diet & nutrition in ca preven

8/9/2019 Diet & Nutrition in CA Preven

1/17

The Importance of Nutrition inCancer Prevention

The American Cancer Society publishesnutrition guidelines to advise the publicabout dietary practices that reduce can-cer risk.1 These guidelines are developed

by expert advisory committees and arebased on existing scientific evidence thatrelates diet and nutrition to cancer risk inhuman population studies as well as inlaboratory experiments.

This evidence suggests that aboutone third of the 500,000 cancer deathsthat occur in the United States each yearis due to dietary factors. Another third isdue to cigarette smoking. Therefore, for

the large majority of Americans who donot smoke cigarettes, dietary choices andphysical activity become the most impor-tant modifiable determinants of cancer

risk.2 The evidence also indicates that al-though genetics is a factor in the develop-ment of cancer, cancer cannot be ex-plained by heredity alone. Behavioralfactors such as cigarette smoking, dietarychoices, and physical activity modify therisk of cancer at all stages of its develop-

ment. The introduction of healthful dietand exercise practices at any time fromchildhood to old age can promote healthand reduce cancer risk.

On the basis of its review of the sci-entific evidence, the American CancerSociety 1996 Advisory Committee onDiet, Nutrition, and Cancer Preventionreaffirms previous conclusions of the So-ciety that dietary practices and physical

activityalong with smoking cessation,avoidance of occupational carcinogens,and early detectionare important fac-tors in the prevention of cancer and can-cer death.

Many dietary factors can affect can-cer risk: types of foods, food preparationmethods, portion sizes, food variety, andoverall caloric balance. Cancer risk canbe reduced by an overall dietary pattern

that includes a high proportion of plantfoods (fruits, vegetables, grains, andbeans); limited amounts of meat, dairy,and other high-fat foods; and a balance ofcaloric intake and physical activity.

Many Americans do not follow suchhealthful practices. Indeed, trends indi-cate an increase in caloric intake, greateruse of high-fat convenience foods, and a

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1

Vol. 46 No. 6 November/december 1996 325

Guidelines on Diet, Nutrition, and Cancer

Prevention: Reducing the Risk of Cancer withHealthy Food Choices and Physical Activity

The American Cancer Society 1996 Advisory Committee

on Diet, Nutrition, and Cancer Prevention

American Cancer Society 1996 Advisory Commit-tee on Diet, Nutrition, and Cancer Prevention:Marion Nestle, PhD, MPH (Chair); Dileep G. Bal,MD, MS, MPH; Diane F. Birt, PhD; Gladys Block,PhD; Tim Byers, MD, MPH; Susan Foerster, MPH,

RD; Peter Greenwald, MD, DrPH; Ervin J.Hawrylewicz, PhD; Brian E. Henderson, MD; DavidHunter, ScD; Lenore A. Kohlmeier, PhD; DavidKritchevsky, PhD; Shiriki K. Kumanyika, PhD, MPH,RD; Lawrence Kushi, ScD; Bonnie F. Liebman, MS;Robert Russell, MD; Henry Thompson, PhD; DavidF. Williamson, PhD, MS; American Cancer SocietyStaff Participants: Lynne Camoosa; Steve Dickinson;Nancy Hailpern; Clark Heath, MD; Roberta Moss,MPH; Mary C. OConnell; Billie Parker; Amy Stone;Michael Thun, MD; Allen Vegotsky, PhD.


2/17

decline in physical activity among Ameri-cans.3 We believe that such unhealthfultrends are due in part to shifts towardconsumption of food outside the home, tomore sedentary lifestyle patterns, and tothe advertising and promotion of high-calorie foods.4 The committee is especial-ly concerned about the effects of suchtrends on the long-term health of chil-dren, who are establishing lifetime pat-terns of food intake and physical activity.5

In this report, the committee pre-sents four broad guidelines to reduce can-cer risk among people aged two years andolder (Table 1). In addition, we offer ad-vice on a wide variety of questions aboutnutrition and cancer that concern thepublic at large. These recommendationsrepresent the committees best efforts to

provide advice based on scientific studiesrelated specifically to the primary preven-tion of cancer. This advice does not applyto cancer treatment or to reducing therisk of cancer recurrence. The commit-tees recommendations are consistent inprinciple with the 1992 Food Guide Pyra-mid,6 the 1995 Dietary Guidelines forAmericans,7 and dietary recommenda-tions of other agencies for general health

promotion and for the prevention ofcoronary heart disease, diabetes, and oth-er diet-related chronic conditions.8-11 Al-though the committee recognizes that nodiet can guarantee full protection againstany disease, we believe that our recom-mendations offer the best nutrition infor-mation currently available to help Ameri-cans reduce their risk of cancer.

Recommendations

1. Choose most of the foods you eat fromplant sources.

Eat five or more servings of fruits and veg-etables each day.

Include fruits or vegetables in everymeal.

Choose fruits and vegetables for snacks.

Eat other foods from plant sources, suchas breads, cereals, grain products, rice,

pasta, or beans several times each day.

Include grain products in every meal. Choose whole grains in preference to

processed (refined) grains. Choose beans as an alternative to meat.

The scientific basis for these recom-mendations is very strong for cancers atmany sites, particularly for cancers of thegastrointestinal and respiratory tracts.12-15

The evidence is particularly strong thatincreased consumption of fruits and veg-etables reduces the risk of colon cancer.16

Evidence is less strong for cancers con-sidered hormonal, such as breast andprostate cancer. Of the many scientific

studies on this subject, the great majorityshow that eating fruits and vegetables (es-pecially green and dark yellow vegetablesand those in the cabbage family, soyproducts, and legumes) protects againstcolon cancer.

Greater consumption of vegetables,fruits, or both together has also been as-sociated with a lower risk of lung can-cer.17 The major risk factor for lung can-

cer is tobacco, but diet also affects risk.Studies have shown that people whosmoke cigarettes tend to eat less healthfuldiets than nonsmokers, but fruits andvegetables reduce cancer risk whether ornot people smoke.

Because many studies indicate thatfoods high in beta carotene protect againstlung cancer, scientists have suggested that

d i e t , n u t r i t i o n , a n d c a n c e r P r e v e n t i o n

326 CaA cancer Journal for Clinicians

The evidence is particularlystrong that increased

consumption of fruits andvegetables reduces the risk

of colon cancer.


