Introduction

Oncological disease is associated with intensive growth and rapid proliferation of tumor cells, as a result of which the demands for nutrient and energy intake increase (Vokurka, 2022). At the same time, the disease causes changes in digestion, absorption, and utilization of nutrients. Severe illness and demanding treatment (chemotherapy, radiotherapy, surgery) lead to various digestive problems, contributing to inadequate patient nutrition and malnutrition (Arends, 2017). Inadequate nutrition in oncology patients is a complex problem affecting multiple organs and organ systems of the human body (Zhang, 2021). From these facts it follows that maintaining an adequate nutritional state is a natural part of anti-cancer treatment. For patients at nutritional risk, an enriched nutritional diet with proteins and concentrated energy is indicated, which in most cases means increased fat intake (ESPEN, 2021, Voleková, 2012). It is often necessary to cancel inappropriate dietary restrictions and eating patterns, including alternative nutrition.

Alternative nutrition

Alternative nutrition includes a broad spectrum of dietary patterns that differ from our usual or expert-recommended diet (Kohout, 2022). Individual dietary practices may be more or less scientifically justified. Therefore, dietary measures should be approached cautiously and ideally in collaboration with a nutrition specialist who can assess risks, and possibly add supplements or coordinate care with the treating physician.

Alternative and modern nutrition trends

The most common alternative ways of eating today, especially among younger and middle-aged populations, include:

  • Vegetarian and vegan diet
  • Macrobiotic diet
  • Raw (uncooked) diet
  • Paleolithic diet
  • Low-carbohydrate diet
  • Organic diet
  • Split diet
  • Blood group diet

Alternative nutrition and oncological disease

Severe tumor disease and the fact that standard anti-cancer treatment may not be sufficiently effective lead patients and their relatives to look for alternative treatment methods and various special diets (Erickson, 2018, Baier, 2021). Over recent decades, many alternative dietary approaches have been developed. However, despite reports by proponents of many individual cases of successful healing, it has not been scientifically proven that these approaches can lead to cure or improvement in the condition of cancer disease.

The most well-known alternative dietary approaches

The most well-known nutrition methods and recommended diets include:

a) Macrobiotic diet
Macrobiotic diet is primarily vegetarian. Its basis is the intake of grains, legumes, vegetables, fruits, and products from seaweed. Meat is excluded from the diet, except for small amounts of fish meat, as are animal fats, milk and dairy products, tropical fruit, sugar, honey, and all syrups. The macrobiotic diet recommends eating two to three times daily and stopping before feeling full. The diet is always prepared fresh (Manková, Vozárová, 2023, Hubner, 2014).
Disadvantages: the large volume of food and low energy content of complete proteins, as well as some vitamins, trace elements, and minerals. The diet lacks vitamin B12, vitamin D, and calcium. Properly setting up the diet is time-consuming and nutritionally difficult to balance.
In supportive treatment of oncology patients no scientific evidence was found that it is an appropriate eating approach for this patient group. There is no evidence that it can help prevent cancer or cure it (Kohout et al, 2022).

b) Vegetarian diet
A vegetarian eating pattern is defined as an animal-meat-free diet. A well-posed diet should contain whole grains, vegetables, legumes, fruit, and quality oils such as olive and rapeseed oil. Offal, caviar, and gelatin are excluded. Milk, cheeses, yogurts, and eggs are allowed. Intake of sweets and high-fat foods is limited (Vokurka et al., 2022).
Benefit of the diet is that adherence to these eating patterns has been shown to reduce the risk of cardiovascular diseases (CVD), ischemic stroke, type II diabetes mellitus (DM II), and some oncological diseases. It does not work as complete prevention.
There is some evidence that consuming foods containing soy and fiber may reduce the risk of breast cancer recurrence. It is important, however, that people following any vegetarian pattern have knowledge of proper meal composition and are aware of risk factors for deficiencies of major nutrients (vitamins, minerals) in the body (Kohout et al., 2022).
Negatives — animal proteins are missing, vitamin D, K, and B12 intake is also insufficient. There is also a deficiency of minerals, especially selenium, iron, and calcium.

