Best and Worst Foods to Lower Your Colorectal Cancer Risk

What is colorectal cancer?

Colorectal cancer (also known as colon cancer, rectal cancer or bowel cancer) refers to cancer of your colon (large intestine) and rectum (gastrointestinal tract connecting the colon to the anus). What you eat and drink plays a role in your risk of colorectal cancer and overall gut health.

Your colon plays an essential role in your digestive system by processing waste through elimination from your body. When the cells lining the colon grow abnormally, they may form polyps or tumours, which can become cancerous over time.

Colorectal cancer is very common; in Singapore, it was the 2nd leading cause of cancer-related deaths according to a 2021 Singapore Cancer Society report. The World Health Organisation (WHO) also reported in 2023 that colorectal cancer was the 3rd most common cancer worldwide and more common in developed countries.

Colorectal cancer treatments

The right combination of treatments and dietary adjustments can help manage the disease effectively. If you develop colon cancer, your doctor will assess your individual situation and the stage your cancer has reached to determine an appropriate treatment plan. Typical cancer treatments include :

• Surgery to remove the cancerous tissue or tumours. If the disease has spread, your surgeon may need to remove an entire section of your intestine and reattach the healthy sections.
• Chemotherapy , which helps eliminate any remaining abnormalities and prevent the cancer from spreading or returning.
• Radiation therapy if the tumour is large or aggressive.
• Participation in clinical trials of new drugs or treatments, if your doctor recommends it.

The role of your diet during treatment

You should always follow your doctor's advice when undergoing treatment for any illness. Cancer is a serious and life-threatening condition and your oncologist will put together the best treatment plan for your individual situation.

Eating healthy to lower colorectal cancer risk

Prevention is better than cure. Research has shown that a diet high in fat, red and processed meats, sugary and ultra-processed foods, and excessive alcohol increase the risk of colorectal cancer.

On the other hand, a fibre-rich diet isn't just about bowel regularity; it supports gut health and is a crucial shield against colorectal cancer. Foods high in fibre, including leafy vegetables, beans, and whole grains, are your colon's best friend. They boost digestive health while keeping things moving smoothly. Fibre-rich foods also help regulate blood sugar levels.

Superfoods to fight colorectal cancer

Your diet plays a key role in reducing colorectal cancer risks. Here are some of the best foods to reduce risk and improve your gut health.

Vegetables

Broccoli and other cruciferous vegetables such as kale, cabbage, and cauliflower contain compounds like sulforaphane that may help reduce cancer risk by supporting detoxification enzymes and regulating cell growth.

Asparagus and spinach are also nutrient-rich green vegetables, providing folate, fiber and carotenoids, which have been associated in large studies with a lower risk of colorectal cancer.

Colourful vegetables such as tomatoes and bell peppers add a splash of colour to your plate while also providing a variety of helpful nutrients.

Beans and legumes

Beans, lentils and chickpeas are high in fibre, resistant starch and plant protein. Research indicates that regular legume consumption is associated with reduced colorectal cancer risk. Black beans and other legumes also produce beneficial short-chain fatty acids in the gut which may help protect colon cells.

Nuts

Nuts and seeds like walnuts, peanuts, flaxseed, and chia are packed with healthy fats, fibre, and antioxidants. In a Journal of Clinical Oncology study, colorectal cancer patients who ate two or more servings a week had lower recurrence and death rates. One serving is about a small handful (28 g or 2 tablespoons of seeds). Because they’re also high in calories, enjoy them in moderation as part of a balanced, cancer‑preventive diet.

Fatty fish

Fatty fish such as salmon, sardines and mackerel are rich in omega-3 fatty acids, which have anti-inflammatory properties. Observational studies suggest that higher fish intake may be linked to reduced colorectal cancer risk, though findings are not entirely consistent. Including fish as part of a balanced diet is supported by cardiovascular as well as cancer-prevention benefits.

Lean poultry

Replacing red and processed meats with lean poultry is a practical step. The World Health Organization classifies processed meat as carcinogenic and red meat as probably carcinogenic. Poultry, on the other hand, is not associated with increased colorectal cancer risk, making it a healthier protein option.

Fruits and berries

Fruits are packed with fibre, vitamins, and antioxidants, which can help lower your risk of colorectal cancer. Fibre-rich fruits such as papaya, banana, pear, and dragonfruit, are a sweet way of adding fibre to your diet, aid in digestion and contain antioxidants to boost heart health . Opt for fruits as a naturally sweet dessert to end your meals.

