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Nutrients - How Other Phytochemicals
Help Protect Against Cancer
Phytochemicals are a fascinating yet mysterious group of thousands of chemicals found
in plant foods. Some protect against cancer when isolated, some are not associated with
cancer at all, and many have yet to be discovered. It is known that many phytochemicals,
when kept in their natural food forms, can protect us from cancer as they interact with
other phytochemicals and the cells in our bodies.
Some of the most extensively researched phytochemicals are phytoestrogens (FY-TOH-ESS-TRO-JENS),
which include isoflavones (EYE-SO-FLAY-VONES) (high amounts of which are
found in soy foods), coumestans (COO-MAY-STANS), and lignans. These
chemicals may protect against breast cancer by protecting cells from estrogen. Because of
their similar structure to estrogen—hence the name
"phytoestrogen"—these plant estrogens are able to take up space on estrogen
receptors where the body's estrogen otherwise would have attached. (See soy isoflavones for more detail) Because these plant
estrogens are much weaker than human estrogen, they help minimize the hormonal activity
that is believed to promote cancer growth.
Other powerful phytochemicals are the isothiocyanates (EYE-SO-THIGH-O-SIGH-A-NATES)
present in cruciferous vegetables (such as broccoli, cauliflower,
and Brussels sprouts), which have been shown to prevent lung cancer
among non-smokers as well as other types of cancer.1,2
(See isothiocyanates for more
detail).
Another important phytochemical is the compound allicin (AL-I-SIN),
found abundantly in fresh garlic and in smaller amounts in onions, chives, and leeks. This
chemical acts as an antioxidant similar to vitamins A, C, and E, and may help protect the
body from free radicals. It is also possible that allicin fights cancer by reacting with
carcinogens and changing their structure so they can no longer initiate tumors or by
speeding the death of cancer cells that have already formed.3-5
The group of phytochemicals called catechins (CA-TE-KINS), found in
black and green teas, wine and some fruits such as apples, function similarly to allicin.
These antioxidants prevent cancer and kill cancer cells that have already formed.6,7 Recent studies have shown that catechins may help prevent
stomach and prostate cancer in particular.8,9
You may have heard about some favorable effects of red wine. This is apparently due to
the phytochemical resveratrol (RES-VEAR-A-TROL), which shows a dramatic
tendency to decrease risk of many types of cancer. The question as to whether or not the
best source of resveratrol is red wine remains debated, considering the high caloric
content of wine and alcohol's possible role in breast cancer. Healthier sources of
resveratrol include grapes, berries, and peanuts. The ways in which resveratrol helps
fight cancer are manifold: Studies show that resveratrol may slow tumor growth in the
lungs by preventing the replication of DNA,10 prevent
tumors from forming both in the lungs and the colon by destroying potential carcinogens,11,12 prevent liver cancer because of its antioxidant activity,13 prevent breast cancer by protecting cells from the harmful
effects of linoleic acid, a type of fatty acid implicated in breast cancer,14
and arrest the growth of leukemia cells.15
Other beneficial phytochemicals include phytic acid found in wheat
bran, which may prevent colon cancer,16
and quercetin (a flavinoid), apigenin, and hexaphosphate, all of
which are found in a variety of fruits and vegetables and are all
thought to prevent many types of cancer.
Food Sources
Here are some phytochemical-rich foods:
| Phytochemical |
Food Sources |
| Allium |
garlic, leeks, chives, onions |
| Apigenin |
Chinese cabbage, bell pepper, garlic, French
peas, guava, celery |
| Catechins |
green tea, black tea, wine, coffee, apples |
| Coumestans |
clover, alfalfa sprouts |
Isoflavones |
tofu, soybeans, tempeh, soymilk,
textured vegetable protein |
| Isothiocyanates |
broccoli, cauliflower, kale,
turnips, collards, Brussels sprouts, cabbage, kohlrabi, rutabaga, Chinese cabbage, bok
choy, horseradish, radish, watercress |
| Lignins |
flax seed |
| Phytic acid |
wheat bran |
| Quercetin |
apples, onions, tea, berries,
brassica vegetables (broccoli, cauliflower, Brussels sprouts, bok choy), various seeds and
nuts, some medicinal botanicals, including Ginkgo biloba and St. John's Wort |
| Resveratrol |
grapes, berries, peanuts, red
wine |
Tips for Increasing Phytochemicals in Your Diet
- Use fresh or frozen vegetables instead of dried or canned.
