Cancer and Nutrition

Cancer and Nutrition Guide

Which foods may be beneficial, and under what conditions, for preventing cancer and/or during cancer treatment? What approach allows us to eat properly?

Nutrition means obtaining sufficient nutrients needed by the body to protect and improve our health and increase quality of life. Knowing which foods to consume and in what quantities contributes significantly to proper nutrition and good health. Most of us complain about how delicious many supposedly unhealthy foods are. Many equally wish that supposedly beneficial foods tasted as good. Foods consumed for their taste sometimes provide insufficient nutrients for the human body, leaving us vulnerable to cancer and many other diseases.

In the news we have read and watched, we have repeatedly encountered many different interpretations of food's effects on cancer. We have tried to form opinions by examining scientific research and sometimes listened to dietitians' advice. We therefore thought we should answer "How can I eat healthily to prevent cancer?" and "How should I eat after a cancer diagnosis?" and clarify the hundreds of studies and resulting confusing interpretations, so we addressed this important subject.

At this point, we asked our oncology specialist dietitian Mehmet Refik Sezgin which foods may be beneficial under which conditions for preventing cancer and/or during treatment, and how to eat properly.

How do you assess the relationship between nutrition and cancer?

We can divide this subject into diets that cause cancer and diets that help prevent it. Nutrition should not bring only food itself to mind: cooking methods and storage conditions also matter. Many dietary mistakes, such as emphasizing fried foods, eating little fiber, emphasizing processed meat, excessive alcohol, high refined carbohydrate intake (particularly sugary foods), excessive acidic drinks, and reduced fruit and vegetables contribute to varying degrees to the development of cancers such as breast and bowel cancer.

How can we eat to prevent cancer? First, let us change our shopping habits toward the most natural, minimally processed foods possible. Another point is choosing cooking methods such as baking, smokeless grilling, and boiling that preserve nutritional value without causing unwanted reactions. Adopting the saying "Let your diet be like a rainbow" is important. It is recommended because food colors correspond to their protective substances. This is why we want fruit and vegetable choices to comprise 1/3 green, 1/3 red, and 1/3 yellow-white vegetables.

Can eating habits protect us against cancer? Or is an unhealthy diet a factor in developing cancer?

Dozens of studies have examined this. For example, high-fiber foods reduce large bowel cancer incidence. Smoked foods contribute to tumor development in the digestive system. Regarding alcohol habits, beer may predispose to large bowel cancer, while stronger drinks may cause pharyngeal and similar cancers. However, we cannot live thinking only about our large bowel or stomach. Nutrition must be addressed as a whole. Obesity can stimulate cancer development as it does many other diseases, so maintaining a healthy weight comes first. Exercise is as important as healthy eating. Food variety and regularity should be established considering all bodily systems. If possible, the body should be nourished with 4-5 equal meals. Fruit and vegetables are particularly important protectors through their active components. The components giving each fruit or vegetable its color are also protective. Hence our term "Eat Like a Rainbow." Our diet should include protease inhibitor-containing legumes (such as lentils and dried beans) and vegetables (green beans, peas); antioxidants (fruit, oilseeds, and vegetables); bioflavonoids (citrus, the mulberry family, and the strawberry family); and allium vegetables (sulfur-containing vegetables such as garlic, onions, and leeks). Naturally, we must not forget grains, our main food source. Choosing brown breads (I most recommend rye or oat flour) is better both nutritionally and for supporting bodily systems.

What should we consider when buying food?

The first rule is developing the habit of reading labels. Production dates, batch numbers, and similar information can help us choose somewhat reliable companies. Another point is chemical residues not naturally present in foods. Many chemicals are used on fruit and vegetables both to accelerate growth and preserve them. Many of our patients diagnosed with hematological diseases in the Mediterranean region work in greenhouses or live in these areas. Buying seasonal fruit and vegetables as much as possible is therefore more appropriate.

Another point concerns foods' natural processes. Oilseeds and spices, which we mentioned as very important for health, may contain aflatoxin, which can cause liver cancer. These foods become moldy under suitable storage conditions, particularly through moisture, and this toxic substance appears. Various studies confirm the association between aflatoxin exposure and liver cancer. This shows that we need to pay attention to food storage conditions.

What nutritional points should a person diagnosed with cancer consider during this process?

A cancer diagnosis changes many things in a person's life. These changes depend on the patient, cancer type, and treatment. Naturally, nutritional status and needs will be adjusted accordingly.

Patient-related changes include psychological and social behavioral changes. For example, anxiety about survival may reduce food intake, or family pressure may lead someone diagnosed with cancer to consume foods they have never eaten before. Nutritional planning should be based on expert advice rather than hearsay. We recommend eating together as a family, prioritizing favorite foods, and eating without stress while conversing.

Regarding cancer-type-related changes, tumor secretions alter many metabolic conditions. Cancer cachexia may occur in particular. Characterized by severe muscle tissue, with or without fat tissue, this condition can threaten a person's life.

Protein requirements increase after a cancer diagnosis. While a healthy adult needs 0,8 grams of protein per kilogram daily, a cancer patient may need up to 1,5-2 grams. Increasing daily milk and yogurt consumption to 400-500 grams, eating 90-100 grams of meat or similar products (such as fish), and increasing cheese consumption to 75-100 grams can help fill the protein gap. Increasing fruit intake to 500 grams and emphasizing quality grains (such as bulgur and pasta) is also necessary to address the energy deficit.

