The role of foods in cancer: a narrative review

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THE ROLE OF FOODS IN CANCER: A NARRATIVE REVIEW

O papel dos alimentos no câncer: uma revisão narrativa

Amanda Cristina Mendes Gusmão1

Jaqueline Rodrigues Aguiar de Carvalho1 Shaila de Jesus Ferreira Pardinho1

Abstract: Cancer is a disease with a silent cause disease and it is the second cause of death in Brazil,

falling behind only to cardiovascular diseases, reaching about six million people, representing 12% of

death all year. Thus, the objective of this work is to elucidate the main types of food that have carcinogenic

and protective effect in the onset of the disease. The paper is a bibliographic-like research. A research

was done for the scientific literature in the following databases and research portals: Scielo, LILACS,

BVS, Pubmed and Academic Google. The descriptors used were cancer, feeding, prevention, carcinogenic

substance. Vitamins A, C, E, as well as carotenoids help in preventing the onset of the disease, also working

as antioxidants. The antioxidant nutrients act by inhibiting the oxidative damages in the DNA, since the

carcinogenic process is characterized by a chronic oxidative state, which characterizes the antioxidant

foods as chemo preventive. Vitamin C is considered one of the most important and the least toxic of the

natural antioxidants. In contrast, some foods are responsible for the onset of the disease, highlighting the

nitrosamines present in the sausages, salami, ham, aflatoxins present in peanuts, corn and nuts from Brazil,

and aromatic and polycyclic hydrocarbons present in roasted meat. Therefore foods have the function

of developing or inhibiting the formation of cancer, being of extreme importance a healthy diet rich in

antioxidant vitamins so that it is possible to change the disease scenario.

Keywords: Cancer; Feeding; Prevention; Carcinogenic Substance.

________________

Corresponding author: Amanda Cristina Mendes Gusmão. E-mail: amandacrismendes@hotmail.com

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REVISTA UNIMONTES CIENTÍFICA

Montes Claros, I Congresso Nacional de Oncologia da Associação Presente - Agosto de 2017.

214 Resumo: O câncer é uma doença de causa silenciosa e é a segunda causa de morte no Brasil, perdendo

apenas para as doenças cardiovasculares, atingindo cerca de seis milhões de pessoas, representando 12%

de morte todo o ano. Com isso, o objetivo do trabalho é elucidar os principais tipos de alimentos que tem

efeito carcinogênico e protetor no surgimento da doença. O trabalho trata-se de uma pesquisa de natureza

bibliográfica. Foram realizadas buscas de literatura científica nas seguintes bases de dados e portais de

pesquisa: Scielo, LILACS, BVS, Pubmed e Google Acadêmico. Os descritores utilizados foram: câncer,

alimentação, prevenção, substância cancerígena. As vitaminas A, C, E, bem como os carotenoides auxiliam na

prevenção do surgimento da doença, funcionando também como antioxidantes. Os nutrientes antioxidantes

atuam inibindo os danos oxidativos no DNA, uma vez que o processo carcinogênico é caracterizado por um

estado oxidativo crônico, o que caracteriza os alimentos antioxidantes como quimiopreventivo. A vitamina

C é considerado um dos mais importantes e o menos tóxico dos antioxidantes naturais. Em contrapartida,

alguns alimentos são responsáveis pelo surgimento da doença, destacando as nitrosaminas presentes

nos alimentos embutidos como: salsicha, salame, presunto, aflotoxinas presentes no amendoim, milho e

castanha do Brasil, e os hidrocarbonetos aromáticos e policíclicos presentes na carne assada. Portanto, os

alimentos têm a função de desenvolver ou inibir a formação do câncer, sendo de extrema importância uma

alimentação saudável rica em vitaminas antioxidantes para que se possa mudar o cenário da doença.

Palavras-chave: Câncer; Alimentação; Prevenção; Substância Cancerígena.

