Cancer Risk Reduction Diet

The following dietary changes have been studied in connection with cancer.

Alcohol and Cancer
Alcohol consumption significantly increases the risk of cancers of the mouth (oral/oropharyngeal cancer), throat (esophageal cancer), and voice box (laryngeal cancer), particularly in conjunction with cigarette smoking. Most studies documenting these associations also report that former drinkers have significantly lower risks for these cancers compared with current drinkers. Strong correlations between alcohol consumption and the risk of having liver cancer have also been reported.

Little is known about the effect of alcohol intake on the risk of female cancers other than breast cancer. Of the few published studies, findings have been inconsistent.

Fiber
Whole grains (such as rye, brown rice, and whole wheat) contain high amounts of insoluble fiber—the type of fiber some scientists believe may help protect against a variety of cancers. In an analysis of the data from many studies, people who eat relatively high amounts of whole grains were reported to have low risks of lymphomas and cancers of the pancreas, stomach, colon, rectum, breast, uterus, mouth, throat, liver, and thyroid. Most research focusing on the relationship between cancer and fiber has focused on breast and colon cancers...

Vegetarianism
The following two possibilities are both strongly supported by research findings:

• Some foods consumed by vegetarians may protect against cancer.
• Eating meat may increase the risk of cancer.

Compared with meat eaters, most, but not all, studies have foundthat vegetarians are less likely to be diagnosed with cancer. Vegetarians have also been shownto have stronger immune function, possiblyexplaining why vegetarians may be partially protected against cancer. Femalevegetarians have been reported to have lower estrogen levels compared with meat-eating women,possibly explaining a lower incidence of uterine and breast cancers. A reducedrisk for various cancers is only partly, not totally, explained bydifferences in body weight, smoking habits, and other lifestyle issues.

Fruits and Vegetables
Consumption of fruits and vegetables is widely accepted as lowering the risk of most commoncancers. Many doctors recommend that people wishing to reduce their risk ofcancer eat several pieces of fruit and several portions of vegetables every day. Optimalintakes remain unknown.

Most doctors also recommend that people should not consider supplements as substitutes forthe real thing. Some of the anticancer substances found in produce have probably not yet beendiscovered, while others are not yet available in supplement form. More important, someresearch, particularly regarding synthetic beta-carotene, does not support the idea that taking supplements has the same protectivevalue against cancer as does consumption of fruits and vegetables.

Flavonoids
Flavonoids are found in virtually all herbs and plant foods. Consumption of flavonoid-richonions and apples contain large amounts of one flavonoid called quercetin. Consumption of flavonoids in general, orquercetin-containing foods in particular, has been associated with protectionagainst cancer in some, but not all, preliminary studies.

Tomatoes
Tomatoes contain lycopene—an antioxidant similar in structure to beta-carotene. Most lycopene in our diet comes fromtomatoes, though traces of lycopene exist in other foods. Lycopene inhibits the proliferationof cancer cells in test tube research.

A review of published research found that higher intake of tomatoes or higher blood levelsof lycopene correlated with protection from cancer in 57 of 72 studies. Findings in 35 ofthese studies were statistically significant. Evidence of a protective effect fortomato consumption was strongest for cancers of the prostate, lung, and stomach, but someevidence of a protective effect also appeared for cancers of the pancreas, colon, rectum,esophagus (throat), mouth, breast, and cervix.

Cruciferous vegetables
Cabbage, Brussels sprouts, broccoli, and cauliflower belong to the Brassica family ofvegetables, also known as “cruciferous” vegetables. In test tube and animalstudies, these foods have been associated with anticancer activity, possibly dueto several substances found in these foods, such as indole-3-carbinol, glucaric acid calcium D-glucarate), and sulforaphane. In a preliminary humanstudy, people who ate cruciferous vegetables were reported to have a lower-than-average riskfor bladder cancer.

Meat (how it is cooked) and childhood cancers
In one report, high consumption of hot dogs was associated with an almost tenfold increase inthe risk of childhood leukemia when compared with low consumption. In anotherreport, maternal consumption of hot dogs and childhood consumption of hamburgers or hot dogsat least once per week were associated with a doubling of the risk of cancers inchildren. A review of nine studies found an association between consumption bypregnant women of cured meat and the risk of brain cancer in their offspring.These associations do not yet constitute proof that eating hot dogs or hamburgers causescancer in children, and evidence linking cured meat consumption to childhood cancers remainssomewhat inconsistent.

