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! 

Vitamin supplements: unexpected consequences

Over the last number of years, the vitamin and nutritional supplement market has grown phenomenally. It is estimated to be worth over $36 billion in the US, up from $17 billion in 2000. It is thought that nearly 70% of the US population take some kind of dietary supplement, and there is much said and written about their use. One thing that cannot be debated however, is the lack of evidence that they do any good. A prime example of this comes from a study published recently about vitamin B supplements.The study looked at vitamin B use and lung cancer. They decided to do this because a previous study had reported an increase in these cancers in people taking vitamins B12 and B9, but that study wasn't designed to look specifically at this, so more work was needed.This study looked at over 77,000 people between the ages of 50 and 76, over a number of years. The results were striking. Vitamin B6 or vitamin B12 use was associated with a doubling in lung cancer risk in men, if taken at above the recommended daily allowance. Since people generally have no idea what the recommended daily allowance is, and the levels of these vitamins can be very high in supplements, there may be many people putting themselves at risk. Indeed, the majority of people taking vitamins unknowingly exceeded the recommended daily allowence.There are a few details that are worth noting. First, the effect was only seen in men and not in women. Second, the association was even stronger in smokers, who are already prone to lung cancer. Third, this effect was present for B6 and B12, but not for people taking B9 (also known as folic acid). Finally, the authors found no beneficial effects of vitamin B supplements in any group.So what does this mean in real terms? Of the 37,049 men in this study, 1966 where found to be taking the highest dose of vitamin B. Of that 1966, 36 were ultimately diagnosed with lung cancer. If they had not been taking vitamin B supplements, this would be expected to be 18 lung cancer diagnoses. That suggests that high vitamin B use was associated with roughly an additional 18 cases of lung cancer. When you consider that this study had over 77,000 people enrolled, 18 additional cases of lung cancer may seem quite small, and these numbers are indeed dwarfed by the additional cases caused by smoking, but it is still significant.As always, I have to point out that this study did not show that vitamin B supplementation caused these extra lung cancers, just that men taking high doses were more likely to get it. As I have previously described, correlation is not the same as causation. However, this was a well carried out study, and the authors controlled for as many variables as they could, making it more believable that the vitamin supplementation is contributing to the cancers.What is clear however, is that vitamin B pills give no benefit on any health outcome. Considering that they may even be doing some harm, it emphasises that we should be cautious when supplementing our diet with unnaturally high levels of vitamins. It is generaly assumed that the more vitamins the better, but as this study points out, that is not the case. A healthy, varied diet more than meets our vitamin needs. Why spend money on supplements if we don't need them?

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.