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INTRODUCTION

Cancer is a disease with a silent cause

disease and it is the second cause of death in Brazil,

falling behind only to cardiovascular diseases,

reaching about six million people, representing

12% of death all year. If preventive measures are

not taken, it is estimated that 84 million people in

the world will die due to this disease over the next

ten years.

1

Cancer is characterized by the uncontrolled

growth of cells forming a mass of tumor. This

disease is defined as a chronic degenerative disease

of genes vulnerable to mutation, however, the

disease can also develop through of genes inherited

from family, what determines a small portion of

cancers. Studies show that environmental factors

are the most worrying for the onset of disease,

among these are the diet, tobacco, radiation, lack of

physical activity and body composition. 80% of the

cases are related to environmental factors and can

be modified by man.

2

Diet is responsible for the onset of about

35% of several types of cancers. The consumption

of foods high in saturated fat, cholesterol, sugars

and low intake of vegetables, fruits and fibers

contribute to the onset of the disease. It is believed

that a healthy diet could prevent three to four

million new cases every year

1

The body imbalance caused by excess

of free radicals is known as oxidative stress, its

accumulation is associated with the aging process

and with the emergence of several diseases,

including cancer. A healthy diet, rich in fruits and

vegetable avoids such stress, as well as cellular

damages.

3

Cancer causes some nutritional damages to

the patient. In recent years, several forms for the

nutritional management of the disease have been

studied. The use of immunomodulatory diets, that

is, rich in immunonutrients is able to modulate the

immune function. It has been observed great results

with the use of the same, concomitant to the use of

antioxidants. Probiotics are part of this group.

4

Probiotics are living organisms that bring

benefits to the host when ingested in a certain

number and are found in foods and supplements.

These have the function to inhibit the growth of

some pathogens by reducing the pH of the lumen,

in addition to improving the function of the barrier

of the mucosa and modulate the innate and adaptive

immune response .

5

_{Thus, the objective of this study}

is to address the main types of foods which play a

protective role in the cancer formation.

METHODOLOGY

This is a narrative, descriptive-like review

of the literature study. A research was done for the

scientific literature in the following databases and

research portals:

Scielo, LILACS, BVS, Pubmed

and Google Academic. The search was carried out in

the first half of 2017, using the descriptors: Cancer,

diet, prevention and carcinogenic substance. The

time delimitation covers the years 2005 to 2017 in

order to evaluate the current scientific production.

The inclusion criteria used were articles in their

entirety and review, published in national and

international journals, between the years mentioned

above.

The articles were totally studied and selected

according to the relevance given to the particular

theme of this study.

In total 96 articles were found,

however, only 23 fit the inclusion criteria.

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Montes Claros, I Congresso Nacional de Oncologia da Associação Presente - Agosto de 2017.

216 LITERATURE REVIEW

Cancer Formation

The cancer formation is slow, thus, a cancer

cell can take years to develop and form a tumor

and this process goes through several stages until

the neoplasm formation. The first stage is known

as initiation stage, in it the cells suffer the effect of

a carcinogenic agent, i.e., an onco initiator agent,

which causes changes in some of their genes. At

this stage the cells are altered, however, it is not

possible yet to detect a tumor clinically. Examples

of carcinogenic chemical substances: Dimethyl,

aflatoxin, dimethyl nitrosamine, and benzopyrene.

6

In the promotion stage, the cells genetically

altered suffer carcinogenic effects. At this stage the

cell is transformed into a malignant cell slowly. For

the cell to become malignant it is necessary a contact

with the carcinogen for a long and continuous

period. At this stage the suspension of contact with

the carcinogen can interrupt the process. In the

last stage, the cancer is already formed, the cells

multiply in an uncontrolled way, this process is

irreversible. Thus, the first signs and symptoms of

the disease begin. The substances that promote the

initiation or progression of the disease are called

carcinogens.

6

Cancer prevalence in the World

The neoplasms represented in beginning of

the 21st century a public health problem throughout

the world. About 26 million new cases are expected

for the year 2030

7

_{. Cancer is characterized as a}

non-communicable disease (NCD), among them, 80%

occur in low-income countries, mainly due to the

high rate of obesity, poor diet and cardiovascular

diseases.

