Dietary Patterns and Their Effect on the Colorectal Cancer Risk

Hongji Zou

University of Liverpool, Liverpool, U.K.

Keywords: Colorectal Cancer, Dietary Patterns, Retrospect, Effect.

Abstract: Colorectal cancer (CRC) the third most commonly diagnosed cancer, excluding skin cancers, worldwide. In

2018 alone, there were close to 2 million new cases all over the globe (World Cancer Research Foundation

International 2019). In 2020, CRC accounted for about 10% of all cancer cases and deaths, recording about

1.9 million new diagnoses and 935,000 fatalities (Sung 2020). In this year, it is projected that there will be an

estimated 104,000 new diagnoses of colon cancer, and about 45,000 new diagnoses of rectal cancer (De

Stefani 2011). There is a 4.3% risk of developing CRC for men, and a 4.0% risk for women (World Cancer

Research Foundation International 2019). Therefore, colorectal cancer has caused a huge burden on social

and economic development worldwide. More and more studies have shown that eating more foods rich in

dietary fiber and dairy products can reduce the incidence of colorectal cancer, while eating more red meat and

processed meat products can increase its incidence (World Cancer Research Fund and American Institute for

Cancer Research 2017).

1 INTRODUCTION

There is evidence that dietary and lifestyle factors

contribute to the risk of developing CRC, and a

number of foods have been studied and reported on in

relation to their associated CRC risk. For instance,

research shows that consuming whole grains, dairy

products, foods high in dietary fibre and taking

calcium supplements lowers CRC risk, while

consuming processed meats, red meat and alcoholic

drinks increases relative CRC risk (World Cancer

Research Fund and American Institute for Cancer

Research 2017). However, the above-named foods

are rarely consumed individually, and instead are

components of a larger dietary pattern. Studying food

and nutrient combinations better elucidates the

dietary patterns of a population and their associated

CRC risk, since chronic diseases usually result from

many interacting variables.

This review looks at studies ranging from 1998 to

2021. We review the literature on the relationship

between different dietary patterns and the relative risk

(RR) for CRC to provide a reference for the public

healthy diet model, and for the primary prevention

strategy of colorectal cancers.

https://orcid.org/0000-0003-2771-2748

2 METHOD

PubMed-NCBI was searched for articles up to June

2021 that researched potential correlations between

dietary patterns or foods and the relative risk for

CRC. The search included the following keywords or

phrases: diet, dietary pattern, colorectal cancer, and

epidemiology. Studies that reported risk estimates

(odds ratios [ORs], and RR) of cancer and measures

of variability (SEs or 95% CIs from which these could

be derived) were selected preferably. Primary papers

were selected preferably where possible, but meta-

analyses were not excluded.

3 RESULTS

The papers studied had a number of different

classifications of dietary patterns. While some of the

studies included less popular dietary patterns,

including the traditional and the substitute patterns,

three patterns were consistently found in at least most

of the papers: Western, drinker and prudent. For this

reason, we have focused on the literature on the three

main dietary patterns. Other patterns mentioned in the

Zou, H.

Dietary Patterns and Their Effect on the Colorectal Cancer Risk.

DOI: 10.5220/0011205900003444

In Proceedings of the 2nd Conference on Artiﬁcial Intelligence and Healthcare (CAIH 2021), pages 141-145

ISBN: 978-989-758-594-4

141

chosen papers have been mentioned briefly in the

final section of the results.

3.1 The Western Dietary Pattern

The Western dietary pattern is described as a

“modern” diet, including a lot of processed foods.

Though the specific elements may vary from study to

study depending on the cultures of origin and the

authors’ research interests, most will be characterized

by red meat and processed meats, eggs, refined

grains. The Western dietary pattern may also include

plenty of processed sugars, fried foods and potatoes,

and low intakes of whole grains, fresh vegetables and

fruits (Tseng 2000). The Western dietary pattern has

shown an association with an increased risk for CRC.

A long study of CRC in Montevideo, Uruguay,

spanning from 1996 to 2004, studied 610 cases, with

1220 controls from the same hospitals (Fawehinmi

2012). With the samples and controls divided into

three dietary patterns for women (Western, prudent

and drinker) and four for men (Western, prudent,

drinker and traditional), the study found that the

Western dietary pattern showed an Odds Ratio of 2.62

(95 % CI 1.36-5.08) for colon cancer in men, and 1.95

(95 % CI 1.00-3.78) in women. Rectal cancer was not

found to be associated with the Western diet, which

was defined as consisting of high quantities of total

eggs, red meat and processed meats.