3/17

beta carotene itself might reduce lungcancer risk. Recent clinical trials of betacarotene supplements, however, haveshown that smokers taking the supple-

ment developed lung cancer at higherrates than those taking a placebo.18,19

These findings support the idea thatbeta carotene may be a proxy for otherprotective nutrients or substances,singly or in combination, within foods.They also suggest that taking a singlenutrient in large amounts may produceadverse effects.

Despite the strength of the evidence

associating consumption of fruits andvegetables with decreased cancer risk, in-take of these foods is low among manyadults and children.20 Concern about lowintake levels has led to a country-wideinitiativethe National 5 A Day for Bet-ter Health Programto increase fruitand vegetable intake to five or more serv-ings of fruits and vegetables daily.21 This

recommendation applies to foods in theirfresh, frozen, canned, dried, or juiceforms, but does not apply to specific nu-trients or other substances that might be

extracted from them.Vegetables and fruits are complexfoods containing more than 100 beneficialvitamins, minerals, fiber, and other sub-stances. Scientists do not yet know whichof the nutrients or other substances infruits and vegetables may be protectiveagainst cancer. The principal possibilitiesinclude specific vitamins and minerals,fiber, and phytochemicalscarotenoids,

flavonoids, terpenes, sterols, indoles, andphenolsthat are present in foods ofplant origin.12,14 How fruits and vegeta-bles exert their protective effects consti-tutes an active area of scientific inquiry.Until more is known about specific foodcomponents, the best advice is to eat 5 ormore servings of fruits and vegetableseach day.

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1


1. Choose most of the foods you eat from plant sources

Eat five or more servings of fruits and vegetables each day

Eat other foods from plant sources, such as breads, cereals,

grain products, rice, pasta, or beans several times each day

2. Limit your intake of high-fat foods, particularly from animal sources

Choose foods low in fat

Limit consumption of meats, especially high-fat meats

3. Be physically active: Achieve and maintain a healthy weight

Be at least moderately active for 30 minutes or more on

most days of the week

Stay within your healthy weight range

4. Limit consumption of alcoholic beverages, if you drink at all

Table 1American Cancer Society Guidelines

on Diet, Nutrition, and Cancer Prevention


4/17

Grains such as wheat, rice, oats, bar-

ley, and the foods made from them con-stitute the base of healthful diets as illus-trated in the Food Guide Pyramid.6

Healthful diets contain six to 11 standardservings of foods from this group eachday. As shown in Table 2, standard por-tion sizes are defined as quite small, andthis number of servings is not difficult toachieve. Grains are an important source

of many vitamins and minerals such as fo-

late, calcium, and selenium, all of whichhave been associated with a lower risk ofcolon cancer.16 Whole grains are higher infiber and certain vitamins and mineralsthan refined flour products. Because thebenefits of grain foods may derive fromtheir other nutrients as well as fromfiber,22 it is best to obtain fiber from fruits,vegetables, and whole grains rather than



Fruits

1 medium apple, banana, orange

1/2 cup of chopped, cooked, or canned fruit

3/4 cup of fruit juice

Vegetables

1 cup of raw leafy vegetables1/2 cup of other cooked or chopped raw vegetables

3/4 cup vegetable juice

Grains

1 slice bread

1 ounce ready-to-eat cereal

1/2 cup of cooked cereal, rice, pasta

Beans and Nuts

1/2 cup cooked dry beans

2 tablespoons peanut butter

1/3 cup nuts

Dairy foods and eggs

1 cup milk or yogurt

1 1/2 ounces of natural cheese

2 ounces processed cheese

1 egg

Meats

2-3 ounces of cooked lean meat, poultry, fish

*Information from US Department of Agriculture and US Department of Health and Human Services.7

Table 2Standard Portion Sizes for Various Foods*


5/17

from fiber supplements.Beans are excellent sources of many

vitamins and minerals, protein, and fiber.Beans are legumes, the technical term forthe family of plants that includes driedbeans, pinto beans, lentils, and soybeans,among many others. Beans are especiallyrich in nutrients that may protect againstcancer23 and can be a useful low-fat buthigh-protein alternative to meat.

2. Limit your intake of high-fat foods,particularly from animal sources.

Choose foods low in fat.

Replace fat-rich foods with fruits, veg-etables, grains, and beans.

Eat smaller portions of high-fat foods. Choose baked and broiled foods in-

stead of fried foods.

Select non-fat and low-fat milk anddairy products. When you eat packaged, snack, conve-

nience, and restaurant foods, choosethose low in fat.

Limit consumption of meats, especiallyhigh-fat meats.

When you eat meat, select lean cuts.

Eat smaller portions of meats. Choose beans, seafood, and poultry asan alternative to beef, pork, and lamb.

Select baked and broiled meats, sea-food, and poultry, rather than fried.

High-fat diets have been associatedwith an increase in the risk of cancers ofthe colon and rectum,16 prostate,24 andendometrium.25 The association between

high-fat diets and breast cancer is muchweaker.26 Whether these associations aredue to the total amount of fat, the partic-ular type of fat (saturated, monounsatu-rated, or polyunsaturated), the caloriescontributed by fat, or some other factor infood fats has not yet been determined.Because a gram of fat contains more thantwice the calories of a gram of protein or

carbohydrate (9 versus 4 kcal/gram),studies cannot easily distinguish the ef-fects of fat itself from effects of the calo-ries it contains. Moreover, people whoeat high-fat diets tend to be heavier andto eat more meat and fewer fruits andvegetables, so their risk of cancer also isincreased for other reasons.

Foods from animal sources remainmajor contributors of total fat, saturatedfat, and cholesterol in the American

diet.

27

Although meats are good sourcesof high-quality protein and supply manyimportant vitamins and minerals, con-sumption of meatespecially red meats(beef, pork, lamb)has been linked tocancers at several sites, most notablycolon and prostate.28 How much of the as-sociation between red meats and cancer isdue to total fat or saturated fat, and howmuch is due to other constituents of meat

or the diet is uncertain at present.16,24,25

For example, in addition to fat, mutageniccompounds such as heterocyclic amines,which are produced when protein iscooked, may help explain the associationbetween meat and colon cancer. Saturat-ed, monounsaturated, and polyunsaturat-ed fats all yield the same number of calo-ries, but may affect cancer risk in different

ways. Even the effects of specific fats, suchas those from vegetable or fish oils, maydiffer in their effects on cancer risk. Thisrelationship of types of fat to cancer risk isunder active investigation.

