relationship between nutrition, lifestyle and colorectal cancer

8/11/2019 Relationship Between Nutrition, Lifestyle and Colorectal Cancer

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Study on relationship between high intake offruit, vegetables, dietary fibre and risk ofcolorectal cancer is still suggestive but notconclusive.


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This study is conducted by cohort prospectiveinvestigation.


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The population is people living in UnitedKingdom between 1980 and 1984.The sample is vegetarian and nonvegetarianwho lives in United Kingdom between 1980and 1984, who volunteered to include in thestudy.


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Vegetarian and nonvegetarian is recruited inUK between 1980 and 1984.Participants were contacted through theVegetarian Society of UK, publicity in nationaland local media, and word of mouth viaparticipants already recruited.Non-vegetarian participants were those

recruited by vegetarian participants.


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Based on this method, the sampling issnowball nonprobability sampling.


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Inclusive Criteria:1) Aged 16-89 years at entry.2) Had not been diagnosed with a malignant

cancer before recruitment except fornonmelanoma skin cancer.3) Could be classified by smoking status and

alcohol consumption.


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Dependent variable: Incidence of colorectalcancer.Independent variable: Dietary factors andlifestyle factors.


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To investigate the relationship betweennutrition and lifestyle on incidence ofcolorectal cancer in United Kingdom.


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Data:1) Primary Direct contact with participants by

questionnaire(independent variable).2) Secondary Information gathered from

follow up using database at UK NationalHealth Service central register on cancerregistration and death(dependent variable).

Instrument:1) Questionnaire


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Incidence ofcolorectal

cancer

Dietary Factors

-Diet group

-Meat

-Fish

-Eggs

-Milk

-Cheese

-Fresh or dried fruit

-Total vegetables

-Brown bread

-White bread

-Breakfast cereals

-Total dietary fibre

-Total animal fat

-Vitamin supplements

Lifestyle Factors

-Smoking

-Alcohol

-Social class

-Exercise

-BMI


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A total of 10 998 participants were included in theanalysis with an average follow-up of 17 years. Therewere 95 incident colorectal cancer cases, 39 invegetarians and 56 in nonvegetarians.Table 1 shows the baseline characteristics of the

participants. Median age at entry was 34 years formen and 33 for women. In all, 38% of men and 45% ofwomen were vegetarians.The Standardized Incidence Ratio (SIR) for colorectalcancer compared to the general population ofEngland and Wales was 0.91 (95% CI: 0.74 1.12). TheSIRs for vegetarians and non-vegetarians were 0.81(95% CI: 0.58 1.11) and 1.00 (95% CI: 0.76 1.30),respectively.


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Coxs proportional hazards model was used toestimate the association between selectednutritional and lifestyle factors and the risk ofcolorectal cancer.All incidence rate ratios were adjusted for age atrecruitment (in 11 categories: o40, 40 44, 85 89years) and sex.Further adjustments were made for smokingstatus (in three categories: never, former, andcurrent smoker) and alcohol consumption (inthree categories: non-/occasional drinker, 1 7 uweek1 and 47 u week1).The statistical analysis was performed using theSTATA statistical package (StatCorp. 2001).


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Table 2 shows relative risks (RRs) andconfidence intervals , nutritional and lifestylefactors, and colorectal cancer risk, adjustedfor age and sex alone and with furtheradjustment for smoking and alcohol.Vegetarians showed a moderately butnonsignificantly lower risk of colorectalcancer compared with the nonvegetarians (RR0.72, 95% CI: 0.48 1.10), but this associationbecame weaker after adjusting for smokingand alcohol (RR 0.85, 95% CI: 0.55 1.32).

Among the nonvegetarians, there was noevidence of a positive association with thefrequency of meat consumption.


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Among the other dietary factors, the onlystatistically significant associations with risk

were for fruit and white bread consumption.Participants with the highest consumption offresh or dried fruit experienced a reduction ofcolorectal cancer risk (RR 0.57, 95% CI: 0.34

0.97, P for trend0.041), although theassociation was no longer statisticallysignificant after adjusting for smoking andalcohol.


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Participants eating 15 or more slices ofwhite bread per week compared with thoseeating less than 15 had significantly higherrisk (RR2.25, 95% CI: 1.25 4.04; P fordifference between groups0.006), whichremained highly significant after adjustingfor alcohol and smoking.


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After adjusting for alcohol intake, bothcurrent and former smokers had an increasedrisk of colorectal cancer compared with thenever smokers (RR1.70, 95% CI: 0.92 3.15and RR1.80, 95% CI: 1.13 2.85,respectively).Among the other lifestyle factors, social class,exercise, alcohol consumption, and bodymass index were not significantly associated

with the risk of colorectal cancer.


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This prospective study had a wide variation in dietdue to the inclusion of a large proportion ofvegetarians. The main limitation is the relativelysmall number of colorectal cancer cases and the

lack of sophistication of the food frequencyquestionnaire.The present analysis did not find a significantdifference in risk between nonvegetarians and

vegetarians. Furthermore, no increase in risk ofcolorectal cancer was seen with higher meatconsumption among nonvegetarians.


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Nevertheless, the lack of statistical association mayreflect the relative small number of cases . Aprevious analysis of mortality in this cohort

(Appleby et al, 2002) showed similar death ratesfor colorectal cancer in vegetarians and non-vegetarians based on 25 and 24 deaths fromcolorectal cancer, respectively.However, in a prospective investigation of

Seventhday Adventists (Singh and Fraser, 1998),cancer of the colon was significantly more commonin non-vegetarians than in vegetarians.It could be suggested that the nonvegetarians inour study represent a healthy group compared withthe population at large , and that this might accountfor the lack of difference between the vegetariansand non-vegetarians; however, the SIR amongnonvegetarians was exactly one.


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Fresh or dried fruit consumption was found to besignificantly associated with colorectal cancerrisk, although this association became

nonsignificant after adjusting for alcohol andsmoking. An approximately 40% decrease in riskwas seen in people eating fresh or dried fruit fiveor more times per week compared with personeating less than this amount.We did not observe a significant association forbrown bread and risk of colorectal cancer, but atwo-fold increase in risk was detected in thoseconsuming 15 or more slices of white bread per

week. White bread consumption may be a markerof an unhealthy diet, although an adverseassociation of refined carbohydrates with risk hasbeen noted before (Chatenoud et al, 1999).


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We did not observe a significant associationbetween fibre and colorectal cancer risk;however, information needed to estimate dietaryfibre intake was unavailable for 32 cases, and theresults are compatible with a recent report of areduction in risk with high fibre intake (Binghamet al, 2003).Our study suggested that smoking wasassociated with an almost two-fold increase inrisk of colorectal cancer, although thisassociation was attenuated by adjusting foralcohol consumption.The apparent adverse effect of alcohol was alsopartially confounded by smoking. Both the WCRFreport (World Cancer Research Fund, 1997) and acomprehensive review by Potter (1999) concludedthat smoking and alcohol are probable riskfactors for colorectal cancer.


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Risk increased in association with smoking,alcohol, and white bread consumption, anddecreased with frequent consumption of fruit.The relative risk in vegetarians compared withnonvegetarians was 0.85 (95% CI: 0.55 1.32).


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relationship between nutrition, lifestyle and colorectal cancer

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