Table 1: Western dietary pattern.

Gende

Odds Ratio 95%CI*

Men 2.62 1.36-5.08

Women 1.95 1.00-3.78

*CI confidence interval

A similar study running for 32 years did a follow-

up of 3260 cases of CRC among health professionals

across the US, comparing CRC risk associated with

Western and prudent diets (Mehta 2017). Participants

who had more of the Western dietary pattern showed

an increased risk of CRC, while those who scored

higher in prudent dietary patterns had a lower risk of

CRC. The relative risk for CRC correlated with the

Western diet was also found to have differences in

anatomic subsites. Distal colon and rectal tumors had

a relative risk of 1.55 (95% CI, 1.22–1.96) and 1.35

(95% CI, 1.03–1.77) respectively. Proximal colon

cancers, in contrast, had an RR of 1.11 (95% CI, 0.91–

1.35). Notably, this paper also studied the correlation

between dietary patterns and different molecular

subtypes of CRC. Though the findings still required

further refining, the study found that the Western

dietary pattern was also more strongly correlated with

BRAF- and KRAS-wildtype, and CIMP-

negative/low tumors.

Table 2: The relative risk.

Index RR 95%CI*

Distal colon 1.55 1.22-1.96

Rectal tumors 1.35 1.03-1.77

Proximal colon 1.11 0.91-1.35

*CI confidence interval

Fung et al. found that a Western diet consisting of

large intakes of sweets and desserts, processed and

red meats, refined grains and French fries reported a

high relative risk for colon cancer, at 1.46 (95% CI,

0.97-2.19) (Giovannucci 2002). This paper studied

121,700 women between the ages of 30 and 55 across

11 states, over 12 years of follow-up. Similar to the

aforementioned study by De Stefani et al. in Uruguay,

this study found little to no significant correlation

between the Western dietary pattern and rectal cancer.

This paper reinforces the earlier study by providing

evidence that the impact of the Western diet on

relative CRC risk is generally the same, irrespective

of sex.

Some studies have gone a step further in their

characterizations of dietary patterns. For instance,

Slattery et al. described the Western diet as containing

a higher intake of dietary cholesterol and total energy,

and a greater body mass (Slattery 1998). This diet was

found to be correlated with a higher RR for colon

cancer in both men and women. A meta-analysis of

40 studies investigating the effects of the Western diet

also showed that this dietary pattern may increase the

RR of CRC (Fung 2003). One study included an

analysis of dietary patterns by the duration during

which the participants partook in them. The results

showed that the duration definitely matters (Song

2015). This study found that partaking in a Western

dietary pattern over an extended period of time was

associated with a higher RR for CRC, highlighting

that the prevalent diet during adolescence has a long-

lasting effect, regardless of adult diet. After a CRC

diagnosis, a higher indulgence in the Western diet

further increases the risk of recurrence after

treatment, and mortality.

3.2 The Drinker Dietary Pattern

The drinker dietary pattern, though not as extensively

studied as the Western and prudent patterns, has also

been studied and implicated in an increased relative

risk for CRC. This pattern is characterized by high

quantities of alcoholic beverages, and this is what

most studies focus on. Some studies have suggested

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that the drinker dietary pattern may include poor

nutritional intake, like Fawehinmi et al. that heavy

and moderate drinkers consumed less favorable

loadings of nutritious and healthy foods than non-

drinkers (Feng 2017).

The drinker dietary pattern was consisted mainly

of younger men who consumed wine, beer and hard

liquors, and also smoked heavily in a study by De

Stefani (Salaspuro 2009). This group showed a

positive association with a higher RR for CRC.

Though the sample of women under the drinker

dietary pattern classification featured less intensive

smokers, they also showed poor nutritional intake and

cholesterol consumption, and mirrored the male

sample in CRC risk. The Slattery et al. definition of

the drinker pattern also included smokers, though this

category featured less red meat and more poultry and

fish in this study (Slattery 1998). The drinker pattern

recorded a very weak positive association with colon

cancer in men. The ‘alcohol-consumption’ pattern, as

it was termed in a meta-analysis ty Feng et al. was

reported to potentially increase the relative risk for

CRC, regardless of gender (Fung 2003).