Much evidence indicates that satu-rated fat may be particularly important inincreasing the risk for cancer as well asfor heart disease. The best way to reduce

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1


High-fat diets have beenassociated with an increasein the risk of cancers of thecolon and rectum, prostate,

and endometrium.


6/17

saturated fat intake is to make wise choicesin the selection and preparation of animalfoods. Choose lean meats and lower-fatdairy products, and substitute vegetableoils for butter or lard. Food labels can bea useful guide to choosing packagedfoods lower in saturated fat. Choosesmaller portions and use meat as a sidedish rather than as the focus of a meal.Emphasize beans, grains, and vegetablesin meals to help shift dietary patterns to

include more foods from plant ratherthan animal sources. Preparation meth-ods are also important; baking and broil-ing foods, rather than frying them, re-duces the overall amount of fat in food.These recommendations for cancer pre-vention are consistent with dietary adviceto reduce cardiovascular disease risk.7-10,29

3. Be physically active: achieve and main-

tain a healthy weight.

Be at least moderately active for 30 min-utes or more on most days of the week.Stay within your healthy weight range(Figure).

Physical activity can help protectagainst some cancers, either by balancingcaloric intake with energy expenditure orby other mechanisms. An imbalance of

caloric intake and output can lead tooverweight, obesity, and increased riskfor cancers at several sites: colon and rec-tum,16 prostate,24 endometrium,25 breast(among postmenopausal women),26 andkidney.30

These findings are supported by ani-mal studies, and by epidemiologic studiesdemonstrating an association betweenphysical activity and a reduced risk of de-

veloping some cancers.31 Activity simplymay prevent obesity, or it may act in oth-er ways to reduce cancer risk. For breastand prostate cancer, physical activity mayact through effects on hormone levels.32,33

For colon cancer, physical activity stimu-lates movement through the bowel, there-by reducing the length of time that thebowel lining is exposed to mutagens.

Both physical activity and controlledcaloric intake are necessary to achieve orto maintain a healthy body weight.34 Thefigure displays healthy weight ranges foradult men and women of all ages. Main-taining a body weight within recommend-ed ranges helps to reduce the risk forchronic diseases such as coronary heartdisease and diabetes as well as cancer.Moderate physical activity may increasecaloric needs and permit people to con-

sume more healthful foodsespeciallyfruits, vegetables, grains, and beanswhile maintaining a recommended bodyweight.

The Centers for Disease Control andPrevention and the American College ofSports Medicine,35 a National Institutesof Health Consensus Conference,36 andthe US Surgeon General37 recommend 30minutes of moderate physical activity

each day as a means to promote health.The 30 minutes does not need to be con-tinuous to be beneficial, and can be ac-complished by walking briskly (3-4 milesper hour) for about two miles, or by a va-riety of other enjoyable activities includ-ing calisthenics, jogging, swimming, gar-dening, yard work, housework, anddancing at a level of intensity equivalentto brisk walking. Studies suggest that

when overweight people intentionallylose weight, they reduce their cancerrisk.38 To lose weight, restrict caloric in-take and increase physical activity. Theeasiest way to restrict calories is to limitserving sizes, particularly of high-fat foods(Table 2). It is important to recognize,however, that many fat-free cakes, cook-ies, snack foods, and frozen and otherdesserts remain high in calories.

4. Limit consumption of alcoholic bever-ages, if you drink at all.

Alcoholic beverages, along with cigarettesmoking and use of snuff and chewing to-bacco, cause cancers of the oral cavity,esophagus, and larynx. Cancer risk in-creases with the amount of alcohol con-




7/17

sumed and may start to rise with intake ofas few as two drinks per day.39-41 A drinkis defined as 12 ounces of regular beer, 5ounces of wine, and 1.5 ounces of 80-proof distilled spirits.

Oral and esophageal cancers aremuch more common in countries wherealcohol consumption is high. The com-bined use of tobacco and alcohol leads togreatly increased risk of oral and esopha-geal cancers. The effect of tobacco and al-cohol combined is greater than the sum oftheir individual effects.39,40

Studies also have noted an associa-

tion between alcohol consumption and anincreased risk of breast cancer. The mech-anism for this effect is unknown, but theassociation may be due to carcinogenicactions of alcohol or its metabolites, to al-

cohol-induced changes in levels of hor-mones such as estrogens, or to some oth-er process. Alcohol may have additionaleffects on cancer risk. Alcoholic bever-ages supply calories but few nutrients;people who drink heavily may be substi-tuting alcohol for nutrient-rich, cancer-protective foods. Regardless of the mech-anism, studies suggest that the risk of

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1


Weight (pounds)

HEALTHYWEIGH

T

MOD

ERATEOVER

WEIGHT

SEVERE

OVERWE

IGHT

Height

6'6"6'5"

6'4"

6'3"

6'2"

6'1"

6'0"

5'11"

5'10"

5'9"

5'8"

5'7"

5'6"

5'5"

5'4"

5'3"

5'2"

5'1"

5'0"

4'11"4'10"

50 75 100 125 150 175 200 225 250

Healthy weight ranges for adult men and women of all ages. The higher weights apply mainly tomen, who have more muscle and bone. To use this chart, find your height in feet and inches (with-out shoes) along the left side of the graph. Trace the line corresponding to your height across thefigure until it intersects with the vertical line corresponding to your weight in pounds (withoutclothes). The point of intersection lies within a band that indicates whether your weight is healthy

or is moderately or severely overweight.7


8/17

breast cancer may increase with an intakeof just a few drinks per week.26

Moderate intake of alcoholic bever-ages has been shown to decrease the riskof coronary heart disease, at least in mid-dle-aged adults. These cardiovascular ben-efits may outweigh the risk of cancer inmen older than 50 years and in womenolder than 60 years.42 Public health offi-cials advise people who already drink al-coholic beverages to limit their intake to

two drinks a day for men and one drinkper day for women.7 Women generallytolerate alcohol less well than men as aresult of smaller body size and greaterability to absorb alcohol. Women with anunusually high risk for breast cancermight reasonably consider abstainingfrom alcohol. Children and adolescents,pregnant women, and people taking cer-tain medications also should abstain from

alcohol consumption.

