Following a cancer diagnosis, many people wish to make positive changes to their lifestyle. Adopting healthy habits, including a balanced diet, regular physical activity and maintaining a healthy weight, can help improve overall health, quality of life and wellbeing during and after treatment.

Before making significant changes to your diet, it is advisable to speak with a registered dietitian, your GP or your oncology specialist, particularly if you are experiencing weight issues, difficulties eating or treatment-related side effects.

What Is a Healthy Diet?

For most people, a healthy diet includes:

• Plenty of fruit and vegetables.
• Wholegrains and other foods rich in complex carbohydrates, such as wholemeal bread, brown rice, oats, pasta, potatoes and pulses.
• Healthy sources of protein, including fish, poultry, eggs, pulses, nuts and seeds.
• Dairy products or fortified alternatives that provide calcium and vitamin D, according to individual needs.
• Healthy fats, particularly extra virgin olive oil, nuts, seeds and oily fish.
• Limited amounts of ultra-processed foods, added sugars, sugary drinks, salt and saturated fats.
• Water as the main drink.

Scientific evidence shows that excess body weight, physical inactivity, alcohol consumption and certain dietary patterns can increase the risk of developing several types of cancer. For this reason, experts recommend a diet based primarily on plant foods and minimally processed ingredients.

How Can a Healthy Diet Help?

A balanced diet, together with regular physical activity, can help to:

• Maintain a healthy weight.
• Preserve muscle mass.
• Reduce the risk of cardiovascular disease and diabetes.
• Improve energy levels and overall wellbeing.
• Support recovery during and after treatment.
• Help reduce the risk of recurrence in some types of cancer and improve overall survival.

If you need to lose or gain weight, it is important to do so under professional supervision to ensure an adequate intake of energy and nutrients.

How Can I Maintain a Healthy Diet?

Gradual changes are often easier to maintain in the long term. Some useful recommendations include:

• Gradually increasing your intake of fruit, vegetables and pulses.
• Choosing fresh and minimally processed foods whenever possible.
• Eating wholegrain foods regularly.
• Limiting red meat consumption.
• Avoiding or reducing processed meats as much as possible.
• Limiting ultra-processed foods and sugary drinks.
• Maintaining good hydration.
• Reading nutrition labels to make healthier choices.
• Avoiding alcohol or limiting consumption as much as possible.

How Does Our Body Use Food?

A balanced diet provides the nutrients needed for the body to function properly.

Carbohydrates

Carbohydrates are the body's main source of energy. It is recommended to prioritise complex, fibre-rich carbohydrates from wholegrains, pulses, fruit and vegetables.

Protein

Protein is essential for maintaining and repairing tissues, preserving muscle mass and supporting recovery, particularly during illness and treatment.

Fats

Fats provide energy and play a vital role in many bodily functions. It is recommended to choose unsaturated fats in preference to saturated and trans fats.

Vitamins and Minerals

Vitamins and minerals are involved in numerous metabolic processes and contribute to the healthy functioning of the immune, nervous and skeletal systems.

Fluids

Hydration is essential for the body to function properly. Requirements vary according to age, health status, environmental temperature and level of physical activity. As a general guide, it is recommended to drink between 1.5 and 2 litres of fluids each day, mainly water.

Frequently Asked Questions About Diet

Many people ask whether diet can reduce the risk of cancer returning. Although there is no specific diet that can completely prevent recurrence, maintaining a healthy weight, eating a balanced diet and engaging in regular physical activity are associated with better health outcomes.

Your healthcare team is the best source of advice on how to adapt these recommendations to your individual circumstances.

Which Foods Should I Avoid?

There is no universal list of foods that all people with cancer should avoid.

However, during treatments that weaken the immune system, it may be advisable to:

• Avoid raw or undercooked eggs.
• Avoid unpasteurised milk and dairy products.
• Avoid raw or undercooked meat, fish and shellfish.
• Follow good food hygiene practices.

Specific recommendations will depend on your treatment and level of immunosuppression.

Should I Take Dietary Supplements?

In general, people who follow a balanced diet do not need vitamin or antioxidant supplements to prevent cancer or reduce the risk of recurrence.

However, supplements may be recommended in specific situations such as:

• Confirmed nutritional deficiencies.
• Problems with nutrient absorption.
• Major digestive surgery.
• Vitamin D deficiency.
• Osteopenia or osteoporosis.

Supplements should only be taken following professional medical advice, as some may interact with certain cancer treatments.

Do "Superfoods" Exist?

There is no scientific evidence that any single food has special properties that can prevent or cure cancer. Health benefits come from an overall healthy diet and lifestyle, not from any individual food product.

The best approach is to eat a wide variety of fruit, vegetables, pulses, wholegrains and other nutritious foods.

Should I Follow a Dairy-Free Diet?

There is currently insufficient evidence to recommend eliminating dairy products to prevent cancer recurrence.

Dairy foods provide protein, calcium and other important nutrients. If dairy products are excluded from the diet, it is important to ensure adequate calcium and vitamin D intake through other foods or fortified alternatives.

Cancer and Sugar

There is a common belief that sugar "feeds" cancer and that completely removing it from the diet can slow tumour growth. However, this is an oversimplification of a much more complex biological process and is not supported by current scientific evidence.

All cells in the body, both healthy and cancerous, use glucose as one of their main sources of energy. Glucose comes from many foods, not only table sugar but also bread, pasta, rice, potatoes, pulses, fruit and dairy products. Even if a person eliminates sugar from their diet, the body will continue to produce glucose from other nutrients to ensure the normal functioning of essential organs such as the brain, muscles and red blood cells.

Reducing or eliminating sugar has not been shown to stop cancer growth or improve survival on its own. There is currently no scientific evidence to support extremely low-carbohydrate diets as a treatment for cancer.

What research has shown is that a high intake of sugary drinks, pastries, sweets and other ultra-processed foods can contribute to weight gain and obesity. Excess body fat is associated with a higher risk of several cancers, including colorectal, postmenopausal breast, endometrial, oesophageal, pancreatic, kidney, liver and ovarian cancers.

The relationship between sugar and cancer is therefore primarily indirect. The issue is not that sugar specifically feeds cancer cells, but that a high intake of foods and drinks rich in added sugars can contribute to excess weight, chronic inflammation, insulin resistance and other metabolic changes associated with an increased risk of cancer.

For this reason, leading international cancer prevention organisations recommend:

• Limiting the consumption of sugary drinks.
• Reducing foods high in added sugars and ultra-processed products.
• Maintaining a healthy weight through a balanced diet and regular physical activity.
• Prioritising fruit, vegetables, pulses, wholegrains and other nutrient- and fibre-rich foods.

Should I Eat Only Organic Foods?

There is currently no scientific evidence showing that an exclusively organic diet prevents cancer or reduces the risk of recurrence compared with a conventional healthy diet.

Whether you choose organic or conventionally produced foods, it is important to:

• Wash fruit and vegetables thoroughly.
• Maintain good food hygiene practices.
• Prioritise fruit, vegetables and pulses regardless of how they are produced.

The choice between organic and conventionally produced foods is a personal one.

Do Anti-Cancer Diets Work?

There is no high-quality scientific evidence showing that so-called "anti-cancer diets" can cure cancer or improve survival.

Some restrictive diets may lead to:

• Malnutrition.
• Loss of muscle mass.
• Vitamin and mineral deficiencies.
• Interference with medical treatments.

For this reason, leading scientific and medical organisations recommend a balanced, varied, enjoyable diet that is tailored to each individual's needs.