3.3 The Prudent Dietary Pattern

Although the description of the prudent dietary

pattern is determined specifically by the authors of a

paper for their study, there are general features that

apply across the board in many studies. This diet

features an abundance of fresh fruits and green

vegetables, salads and carrots (Salaspuro 2007). Each

of the studies discussed above has slightly different

qualifiers of a “prudent” dietary pattern, but they are

all built on the same basics as listed. These studies

have one other thing in common: they all provide

evidence that the prudent dietary pattern protects

against colon and rectal cancers.

For the study in Montevideo, Uruguay, the

prudent diet was described as having high intakes of

dairy foods, white meat, total fruits and raw

vegetables. This pattern was found to be strongly

effective in preventing rectal cancer (Pietinen 1999).

Mehta et al demonstrated that prudent dietary

patterns, consisting of high quantities of whole grains,

fruits, vegetables and fish, generally have a lower

association with colon and rectal tumors, irrespective

of molecular subtypes and anatomical subsites

(Pöschl 2004). In Fung et al. prudent dietary

patterns including the regular whole grains, fruits and

vegetables plus poultry, legumes and fish, showed an

inverse correlation with colon cancer, but showed

little to no significant correlation with RR for rectal

cancer in women (Cancer.org. 2021).

Slattery et al described the prudent dietary pattern

as being associated with smaller body size, rigorous

leisure physical activity and higher quantities of

dietary folates and fibers (Pietinen 1999). This study

included age variations in the subjects, and found that

the prudent diet was correlated with a decreased RR

for colon cancer, particularly in younger individuals.

These results were further confirmed by a meta-

analysis by Feng et al (Fung 2003), which showed

that the ‘healthy’ dietary pattern, with the same

features as the prudent dietary pattern, may reduce the

RR for CRC. Song, Garrett and Chan showed that the

prudent pattern is protective against CRC, especially

when the diet is adhered to from adolescence (Song

2015). This study also showed that following a

diagnosis of CRC, the prudent dietary pattern is

recommended to prevent recurrence and to improve

disease prognosis.

3.4 Other Dietary Patterns

Although the three dietary patterns discussed above

are the most commonly studied in the literature, some

studies include less common patterns. De Stefani et al

studied the traditional dietary pattern but only in men

(Salaspuro 2009). It was described as having high

quantities of cooked vegetables, desserts, legumes

and tubers. This diet shared many similarities with the

Western diet, but was classed separately considering

the geographical location and cultural background of

the area under study. Most of the men who reported

under the traditional pattern were poorly educated and

lived in the rural areas of Uruguay. The traditional

dietary pattern was found to have an inverse

association with both colon and rectal cancers.

Slattery et al had five dietary patterns: prudent,

drinker, Western, substituters and high fat/sugar dairy.

The first three have been discussed above (Pietinen

1999). Substituters switched out butter, red meat, high

fat dairy products and refined grains in favor of

margarine, poultry, low fat dairy products and whole

grains, respectively. This pattern is perceived as

healthier than the Western pattern. However, this

study showed that this substitution did not

significantly reduce the RR for colon cancer. The high

fat/sugar dairy pattern contained high quantities of

yogurt and dairy products rich in fat and sugar. This

dietary pattern was not studied for relative risk of

colorectal cancer.

4 DISCUSSIONS

Most of the papers studied for this review found that

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143

dietary patterns have an association with the relative

risk for CRC in both men and women. The exception

was Pietinen et al which studied the relative risk for

CRC of different diet components rather than dietary

patterns, and found that high intake of calcium, milk

products and milk protein had an inverse correlation

with the RR for CRC, while high intake of fat, dietary

fiber, fried meats, vegetable and fruits had no

significant association with risk for CRC (Pöschl

2004). The food components found to have no

association with CRC risk cut across both the prudent

and Western dietary patterns, by the general

characterizations of both patterns. Extrapolating the

results of this study to our model of dietary patterns,

Pietinen et al. found that dietary patterns in general

have no correlation to the relative risk of CRC, and

rather it is specific foods, especially dairy products

and other calcium-rich foods that have an impact on

CRC relative risk.

The main tentative conclusion of this review is

that the Western and drinker dietary patterns show a

positive correlation with an increased relative risk for

colon cancers, but this association is much less

definite in rectal cancers.

This review highlights the differences in the

constitutions of different dietary patterns, as well as

the differences in classifications, to different

researchers. Though these differences may seem

subtle (the difference is usually only in a few food

groups), when considered as forming a daily diet that

spans decades of an individual’s life, individual foods

make a significant difference in the overall effect of a

diet. This consideration thus has us wondering

whether it is in fact effective to study the effect of

broad dietary patterns rather than isolated foods.