c) Vegan diet
A diet without foods of animal origin—meat, dairy products, eggs. The lifestyle and eating pattern are currently very popular. The term “vegan” originated in 1944.
Benefit of the diet is higher fiber content and lower cholesterol and sodium. The diet lowers the risk of CVD and DM II and supports weight loss (Manková, Vozárová, 2023, Zlatohlávek, 2016).
Data from scientific studies on long-term health are mixed because there are no studies that have followed long-term followers of this lifestyle and way of eating. A possible benefit is that people pay more attention to their health and also combine their diet with a healthy lifestyle (physical activity, avoiding addictive substances, etc.) (Kohout et al, 2022, Manková, Vozárová, 2023).
Negatives — does not provide enough nutrients, especially calcium, B12, and omega-3 fatty acids. Vegan products may contain many stabilizers and additives. High intake of plant fiber in early stages of oncological disease can lead to satiety or gastrointestinal problems (Paulová, 2021).
This diet is not suitable under increased physiological stress. It is not recommended for children, pregnant and breastfeeding women, or older adults. In patients with oncology disease, given the need for complete proteins, it is also not recommended (Šachlová, 2016).

d) Alkaline diet
The theory of this diet is that an acidic body environment supports diseases such as cancer and an alkaline environment contributes to good health. The diet became very popular in the media, but all studies presenting these results were conducted under laboratory conditions (Baier, 2021).
There is no evidence that following an alkaline diet reduces cancer risk or protects against cancer. Following an alkaline diet (where meat and dairy are often not consumed) does not change blood pH or pH of any other organ. Following this restrictive diet may contribute to weight loss and to inadequate intake of many nutrients, including calcium, vitamin D, vitamin B12, and proteins, which may negatively affect the patient’s overall condition and treatment. Although the diet can change urinary pH, it is important to note that an alkaline environment may interfere with chemotherapy effectiveness (Kohout et al, 2022, Šachlová, 2016).

e) Gerson diet
It is based on attempting to support weakened defense capacity and help remove toxic products of tumor cells from the body. The basis is high potassium and low sodium intake, with protein limitation and fat exclusion. Food items completely excluded are salt, oil, nuts, candied and canned foods, and other chemically processed foods (Kohout et al, 2022).
It is an organic vegetarian diet that includes drinking freshly pressed juices, administration of coffee enemas, and use of natural supplements. The core of Gerson therapy is consuming up to 10 kilograms of fruits and vegetables daily. Fresh juices are taken 13 times per day.
Solid food is mainly consumed as raw vegetables and fruits and a small amount of cooked vegetarian food (Hubner, 2013).
Disadvantage — protein intake is restricted. It requires substantial financial and lifestyle commitment.
Scientific studies do not indicate a beneficial effect in the treatment of oncological diseases. This is also supported by the fact that following the Gerson diet involves reducing intake of animal fats (dairy products) and proteins. These food groups play an important role in maintaining stable body weight and preserving muscle mass, which is desirable in oncology patients. High doses of vitamin and mineral supplements can negatively affect anti-cancer treatment, such as chemotherapy, and reduce its effectiveness (Paulová, 2021, Šachlová, 2016).
Coffee enemas can cause gastrointestinal problems such as nausea, vomiting, and diarrhea. Additional side effects include dizziness, dehydration, electrolyte abnormalities, acute kidney failure, bowel perforation, and increased infection risk.
Most Gerson practitioners encourage people to stop chemotherapy while following the Gerson diet. Stopping or postponing conventional treatment recommended by a physician can markedly reduce overall survival and may be harmful to the patient’s health (Hubner, 2012).

f) Ketogenic diet
This is a low-carbohydrate, high-fat diet that requires large fat intake and moderate protein intake, while carbohydrates are restricted to a minimum. The ketogenic diet lacks fiber, fruit, and vegetables. It can also lead to low levels of calcium, vitamin D, and other salts (electrolytes). It may cause kidney stones in people with family history of this condition (Manková, Vozárová, 2023, Kohout et al, 2022).
The diet is presented as an alternative therapeutic method and as a basis for increasing the effectiveness of chemotherapy or radiotherapy, or as an adjunct to improve tolerance of these therapies.
No scientific evidence has yet been provided for this form of eating with positive outcomes regarding survival, treatment response, or treatment tolerability. No major oncology research and therapy organization recommends a ketogenic diet for patients. It is also not recommended for prevention of oncological diseases (Valovičová, 2007, ESPEN 2021).