Diet and Activity Factors thatAffect Risks for the Most CommonCancers

BREAST CANCER

Breast cancer is the leading site for can-

cer cases among American women and issecond only to lung cancer in cancerdeaths. Breast cancer is influenced by fac-tors that affect circulating hormone levelsthroughout life: age at first menstruation,number of pregnancies, breast feeding,obesity, and physical activity. Many stud-ies suggest that consuming alcoholic bev-erages may increase the risk of breastcancers, even when consumed in modera-

tion. Some studies suggest that diets highin fruits and vegetables decrease the riskof breast cancer, although this evidence ismuch weaker than that for other cancersites. At the present time, the best adviceto reduce the risk of breast cancer is tolimit intake of alcoholic beverages, eat adiet rich in fruits and vegetables, be phys-ically active, and avoid obesity.26

COLORECTAL CANCER

Colorectal cancers are the second leadingcause of cancer death among Americans.Diets high in foods from plant sources(vegetables, fruits, whole grains, beans)have been associated with a decreasedrisk, whereas diets high in fat and redmeat have been associated with an in-creased risk of colorectal cancer. Obesityand physical inactivity also appear to in-crease risk. Currently, the best approach

to reducing the risk of colorectal cancer isto consume fewer high-fat foods, limit in-take of red meats, eat more vegetables,fruits, and whole grains, be physically ac-tive, and avoid obesity.16

ENDOMETRIAL CANCER

Studies of endometrial cancer consistent-ly find that being overweight increases

risk. The association may be due to theincrease in estrogen levels that occursamong postmenopausal women who areoverweight. To reduce the risk of en-dometrial cancer, maintain a healthyweight through regular physical activityand healthy food choices.25

LUNG CANCER

Lung cancer is the leading cause of cancerdeath among Americans. More than 80percent of lung cancer cases occur as a re-sult of tobacco smoking. Many studieshave demonstrated that the risk of lungcancer among both smokers and non-smokers is lower among people who con-sume recommended amounts of fruitsand vegetables. To reduce the risk of lungcancer, do not smoke tobacco, and eat at

least five servings of vegetables and fruitsevery day.17

ORAL AND ESOPHAGEAL CANCERS

Tobaccoincluding cigarettes, chewingtobacco, and snuffand alcohol, singlyand together, increase the risk of cancersof the mouth and esophagus. Eating rec-




9/17

ommended amounts of fruits and vegeta-bles decreases that risk. To protect againstthese cancers, do not use tobacco in anyform, do not drink more than one or twoalcoholic beverages each day, and eat atleast five servings of fruits and vegetableseach day.39-41

PROSTATE CANCER

Prostate cancer is the leading cancer

among American men. Scientists knowthat prostate cancer is related to malehormones, but are uncertain as to the ex-act mechanism involved. Intake of animalfat, red meats, and dairy products hasbeen found to be associated with an in-crease in the risk of prostate cancer, sug-gesting a role for saturated fat.24 To re-duce the risk of prostate cancer, limitintake of foods from animal sources, es-

pecially saturated fats and red meats.

STOMACH CANCER

The incidence of stomach cancer is de-creasing worldwide, especially in theUnited States. Year-round consumptionof fresh foods, refrigeration, and other im-provements in food-preservation methodshave helped reduce risk. Infection with

the bacterial species Helicobacter pylorimay increase risk. To reduce the risk ofstomach cancer, eat at least five servingsof fruits and vegetables each day.43

Common Questions About Dietand Cancer

Because people are interested in the rela-tionship of specific foods or nutrients to

specific cancers, research in this area is of-ten widely publicized. No one study is thelast word on any subject, and it is easy tobecome confused by what may appear tobe contradictory and conflicting advice.Each study should be considered in thelight of existing knowledge, but in briefnews stories, reporters cannot always putnew research findings in context. The best

advice is to use common sense; it is rarely,if ever, advisable to change your dietbased on a single study or news report, es-pecially if the data are reported as pre-liminary.

ANTIOXIDANTS

What are antioxidants and what do theyhave to do with cancer? Certain nutrientsin fruits and vegetables appear to protect

the body against the oxygen-induceddamage to tissues that occurs constantlyas a result of normal metabolism. Be-cause such damage is associated with in-creased cancer risk, antioxidant nutrientsare thought to protect against cancer.12

Antioxidant nutrients include vitamin C,vitamin E, selenium, and carotenoids.Studies suggest that people who eat morefruits and vegetables containing these an-

tioxidants have a lower risk for cancer.13

Clinical studies of antioxidant supple-ments, however, have not demonstrated areduction in cancer risk (see Beta Caro-tene, Supplements).

ARTIFICIAL SWEETENERS

Do artificial sweeteners cause cancer?Several years ago, experiments on rats

suggested that saccharin might cause can-cer. Since then, however, studies of pri-mates and humans have shown no in-creased risk of cancer from either saccharinor aspartame.

BETA CAROTENE

Does beta carotene reduce cancer risk?Because beta carotene, an antioxidant,

is found in fruits and vegetables, and be-cause eating fruits and vegetables isclearly associated with a reduced risk ofcancer, it seemed possible that takinghigh doses of beta carotene supple-ments might reduce cancer risk. In threemajor experiments, people were givenhigh doses of synthetic beta carotene inan attempt to prevent lung and other

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1



10/17

cancers. Two of these studies found betacarotene supplements to be associatedwith a higher risk of lung cancer in ciga-rette smokers18,19 and a third found nei-ther benefit nor harm from beta carotenesupplements.44 Thus, research has not re-produced the beneficial effects of fruitsand vegetables by giving high-dose sup-plements of beta carotene. For cigarettesmokers, such supplements may beharmful.18

BIOENGINEERED FOODS

What are bioengineered foods, and arethey safe? Foods made through tech-niques of bioengineering or biotechnolo-gy have been altered by the addition ofgenes from plants or other organisms toincrease resistance to pests, to retardspoilage, or to improve transportability,

flavor, nutrient composition, or other de-sired qualities. Few such foods have as yetbeen marketed. At present, there is noreason to believe that these foods will ei-ther increase or decrease cancer risk.

CALCIUM

Is calcium related to cancer? Some re-search has suggested that foods high in cal-

cium might help reduce the risk of colorec-tal cancer, but this relationship is notproven. Whether or not calcium intake af-fects cancer risk, eating foods containingthis mineral is important to reduce the riskof osteoporosis. Low-fat and non-fat dairyproducts are excellent sources of calcium,as are some leafy vegetables and beans.

