ABSTRACT
The strongest evidence for protection is from ingestion probably in excess of physiologic needs. Howev-er, there of tr,e complex long-chain carboh'(drates, rather than from is little evidence relating protein intake to neoplasia per the simple sug::Jr ~;u~;rose. llctiJ::JIIy, in both experirnent::JI se; the protein foods ::Jncl the effects of their cooking are and epidemiologic studies, a high intake of sucrose was discw;sed below. 4 found to potentiate the risk for colorectal cancer.4 ~~ consistently high intAke of sucrose ::Jnd eAsily digested ::Jnd absorbed foods, mainly starches having a high 'glycemic Minor dieta1·y constituents (mi1~ronutrientl~) index', is usually accompanied by a relatively low intake of other dietAry constituents, in~;luding pi·otective cliet::Jry f::Jc-These are ·:he vit::Jmins And minerals th::Jt hAve been extentors. It has also been suggested that persistent hyper-sively investigated and, in the main, are protective against glycemia, and consequent insulin response, is a stimulus colorectal cancer. Their anticarcinogenic roles seem to be for colonic: epitheli:)l prolifer<ltion and risk for c:::Jn<;er8 The minor, ::Jc:ting on the intr::Jiumin::JI contents and,! or by complex carbohydrate-containing foods should provide strengthening the resistance of the large-bowel epithelium 45-130% of the total energy intake and refined sugar to carcinogens and tJy correcting genetic damage. The list <1 0%4 of these nutrients is numerous :)nd 1:hey h::Jve v::Jrious
functions; they include selenium, calcium, vitamins A Fibm ar1d fluid intake (carotenoids), C, D, and E, and folic acid.420·24 Their beneThe ferment::Jtion bre::Jkdown products of complex carbo-fic:i::JI or deleterious ph::Jrm::Jc:ologic: use AS c:hemoprevertive hydrates are important in maintaining healthy colonic agents is discussed in Chapter 5. Vitamin supplements are epitt1elial cells an,j bowel function.21 In addition, nneta-not needed when eating the recommended five portions an::Jiysis of epidemiologic: sti.Jdies ev::JiiJAting fiber int<lke in per d:;1y of fruits and s::Jiwis. preventing colorectal cancer indicates a low but protective There has been considerable interest in the colon canrole for fiber, especially from that of wheat origi n.4 •7 •15 The cer protective role of calcium and vitamin D. The strongest stronges1 evidence is from ::l miJitinAtion::JI Furope::Jn study evidence for this is exp!~riment::JI, AS shown by givirg ::l of fiber intake in over 500 000 persons, which demon-'Western-style' diet to mice and suppressing the resulting strated a significantly reduced risl~ for cancer in those hav-hyperproliferative response of the colonic epithelium by ing the highest intAke. The effect W::lS m:;linly on c:olonir: ::Jdding dietary c::Jic:ium 2~' The epidemiologic evi(lenc:e is and not rectal cancers and was irdependent of the source not supportive for a strong anticarcinogenic role, but of fiber. 22 Similarly, in a large US screening study, dietary rather for a modulating, protective role within a 'carcinofiber, indepen(ient of source, W::lS significantly <ISSOC:i::Jted genic:' We~;tern diet (Sef~ section on milk prod1wts). In with a reduced risk for colonic adenoma.2 ' The beneficial adenoma patients, suppression of rectal epithelial prolifeffects of whole grain foods are also discussed below. eration by long-term calcium dietary supplements is great-
It W::lS recently shown in epidemiologic studies of both est when their cliet::Jry int<)ke is high in c:::JrbohydrPJte, fiber, colorectal cancer and adenoma patients that the protec-and water and low in fat, with low tobacco use.26 Longtive effect provided t:•y fiber was potentiated by the term calcium supplements will slightly but significantly individu::JI's totAl fluid intAke, independent of type ol' fluid reduce the re~;1menc:e r<lte of I::Jrge-bowel '3denom::Jtous drunk.7 The type of fiber ingested and types and polyps by 18%, especially when allied to an adequate amounts of other dietary constituents (e.g. fat , calcium, intake of vitamin DY The vitamin D plasma metabolite 25and fluid! ::Jre likely to infh.J•~nce the protective role th::Jt hydroxyvit::Jmin n levels were ·found to h::Jve beP.n fiber has to play within the intracolonic environment_., significantly lower in persons eventually developing distal The reconnmended daily intake of fiber is 25-.35 g.4 colorectal cancer after long-term follow-up. This was
