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When it comes to cancer there are no guarantees. However, there are choices you can make to significantly reduce your risks. According to research or other evidence, the following self-care steps may be helpful:

These recommendations are not comprehensive and are not intended to replace the advice of your doctor or chemist. Continue reading the full cancer prevention and diet article for more in-depth, fully-referenced information on medicines, vitamins, herbs, and dietary and lifestyle changes that may be helpful.
Cancer refers to a large number of diseases categorized by unregulated replication of cells.
The contents of this article are limited to information about diet and to a discussion of cancer prevention—not treatment. Prevention of cancer in a person who has never had cancer is called “primary” prevention. Primary prevention is the focus of this article.
This article includes a discussion of studies that have assessed whether certain dietary ingredients may be beneficial in connection with the reduction of risk of developing cancer.
This information is provided solely to aid consumers in discussing supplements with their healthcare providers. It is not advised nor is this information intended to advocate, promote, or encourage self-use of this information for cancer risk reduction. Some studies suggest an association between high blood or dietary levels of a particular dietary ingredient with a reduced risk of developing cancer. Even if such an association were established, this does not mean that dietary supplements containing large amounts of the dietary ingredient will necessarily have a cancer risk reduction effect.
Prevention of a recurrence in a cancer patient who is in remission is called “secondary” prevention. Whether the information in this article would be helpful to people interested in secondary prevention is, for the most part, unknown. However, of cancer patients who are in complete remission, the information presented here is unlikely to help people who were ever diagnosed with metastatic cancer (also known as stage IV, or advanced, cancer).
Cancer is the second leading cause of death in Americans. Information on the prevention of breast, colon, lung, and prostate cancers is not provided in this article. To find out more about these specific forms of cancer, read the Breast Cancer, Colon Cancer, Lung Cancer, and Prostate Cancer articles.
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.1 2 3 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.4
5
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.6 7 8 9
Fibre
Whole grains (such as rye, brown rice, and whole wheat) contain high amounts of insoluble
fibre—the type of fibre 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.10 Most
research focusing on the relationship between cancer and fibre has focused on breast and colon
cancers.
Consuming a diet high in insoluble fibre is best achieved by switching from white rice to brown rice and from bakery goods made with white flour or mixed flours to 100% whole wheat bread, whole rye biscuits, and whole grain pancake mixes. Refined white flour is generally listed on food packaging labels as “flour,”“enriched flour,”“unbleached flour,”“durum wheat,”“semolina,” or “white flour.” Breads containing only whole wheat are often labelled “100% whole wheat.”
Vegetarianism
The following two possibilities are both strongly supported by research findings:
Compared with meat eaters, most,11 but not all,12 studies have found that vegetarians are less likely to be diagnosed with cancer. Vegetarians have also been shown to have stronger immune function, possibly explaining why vegetarians may be partially protected against cancer.13 Female vegetarians have been reported to have lower oestrogen levels compared with meat-eating women, possibly explaining a lower incidence of uterine and breast cancers.14 A reduced risk for various cancers is only partly,15 not totally,16 explained by differences 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 common
cancers.17 Many doctors recommend that people wishing to reduce their risk of
cancer eat a few pieces of fruit and a few portions of vegetables every day. Optimal intakes
remain unknown.
Most doctors also recommend that people should not consider supplements as substitutes for the real thing. Some of the anticancer substances found in produce have probably not yet been discovered, while others are not yet available in supplement form. More important, some research, particularly regarding synthetic beta-carotene, does not support the idea that taking supplements has the same protective value against cancer as does consumption of fruits and vegetables.
Flavonoids
Flavonoids are found in virtually all herbs and plant foods. Consumption of flavonoid-rich
onions and apples contain large amounts of one flavonoid called quercetin. Consumption of flavonoids in general, or
quercetin-containing foods in particular,18 has been associated with protection
against cancer in some,19 but not all,20 preliminary studies.
Tomatoes
Tomatoes contain lycopene—an anti-oxidant similar in structure to beta-carotene. Most lycopene in our diet comes from
tomatoes, though traces of lycopene exist in other foods. Lycopene inhibits the proliferation
of cancer cells in test tube research.21
A review of published research found that higher intake of tomatoes or higher blood levels of lycopene correlated with protection from cancer in 57 of 72 studies. Findings in 35 of these studies were statistically significant.22 Evidence of a protective effect for tomato consumption was strongest for cancers of the prostate, lung, and stomach, but some evidence of a protective effect also appeared for cancers of the pancreas, colon, rectum, oesophagus (throat), mouth, breast, and cervix.
