t as strong. Two papers in 2013 suggested that statin use in low-risk patients did more harm than good, but both of these papers have been heavily criticised, and the authors of both have retracted statements regarding the frequency of side-effects. A large review of the literature confirmed that statins were safe and effective at reducing heart attacks and stroke in low-risk groups, but that the benefits were quite small, and that more could be done through life-style changes than statin prescription.The point of this blog is not to write about the use of statins however; it is to highlight the terrible way in which it is reported. A cursory glance at the infographic above shows how confusing the reporting on statins is. As the graphic shows (click image for expanded view), in the Daily Express alone there has been 15 separate stories about statin use this year, 8 negative and 7 positive. The Daily Express isn't alone in this. The Telegraph had 7 stories (3 positive and 4 negative) and the Daily Mail had a staggering 27 (14 positive and 13 negative).The current consensus is that statins do far more good than harm, however poor reporting such as this causes people to stop taking their medication. This happened in Australia following a documentary into statin use, when an estimated 60,000 people stopped taking their prescription. This almost certainly led to fatalities. Shortly after that, an investigation concluded that the documentary had breached standards of impartiality, and the programme was withdrawn. We have seen the same pattern with vaccine use, among other things.Science is an ongoing process and studies into things such as health must be put in to perspective. Most stories in science need to be seen in context, something which rarely happens in tabloids. Reporting on every little study, regardless of the quality of the study, can leave people with the impression that disagreement within the scientific community is much greater than it actually is. This can lead to problems, as we have seen in climate change and vaccines for example.Science communication and reporting is absolutely vital for generating enthusiasm in science, which itself is essential for progress. The more scientists and engineers we have, the better.Unfortunately, people are too easily persuaded to stop taking their prescriptions, or to stop vaccinating their kids. It is true that there must be some public oversight of health interventions, but the pages of tabloids is not the place for this. Unfortunately, scare stories and testimonies of miracle cures sell papers, so this is a problem that we may unfortunately be stuck with.

Can we predict cancer a decade in advance?

The Daily Mail, The Telegraph and The Independent are among the many media outlets that reported this week that we could predict cancer a full decade before it appears. Some outlets even went as far as to claim that we could predict it with 100% accuracy 13 years in advance. Unfortunately however, this is media hype of a study that makes claims its data cannot support, helped by a poor press release. There is some interesting science behind this headline, but the simple fact is that we cannot detect cancer that far in advance. If a news story appears too good to be true, then it probably is.The cancer test that these articles are referring to is telomere measurement. Telomeres are protective caps on our DNA. They are found at the end of every chromosome and protect the DNA from degradation. They are often compared to the plastic tips at the end of shoelaces, which protect them from unravelling. They are needed because cells in your body divide at an incredible rate, and every time a cell divides new errors can be introduced to the DNA.To try to get around this problem, every very time a cell divides the telomeres get a little shorter, and when the telomeres get too short, the cell stops dividing. This ensures that no more damage is accumulated, and makes sure that older, damaged cells stop dividing. As a result, telomeres play an important role in ageing (older cells have shorter telomeres than young cells), but also in cancer. Cancer cells, which divide indefinitely, are able to overcome this natural stopping mechanism by building their telomeres back up. Because of this, telomeres have been studied in cancer for decades.This week, a study was published in EBioMedicine which tried to relate changes in telomere size with the odds of developing cancer. To do this, the authors tracked the changes in telomeres in our blood cells over the course of 14 years. They then looked at these changes in patients who developed cancer during the course of the study, as opposed to those who were cancer free. What they report is that patients who are going to develop cancer lose their telomeres at a quicker rate until 3 – 4 years pre-diagnosis, when the trend reverses and the telomeres loss slows down. They suggest that this could be used to predict cancer years before standard diagnosis is possible.The paper has several problems, particularly with the interpretation of the findings. I have included a more technical explanation of some of these problems in “Further Explanations” below, but the authors themselves acknowledge some of these in their discussion.

“Thus, caution should be exercised in interpreting our results as different cancer subtypes have different biological mechanisms, and our low sample size increases the possibility of our findings being due to random chance and/or our measures of association being artificially high.”Hou et al. EBioMedicine 2015

They correctly point out that various cancers act very differently, and crucially that their conclusions may be down to pure chance. This type of correlational study (where measurements are taken and then compared with other things to see if they correlate) is useful as initial data to inform what needs to be studied further, but it is very prone to false positives. It is inevitable that pure chance will cause some correlations in the data. For example, in this study they also reported that less educated people have longer telomeres than their more educated counterparts. Whether this, or the correlation they found with cancer, is true or not can’t be determined without further study.The scientific method is based on the reproducibility of experiments, with the more implausible the finding, the greater the need for repetition. In this case we have an implausible finding using questionable interpretations of the data. While it can’t be ruled out that there is some truth in this finding, it would need to be extensively studied further before any concrete conclusions can be drawn about telomere length in the blood and cancer. But for the time being, we can say that we won't be predicting cancer with this method any time soon.Further ExplanationThe biggest problems I have with this paper are in Figure 2 (above). Firstly, the authors base their conclusion on the fact that there is a statistically significant difference between the groups 3 – 5 years pre-diagnosis (demonstrated in the Figure with “*”). This seems like “cherry picking”, whereby people pick their data to suit their hypothesis. As you can see, any difference between the groups disappears in the 1 – 2 years before diagnosis, a fact that is ignored by the authors. Should their hypothesis be correct (and the cancer is causing decreased telomere degradation), the difference in telomere length should persist.Secondly, the comparison they make in this figure is between the years before people got diagnosed with cancer, versus years before the end of the experiment. As the people who get cancer are inevitably younger than the people who get to the end of the experiment without it, the cancer-free people in this analysis are likely to be significantly older than those diagnosed with the disease. The authors have already shown that telomere length declines with age, so this could be playing a major role in the observed results.