g) Breuss diet
The essence of this diet is the theory that a tumor in cancer feeds only on solid food and will disappear on its own if the patient is allowed to starve it.
It is an extreme diet that instructs patients, after finishing treatment, to not eat and drink anything for 42 days except vegetable juices and herbal teas (Baier, 2021). Some patients are guided to stop standard treatment (chemotherapy, radiotherapy).
Disadvantage — low caloric and protein value, leading to patient weight loss and deterioration of overall nutritional and health status. The diet is one-sided and based mainly on vegetable juices, with deficiency of all nutrients needed to sustain life. It causes too rapid weight loss and constant hunger. The consumer has no energy, constant fatigue, drowsiness, depression, severe exhaustion, headaches, digestive problems (Hubner, 2014, Maritess, 2005).
Fasting deepens cachexia but does not affect tumor growth. Patients following the so-called Breuss diet often arrive in a condition that already prevents further oncological treatment (Baier, 2021).

h) Budwig diet
The Budwig diet favors unprocessed whole foods such as fruits and vegetables and flaxseed oil, which are rich in important nutrients such as vitamins, minerals, and antioxidants.
Key foods to avoid in the Budwig diet include meat and seafood: pork and shellfish, processed meat: bacon, bologna, salami, and hot dog; refined grains: pasta, white bread, crackers, fries, and white rice; sugars: granulated sugar, brown sugar, molasses, agave, and corn syrup; soy products: tofu, tempeh, soy milk, edamame, and soybeans; fats and oils: margarine, butter, and hydrogenated vegetable oil; processed foods: cookies, ready-made meals, pastries, fries, chips, and candies (Hubner, 2012).
The Budwig diet requires high amounts of flaxseed oil. In some people, this oil can cause digestive problems and diarrhea.
The Budwig diet has not been studied in any clinical trials and is based on unofficial evidence. It also contains large amounts of flaxseed oil and is very restrictive, which can cause nutritional deficiencies in patients with oncological disease (Šachlová, 2016).

i) Eating according to blood groups
The author is Dr. Peter J. D´Adamo, who in his theory states that people should eat according to how their blood group is characterized (Table 1). The essence of his theory is that life conditions and nutrition influenced the evolution of blood groups, so people should eat mainly foods that contributed to the development of their blood group and therefore harmonize with it.

Table 1. Suitable food groups by blood type

Analysis of more than 1000 studies, however, found no evidence that adherence to this diet has any health benefit. Blood groups developed differently from what the theory claims (Kohout et al, 2022).
Negative of the diet is limiting food choices—even of basics (milk, legumes, etc.). Nutrition may not ensure balanced intake of all nutrients into the body. The diet cannot be considered a reliable way to improve health status; on the contrary, it may also cause harm. It is not an appropriate dietary pattern for oncology patients, even during remission (Manková, Vozárová, 2023, Zlatohlávek, 2016).

Alternative nutrition - findings from clinical practice

From the presented text, which includes analyzed findings from scientific studies, professional literature, and guidelines, evidence emerges about the inappropriateness or risk of consuming alternative diets and nutrition. This fact led us to research carried out in clinical practice, which consisted of multiple steps and included the choice of empirical methods. The research is part of project KEGA 009 KU-4/2022 Nutrition and physical activity as basic pillars of care for patients at risk.

The objective of the study was: To determine how consumption of modified, alternative nutrition affects the health status of a patient with oncological disease.

Partial objectives were to determine:

  • which alternative diets oncology patients consume,
  • the demographic characteristics of patients consuming alternative nutrition.

Research methods

We used methodological triangulation, a combination of qualitative and quantitative methods. Methods used were: nutritional anamnesis, interview, medical record analysis, and case studies.