8

_{Breast cancer in women and lung cancer}

in men are the types of cancers that most affects

the population in developing countries, whereas

the countries developed, breast cancer for women

continues to be the main type of tumor, and for men

is prostate cancer, followed by lung cancer.

9

Cancer preventive foods

A proper diet is of utmost importance

to maintain health, because it contributes to the

reduction of risk of disease. Through a healthy diet

it is possible to promote recovery, rehabilitation, as

well as the detoxification of cells, which provides a

greater vitality to the organs and tissue.

10

With the increase in the cancer development,

studies have been made with phytochemical

compounds, i.e., those that have antioxidant

properties , in order to demonstrate the power of

protection against this disease. Vitamins A, C and

E comprise this group. The carotenoids also help in

preventing the onset of the disease. The antioxidant

nutrients act by inhibiting the oxidative damages

in the DNA, since the carcinogenic process is

characterized by a chronic oxidative state, mainly

at the promotion stage, which characterizes the

antioxidant foods as chemo preventive.

Antioxidants are responsible for protecting

the cells against oxidative stress that can initiate

and promote the carcinogen process.

12

_{Vitamin C}

is considered one of the most important natural

antioxidants, which can be mainly found in citrus

food, acerola, guava, kiwi, orange and some

vegetables like Broccoli, cabbage, peppers.

13

The flavonoids have antioxidant properties,

as well as anti-inflammatory, thus, contribute to

the treatment of various chronic-degenerative

diseases, such as: cardiovascular diseases, diabetes,

atherosclerosis and cancer, these diseases are

closely linked to the oxidative and inflammatory

processes. These also have the function of

preventing or delaying the development of some

types of cancer, especially colon cancer , which is

related to obesity.

14

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Probiotics and colon cancer

The cancer of the colon and rectum is the

third most common cause of cancer in the world

both in males and females. This type of pathology

has a survival of 5 years in 63% of cases. Both

sexes are equally affected. When located only in the

intestine, this disease is highly curable and treatable.

Among the risk factors for the development of the

disease stands out the family history of cancer of

the colon and rectum, genetic predisposition to the

development of chronic diseases of the intestine

as the polyposis and adenomatosas, in addition to

diets rich in fats, low intake of fruits, vegetables and

cereals. It should be emphasized that the practice

of physical activity is associated with a low risk of

developing cancer of the colon and rectum.

17

A study was performed in rats which

developed colon cancer and had phenotypes of

obesity The flavonoids employees were the chrysin,

quercetin and mobilitin, the results suggest that these

substances are able to eliminate the initial phase of

carcinogenesis of colon cancer in obese rats, since

these have properties to inhibit the activity of cell

proliferation. The authors also mention that they

indicate that the flavonoids may be used in the

prevention of colon cancer in obese humans.

15

The lycopene (precursor of vitamin A) also

has a preventive function in the development of

cancer, because it has antioxidant properties and

its continuous use is able to prevent cancer. The

presence of this nutrient stands out in tomato, since

this has an average of 31μg lycopene/g of fruit.

This carotenoid give the tomatoes the red color and

can be found in other foods, such as papaya, guava,

watermelon, Brazilian cherry, among others.

3

The lycopene acts as chemo preventive

agent, antioxidant, combats free radicals, slows

the aging and protects against cancer, especially

prostate cancer, it is also found in plasma and in

human body tissues, however, its absorption by the

body is higher in sauces than the fruit in natura, once

the thermal processing enhances its bioavailability.

3

Table 1 - Antioxidant foods and their sources.

Antioxidants

Foods sources

Vitamin C

Acerola, lemon, orange, kiwi fruit, guava, tangerine, peach, cherry,

strawberry.

Vitamin E

Almond, hazelnut, chestnut of Brazil, walnuts, mayonnaise, avocado oil,

corn and sunflower seeds, eggs, butter, margarine.

Carotenoids

Dark-green and orange vegetables and fruits , carrot, sweet potato,

tomato, spinach, mango, papaya, apricot, broccoli, tomato sauce and ketchup.

