If you've been grocery shopping lately, you know that there are many new food products positioned to enhance health or reduce the risk of disease. Many consumers want to take charge of their health and well being and are seeking foods that optimize their health. One health concern that some people are addressing with food is cancer. Experts now believe that what we include in our diet is just as important as what we exclude.
Many consumers believe that food plays a significant role in maintaining or improving overall health and are aware that certain foods may have health benefits beyond basic nutrition. The Food Marketing Institute/Prevention's Shopping for Health 2000 survey reported that more than 70 percent of consumers make grocery store purchases on the basis of their desire to reduce their risk of specific illnesses. In addition, more than 9 in 10 consumers believe that fruits, vegetables, and grains contain naturally occurring substances that can help reduce the risk of diseases such as cancer.
Cancer Facts
Cancer is a generic term describing more than 100 diseases that share the uncontrolled reproduction of abnormal cells. Scientists are just beginning, however, to understand the many causes of cancer and the complex process by which cancer cells grow (see the sidebar How Does Cancer Begin?). Each year in the United States almost 1.4 million new cases of cancer are diagnosed and cancer causes more than 500,000 deaths.
Over the past two decades, it has become increasingly clear that what we eat plays a significant role in our risk of cancer. Scientists estimate that approximately 30 to 40 percent of all cancers are linked to diet and related lifestyle factors. In short, simple changes in eating patterns could have a dramatic impact on reducing cancer rates.
The Food-Cancer Connection
The idea that foods may play a role in reducing one's risk of cancer first emerged from findings that linked higher levels of intake of fruits and vegetables with a lower risk of cancer. Since then, many studies have explored the connection between food and cancer risk. Alan Kristal, associate head of the Cancer Prevention Research Program at the Fred Hutchinson Cancer Research Center, explains why results are still speculative: "With cardiovascular disease, blood cholesterol level is a key biomarker for measuring the effects of diet. We're just now learning about some of the various biomarkers for cancer because it is such a complex process."
To date, we believe that the functional components of food that may reduce one's risk of cancer include traditional nutrients, such as folic acid, vitamins A and C, fiber, and selenium, as well as recently discovered compounds, such as phytochemicals and many other naturally occurring elements in both plant and animal foods. Some functional components, lycopene in tomatoes and tomato products, act as potent antioxidants, protecting cells against harmful damage from oxidation. Interestingly, research shows that lycopene is more bioavailable in processed tomatoes. Others, such as soy, have hormone-like actions, helping to protect against hormone-dependent cancers like endometrial and ovarian cancers.
More recently, it has been discovered that compounds in food-such as sulforaphane in broccoli-can encourage the body's production of protective enzymes, called phase II enzymes. These enzymes help to detoxify cancer-causing substances and prevent cell damage that can lead to cancer. Other such foods include cruciferous vegetables (e.g., cabbage, cauliflower, brussels sprouts, and bok choy), garlic, onions, berries, and grapes.
Certain food components may also be able to help delay, regress, or inhibit the advancement of cells to the clinical stage of cancer. However, Dr. John Milner, chief of the Nutritional Science Research Group at the National Cancer Institute, cautions that "one size does not fit all" when it comes to benefits from functional foods.
"The evidence is compelling that functional foods can modify cancer risk, especially with increased intakes of fruits and vegetables," says Milner. "But it also appears that not everyone gets the same benefits. An individual's genetic makeup probably influences the extent of the response to functional food components." According to Milner, this may explain why some people seem to experience positive effects from functional components of food while others do not. "Until more targeted intervention-based research is conducted, it's difficult to predict who might benefit from functional foods."
The table below, Functional Foods that May Reduce Risk of Cancer, lists some functional compounds in foods and their potential roles in cancer risk reduction.