Study sample

A total of 108 patients participated in interviews and data collection on eating patterns; they were hospitalized and followed at the Department of Radiation and Clinical Oncology at ÚVN SNP Ružomberok-FN.
We also analyzed medical documentation of patients hospitalized during the project period—from April 2022 to September 2023—with a total number of 343.
We processed case studies of four patients—1 male and 3 female. Prerequisites for inclusion in qualitative research were: treatment of oncological disease, use of alternative nutrition, and patient consent to participate in the study.

Study results

Through nutritional anamnesis (Table 2), which is part of the set of tools used to assess nutritional and physical status in at-risk patients, we found that out of the total 108 patients, 11 reported alternative nutrition.

Table 2 Use of alternative nutrition in oncology patients

In the analysis of medical documentation, we focused on the areas listed in Table 3.

Table 3 Areas of analysis of patient medical documentation

From the analyzed data, the most relevant for the study were:

  • The mean age of patients who reported an alternative eating pattern was 40.1 years.
  • It was more often younger women, age category 30–40 years.
  • The most common alternative eating patterns were vegan, vegetarian, juice drinking—Breuss diet.
  • We also recorded a combination of hospital and self-directed diet.
  • Diet modification and restriction of animal proteins had a negative effect on overall health status. Patients had weight loss and confirmed malnutrition, documented by MNA and laboratory parameters.

Clinical case results

In the sample description, we stated that we processed clinical case studies in four patients. These were patients followed and treated outpatient and inpatient at the Department of Radiation and Clinical Oncology at ÚVN SNP Ružomberok-FN. Patients were followed over the long term and their overall health status was monitored continuously; the effect of treatment and adverse effects of chemotherapy and radiotherapy were also tracked. Nutritional status and overall performance were monitored using Mini Nutritional Assessment, Barthel test, Karnofsky index, and Physical Fitness Test—SARS-F (a test that identifies sarcopenia risk and muscle mass loss). Weight, BMI, and laboratory parameters were also monitored.
Because of the large volume of data, we present priority findings in the results that provide evidence of the negative impact of using alternative treatment and nutrition.

Case study 1

A 55-year-old man with diagnosis: laryngeal carcinoma. The oncological disease was confirmed in April 2020.
At the start of treatment, the patient cooperated and completed chemotherapy and radiotherapy. At the start of therapy (May 2020), his weight was 90 kg. He ate without restrictions and consumed hospital food.
In the middle of chemotherapy cycles (November 2020), he interrupted therapy and began a 40-day diet. He consumed only vegetables, fruit, and juices. At his last hospitalization record, he weighed 75 kg.
After alternative treatment, he was only 40 kg. He became cachectic, and disease progression occurred.
Due to worsened health status, further targeted therapy was not possible. The patient died at home (February 2021).

Case study 2

A 40-year-old woman with diagnosis C 90- multiple myeloma.
At diagnosis (September 2019), the patient refused treatment. She treated herself with plant-based and natural food and was a vegan. After 1 year (October 2020) from diagnosis, she agreed to therapy. A comprehensive examination was performed with additional laboratory tests and imaging (RTG, USG, CT). After evaluation of results, disease progression was recorded. Metastases were confirmed in bone, lungs, and liver.
Oncological treatment was initiated and the patient was hospitalized, but during therapy (February 2021) she died. The patient was malnourished, and her body could not tolerate intensive treatment.

Case study 3

A 35-year-old woman with diagnosis C 50 malignant breast tumor. At confirmation of the diagnosis (May 2018), she refused treatment, followed Ayurveda, and lived a healthy lifestyle as a vegetarian.
Similarly, about a year later (April 2019), evaluation was transferred and disease progression with metastases in bones, liver, and lungs was found. The patient was admitted to the clinic and comprehensive treatment was initiated. After education, she also agreed to change her diet and consumed poultry and fish.
Two months after therapy ended (March 2020), the patient died. A change in attitude and diet adjustment did not influence disease progression, which had moved to terminal stage.