CAROTENOIDS

What are carotenoids, and do they re-duce cancer risk? Carotenoids are agroup of pigments in fruits and vegetablesthat include alpha carotene, beta caro-tene, lycopene, lutein, and many othercompounds. Consumption of foods con-taining carotenoids is associated with areduced cancer risk (see Beta Carotene).

CHOLESTEROL

Does cholesterol in the diet increase can-cer risk? Cholesterol in the diet comesonly from foods from animal sourcesmeat, dairy, eggs, and fats. At present, lit-tle evidence is available to determinewhether dietary cholesterol itself or thefoods containing this substance might beresponsible for the increase in cancer riskassociated with eating foods from animalsources. Low blood cholesterol has been

found to be more common in people withcancer, but is an effect of cancer, not itscause. There is no evidence that loweringblood cholesterol causes an increase incancer risk.

COFFEE

Does drinking coffee cause cancer? Sev-eral years ago, a highly publicized study

suggested that coffee might increase riskfor cancer of the pancreas. Because caf-feine may heighten symptoms of fibrocys-tic breast lumps in some women, mediastories also have focused on concernsabout coffee and breast cancer. Manystudies in recent years, however, havefound no relationship at all between cof-fee and the risk of pancreatic, breast, orany other type of cancer.

COOKING METHODS

Does cooking affect cancer risk? Ade-quate cooking is necessary to kill harm-ful microorganisms in meat. However,some research suggests that frying orcharcoal-broiling meats at very hightemperatures creates chemicals thatmight increase cancer risk. Preserving

meats by methods involving smoke alsoincreases their content of potentiallycarcinogenic chemicals. Although thesechemicals cause cancer in animal experi-ments, it is uncertain whether they actu-ally cause cancer in people. Techniquessuch as braising, steaming, poaching,stewing, and microwaving meats do notproduce these chemicals.




11/17

CRUCIFEROUS VEGETABLES

What are cruciferous vegetables and arethey important in cancer? Cruciferousvegetables belong to the cabbage family,which includes broccoli, cauliflower, andbrussels sprouts. These vegetables con-tain certain chemicals thought to reducethe risk of colorectal cancer. The best ev-idence suggests that a wide variety ofvegetables, including cruciferous andother vegetables, reduces cancer risk

(see Phytochemicals).

FIBER

What is dietary fiber and can it preventcancer? Dietary fiber includes a widevariety of plant carbohydrates that arenot digested by humans. Specific cate-gories of fiber are soluble (like oatbran) and insoluble (like wheat bran).

Insoluble fiber is thought to help reducethe risk of colorectal cancer, althoughthe mechanism of this action is uncer-tain. Soluble fiber helps to reduce bloodcholesterol and, therefore, to lower therisk of coronary heart disease. Goodsources of fiber are beans, vegetables,whole grains, and fruits.

FISH OILS

Does eating fish protect against cancer?Like all fats, fish oils are high in calories.Fish fats are rich in omega-3 fatty acids.Studies in animals have found thatomega-3 fatty acids suppress cancer for-mation, but there is no direct evidencefor protective effects in humans at thistime.

FLUORIDES

Do fluorides cause cancer? Extensiveresearch has examined the effects of flu-orides given as dental treatments oradded to toothpaste, public water sup-plies, or foods. Fluorides do not in-crease cancer risk.

FOLIC ACID

What is folic acid and can it prevent can-cer? Folic acid (sometimes called folateor folacin) is a B vitamin found in manyvegetables, beans, fruits, whole grains,and fortified breakfast cereals. Folic acidmay reduce the risk of some cancers. Sup-plements are sometimes recommendedfor women who are capable of becomingpregnant as a means to reduce the risk ofspina bifida and other neural tube defects

in their infants. Current evidence sug-gests that to reduce cancer risk, folic acidis best consumed along with the full arrayof nutrients found in fruits, vegetables,and other foods.

FOOD ADDITIVES

Do food additives cause cancer? Manysubstances are added to foods to pre-

serve them and to enhance color, flavor,and texture. Additives are usually pre-sent in very small quantities in food, andno convincing evidence exists that anyadditive at these levels causes humancancers.

GARLIC

Can garlic prevent cancer? The health

benefits of the allium compounds con-tained in garlic and other vegetables inthe onion family have been publicizedwidely. Garlic is currently under study forits ability to reduce cancer risk, but insuf-ficient evidence supports a specific rolefor this vegetable in cancer prevention.

GENETICS

If our genes determine cancer risk, howcan diet help prevent cancer? Genes thatincrease or decrease cancer risk can be in-herited or acquired by mutations through-out life. Nutrients and nutritional factorsin the diet can protect DNA from beingdamaged and can delay or prevent the de-velopment of cancer even in people withan increased genetic risk for the disease.

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1



12/17

IRRADIATED FOODS

Why are foods irradiated, and do irradiat-ed foods cause cancer? Radiation is in-creasingly used to kill harmful organismson foods so as to extend their shelf life.Radiation does not remain in the foodsafter treatment, and there is no evidencethat consuming irradiated foods increasescancer risk.

NITRITES

Should I avoid nitrite-preserved meats?Most lunch meats, hams, and hot dogs arepreserved with nitrites to maintain colorand to prevent contamination with bacte-ria. Nitrites can be converted to carcino-genic nitrosamines in the stomach, whichmay increase the risk of gastric cancer.

Vitamin C and related compounds are of-ten added to foods to inhibit this conver-sion. Diets high in fruits and vegetablesthat contain vitamin C and phytochemi-

cals, such as phenols, retard the conver-sion of nitrites to nitrosamines. Nitrites infoods are not a significant cause of canceramong Americans.

OLESTRA

What is olestra and is it related to cancer?Some synthetic fat substitutes are not ab-sorbed by the body. Although several fat

substitutes are under development foruse in the food supply, only one of thistypeolestra (trademarked Olean)hasbeen approved for marketing. Olestramay reduce fat intake, but it also reducesthe absorption of fat-soluble carotenesand other potentially cancer-protectivephytochemicals in fruits and vegetables.45

Although reducing absorption of these

substances might also reduce the healthbenefits of fruits and vegetables, the over-all effect of this type of fat substitute oncancer risk is unknown at present.

