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Eating plenty of wholegrains cuts your risk of bowel cancer, according to a new report.

And it seems we can reap the benefits without making wild changes to our diets (unless your diet is mainly hot dogs and fry-ups).

The news comes from a report produced by the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR), outlining the latest evidence on how we can reduce our risk of bowel cancer.

It focusses on the effects of diet, weight, physical activity and alcohol on bowel cancer risk. And with bowel cancer being the fourth most common cancer in the UK, finding ways to reduce our risk of the disease are important.

The WCRF studies all the evidence on a potential cause of cancer and decides whether that evidence is strong enough to support recommendations on ways we can reduce our risk.

For bowel cancer, we already recommend that people include plenty of wholegrain options in their diet. So the new report is welcome.

But what is a wholegrain? We take a look at what they are and how you can get more into your diet.

What’s new in the report?

The proven things you can do to reduce the risk of bowel cancer have remained constant over the years, and this report reinforces that.

What was true yesterday is even more true today.

The most interesting finding from the new report is that for the first time, the WCRF team looked at the effect of wholegrains on their own (a food high in fibre and other nutrients).

Previously, WRCF has only looked at the combined effects of foods high in fibre, and found that eating more of these can reduce the risk of bowel cancer. But other research looking at different types of high fibre foods has found that the strongest evidence for reducing bowel cancer risk comes from wholegrains.

And the conclusion of the latest report is that there is now strong evidence that both wholegrains specifically and a high fibre diet in general reduce the risk of bowel cancer.

What’s a wholegrain?

A grain is the seed of a plant. Grains are made up of three parts: the bran, germ and endosperm. During the milling process, the bran and germ are lost, leaving whiter refined grains, such as white flour. This part of the grain is mainly an energy store, so refined grains give you carbohydrates and some protein but not much else.

A wholegrain still has its bran and germ, such as in wholemeal flour. Most of the nutrients and fibre are found in these bits, which means that wholegrains are naturally more nutritious than refined grains. And this is the likely reason why wholegrains are linked with a reduced risk of bowel cancer.

How do wholegrains cut bowel cancer risk?

This is most likely down to the fibre they contain.

Fibre increases the size of your poo, dilutes it, and helps it move through your system quicker. This reduces the amount of time harmful chemicals stay in contact with the bowel, potentially reducing the damage caused to cells.

Fibre may also help gut bacteria produce helpful chemicals that change the conditions in the bowel.

This is why foods high in fibre have been linked with reducing the risk of bowel cancer for many years now.

But other things in wholegrains, such as phenolic acids, could also be playing a role, and may partly explain why wholegrains seem to show a strong link on their own.

Eating more high-fibre wholegrains and fewer refined grains can help you keep a healthy weight by feeling fuller for longer. This not only cuts the risk of bowel cancer, but 12 other cancers too.

How much wholegrain should we be eating?

The UK’s dietary guidelines recommend that we base our meals on starchy foods, and where possible choose wholegrain versions. But there aren’t any specifics on how much we should eat.

The WCRF report found, based on all the studies published on wholegrains and bowel cancer to date, that for every 90g of wholegrains eaten daily, there was a 17% reduction in bowel cancer risk. This is what’s known as a relative risk (more on that here), which tells us how much more, or in this case less, likely the disease is to occur in one group (people eating 90g of wholegrains), compared to another (people who didn’t eat wholegrains). And because this is for every 90g eaten it underlines that the benefits increase the more wholegrains you eat.

This isn’t a guarantee though, because relative risk can’t tell us about the overall likelihood of bowel cancer being diagnosed in any one person. But with more than 41,000 cases of bowel cancer diagnosed in the UK each year, a 17% reduction in risk could make a sizeable dent.

For example, we already know that eating more foods containing fibre, of which some will be wholegrains, could lead to 5,100 fewer cases of bowel cancer each year in the UK.

So 90g isn’t a magic number, and it doesn’t mean you need to start weighing your food. The key thing here is that by switching to wholegrain versions of your everyday starchy foods you can easily meet this amount and more. And every bit counts.

So whether it’s switching to wholemeal breads, opting for a wholegrain cereal at breakfast (such as porridge oats, shredded wheat, or Weetabix (or your supermarket’s own brand), having plain popcorn instead of crisps or choosing brown rice and whole wheat pasta, all these swaps can make a big difference. If you don’t eat many wholegrains, try switching for just one meal a day.

Wholegrains vs. hot dogs

It’s not just wholegrains we should be thinking about when it comes to bowel cancer and diet.

The latest report also found strong evidence that processed and red meat increase the risk of bowel cancer. This isn’t a new finding, and is something we’ve written about before.

This doesn’t mean you have to be a vegetarian. Too much meat isn’t very good for you but eating it a few times a week probably won’t do much harm. It’s all about balance.

Tried-and-true advice

Beyond diet, this report reinforced the strong evidence that being overweight and drinking too much alcohol also increase the risk of bowel cancer, while being more physically active decreases the risk, adding more weight to previous similar findings.