Case study 4

A 33-year-old patient with diagnosis breast carcinoma. At the time of diagnosis confirmation (April 2015), she was a breastfeeding mother. The patient had surgery recommended—breast-conserving surgery. After recovery, adjuvant postoperative chemotherapy and radiotherapy were indicated. The patient refused treatment.
About six months later (November 2015), resistance measuring 5 x 6 cm, protruding 4 cm, was found on the left side of the sternum medially from the surgical scar; recurrence was confirmed.
The patient continues to refuse targeted oncological treatment and is treated with natural, alternative methods. She consumes a plant-based diet mainly in raw form.
She is followed at the oncology outpatient clinic and accepts only monitoring.
In January 2016, due to pronounced anemia found in laboratory tests and based on her subjective condition—fatigue and dizziness—the patient consented to receiving Erymasa, which was given twice. She was then admitted to internal medicine for moderate anemia. During this period she remained on a raw-food diet for 8 months.
After stabilization, she consented to treatment. In February 2016, she was admitted to the clinic, where radiotherapy was administered. At the same time, she also used alternative treatment—receiving energy therapy by phone from a healer. She adjusted her diet herself. She ate both hospital and home food brought by relatives. Treatment was successful. In 2017, after examination and PET/CT, structural changes consistent with fibrotic reorganization of the costocostal junction were described, without recurrence. Diagnostic conclusion: remission. In 2022, the patient became pregnant and gave birth to a healthy child.

Discussion

Based on the characteristics of individual dietary approaches, but especially on findings from long-term work at the Department of Radiation and Clinical Oncology (KRaKO), we agree with the statement that although alternative dietary approaches often include certain elements of healthy nutrition, as a whole they do not meet the requirements of complete nutrition (Hubner et al., 2012, 2013). Every inappropriate diet merely promotes weight loss. In oncology disease, this is accompanied by protein loss, which further worsens overall patient condition, immunity, and tissue healing capacity. Ultimately, it very often leads to worsening of overall treatment outcome. Even in Baier et al. (2021), it is stated that these diets often require unnecessary food restrictions and can lead to negative consequences for patients regardless of their disease state. The most serious consequence is malnutrition.
Beyond processing facts from analyzed documents, our objective was to determine which alternative diets or eating patterns are used by patients followed and treated at KRaKO. A positive finding was that out of 108 respondents, only 11 still practice an alternative eating pattern. These were vegetarian, vegan, macrobiotic, split diet, and fasting. Hubner et al. (2012, 2014) also addressed this area and found that the most common “cancer diets” their respondents reported were the Budwig diet, Gerson regimen, low-carbohydrate diet, Breuss cancer treatment, and macrobiotic diet. The authors also identified the reason for choosing these diets: patients believed they could heal themselves through adherence to a specific diet or at least contribute significantly to cure. These views are also supported by diet creators themselves.
Another objective was to determine demographic characteristics of respondents. From analysis of medical documentation, we found that women in younger and middle adulthood most commonly maintain alternative eating patterns. This was also confirmed by case studies. And similarly to the other methods used, modern eating patterns—plant-based eating—and the cancer diets Breuss and fasting prevailed. Evidence of harmful effects of incomplete nutrition was presented in the clinical case studies. In all patients, in consequence of inappropriate nutrition or its restriction, deterioration of the primary disease occurred. In the first three cases, even later correction of nutrition and undergoing oncological treatment could not reverse the poor prognosis.

Conclusion

Nutritional status plays an important role in the comprehensive treatment of oncology patients. Weight loss and related muscle mass loss lead to reduced functional capacity, higher complication rates, longer hospitalization, and increased mortality (Cvek, Halámka, 2023). Attention to nutrition is therefore important already at diagnosis. The role of healthcare professionals is not only to follow care standards, which include screening, determining nutritional status, recommending an appropriate dietary approach, providing systematic and sustained nutritional support, and increasing support intensity during complications and side effects of oncological treatment (ESPEN 2021, Erickson, 2018). It is essential to educate and motivate the patient to take complete nutrition. Only appropriately tailored nutritional support has the potential to improve overall outcomes of anti-cancer therapy.

Authors: PhDr. Katarína Zrubáková, PhD.
Katedra ošetrovateľstva Fakulta zdravotníctva KU Ružomberok

Mgr. Anna Herinková
Klinika radiačnej a klinickej onkológie, ÚVN SNP Ružomberok-FN

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