Third are treatment-related changes. Losses of taste and texture and nausea during chemotherapy particularly impair quality of life. We advise patients experiencing nausea not to arrive very hungry on treatment day, to bring easily eaten foods such as pretzel sticks, biscuits, rusks, or homemade cheese toast, and not to consume excessive liquid foods in the first 2-6 hours after treatment. We also remind them that foods such as mint, mint sweets, and ginger may reduce nausea somewhat. For those with problems in the mouth's taste texture, we suggest gargling with a little mineral water before eating to make meals more enjoyable. Another common side effect is a sluggish bowel, or constipation. We explain that increased fruit and vegetables, plenty of water, and persistence with daily movement can relieve bowel processes.

Can drugs used in cancer treatment interact with foods and cause side effects?

Yes, food-drug interactions are an important and life-threatening problem. Before using anything additional, the patient and/or relative must consult the treating physician, oncology pharmacist, and oncology dietitian. Explaining why they want the product and what they expect helps manage the process. A study in 2006 demonstrated the already-known possibility that grapefruit, blood orange (red orange–Seville orange), and pomegranate juice can interact with chemotherapy drugs. Anthracycline, commonly used in breast cancer, also interacts with green tea. Very serious allergic side effects have occurred in some of our patients using nettle and certain products (such as royal jelly, pollen, and propolis).

Some foods are said to help but do not work. Donkey milk, for example, has become a source of profit because it resembles human milk. Yes, breast milk is a very powerful, important food. However, as people physically develop and grow, their protective mechanisms also develop and change. We then consume foods benefiting those mechanisms. We should know that malignant cancers can also occur in breastfed children. Unfortunately, many cancer patients remain vulnerable to financial and emotional exploitation, benefiting opportunists. Before consuming donkey milk or another food, it is therefore best to consult the cancer-treating doctor and an oncology specialist dietitian. This also avoids lending credibility to opportunists promising treatment.

What points guide nutritional planning for someone with cancer? Do cancer type, stage, and treatments play an effective role?

We consider three main points: previous nutrition and weight, and secondly current weight and nutrition. In some diseases, disease-related weight loss called cachexia occurs. If the patient has appetite loss, it should be addressed, food intake assessed, and deficits corrected when necessary. Special nutritional supplements may sometimes be needed. The dietitian closely monitoring the patient should inform the physician at this point.

A third point is the expectations of the physician or physicians planning treatment. Another point must not be overlooked: health problems that may change with the patient's previous dietary tendencies, such as diabetes or kidney disease.

Cancer stage, treatments, and affected organs may influence nutrition. Depending on head and neck cancer treatment protocols, patients may experience difficulty swallowing, diarrhea, and mouth sores. Supportive treatments are needed in these situations. For example, a patient operated on for pancreatic cancer may develop disrupted blood sugar balance and particularly problems digesting fats. Blood sugar balance must be maintained during nutrition and a diabetic meal plan arranged. Many chemotherapy drugs can also cause sensitivity to smells and severe nausea. During these brief periods, instead of strongly smelling foods (particularly meat dishes) and very liquid foods, breakfast foods such as cheese and bread may soothe the stomach if necessary. Going outside while food cooks at home or eating home-cooked meals outdoors in a picnic setting plays an important protective role for both appetite and nausea. Many patients taking painkillers also experience constipation. Their fiber intake should be increased, they should be motivated to be active, and fluid intake increased.

We may consider cancer stage the part that challenges us most psychologically. Families of terminally ill patients with advanced disease and no chance of treatment expect all nutritional requirements to be met. However, scientific data and the patient's capacity favor a comfortable final period rather than such intensive feeding. For example, reducing pain in a terminal patient is far more valuable than feeding that patient.

Should a cancer patient seek help from any nutrition specialist, or prefer a dietitian with knowledge and training in this disease? Why?

Unfortunately, few of my colleagues in private hospitals in our country work specifically in cancer. In public institutions, colleagues covering several clinics try to shoulder this burden. As noted earlier, nutrition is important in both cancer development and treatment, so support from the clinic's nutrition specialist is naturally preferable if available. Otherwise, support should be obtained from a dietitian recommended by the physician and able to remain in contact with the treating physician.

Are there points that patients who have completed treatment and recovered should consider?

Yes. These people may now be considered to have entered a healthy life. However, there is an important red line in nutrition: they must now be more careful than before. They know their risks and must remember that these risks may also affect other organs. First, all unnecessary weight should be lost. They should lead lives prioritizing fruit and vegetables, avoiding processed foods and refined carbohydrates, with exercise as a cornerstone.

Countless completed and ongoing scientific studies have examined foods and scrutinized their benefits and harms to human health. Foods found harmful in some studies appear supported by completely opposite findings in others. What do you think? How should cancer patients and their relatives take these studies into account? Or should they?

I believe it is wrong to label a food good or bad based on just one study. Unfortunately, this is how current media operate. A food may be called good one day and become bad the next. Such studies should, in my view, be interpreted and communicated accurately by the specialists responsible for the cancer patient's treatment plan. In summary, because different treatments are used for different cancers, the patient's nutritional plan also varies accordingly.

We offer our sincere thanks to Nutrition Specialist Mehmet Refik Sezginfor sharing his valuable views with us.