The relationship between diet and intestinal cancer is not a hypothesis — it is one of the most consistent fields within evidence-based preventive medicine.

But there is an important problem: much information circulates in simplified or even distorted form.

Not every food "causes cancer".

And not every healthy habit is sufficient, on its own, to prevent it.

Here, the central point is accumulated risk over time.

What are the main intestinal cancers?

When we talk about "intestinal cancer", most people think only of colorectal cancer, but there are other relevant types:

Colorectal cancer (colon and rectum)

  • The most common

  • Usually starts as a benign polyp that transforms over years

Small intestine cancer

  • Rarer, but it exists

  • Can be more difficult to diagnose early

Intestinal neuroendocrine tumours

  • Slower growth

  • Often discovered incidentally

Intestinal lymphomas

  • Associated with the immune system

Despite the differences, there are common dietary and inflammatory factors that influence risk.

The role of diet: where is the real risk?

Red meat and processed meats

Here there is a well-established association:

  • Frequent consumption (mainly in excess)

  • Preparations at high temperature (grilled, barbecued)

  • Presence of compounds such as nitrites/nitrates (in processed meats)

All of this increases the risk of colorectal cancer

Important:

It is not about "prohibiting", but about frequency and quantity.

Ultraprocessed foods

  • Rich in saturated fat, sugar and additives

  • Low nutritional value

  • Associated with chronic inflammation

Persistent inflammation = favourable environment for tumour development

Low fibre intake

This is one of the most neglected points:

  • Fibre increases intestinal transit

  • Reduces the contact time of potentially carcinogenic substances with the mucosa

  • Feeds healthy gut microbiota

Diets low in fibre increase the risk of intestinal cancer

Alcohol

  • Direct carcinogenic effect

  • Dose-dependent relationship

The greater the consumption, the greater the risk

Symptoms: when the body begins to signal

One of the biggest problems is that symptoms can be silent at the beginning.

When they appear, the most important ones are:

  • Blood in stool (visible or hidden)

  • Change in bowel habit (persistent diarrhoea or constipation)

  • Frequent abdominal pain

  • Sensation of incomplete evacuation

  • Unexplained weight loss

  • Anaemia (especially iron deficiency)

  • Persistent fatigue

None of these signs should be ignored, especially if they persist for weeks.

How to reduce risk in practice

Here is a strategic point: prevention is not a single isolated habit.

It is a combination.

Diet

  • Increase fibre intake (fruits, vegetables, legumes, whole grains)

  • Reduce red meat (mainly frequent consumption)

  • Avoid processed meats (processed meat products)

  • Prioritise unprocessed foods

Lifestyle

  • Regular physical activity

  • Weight control

  • Avoid smoking

  • Reduce alcohol

Screening (ESSENTIAL)

  • Colonoscopy as per age and risk

  • Faecal occult blood test

This is the point that most reduces mortality.

When to seek medical help

You should seek evaluation if there is:

  • Blood in stool

  • Persistent change in bowel habit

  • Recurrent abdominal pain without explanation

  • Anaemia detected in tests

  • Family history of intestinal cancer

  • Age above 45–50 years (even without symptoms)

Waiting to "improve on its own" is one of the biggest mistakes in this scenario.

The most important point

Diet is not the only factor — but it is one of the most modifiable.

And this completely changes the game.

You cannot control your genetics.

But you control, every day, the environment in which your body functions.

And in the case of intestinal cancers, this makes a real difference — not a theoretical one.

Dr. Rebeca Soares Andrade CRM-GO 39335