So our advice remains the same: choose wholegrains and other fibre-rich foods, eat plenty of fruit and veg, keep active, limit your alcohol, and keep a healthy weight.

The science is clear: it’s putting it into practice that’s trickier. We have plenty of hints and tips on our website and we’re also working for better government policy to make being healthier easier for everyone.

Emma Shields is a health information officer at Cancer Research UK

Comments

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Emma Shields October 18, 2017

Hi Anna,

Thanks for your comment. We’re sorry to hear you lost your mum recently. When we were developing the infographics in this post we checked with the World Cancer Research Fund, who told us the 90g amount they found in their study was referring to the weight of cooked food.

As we said in the blog post though, 90g isn’t a magic number, and you don’t have to eat your daily wholegrains all in one go. The key thing is that by switching your everyday starchy foods (like bread, cereal and rice) to wholegrain versions, it’s easy to eat more fibre and cut the risk of bowel cancer.

Of course, everyone’s portion sizes will be different. We hope this is useful, and you keep enjoying your porridge!

Emma, Cancer Research UK

Anna October 16, 2017

Is a bowl of porridge really 90g of wholegrain? I make mine with 40-50g oats plus milk/water. That’s a pretty big bowl when made but how can the weight of the wholegrain itself increase? Please explain. I’m keen to know & take steps as I lost my mum to bowel cancer recently.

Mrs P Lilley October 7, 2017

I am hopeful that my other half will stop eating processed meats on his sandwiches. I just need more recipes that are easy to make & doesn’t involve too many spicy ingredients that I will not use very often & end up having to throw them away.

Stephen Hill October 6, 2017

Thank you for the very important information contained in your bulletin. I then read, with some alarm, the comment that Kathryn Stringer wrote. I was sorry to read of her having suffered with bowel cancer on two occasions at fifty eight years of age and a sense of unfairness is very evident considering her implacable lifestyle. Kathryn mentions a lack of family history of bowel cancer but it is worth knowing that hereditary conditions often miss generations and may come from way back. Also, as unfair as it is, where there are those such as Kathryn doing all the right things, to mitigate against disease, there are others who do just the opposite and remain disease free – it’s just like the roll of the dice but one thing I am certain of is that, for most of us, if we follow the advice given in your article we will reduce the possibility of suffering from bowel cancer.

Kathryn Stringer October 6, 2017

I have never smoked, drink only socially some weeks no alcohol at most 3-4 units a week.I am 5 foot 4 ins tall , weigh 8 st 8 lbs . I attend the gym 3-4 times a week and walk 5- 10 miles at weekend. I eat a healthy diet, porridge every day, whole meal bread and plenty of fruit and vegetables. Yet I have had bowel cancer treated with surgery and chemo- therapy at the age of 58 yrs. I have no family history of bowel cancer or any cancer at all. I know a healthy life style helps but sometimes nothing can prevent this happening.

Christine Taylor October 6, 2017

I find your blog posts very interesting and informative and as a volunteer fundraiser for Cancer Research I like to pass this information onto my friends, family and supporters. Regarding Wholegrains I recommend Swedish Krisrolls I usually have them for lunch but they’re also great for snacking on while waiting for your mealtime.

Fiona Newton October 6, 2017

Very helpful explanation, I find whole grain foods more tasty anyway than bland refined foods eg brown rice and pasta so it’s good they are beneficial to health

Emma Shields September 11, 2017

Hi Alice,

Thanks for your comment. The WCRF report found what’s called a dose-response relationship between wholegrains and bowel cancer risk. This means you are right, the more wholegrains eaten, the more they found that risk was reduced, which is good news. But it’s important to point out that this is a relative risk, not an absolute risk (we’ve written about what that means in detail here). A relative risk can’t tell us definitively what will happen on an individual level, only how more or less likely it is to happen between two groups (in this case the likelihood of developing bowel cancer between people eating wholegrains and people not eating wholegrains). There will also be lots of different factors that come together to form an individual’s risk of cancer. That’s why our advice for reducing the risk of bowel cancer includes choosing wholegrains and other fibre-rich foods, eating plenty of fruit and veg, keeping active, limiting your alcohol, and keeping a healthy weight.

For more detail on the findings, you can read WCRF’s full review here.

Best wishes,
Emma, Cancer Research UK

Alice September 8, 2017

In generally I really like your blog posts and I think the infographics are great to clearly communicating important information about cancer to a variety of audiences. I work in Cancer Research and I always keen to read them. However I have one concern about this post. In the “Easy way to eat wholegrains” infographic you state that there is a 17% reduction in bowel cancer for every 90g wholegrain per day. I interpret this as 90g = 17% risk reduction, 180g = 34% risk reduction, 360g = 68% risk reduction etc.
I know this cannot be the case but stating “every” 90g seems to suggest this. Could you clarify?