not::Jble in the older-.3ged study popui::Jtion ::Jnd could <llso Proitein be related to their inadequate sun exposure as well as As protein is derived from bot i1 vegetable and animal diet.2" sources, it is diffir;IJit to evAluate its role in ~;olorec:t<ll <;::Jr-Wh<lt seems importAnt ::Jbout the c:::Jicium intAke is not cinogene.sis separately from these food sources or from its source, but rather its total intake: up to 1500-2000 mg the means of ·food preparation. Protein intake is highest in calciunn ionjday. Tt1e dietary reference intake for calthose countries at highest risk for colorectal cancer and is cium has been increased to 1:200 mg,lday for adults aged
50 years or older.29 This discrepancy in dosage probably health led the Health Authorities in the United States and reflects thH difference between desirable minimal Canada to require all flour and uncooked Cl3reals be forti· arr1ounts for physiologic needs and pharmacologic tied 'Nith 1~o!!c acid.33 effects. Very few adults have even this minimal intahe The overall impression is that an adequate dietary when eating their Western diet. A higher intake of calcium intake of all these micronutrients is important in the can be obta !ned by providing a diet rich in ca!c!urr!, such defense against carcinogenesis (see also Chapter 5;~. as calcium-containing low-fat m1lk products. Tl1is d1et has been st10wn to be practica I in volunteers and suppresses Bioactive compounds their !arge-bowe! epithelia! pro!i·feration.30 Ho\·vever, it has Bioactive corr1pounds is a genera! term that includes not been proven to prevent neoplasia, nor ere its long-numerous chemicals found 1n fruits, vegetables, spices, term effects known. Othe1·, non-dairy sources of ·::Jietary condiments, herbs, etc., that in som(3 cases have been calcium are listed in 12b!e 4.3. proven to have anticarcinogenic properties. So!T1e of the
There is now some epidemiologic and experimental evi-best known and studied are those found in green tea, dence to link a high intake of iron and having high bo,jy tomatoes, onions, carrots, lemons, curry, and garlic. A stores of iron, especia!!y \AJhen due to supplements or partial list ls given in Tab!e 4.4. Even though their ef'fects genetic reasons for iron overload, with an increased risk have been demonstratHd experimentally, it is not clear for colorectal cancer. High dietary or supplemental how important is their occasional ingestion within the sources of iron !ead to increasing concentrations of intra-mixed \AJestern diet. Ho·wever, tt1ere are some national luminal free radicals, which have been associated with groups or individuals where their consistent intake may risk for cancer.4 ·''1 If confirmed . these observations may have a significant contribution as anticarcinogens, e.g. have an important implication on the c!in!ca! practice of gree'l teE!, curry, etc. 20·34-36 The consistent ingestion of maintaining full body stores of ion. isoflavonoids and lignans found in soya beans an<l rye
A low intake of folic acid has been associated w1th ri~;k cereal have b(3en assoc:iatecl witt\ a lower risk of cancer, for co!orecta.! cancer. These patients have a !ovver inta~<e especia!!y breast ·cancer, in Asia and Scand!navia.37·38 and blood levels of folic acid. Th1s is exacerbc:1ted in Their effect in preventing colorectal cancer is less well chronic alcoholism and in pmsons having a specii'ic documented.311 genetic po!ymorphisnl that interferes \J\Jith folic ac id metabolism. 32•33 The Importance of folic acid on overall
Cheese f~elp
Sardines Vegetable greens Nuts Beans Tofu Whole milk Spinach Sesame
Highest
Moder<lte
Lower
The above foods have a calcium content ranging from about i OOO mg/i OO g in the highest caicium-conta1ning food to 100-200 mg/100 g ·In the lowest calciumcontaining food.