Berries are especially beneficial, thanks to their high levels of anthocyanins and other phytonutrients. In fact, some research suggests that black raspberries may even help prevent precancerous changes in the colon. By incorporating a variety of fruits and berries into your diet, you can support your gut health and overall wellbeing.

Coffee

Coffee has been linked to lower recurrence and mortality in colorectal cancer patients. A Journal of Clinical Oncology study found that patients with stage III colorectal cancer who drank at least four cups per day had a 42% lower risk of recurrence and 33% lower risk of death compared to non-drinkers. Moderate coffee consumption also supports metabolic health.

What are the foods to avoid for colorectal cancer?

To reduce your risk of colorectal cancer, here are some of the worst foods to avoid.

High glycaemic load foods

Foods with high glycaemic load (e.g. white rice, noodles, cakes, sugar) are associated with adverse outcomes in patients who are overweight or diabetic.

High glycaemic load diets are associated with increased colorectal cancer risk, likely through effects on insulin and growth factors. This is because these foods trigger a greater tendency toward insulin resistance. Insulin and its associated hormones are thought to increase cancer risk.

Glycaemic load is a measure that takes into account the amount of carbohydrate in a portion of food together with how quickly it raises blood sugar levels. A high glycaemic load refers to foods with a value of 20 and above.

Red meat

Red meat such as beef and pork has been associated with a modest but significant increase in risk. There are several potential reasons to explain how red meat may cause colon cancer. Red meat contains a compound called haem, which gives its red colour. This compound promotes the formation of N-nitroso compounds that can potentially cause cancer. Additionally, when red meat is cooked at high temperatures, carcinogenic compounds are produced that can cause colon cancer in people who have a genetic predisposition.

Limit your red meat intake and swap it for fish, lean white meat or plant protein like tofu instead.

Processed meats

Processed meats often contain chemicals and preservatives that research suggests may be carcinogenic. A carcinogen is an agent with the capacity to cause cancer. They work by interacting with a cell's DNA and inducing changes to it (mutations).

Processed meat refers to meat that has been preserved by curing, salting or adding preservatives. This includes ham, sausage, bacon, deli meats such as salami, canned meat such as corned beef and sliced luncheon meats, including those made from chicken and turkey.

Processed meats have compounds called nitrites and nitrates that are added as preservatives, which are thought to cause cancer. Processing also changes the nature of the meat, which may play a role in its link to cancer. The majority of your diet should be made up of fresh food.

Ultra-processed food

Ultra-processed food (UPFs) refer to foods that have been heavily modified from their original form and often contain added sugars, salts, fats, or oils that are refined from other ingredients. UPFs include instant noodles, nuggets, hot dogs, and sweetened soft drinks. A 2023 study found that men who consumed more ultra-processed foods had a 29% higher risk of developing colorectal cancer compared to those who consumed the least.

While research is still developing, the evidence supports limiting UPFs and choosing fresh, minimally processed foods instead.

Alcohol

Drinking alcohol can increase your risk of colorectal cancer and other conditions. Studies have shown that moderate to heavy drinking can raise the risk by 20-50%. This is because alcohol can damage DNA, cause oxidative stress, and affect how your body absorbs nutrients.

It is best to limit your intake or avoid alcohol altogether if you want to reduce your cancer risk, as even light drinking carries some risk.

A balanced diet is key

The most important dietary change to remember is that a healthy, balanced diet will give you the best chance of maintaining your health and fighting illness or disease. Include adequate fruits, vegetables, whole grains and lean protein in your nutritional intake and minimise your intake of simple carbohydrates and processed food. Some recipe ideas that include cancer-fighting superfoods are:

• Stir-fry vegetables such as broccoli, tomatoes and carrots with garlic 
• Steamed chicken rice with tofu and kang kong
• Baked salmon with pesto sauce and quinoa salad
• Sliced fish soup with tomatoes and spinach and brown rice or bee hoon
• Acai bowls or protein shakes topped with walnuts, flaxseed and blueberries
• Chia pudding with berries and almond
• Lentil and vegetable curry served with wholegrain chapatti

When should you talk to your doctor?

If you are undergoing cancer treatment, speak with your doctor for a personalised health plan before making any significant changes to your diet or lifestyle.

Working with a dietitian can help make healthy changes feel more achievable. Simple swaps, like choosing wholegrains over white rice or opting for fish instead of red meat, can make a big difference to your digestive health and cancer risk. Also, enjoying fresh fruit as a sweet treat is a great way to cut back on sugary desserts.