Whole Foods vs. Prepared Foods
Whole foods, namely fruits and vegetables, represent the simplest example of functional foods. Prepared foods, such as breads, cereals, dairy products, and juices, that have been enriched or fortified with "traditional" nutrients, are also functional foods. Some newer functional foods include foods that have been enhanced with phytochemicals, botanicals, or other functional substances.
Although it may be possible to isolate specific components of food that may reduce the risk of diseases like cancer, it is unclear whether isolated active compounds added to food have the same health benefits as whole foods because compounds in foods may act synergistically to impart health benefits.
"It's likely that the protective effects of functional foods come from vitamins, minerals, enzyme-boosting phytochemicals, and perhaps other not-yet-identified substances in food, all working together," said Clare Hasler, executive director of the Functional Foods for Health Program at the University of Illinois. "As we learn more about actions of functional components and the effects on individuals," she adds, "we may be able to tailor functional food recommendations based on an individual's genetic profile."
There's no doubt that functional foods' role in reducing the risk of cancer is promising. For now, getting the full range of "functions" from food means eating a variety of foods and including plenty of fruits and vegetables in your diet. Until we know more, this strategy along with an overall healthful lifestyle offers the best bet for improving the odds against developing cancer.
For More Information on Functional Foods
How Does Cancer Begin?
This box provides a simplified explanation of the stages that occur before cancer becomes evident.
The first stage, called initiation, occurs when a normal cell is exposed to a carcinogen, such as chemicals, viruses, radiation, or specific dietary factors. Essentially, anything that causes damage to the cell membrane or the DNA material within the cell can be classified as a carcinogen. DNA repair mechanisms can usually restore the cell to its normal state. If the cell is unable to repair itself, however, it mutates. A mutated, or initiated cell, passes on its mutation when it replicates, thus advancing from the initiation to the promotion stage. At the promotion stage, the cell may experience spontaneous remission back to the initiation stage, or it may be exposed to growth inhibitors or antipromoters, such as antioxidants and phytochemicals, that will allow regression back to the initiation stage. However, the mutated cell may eventually lose its integrity and develop into a premalignant lesion such as dysplasia, carcinoma in situ, or polyps. As the cell continues to lose control over its function and structural integrity, progression to the clinical stage of cancer occurs with disruption of normal body functions. The entire process, from exposure to a carcinogen to development of cancer, typically takes years.
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Functional Foods that May Reduce Risk of Cancer
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| Food |
Functional Components* |
Possible Role(s) in Cancer Risk Reduction |
| Broccoli and broccoli sprouts |
Sulphoraphane |
Stimulates the body to produce its own protectivephase II enzyme, neutralizes free radicals |
| Tomatoes and tomato products |
Lycopene |
Potent antioxidant that may reduce risk of prostate cancer |
| Garlic and onions |
Allyl sulfides |
Boosts levels of naturally occurring enzymes that may help maintain healthy immune system |
| Soybeans |
Isoflavones (genistein and daidzein) |
May act as an antiestrogen, plugging up receptors for estrogen which may reduce the risk of estrogen-dependent cancers; may inhibit the formation of blood vessels that assist tumor growth |
| Grapes, strawberries, and raspberries |
Ellagic acid |
May block the body's production of enzymes needed for cancer cells to replicate |
| Oranges and lemons |
Limonene |
Boosts levels of naturally occurring enzymes that may break down carcinogens |
| Green tea |
Polyphenols (catechins) |
May help block damage to DNA by neutralizing free radicals and reducing cancer risk |
| Beef and dairy |
Conjugated linoleic acid (CLA) |
May decrease risk of certain cancersproducts |
| Dairy products |
Sphingomyelin Calcium |
May inhibit tumor cell growth and induce cell death |
| Flaxseed |
Lignans |
Acting as a phytoestrogen, may offer reduced risk of certain kinds of cancer |
| Whole wheat |
Phytic acid |
May suppress the oxidative reactions in the colon that produce damaging free radicals |
| * These represent just one example of functional components in the corresponding food. Most functional foods contain many active components with potential health benefits. |