In the report studying the effects of eating hot dogs and hamburgers, the associationbetween meat eating and leukemia was weakest among children who took vitamin supplements. Processed meats, such as hotdogs, contain nitrates and nitrites—precursors to carcinogens. Antioxidants found in multivitamins keep nitrates andnitrites from converting into those carcinogens. Therefore, the association between vitaminconsumption in children and protection against childhood cancers remains plausible, thoughunproven.

Fish
Fish eaters have been reported to have low risks of cancers of the mouth, throat, stomach,colon, rectum, pancreas, lung, breast, andprostate. The omega-3 fatty acidsfound in fish are thought by some researchers to be the components of fish responsible forprotection against cancer.

Coffee
Years ago, researchers reported the greater the consumption of coffee in a country, the higherthe risk of pancreatic cancer in that country. An analysis of data from studiespublished between 1981 and 1993 did find some association between high consumption of coffeeand an increased risk of pancreatic cancer. Surprisingly, however, the samereport found that people drinking only one or two cups of coffee per day had, on average, alower risk of pancreatic cancer compared with people who never drink coffee.

Most, but not all, published reportshave shown coffee drinkers are at increased risk of bladder cancer, though in one case therelationship was found only in men. In another study, the association was foundonly with caffeinated coffee. A review of 35 trials found a small (7%) increasedrisk of bladder cancer in coffee drinkers compared with people not drinking coffee—adifference not statistically significant.

Calories
Scientists have known for many years that severe restriction of calories dramatically reducesthe risk of cancer in laboratory animals. Scientists speculate that caloriccontent of the human diet may also affect cancer rates, though much less is knownabout the effect, if any, of moderate caloric restrictions in humans. In one report, adultswith cancer were more likely to have consumed more calories during childhood compared withhealthy adults. In other reports, attempts to find associations between reducedintake of calories and cancer have produced mixed results.

Only severe restriction in caloric intake provides significant protection inanimal studies. As most people are unlikely to severely restrict calories, the associationbetween caloric restriction and protection from cancer may ultimately prove to only be ofacademic interest.

Dietary Fat
In studying data from country to country, incidence of ovarian cancer correlates with dietaryfat intake. According to preliminary research, consumption of saturated fat,dietary cholesterol (as found in eggs), and animal fat in generalcorrelates with the risk of ovarian cancer.

Preliminary studies suggest dietary fat may correlate with the risk of uterinecancer. Some of the excess risk appears to result from increased body weight thatresults from a high-fat diet.

Many years ago, researchers reported that animals on a high-fat diet formed skin cancersmore rapidly than did other animals. Although some preliminary human research hasfound no relationship between dietary fat intake and the risk of skin cancer,patients with basal cell and squamous cell skin cancers who were put on a low-fat diet for two years were reported to show asignificant decrease in the number of new skin cancers compared with patients who maintained ahigh-fat diet. Similarly, precancerous lesions of the skin have been prevented inpeople put on a low-fat diet.

Polyunsaturated Fats
A chain of carbon atoms in which several are not attached to the maximum possible amount ofhydrogen is called “polyunsaturated”––in other words, unsaturated withhydrogen in several places. When nutrition researchers talk about polyunsaturated fatty acids,they are often referring primarily to linoleic acid—a fatty acid found in nuts and seedsand most vegetable oils.

In animal research, the consumption of polyunsaturated fatty acids increases the risk ofsome cancers. However, in humans, most, though not all, reports do not find an association between polyunsaturates andcancer risks.

Sugar
A preliminary study has reported an association between an increasing intake of sugar orsugar-containing foods and an increased risk of gallbladder cancer. Whether thisassociation exists because sugar directly promotes cancer or because sugar consumption is onlya marker for some other dietary or lifestyle factor remains unknown.

Salt
In preliminary research, increasing intake of salt correlates with increased risk of stomachcancer. Associations between foods preserved with salt and the riskof cancers of the head and neck have also been reported.

Animal studies suggest that the antioxidant or immune-enhancing effect of whey protein may produce anti-cancereffects. Preliminary human case reports suggest that30 grams per day of whey protein may improve responses to anti-cancer medications, but moreresearch is needed.