Even so, the majority of the papers studied for this

review showed that the prudent dietary pattern is the

healthiest and the most protective, with the highest

negative association with colorectal cancers,

regardless of gender, age, molecular subtypes and

anatomical subsites. The prudent dietary pattern

notably contains fresh green vegetables (some papers

specify that the green vegetables have to be eaten raw

to qualify under the prudent pattern). Fresh green

vegetables are high in dietary fiber. Fruits and cereals,

which may also be indicated as part of this diet are

also sources of fiber. It was demonstrated in a

screening trial that participants who regularly

consumed higher quantities of dietary fiber had a

lower risk of colorectal adenomas (Mehta 2017).

Further, the components of the prudent dietary pattern

are also high in antioxidants, which would confer

protection, not just from colorectal cancers, but from

other cancers as well.

The Western dietary pattern, in all its versions in

the papers studied for this review, included high

loadings of processed meats and red meat, and it has

been shown definitively to have an increased relative

risk for CRC. These results are consistent with the

findings of the International Agency for Research on

Cancer (IARC) (Cancer.org. 2021), which reported

that consumption of red meat and processed meats is

mutagenic and carcinogenic to humans. Though red

meat contains high quantities of important proteins

and micronutrients like iron and vitamin B, it also

contains haem iron which when broken down, forms

N-nitroso-compounds (NOC) are released, which are

carcinogenic. Meat processing and cooking can also

result in the formation of NOC and polycyclic

aromatic hydrocarbons (PAH), particularly with high-

temperature preparations such as barbecuing or

grilling. It is therefore no wonder that diets featuring

high loadings of these meats would show a higher RR

for CRC and other cancers (Aykan 2015).

The drinker dietary pattern has been consistently

shown to increase the risk of CRC by the papers in

this study, even though it is more consistently

associated with colon cancers than with rectal

cancers. These results are backed up by research that

shows that alcohol consumption has a causal

relationship with an increased risk of digestive system

cancers, including those of the colon and rectum, and

also of the breast in women (Bouvard 2015). The

exact mechanism of the association of alcohol

consumption and colorectal cancer is still under

study. One epidemiological study suggested that this

action is because alcohol affects the metabolism of

dietary folates, where folates are thought to reduce the

relative risk of CRC and other cancers (Kunzmann

2015). A more substantial explanation for the

correlation between CRC and alcohol consumption is

that ethanol metabolism releases acetaldehyde and

reactive oxygen species (ROS). Acetaldehyde has

been shown to be mutagenic and carcinogenic, and

has been implicated as a common denominator in the

development of many alimentary tract cancers

(Salaspuro 2009). It binds to proteins and DNA and

disrupts folate. Research has also shown that

acetaldehyde can be produced by oral bacteria. The

fact that the drinker dietary pattern is commonly

characterized by moderate to heavy smoking may

also be a factor in the results seen. Smoking is known

to alter the flora of oral bacteria, which may impact

the production of acetaldehyde (Pöschl 2004).

Cigarettes also contain acetaldehyde (Salaspuro

2007).

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5 CONCLUSIONS

The study of dietary patterns and their disease

association has become popular as a way to better

understand the impact of combining well studied and

documented individual foods. The literature shows

multiple classifications of dietary patterns, but the

three most common are the “Western” diet, the

“drinker” diet and the “prudent” diet. Of the three, the

Western diet has consistently shown the highest

positive association with an increased relative risk for

CRC, though the association is stronger with colon

cancers than with rectal cancers. This is presumably

because of the high intake of carcinogenic meats, and

the low intake of beneficial vitamins and

antioxidants. The drinker dietary pattern has shown a

less consistent association with an increased risk for

CRC, but it has not shown a negative correlation in

any of the studies reviewed in this paper. The prudent

dietary pattern has consistently shown to be the

healthiest, even when other patterns such as the

substitute pattern are considered. This pattern

provides high quantities of beneficial nutrients and

antioxidant, and contains low quantities of

carcinogenic foods. Even so, the vast differences in

how each of these dietary patterns is characterized in

the literature could be a potential avenue for

confusion. The research shows that perhaps

recommending an increase in some foods and a

reduction of others may be more beneficial in creating

guidelines for healthy living and the prevention of

CRC, than recommending a larger dietary pattern

whose details are left to interpretation.

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