OLIVE OIL

Does olive oil affect cancer risk? Olive oil,like all fats, is high in calories, but its fat ismostly monounsaturated. Consumptionof olive oil is not associated with any in-

crease in risk of cancer, and most likely isneutral with respect to cancer risk.46

PESTICIDES AND HERBICIDES

Do pesticides and herbicides on fruits andvegetables cause cancer? Pesticides andherbicides can be toxic when used in high

doses. Although fruits and vegetablessometimes contain low levels of thesechemicals, overwhelming scientific evi-dence supports the overall health benefits

and cancer-protective effects of eatingfruits and vegetables.47 In contrast, cur-rent evidence is insufficient to link pesti-cides in foods with an increased risk ofany cancer.

PHYTOCHEMICALS

What are phytochemicals, and do theyreduce cancer risk? The term phyto-

chemicals refers to a wide variety ofcompounds produced by plants. Someof these compounds protect plantsagainst insects or have other biological-ly important functions. Some have ei-ther antioxidant or hormone-like ac-tions both in plants and in people whoeat them. Because consumption of fruitsand vegetables reduces cancer risk, re-



Nutrients and nutritional factors in the diet canprotect DNA from being damaged and can delay orprevent the development of cancer.


13/17

searchers are searching for specific com-pounds in these foods that might ac-count for the beneficial effects. There isno evidence that taking phytochemicalsupplements is as beneficial as consum-ing the fruits, vegetables, beans, andgrains from which they are extracted.

SALT

Do high levels of salt in the diet increase

cancer risk? Some evidence links dietscontaining large amounts of foods pre-served by salting and pickling with an in-creased risk of cancers of the stomach,nose, and throat. Little evidence suggeststhat moderate amounts of salt or salt-pre-served foods in the diet affect cancer risk.

SELENIUM

What is selenium and can it reduce cancerrisk? Selenium is a mineral needed by thebody as part of antioxidant defense mech-anisms. Animal studies suggest that sele-nium protects against cancer, but humanstudies are inconclusive. Selenium sup-plements are not recommended, as thereis only a narrow margin between safe andtoxic doses. Grain products are goodsources of selenium.

SOYBEANS

Can soybeans reduce cancer risk? Soy-beans are an excellent source of proteinand a good alternative to meat. Nonfer-mented soybeans have high levels of phy-toestrogens and other phytochemicalsthat appear to have beneficial effects onhormone-dependent cancers in animal

studies.23 These effects remain to beproven in humans, however.

SUPPLEMENTS

Can nutritional supplements lower can-cer risk? Strong evidence associates adiet rich in fruits, vegetables, and otherplant foods with reduced risk of cancer,

but there is no evidence at this time thatsupplements can reduce cancer risk. Thefew studies in human populations thathave attempted to determine whethersupplements can reduce cancer risk haveyielded disappointing results. Vitaminand mineral supplements have beenshown to reduce the risk of stomach can-cer in one intervention study in China,48

but other studies using high doses of sin-gle nutrients have shown no benefit and

even unexpected evidence for harm (seeBeta Carotene). Although supplementsdo not substitute for healthful diets in re-ducing cancer risk, it is possible thatsome people, such as pregnant women,women of childbearing age, and peoplewith restricted dietary intakes, mightbenefit from taking moderate doses ofvitamin and mineral supplements forother reasons.

TEA

Can drinking tea reduce cancer risk?Some researchers have proposed that tea,especially green tea, might protect againstcancer because of its content of antioxi-dants (see Antioxidants). In animal stud-ies, some teas have been shown to reducecancer risk, but beneficial effects of tea on

cancer risk in people are not yet proven.

VITAMIN A

Does vitamin A lower cancer risks? Vita-min A (retinol) is obtained from foods intwo ways: as preformed from animal foodsources and as derived from beta caro-tene found in plant foods. Vitamin A isneeded to maintain healthy tissues. Vita-

min A supplements have not been shownto lower cancer risk, however. If supple-ments are taken, they should remainwithin recommended levels, as high dosesof preformed vitamin A can be harmful,especially to pregnant women. Becausethe body does not convert beta caroteneto vitamin A when vitamin A levels arewithin normal ranges, eating fruits and

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1



14/17

vegetables containing beta carotene can-not lead to vitamin A toxicity.

VITAMIN C

Does vitamin C lower cancer risk? Vita-min C is found in many fruits and vegeta-bles. Many studies have linked consump-tion of vitamin C-rich foods with areduced risk of cancer. The few studies inwhich vitamin C has been given as a sup-

plement, however, have not shown a re-duced risk of cancer.49,50

VITAMIN E

Does vitamin E lower cancer risk? Vita-min E may lower the risk for coronaryheart disease. Vitamin E supplements,however, have not been shown to reducecancer risks.18,50

American Cancer SocietyCommitment to Nutrition andCancer Prevention

The American Cancer Society has a long-standing commitment to nutrition re-search. The Society recognizes that manyimportant questions about diet, nutrition,and cancer risk remain unanswered. The

Society, therefore, continues to supportnutrition research in two ways: by con-ducting its own research and by fundingoutstanding research projects throughoutthe country. Staff scientists of the Societyare conducting epidemiologic research inwhich they analyze and interpret data re-lated to cancer deaths and lifestyle amonga population of more than one millionpeople. In addition, scientists from

throughout the United States apply forresearch grants for their own investiga-tions. The Society reviews these applica-tions rigorously, and awards funding toonly the most meritorious proposals.Studies supported by the Society on theeffects of diet, nutrition, and exercise oncancer risk have been made possible by

the efforts of nearly 100,000 volunteersand the financial contributions of millionsof Americans.

The American Cancer Society peri-odically reviews the scientific evidence re-lating dietary practices to cancer risk andrevises dietary guidelines based on thisinformation. The Society uses its dietaryguidelines to advise the public about is-sues related to nutrition and cancer, todevelop education programs and inter-

ventions to improve nutrition, and to in-fluence legislative and regulatory issuesthat support cancer prevention. The Soci-ety first issued provisional nutritionguidelines in 198451 and then publishednew guidelines in 1991.1 Also in 1991, theSociety endorsed the 1990 federal Di-etary Guidelines for Americans,52 anddesignated nutrition as a high priority forthe Society.

