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Anticancer Compounds Found in Foods

Anticancer Compounds Found in Food

Many anticarcinogenic compounds are found in foods, with the exception of monoterpenes which are in essential oils. This handout describes some of these compounds, with the associated rationales for why each is anticancerous, food sources of each compound, and a listing of which cancers were studied for each thus far. Some compounds are more extensively studied than others, so it is important to refer to the references if you are interested in learning more details about a particular compound.

Overall, most of these compounds exert anticarcinogenic effects via a few different pathways:

Promoting cancer cell apoptosis (programmed death)
Reducing free radicals/oxidation rates of cells
Inhibiting the creation of carcinogenic molecules
Downregulating cancer-inducing gene expression pathways
Promoting stable DNA and cell formation (reduced risk of mutation and cancer cell formation)

Nutrition guidelines
The following are the nutrition guidelines produced by the American Cancer Society in its 2011 statement:

Eat a healthy diet, with an emphasis on plant sources

Choose foods and drinks in amounts that help achieve and maintain a healthy weight
Eat five or more servings of a variety of vegetables and fruits each day
Choose whole grains over processed (refined) grains
Limit intake of processed and red meats

If you drink alcoholic beverages, limit your intake

Drink no more than one drink/day for women or two drinks/day for men

Compounds and cancer prevention
The following components in plant foods have an effect on cancer prevention.

Lignans
Rationale: Lignans are broken down into phytoestrogen compounds, such as enterodiol and enterolactone, which are shown to have antiestrogenic effects on estrogen receptor-positive breast cancer.

Sources of lignans include:

Flaxseed
Wheat
Soy

Studies for the following cancers:

Colon
Breast
Prostate (pending studies)

Studies/articles referenced:

Allium
Rationale: Organosulfur compounds present in allium vegetables are perhaps responsible for the beneficial effects of these herbs. Scientists have proposed several mechanisms to explain the cancer-preventive effects, including inhibition of mutagenesis, modulation of enzyme activities, inhibition of DNA adduct formation, free-radical scavenging, and effects on cell proliferation and tumor growth. These mechanisms still are speculative, and further research is needed to support causality.

Sources of allium include:

Garlic (mainly studied)
Onion
Leeks
Scallions
Chives

Studies for the following cancers:

Stomach
Colorectal
Prostate

Studies/articles referenced:

Sulforaphane and indole-3-carbinol
Rationale: The chemoprotective effect of cruciferous vegetables is because of their high glucosinolate content and the capacity of glucosinolate metabolites, such as isothiocyanates (ITC) and indoles, to modulate biotransformation enzyme systems (eg, cytochromes P450 and conjugating enzymes). Data from molecular epidemiologic studies suggest that genetic and associated functional variations in biotransformation enzymes, particularly glutathione S-transferase (GST)M1 and GSTT1, which metabolize ITC, alter cancer risk in response to cruciferous vegetable exposure. These compounds also induce apoptosis, alter steroid hormone metabolism, regulate estrogen receptor response, and stabilize cellular proliferation.

Sources of sulforaphane and indole-3-carbinol include:

Broccoli
Broccoli sprouts (highest concentration)
Cauliflower
Cabbage
Brussels sprouts
Kale

Studies for the following cancers:

Breast
Bladder
Lymphoma
Prostate
Lung

Studies/articles referenced:

Capsaicin
Rationale: Capsaicin has a profound antiproliferative effect on prostate cancer cells, inducing apoptosis of both androgen receptor (AR)-positive (LNCaP) and AR-negative (PC-3, DU-145) prostate cancer cell lines associated with an increase of p53, p21, and Bax. Capsaicin downregulates the expression of prostate-specific antigen (PSA), AR, and also has a direct inhibitory effect on PSA transcription. Capsaicin inhibited NF-κ activation by preventing its nuclear migration. In further studies, capsaicin inhibited tumor necrosis factor-α–stimulated degradation of IκBα in PC-3 cells, which was associated with the inhibition of proteasome activity.

Sources of capsaicin include:

Chili peppers
Jalapeños
Red pepper

Studies for the following cancers:

Prostate
Leukemia

Studies/articles referenced:

Curcumin
Rationale: Curcumin is a diferuloylmethane derived from the Indian spice turmeric. It is shown to exhibit anticancerous effects by interfering with multiple cell-signaling pathways, including cell cycle (cyclin D1 and cyclin E), apoptosis (activation of caspases and downregulation of antiapoptotic gene products), proliferation (human epidermal growth factor-2 [HER-2], epidermal growth factor [EGFR], and activator protein 1 [AP-1]), survival (phosphatidylinositol-3-kinase [PI3K]/AKT pathway), invasion (matrix metallopeoteinase-9 [MMP-9] and adhesion molecules), angiogenesis (vascular endothelial growth factor [VEGF]), metastasis (chemokine receptor type 4 [CXCR4]) and inflammation (NF-jB, tumor necrosis factor [TNF], interleukin [IL]-6, IL-1, cyclooxygenase-2 [COX-2], and 5-lipoxygenase [5-LOX]). Research is favorable in animal studies, but is still in the early stages in humans, so definitive recommendations are not made at this time.

Sources of curcumin include:

Turmeric

Studies for the following cancers:

Leukemia
Lymphoma
Carcinoma
Lung cancer
Melanoma
Gastrointestinal
Breast
Ovarian
Head/neck squamous cell
Neurological
Sarcoma

Studies/articles referenced:

Chlorophyll
Rationale: Chlorophyll and its derivatives, such as chlorophyllin, are very effective at binding polycyclic aromatic hydrocarbons (carcinogens largely from incomplete combustion of fuels), heterocyclic amines (generated when grilling foods), aflatoxin (a toxin from molds in foods which causes liver cancer), and other hydrophobic molecules. The chlorophyll-carcinogen complex is much harder for the body to absorb, so most of it is swept out with the feces.

