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United States Department of Agriculture

Agricultural Research Service

Everyday veggies contain promising anticancer agent
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By: Huawei Zeng

Next to heart disease, cancer is the second major cause of death in the United States. The probability of getting cancer is coupled with age, and people older than 65 are in higher risk. Cancer claims the lives of more than half a million Americans each year out of the nearly 1.4 million who get the disease.

It is believed that cancer is begun with a mutation in a single cell, but a cell will not be cancerous overnight. Several subsequent mutations are required to create all the characteristic features of cancer. Usually, cells have a self-defense system that causes them to die when mutations occur. However, certain developing cancer cells escape this mechanism and gradually become cancer cells. The rate of cancerous mutations is directly related to the exposure of carcinogenic substances (e.g. cigarette smoke), which give rise to cell changes that eventually lead to tumor growth and cancer.

On the other hand, the health benefits of vegetables have been well-recognized. Over the last two decades, there is an increasing body of evidence supporting the health benefits of eating veggies. The recent promising findings demonstrate that certain vegetable constituents, which are called phytochemicals, enhance the human body’s defenses against cancer. These phytochemicals act as a natural defense system for host plants and provide color, aroma and flavor.

Diet

It is known that diet is a major source of phytochemicals, and diets that do not provide enough such bioactive compounds are likely to increase the risk of specific cancers. Numerous epidemiological studies generally have demonstrated that vegetable and fruit consumption is inversely associated with cancer incidence and mortality. In particular, consuming cruciferous vegetables, such as broccoli, cauliflower, cabbage, kale, Brussels sprouts and radishes, is more strongly associated with cancer protection than consuming vegetables in general.

Although cruciferous vegetables contain many bioactive components, sulforaphane is one of the major phytochemicals found in these healthy vegetables, and its precursor generally is found in high concentrations in broccoli. Sulforaphane has been suggested to be an anticancer, and antimicrobial phytochemical that is produced by chewing cruciferous vegetables such as Brussels sprouts, broccoli, cabbage, cauliflower, bok choy, kale, collards, broccoli sprouts, chinese broccoli, broccoli raab, kohlrabi, mustard, turnip, radish, rocket and watercress.

The enzyme myrosinase transforms glucoraphanin (a glucosinolate) into sulforaphane upon damage to the plant (such as from chewing). The young sprouts of broccoli and cauliflower are particularly rich in glucoraphane.

Research

Here, at Grand Forks Human Nutrition Research Center, we investigated the molecular mechanism of sulforaphane’s anticancer action and compared the effect of sulforaphane on different human colon cells. Our recent study found that a prolonged sulforaphane treatment inhibits cell growth and induces cell death in colon cancer cells, but to a lesser extent in normal colon cells. These differences in sulforaphane susceptibilities of colon cancer versus nontumorigenic cell lines may, at least in part, account for the molecular basis of its anticancer action.

There are many other studies, and sulforaphane has proved to be an effective chemoprotective agent in cell culture, carcinogen-induced and genetic animal cancer models.

Sulforaphane can function by blocking tumor initiation step via inhibiting Phase 1 enzymes that convert procarcinogens to carcinogens. Sulforaphane also induces Phase 2 enzymes that detoxify carcinogens and facilitate their excretion from the body. Once cancer is initiated, sulforaphane can act via several mechanisms that modulate cell growth and cell death signals to suppress cancer progression.

Good fight

Boosting our internal detoxification system is the best way to counteract carcinogens. Sulforaphane is a powerful tool to achieve this goal. Foods containing phytochemicals are already part of our daily diet. In fact, most foods contain phytochemicals, except for some refined foods such as sugar or alcohol.

Some foods, such as whole grains, vegetables, beans, fruits and herbs, contain many phytochemicals. Therefore, the most common way to get more phytochemicals is to eat more fruit such as blueberries, cranberries, cherries and apples and vegetables such as cauliflower, cabbage, carrots and broccoli.

The amount of vegetables you need to eat depends on your age, sex and level of physical activity. To see a chart at MyPyramid.gov showing how many vegetables are needed daily or weekly, go to www.mypyramid.gov/pyramid/vegetables_amount_table.html.

Fruits and vegetables are rich in minerals, vitamins and fiber and are low in saturated fat. Although phytochemicals are not essential nutrients — defined as nutrients required by the human body for sustaining life — they are healthful. Thus, following the often-repeated advice to eat a variety of vegetables every day is a sound strategy, and include broccoli and broccoli sprout in your menu.


Last Modified: 10/25/2010
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