To update the 1991 guidelines, theSociety commissioned a national panelof experts in cancer research, preven-tion, epidemiology, public health, andpolicy to provide advice about dietaryguidelines for cancer prevention. Mem-bers of the 1996 advisory committee metin Atlanta from March 11-13, 1996, toreview previous American Cancer Soci-ety guidelines in the context of recentresearch studies and in light of the re-cently revised US Dietary Guidelines.7

During that meeting, members of thecommittee achieved consensus on rec-ommendations for new guidelines. Thisreport reflects that consensus. The com-mittee agreed that the Society shouldcontinue to support an ongoing pro-gram of research that addresses biolog-

ic, clinical, epidemiologic, behavioral,and policy studies on the role of nutri-tion in cancer prevention. The commit-tee also agreed that greater efforts of in-dividuals in public and private agenciesare needed to carry these recommenda-tions into effective action to reduce theburden of cancer among Americans.




15/17

Appendix

Members of the American Cancer Soci-ety 1996 Advisory Commitee on Diet,Nutrition, and Cancer Prevention:Marion Nestle, PhD, MPH (Chair),*Professor and Chair, Department of Nu-trition and Food Studies, New York Uni-versity, New York, New York; Dileep G.Bal, MD, MS, MPH, Chief, Chronic Dis-ease Control Branch, California Depart-

ment of Health Services, Sacramento,California; Diane F. Birt, PhD, Professor,Eppley Institute for Research in Cancer,University of Nebraska Medical Center,Omaha, Nebraska; Gladys Block, PhD,Professor, Department of Nutrition, Uni-versity of California, Berkeley, School ofPublic Health, Berkeley, California; TimByers, MD, MPH,* Professor, Depart-ment of Preventive Medicine and Bio-

metrics, University of Colorado HealthScience Center, Denver, Colorado; SusanFoerster, MPH, RD, Chief, Nutrition andCancer Prevention Program, CaliforniaDepartment of Health Services, Sacra-mento, California; Peter Greenwald,MD, DrPH, Director, Division of CancerPrevention and Control, National CancerInstitute, Bethesda, Maryland; Ervin J.Hawrylewicz, PhD, Director of Re-

search, Mercy Hospital and Medical Cen-ter, Chicago, Illinois; Brian E. Hender-son, MD, Professor, Department ofPreventive Medicine, Norris Comprehen-sive Cancer Center, University of South-ern California, Los Angeles, California;David Hunter, ScD, Associate Professorof Epidemiology, Channing Laboratory,Harvard Medical School, Boston, Massa-chusetts; Lenore A. Kohlmeier, PhD,

Professor, Departments of Epidemiologyand Nutrition, University of North Car-olina, Chapel Hill, North Carolina; David

Kritchevsky, PhD, Caspar Wistar Schol-ar/Professor, The Wistar Institute ofAnatomy and Biology, Philadelphia,Pennsylvania; Shiriki K. Kumanyika,PhD, MPH, RD, Professor and Head,Department of Human Nutrition and Di-etetics, The University of Illinois atChicago, Chicago, Illinois; LawrenceKushi, ScD, Associate Professor, Divi-sion of Epidemiology School of PublicHealth, University of Minnesota, Min-

neapolis, Minnesota; Bonnie F. Liebman,MS, Director of Nutrition, Center for Sci-ence in the Public Interest, Washington,DC; Robert Russell, MD, Associate Di-rector, USDA-Human Nutrition Re-search Center on Aging, Tufts University,Boston, Massachusetts; Henry Thompson,PhD, Director, Division of LaboratoryResearch, AMC Cancer Research Cen-ter, Denver, Colorado; David F.

Williamson, PhD, MS, Acting Director,Diabetes Division, National Center forChronic Disease Prevention and HealthPromotion, Centers for Disease Controland Prevention, Atlanta, Georgia. Ameri-can Cancer Society Staff Participants:Lynne Camoosa, Manager, Medical/Sci-entific Communications; Steve Dickinson,National Vice President, Public Relations;Nancy Hailpern, Manager, Grassroots

Development; Clark Heath, MD,* VicePresident, Epidemiology/Surveillance;Roberta Moss, MPH, Director, ProgramDevelopment and Application; Mary C.OConnell, Director, Prevention/Nutri-tion; Billie Parker, Staff Assistant; AmyStone, Scientific and Medical Communi-cations; Michael Thun, MD,* Director,Analytic Epidemiology, Allen Vegotsky,PhD, Scientific Program Director.

*Member, Executive Editorial Subcom-mittee

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1



16/17



References1. The Work Study Group on Diet, Nutrition, and

Cancer: American Cancer Society Guidelines onDiet, Nutrition, and Cancer: CA Cancer J Clin 1991;41:334-338.2. McGinnis JM, Foege WH: Actual causes of deathin the United States. JAMA 1993;270:2207-2212.3. Frazo E: The American Diet: Health andEconomic Consequences (Agric InformationBulletin 711). Washington, DC, US Department ofAgriculture, 1995.4. Institute of Medicine: Improving Americas Dietand Health: From Recommendations to Action.Washington, DC, National Academy Press, 1991.

5. Kennedy E, Goldberg J: What are American chil-dren eating? Implications for public policy. NutrRev 1995;53:111-126.6. US Department of Agriculture: The Food GuidePyramid (Home and Garden Bull 252). Washing-ton, DC, USDA, 1992.7. US Department of Agriculture and USDepartment of Health and Human Services:Nutrition and Your Health: Dietary Guidelines forAmericans, ed 4 (Home and Garden Bull 232).Washington, DC, US Government Printing Office,1995.8. US Department of Health and Human Services:

The Surgeon Generals Report on Nutrition andHealth, (DHHS [PHS] Publ. No. 88-50210).Washington, DC, US Government Printing Office,1988.9. National Research Council: Diet and Health:Implications for Reducing Chronic Disease Risk.Washington, DC, National Academy Press, 1989.10. US Department of Health and Human Services:Healthy People 2000: National Health Promotionand Disease Prevention Objectives (DHHS [PHS]Publ. No. 91-50212). Washington, DC, GovernmentPrinting Office, 1990.