Sources of chlorophyll include:

All green vegetables, particularly spinach
Asparagus
Bell peppers
Broccoli
Brussels sprouts
Green cabbage
Celery
Collard greens
Green beans
Green peas
Kale
Leeks
Green olives
Parsley
Romaine lettuce
Sea vegetables
Spinach
Swiss chard
Turnip greens

Most studies have focused on chlorophyll’s impact on carcinogenic substances. New studies are looking at the following cancers:

Liver
Skin
Colon

Studies/articles referenced:

Carotenoids (alpha-carotene, beta-carotene, lycopene, lutein, cryptoxanthin, and zeaxanthin)
Rationale: A variety of dietary carotenoids (not supplements) are shown to have antioxidant effects, thereby reducing free-radical oxidation rates of cells and providing an anticancer effect. Overall intake of carotenoids is more protective than a high intake of a single carotenoid.

Carotenoids are found in a wide variety of fruits and vegetables, particularly:

Carrots
Pumpkin
Winter squash
Tomatoes
Citrus fruits
Red sweet peppers

Studies for:

Overall cancer rates
Prostate cancer

Studies/articles referenced:

Monoterpenes
Rationale: The blocking chemo-preventive effects of limonene and other monoterpenes during the initiation phase of mammary carcinogenesis are likely because of the induction of phase II carcinogen-metabolizing enzymes, resulting in carcinogen detoxification. The tumor suppression activity of monoterpenes is possibly because of the induction of apoptosis and/or inhibition of the post-translational isoprenylation of cell growth-regulating proteins.

Sources of monoterpenes include essential oils of plants:

Limonene (orange peel)
Perillyl alcohol (peppermint, spearmint, sage, cherries, cranberries, caraway, and celery seeds)

Studies for the following cancers:

Breast
Liver
Lung
Leukemia

Studies/articles referenced:

Phytochemicals
The most commonly known phytochemicals and the ones with the most studies are:

Polyphenols (including resveratrol)
Flavonoids/bioflavonoids (including quercetin, epigallocathechin gallate [EGCG], and kaempferol)

Rationale: According to Waladkhani AR and Clemens MR (http://www.ncbi.nlm.nih.gov/pubmed/9852292), “There are many biologically plausible reasons why consumption of plant foods might slow or prevent the appearance of cancer. These include the presence in plant foods of such potentially anticarcinogenic substances as carotenoids, chlorophyll, flavonoids, indole, isothiocyanate, polyphenolic compounds, protease inhibitors, sulfides, and terpens. The specific mechanisms of action of most phytochemicals in cancer prevention are not yet clear but seem varied. Considering the large number and variety of dietary phytochemicals, their interactive effects on cancer risk is extremely difficult to assess. Phytochemicals can inhibit carcinogenesis by inhibiting phase I enzymes, and induction of phase II enzymes, scavenge DNA reactive agents, suppress the abnormal proliferation of early, preneoplastic lesions, and inhibit certain properties of the cancer cell.”

Sources of phytochemicals include:

Most fruits and vegetables
Whole grains
Nuts
Tea
Red wine
Olive oil
Raspberries
Red grapes

Studies for many types of cancers, including:

Esophagus
Lung
Mouth
Pharynx
Endometrium
Pancreas
Prostate
Colon

Studies/articles referenced:

Beta-glucans
Rationale: Found in both bacterial and fungal cell walls, beta-glucans are implicated in the initiation of antimicrobial immune response. Based on in vitro studies, beta-glucans act on several immune receptors and trigger a group of immune cells, including macrophages, neutrophils, monocytes, natural killer cells, and dendritic cells, which can potentially exert anti-tumor effects.

Sources of beta-glucans include:

Mushrooms
Oats
Barley
Yeast

Early stages of study on:

Isolated cancer cells/tumors

Studies/articles referenced:

Prebiotics/probiotics
Rationale: Beneficial bacteria produce natural antibiotics to keep pathogenic bugs in check (preventing diarrhea and infections) and produce some B vitamins in the small intestine where the body can utilize them. Beneficial bacteria help with food digestion and promote gut health. Ingestion of viable probiotics or prebiotics is associated with anticarcinogenic effects, one mechanism of which is the detoxification of genotoxins in the gut. Probiotics may suppress the growth of bacteria that convert procarcinogens into carcinogens, thereby reducing the amount of carcinogens in the intestine.

Sources of prebiotics/probiotics include supplements and fermented products, such as:

Yogurt
Kefir
Miso
Kimchi
Tempeh
Pickled products

Although research is still in the early stages, studies have shown potentials effects on the following cancers:

Colon
Bladder

Studies/articles referenced:

Conclusion
Despite promising research, it is important to note that doses of specific compounds found in foods that can prevent cancer are not known at this time. Experts recommend consuming these compounds through food sources when possible. Research on supplements is not adequate to recommend supplements for cancer prevention.

Reference
American Cancer Society. ACS guidelines on nutrition and physical activity for cancer prevention. Available at: http://www.cancer.org/Healthy/EatHealthyGetActive/ACSGuidelinesonNutritionPhysicalActivityforCancerPrevention/acs-guidelines-on-nutrition-and-physical-activity-for-cancer-prevention-intro. Accessed February 10, 2012.

Contributed by Jason Machowsky, MS, RD, CDN, CSCS

Review Date 2/12
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