Flavonoids

Soya milk, soya flour, grape and raisins.

(Adapted from Nelliet al., 2015)16

Many are the effects of probiotics such as

relief of symptoms caused by lactose intolerance,

treatment of diarrhea, increased immune response,

anticarcinogenic effects, among others. The most

common form of probiotics is in dairy products

containing lactobacillus and bifidobacterium in

most times.

18

The lactic acid bacteria (LAB) have been

studied for their protective effect against colon

tumors. They play an important role in delaying

the development of this type of pathology by the

possibility to influence metabolic immunological

and protective functions,. Probiotics have been

studied by showing action on the activity of the

bacterial enzymes with carcinogenic effects,

namely: B=glucoronidase, Nitro reductase and

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The role of foods in cancer: a narrative review. GUSMÃO, A. C. M.; CARVALHO , J. R. A.; PARDINHO, S. J. F. ISSN 2236-5257

218 azorredutase, these enzymes are related to the

formation of aromatic amines which are harmful to

the body.

18

_{There are several studies that cite the}

role of these bacteria against the cancer of the colon

and rectum, even though there is no clear evidence

on this protective role.

19

Interaction of carcinogenic substances

The industrialized foods, especially cured

meats such as sausage and ham are directly related

with the onset of cancer, because these have in

their composition nitrites and nitrates, used as

a preservative for food, and stand out for being

important carcinogenic agent. These types of food

are responsible for the high rate of cancer stomach,

once the nitrites and nitrates in the stomach are

transformed into nitrosamines, highly carcinogen

substance.

1

The intake of foods containing nitrites and

nitrates causes cells to form tumors by mechanisms

that increase the nitrous compounds and, added

to the increase of free radicals, causing injury to

the cells on the stomach wall, decreasing thus the

production of mucus, an important protective factor

of the stomach, which increases the chance of

developing malignant tumor in this location.

11

_The

main concern with the use of nitrates in food is due

to its excess in the diet, as well as the endogenous

formation of nitrosamines. The process of

endogenous nitration can be blocked by the action

of antioxidants, because this situation does not

occur in the presence of ascorbic acid (vitamin C),

which blocks the conversion of nitrate and nitrite.

20

The aflatoxin is another mycotoxin that

has carcinogenic effect. These are produced by the

fungi Aspergillus flavus, Aspergillus parasiticus

and Aspergillus nomius, the most widespread

mycotoxin in Brazil. The mechanism of

carcinogenesis generated by aflatoxin involves the

onset or the progression of the tumor. It participates

in the activation of proto-oncogenesis causing also

mutations in the p53 gene . p53 is a phosphoprotein

involved in the process of cellular growth and

differentiation. When the phosphoprotein p53

loses its functions the mutations are transmitted

to the cells and at some time triggers the cellular

transformation. The aflatoxins contaminate mainly

the peanuts, but it can cause contamination in maize

and in brazil nut. It is known as the most powerful

carcinogenic power natural substance due to its

hepatotoxicity.

21

The use of roast beef has been shown

to be another risk factor for cancer, especially

of the stomach and esophagus, because they

produce compounds such as polycyclic aromatic

hydrocarbons and heterocyclic amines which have

carcinogenic effect

1

_{. The polycyclic aromatic}

hydrocarbons are formed from the process of

combustion of organic material and have a wide

distribution in the environment, is considered

highly carcinogenic due to being metabolized by

hepatic enzymes that bind to DNA causing errors

of replication and mutation.

22

CONCLUSION

It can be concluded that environmental

factors such as, for example, the inadequate diet,

i.e., rich in fatty, sugar and industrialized foods

corroborate to the cancer onset, however a healthy

diet rich in antioxidant vitamins can change the

scenario of the disease, especially in its initial phase

by preventing the oxidative damage in the DNA of

the cells.

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measures such as lectures on healthy eating,

nutrition education, accessibility to early diagnosis

in order to change the alarming figures of new cases

of the disease.

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