11. Butrum RR, Clifford CK, Lanza E: NCI dietaryguidelines: Rationale. Am J Clin Nutr 1988;48(suppl 3):888-895.12. Willett WC: Micronutrients and cancer risk. AmJ Clin Nutr 1994;59(suppl 5):1162s-1165s.13. Steinmetz KA, Potter JD: Vegetables, fruit, andcancer. I. Epidemiology. Cancer Causes Control1991;2:325-357.14. Steinmetz KA, Potter JD: Vegetables, fruit, andcancer. II. Mechanisms. Cancer Causes Control1991;2:427-442.15. Ames BN, Gold LS, Willett WC: The causes and

prevention of cancer. Proc Natl Acad Sci U S A1995;92:5258-5265.16. Potter JD: Nutrition and colorectal cancer.Cancer Causes Control 1996;7:127-146.17. Zeigler RG, Mayne ST, Swanson CA: Nutritionand lung cancer. Cancer Causes Control 1996;7:157-177.18. The Alpha-Tocopherol, Beta Carotene CancerPrevention Study Group: The effect of vitamin Eand beta carotene on the incidence of lung cancerand other cancers in male smokers. N Engl J Med

1994;330:1029-1035.19. Omenn G, Goodman GE, Thornquist MD, et al:

Effects of a combination of beta carotene and vita-min A on lung cancer and cardiovascular disease. NEngl J Med 1996;334:1150-1155.20. Life Sciences Research Office, FASEB: ThirdReport on Nutrition Monitoring in the UnitedStates, Vol 1. Washington, DC, US GovernmentPrinting Office, 1995.21. Havas S, Heimendinger J, Damron D, et al: 5 ADay for better health: Nine community researchprojects to increase fruit and vegetable consump-tion. Public Health Rep 1995;110:68-79.22. Slavin JL: Whole grains and health: separating

the wheat from the chaff. Nutrition Today 1994;29:6-11.23. Messina M, Erdman JW (eds): First internation-al symposium on the role of soy in preventing andtreating chronic disease. J Nutr 1995;125(suppl 3):567s-808s.24. Kolonel LN: Nutrition and prostate cancer.Cancer Causes Control 1996;7:83-94.25. Hill HA, Austin H: Nutrition and endometrialcancer. Cancer Causes Control 1996;7:19-32.26. Hunter DJ, Willett WC: Nutrition and breastcancer. Cancer Causes Control 1996;7:56-68.27. Gerrior SA, Zizza C: Nutrient Content of the

US Food Supply, 1909-90 (Home Econ Res Rep52). Washington, DC, US Department of Agri-culture, 1994.28. Kushi LH, Lenart EB, Willett WC: Healthimplications of Mediterranean diets in light of con-temporary knowledge. 2. Meat, wine, fats, and oils.Am J Clin Nutr 1995;61(suppl 6):1416S-1427S.29. Chait A, Brunzell JD, Denke MA, et al:Rationale of the diet-heart statement of theAmerican Heart Association: Report of the nutri-tion committee. Circulation 1993;88:3008-3029.30. Wolk A, Lindblad P, Adami H-O: Nutrition and

renal cell cancer. Cancer Causes Control 1996;7:5-18.31. Albanes D: Energy balance, body size, and can-cer. Crit Rev Oncol Hematol 1990;10:283-303.32. Shephard RJ: Exercise in the prevention andtreatment of cancer: An update. Sports Med 1993;15:258-280.33. Friedenreich CM, Rohan TE: A review of phys-ical activity and breast cancer. Epidemiology 1995;6:311-317.34. Institute of Medicine: Weighing the Options:Criteria for Evaluating Weight-Management

Programs. Washington, DC, National AcademyPress, 1995.35. Pate RR, Pratt M, Blair SN, et al: Physical activ-ity and public health: A recommendations from theCenters for Disease Control and Prevention andthe American College of Sports Medicine. JAMA1995;273:402-407.36. NIH Consensus Development Panel on PhysicalActivity and Cardiovascular Health: Physical activ-ity and cardiovascular health. JAMA 1996;276:241-246.


17/17

37. US Department of Health and Human Services:Physical Activity and Health: A Report of theSurgeon General. Atlanta, GA, Centers for DiseaseControl and Prevention, National Center forChronic Disease Prevention and Health Promotion,Presidents Council on Physical Fitness and Sports,1996.38. Williamson DF, Pamuk E, Thun M, et al:Prospective study of intentional weight loss andmortality in never-smoking overweight US whitewomen aged 40-64 years. Am J Epidemiol 1995;141:1128-1141.39. Marshall JR, Boyle P: Nutrition and oral cancer.Cancer Causes Control 1996;7:101-112.40. Cheng KK, Day NE: Nutrition and esophageal

cancer. Cancer Causes Control 1996;7:33-40.41. Riboli E, Kaaks R, Estve J: Nutrition andlaryngeal cancer. Cancer Causes Control 1996;7:147-156.42. Ashley MJ, Ferrence R (eds): Moderate drinkingand health: the scientific evidence. ContemporaryDrug Problems 1994;21:1-204.43. Kono S, Hirohata T: Nutrition and stomach can-cer. Cancer Causes Control 1996;7:41-55.44. Hennekens CH, Buring JE, Manson JE, et al:Lack of effect of long-term supplementation withbeta carotene on the incidence of malignant neo-

plasms and cardiovascular disease. N Engl J Med1996;334:1145-1149.45. Weststrate JA, van het Hof KH: Sucrose poly-ester and plasma carotenoid concentrations inhealthy subjects. Am J Clin Nutr 1995;62:591-597.

46. Trichopoulou A, Katsouyanni K, Stuver S, et al:Consumption of olive oil and specific food groups inrelation to breast cancer risk in Greece. J NatlCancer Inst 1995;87:110-116.47. National Research Council: Carcinogens andAnticarcinogens in the Human Diet: A Com-parision of Naturally Occurring and SyntheticSubstances. Washington, DC, National AcademyPress, 1996.48. Blot WJ, Li JY, Taylor PR, et al: Nutrition inter-vention trials in Linxian, China: Supplementationwith specific vitamin/mineral combinations, cancerincidence, and disease-specific mortality in the gen-eral population. J Natl Cancer Inst 1993;85:1483-

1492.49. Block G: Vitamin C and cancer prevention: Theepidemiologic evidence. Am J Clin Nutr 1991;53(suppl 1):270s-282s.50. Byers T, Perry G: Dietary carotenes, vitamin Cand vitamin E as protective antioxidants in humancancers. Annu Rev Nutr 1992;12:139-159.51. American Cancer Society: Nutrition and cancer:Cause and prevention: An American CancerSociety special report. CA Cancer J Clin 1984;34:121-126.52. US Department of Agriculture and US

Department of Health and Human Services:Nutrition and Your Health: Dietary Guidelines forAmericans, ed 3 (Home and Garden Bull 232).Washington, DC, US Government Printing Office,1990.

C A C a n c e r J C l i n 1 9 9 6 ; 4 6 : 3 2 5 - 3 4 1


diet & nutrition in ca preven

Documents