Cruciferous vegetables
Cabbage, Brussel sprouts, broccoli, and cauliflower belong to the Brassica family of
vegetables, also known as “cruciferous” vegetables. In test tube and animal
studies, these foods have been associated with anticancer activity,23 possibly due
to a few substances found in these foods, such as
indole-3-carbinol,24 glucaric acid (calcium D-glucarate),25 and sulforaphane.26 In a preliminary human
study, people who ate cruciferous vegetables were reported to have a lower-than-average risk
for bladder cancer.27
Meat (how it is cooked) and childhood cancers
In one report, high consumption of hot dogs was associated with an almost tenfold increase in
the risk of childhood leukaemia when compared with low consumption.28 In another
report, maternal consumption of hot dogs and childhood consumption of hamburgers or hot dogs
at least once per week were associated with a doubling of the risk of cancers in
children.29 A review of nine studies found an association between consumption by
pregnant women of cured meat and the risk of brain cancer in their offspring.30
These associations do not yet constitute proof that eating hot dogs or hamburgers causes
cancer in children, and evidence linking cured meat consumption to childhood cancers remains
somewhat inconsistent.31
In the report studying the effects of eating hot dogs and hamburgers, the association between meat eating and leukaemia was weakest among children who took vitamin supplements. Processed meats, such as hot dogs, contain nitrates and nitrites—precursors to carcinogens. Anti-oxidants found in multivitamins keep nitrates and nitrites from converting into those carcinogens. Therefore, the association between vitamin consumption in children and protection against childhood cancers remains plausible, though unproven.
Fish
Fish eaters have been reported to have low risks of cancers of the mouth, throat, stomach,
colon, rectum, pancreas,32 lung,33 breast,34 and
prostate.35 The omega-3 fatty acids
found in fish are thought by some researchers to be the components of fish responsible for
protection against cancer.36
Coffee
Years ago, researchers reported the greater the consumption of coffee in a country, the higher
the risk of pancreatic cancer in that country.37 An analysis of data from studies
published between 1981 and 1993 did find some association between high consumption of coffee
and an increased risk of pancreatic cancer.38 Surprisingly, however, the same
report found that people drinking only one or two cups of coffee per day had, on average, a
lower risk of pancreatic cancer compared with people who never drink coffee.
Most,39 40 41 but not all,42 published reports have shown coffee drinkers are at increased risk of bladder cancer, though in one case the relationship was found only in men.43 In another study, the association was found only with caffeinated coffee.44 A review of 35 trials found a small (7%) increased risk of bladder cancer in coffee drinkers compared with people not drinking coffee—a difference not statistically significant.45
Calories
Scientists have known for many years that severe restriction of calories dramatically reduces
the risk of cancer in laboratory animals.46 Scientists speculate that caloric
content of the human diet may also affect cancer rates,47 though much less is known
about the effect, if any, of moderate caloric restrictions in humans. In one report, adults
with cancer were more likely to have consumed more calories during childhood compared with
healthy adults.48 In other reports, attempts to find associations between reduced
intake of calories and cancer have produced mixed results.49 50
51
Only severe restriction in caloric intake provides significant protection in animal studies. As most people are unlikely to severely restrict calories, the association between caloric restriction and protection from cancer may ultimately prove to only be of academic interest.
Dietary Fat
In studying data from country to country, incidence of ovarian cancer correlates with dietary
fat intake.52 According to preliminary research, consumption of saturated fat,
dietary cholesterol (as found in eggs),53 and animal fat in general54
correlates with the risk of ovarian cancer.
Preliminary studies suggest dietary fat may correlate with the risk of uterine cancer.55 Some of the excess risk appears to result from increased body weight that results from a high-fat diet.56
Many years ago, researchers reported that animals on a high-fat diet formed skin cancers more rapidly than did other animals.57 Although some preliminary human research has found no relationship between dietary fat intake and the risk of skin cancer,58 patients with basal cell and squamous cell skin cancers who were put on a low-fat diet for two years were reported to show a significant decrease in the number of new skin cancers compared with patients who maintained a high-fat diet.59 Similarly, precancerous lesions of the skin have been prevented in people put on a low-fat diet.60
Polyunsaturated Fats
A chain of carbon atoms in which a few are not attached to the maximum possible amount of
hydrogen is called “polyunsaturated”––in other words, unsaturated with
hydrogen in a few places. When nutrition researchers talk about polyunsaturated fatty acids,
they are often referring primarily to linoleic acid—a fatty acid found in nuts and seeds
and most vegetable oils.
In animal research, the consumption of polyunsaturated fatty acids increases the risk of some cancers.61 However, in humans, most,62 63 64 though not all,65 reports do not find an association between polyunsaturates and cancer risks.
Sugar
A preliminary study has reported an association between an increasing intake of sugar or
sugar-containing foods and an increased risk of gallbladder cancer.66 Whether this
association exists because sugar directly promotes cancer or because sugar consumption is only
a marker for some other dietary or lifestyle factor remains unknown.
Salt
In preliminary research, increasing intake of salt correlates with increased risk of stomach
cancer.67 68 Associations between foods preserved with salt and the risk
of cancers of the head and neck have also been reported.69
Animal studies suggest that the anti-oxidant or immune-enhancing effect of whey protein may produce anti-cancer effects.70 71 72 Preliminary human case reports suggest that 30 grams per day of whey protein may improve responses to anti-cancer medications, but more research is needed.73
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications.