Nutrition - colon (colorectal/bowel) cancer

Tuesday 08 May 2018

This month we are going to look at how to support the body during and after treatment for bowel cancer (colorectal cancer). We are going to cover this topic over two blogs. Firstly we are going to look at how to support the body whilst going through treatment, including a low residue diet, and next month we will look at how to help your body recover after treatment. Here is a link to the blog about nutrition post-treatment.

In July 2017 I wrote a blog called the ‘ideal diet'. As I wrote, this is the diet I would recommend as being the ideal way of eating, if you are in a position to follow it. The reason I have called it ‘ideal’ is because it doesn’t mean you have to follow it exactly but it is a good framework to base your day to day eating on. Obviously when you have been diagnosed with cancer, are going through treatment, or even after treatment, your appetite and digestive system can be very affected. This can impact on how easy it is to follow this eating plan.

Some people who have colorectal cancer may be advised to follow a low residue diet for a period of time to support the functioning of their bowel. This can be for many different reasons.

What is the low residue diet?

A low residue diet can be recommended to people to help prevent blockages in the bowel which can occur because of the tumour growth which can narrow the digestive tract. This means reducing foods which are poorly or partially digested. These types of foods are usually high in fibre which adds bulk to the stool and can cause the blockage.

As well as following a low residue diet, people can also find that very fatty foods might be difficult to digest and may cause discomfort if eaten in large quantities. Spicy foods can also cause some discomfort.

Vegetables that are part of the brassica family of vegetables – these include broccoli, cauliflower, cabbage and Brussel sprouts – can all create wind and bloating in the bowel, and are ones that people may need to be mindful of when following a low residue diet.

Usually low residue diets are not recommended for long periods of time, but can be recommended when re-introducing food after surgery or during treatment to prevent bulking in the bowel. Normally the cancer care specialist in the hospital or the dietitian will give you guidelines on a low residue diet.

How to help your nutrient intake when on a low residue diet

If you have been advised to follow a low residue diet, it is important to follow this advice, especially as this is usually for a short period of time. When following a low residue diet, it is more challenging to get high levels of nutrients into the diet. When on a low residue diet, within the foods you can eat, you can still choose ones that have the highest phytochemical content possible – these have the brightest colour, strongest odour and ones that taste the way they should. I wrote a blog about phytochemicals which contains more information you may want to read.

I often get asked about wheatgrass and if it is possible to have this when you are on a low residue diet. Yes it is possible, and it is a very good way to get a good range of essential nutrients into your diet when needing to follow a restricted diet. Wheatgrass contains potassium, Vitamins B, A, C, E, K, zinc, copper, manganese and selenium, as well as being a good source of protein. It could be added to cold drinks, or sprinkled onto foods.

What to do if you are struggling with the side effects of treatment

Unfortunately, treatments for cancer can come with side effects that can affect our digestive system, and also our appetite. If you are suffering from these, then you have to listen to your body and just do what you can do on that given day. In July 2012 I wrote blogs on how to deal with the side effects of constipation and diarrhoea, how to cope with the change of taste and smell, and also difficulty swallowing. These would be worth reading to see how you can support yourself with these changes.

What can you do to support your body during treatment?

The best approach to adopt while going through treatment as mentioned above is to base your eating pattern on the ideal eating plate. This will be very nourishing for the body, and most importantly is aimed at really helping to support and boost your immune system. Our immune system is incredibly important for our overall health, and by boosting this you will be doing everything you can to help your body to heal itself. I wrote a blog about nutrients to boost the immune system, that you might find helpful.

When going through treatment, the balance of bacteria in our bowels will be affected, as treatment can destroy our levels of positive bacteria that usually live in our gut, especially if the treatment is directed at the colon. Next month we will spend a lot of time focusing on how to redress this balance after treatment by revisiting the role of probiotics in our diet. During treatment, it is not normally recommended to take probiotics, which are the living positive bacteria. Instead, during treatment, if you are not following the low residue diet, you can look at ensuring you have a positive intake of a food group called pre-biotics. These are not the positive bacteria, but instead these are the food that feed them when it reaches our gut. These are predominantly found in the residue of fruits and vegetables.

Are there any other areas of interest?


This year, the American Society of Clinical Oncology carried out an observational study on 826 stage III colon cancer patients. They found that the patients who consumed 2 ounces or more of nuts per week had a 42% lower chance of cancer recurrence and 57% lower chance of death compared to those who didn’t eat nuts. This research, however, did show the benefits were only found from the nuts of trees and peanuts were not included, perhaps because they have a different composition to tree nuts. The intended next steps from this research is to understand exactly what part of the tree nut creates the health benefit and then move forward towards a clinical trial. Remember observational studies are interesting but not the gold standard.


Another piece of interesting literature was shown in the Journal of Cancer in June 2016. The research was from University of Saint Louis, and showed that combining two herbs – milk thistle and curcumin –  had the potential to inhibit colon cancer cells from multiplying and spreading. Again, more research is needed but initial signs are promising.


On Cancer Research UK's website is a trial looking at the role of resveratrol during treatment. They believe that when we have resveratrol in our diet, some of it is absorbed and used by the body, whilst some stays in our mucosa lining of the digestive tract, where it has the potential to affect the growth of cancer cells in the colon. We are waiting for the findings from this research to be posted and is something to look out for.

Please remember – before taking any supplements during treatment, you need to speak with your oncologist first.

This blog gives general guidelines only as it is quite difficult to give anything too specific because colorectal cancer affects people in so many different ways depending on where the cancer is in the bowel and its extent. Also, people's bowels are like fingerprints – individual to that person, consequently recommendations can be very individual.

Useful blogs

Phytochemicals - (part 1)

Phytochemicals - (part 2)

Phytochemicals update

Blog originally written by Caroline October 2017 – links updated April 2021

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