- Keep cooking to a minimum. Most phytochemicals do not fare well
when exposed to high temperatures.
- Add fresh garlic (not garlic powder) to almost any meal. Or
if a recipe already calls for garlic, just add more than it recommends.
- Eat whole, not refined, grains. Phytochemicals are found
in the highest concentrations in the nutrient-rich fiber that
coats the starchy center of the grain. During processing, this
fiber is usually lost.
- Eat a variety of vegetables. Try something new at least once
a week and continue to incorporate the new vegetables into your
meals.
- Try cooking meals from other cuisines. Check out your local
Asian or Latin American grocery store to discover some new vegetables.
References
1. Michaud DS, Feskanich D, Rimm EB, et al. Intake of specific carotenoids and risk
of lung cancer in two prospective U.S. cohorts. Am J Clin Nutr 2000;72:990-7.
2. Lewis S, Brennan P, Nyberg F, et al. Cruciferous vegetable intake, GSTM1
genotype and lung cancer risk in a non-smoking population. Abstract from the European
Conference on Nutrition and Cancer, Lyon, France, June 21-24, 2001: 55, www.nutrition-center2001.com.
3. Borek C. Antioxidant health effects of aged garlic extract. J Nutr
2001;131:1010S-5S.
4. Thatte U, Bagadey S, Dahanukar S. Modulation of programmed cell death by
medicinal plants. Cell Mol Biol (Noisy-le-grand) 2000;46:199-214.
5. Le Bon AM, Siess MH. Organosulfur compounds from allium and the chemoprevention
of cancer. Drug Metabol Drug Interact 2000;17:51-79.
6. Maeda H, Kanazawa A. Peroxyl radical-scavenging activity of beverages,
especially of tea, coffee and wine in vitro. Abstract from the European Conference on
Nutrition and Cancer, Lyon, France, June 21-24, 2001: 77, www.nutrition-center2001.com.
7. Eberhardt MV, Lee CY, Liu RH. Antioxidant activity of fresh apples. Nature
2000;405:903-4.
8. Chung LY, Cheung TC, Kong SK, et al. Induction of apoptosis by green tea
catechins in human prostate cancer DU145 cells. Life Sci 2001;68:1207-14.
9. Hibasami H, Komiya T, Achiwa Y, et al. Induction of apoptosis in human stomach
cancer cells by green tea catechins. Oncol Rep 1998;5:527-9.
10. Kimura Y, Okuda H. Resveratrol isolated from Polygonum cuspidatum root prevents
tumor growth and metastasis to lung and tumor-induced neovascularization in Lewis lung
carcinoma-bearing mice. J Nutr 2001;131:1844-9.
11. Mollerup S, Ovrebo S, Haugen A. Lung carcinogenesis: resveratrol modulates the
expression of genes involved in the metabolism of PAH in human bronchial epithelial cells. Int J Cancer 2001;92:18-25.
12. Schneider Y, Vincent F, Duranton B, et al. Anti-proliferative effect of
resveratrol, a natural component of grapes and wine, on human colonic cancer cells. Cancer
Lett 2000;158:85-91.
13. Kozuki Y, Miura Y, Yagasaki K. Resveratrol suppresses hepatoma cell invasion
independently of its anti-proliferative action. Cancer Lett 2001;167:151-6.
14. Nakagawa H, Kiyozuka Y, Uemura Y, et al. Resveratrol inhibits human breast
cancer cell growth and may mitigate the effect of linoleic acid, a potent breast cancer
cell stimulator. J Cancer Res Clin Oncol 2001;127:258-64.
15. Bernhard D, Tinhofer I, Tonko M, et al. Resveratrol causes arrest in the
S-phase prior to Fas-independent apoptosis in CEM-C7H2 acute leukemia cells. Cell Death
Differ 2000;7:834-42.
16. Jenab M, Thompson LU. Purified and endogenous phytic acid in wheat bran affects
early biomarkers of colon cancer risk. Abstract from the European Conference on Nutrition
and Cancer, Lyon, France, June 21-24, 2001: 75, www.nutrition-center2001.com.
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