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Foods for Cancer Prevention
Of the
many diseases that affect people these days, cancer is among the
most feared. But despite a wealth of scientific data, most people
remain unaware of how they can reduce their risk of developing cancer.
According to the National Cancer Institute, as much as 80 per cent
of all cancers are due to identified factors, and thus are potentially
preventable. Thirty percent are due to tobacco use, and as much
as 35 to 50 per cent are due to foods. It is easy to control these
and other risk factors.
What Is Cancer?
Cancer begins as a single abnormal cell that begins
to multiply out of control. Groups of such cells form tumors and
invade healthy tissue, often spreading to other parts of the body.
Carcinogens are substances that promote the development of cancerous
cells. They may come from foods, from the air, or even from within
the body. Most carcinogens are neutralized before damage can occur,
but sometimes they attack the cell’s genetic material (DNA)
and alter it. It takes years for a noticeable tumor to develop.
During this time, compounds known as inhibitors can keep the cells
from growing. Some vitamins in plant foods are known to be inhibitors.
Dietary fat, on the other hand, is known to be a promoter that helps
the abnormal cells grow quickly.
Fiber Fights Cancer
In 1970, British physician, Dennis Burkitt, observed
that a high-fiber diet reduces diseases of the digestive tract.
He observed that in countries where diets are high in fiber (that
is, plant-based diets), there were fewer cases of colon cancer.
Around the world, this has proven true. The highest fiber intakes
are found in non-industrialized nations where meat is scarce and
plant foods fill the menu. Animal products contain no fiber. The
U.S. and other Western nations whose diets are based upon animal
products have the highest rates of colon cancer.
While no one is certain exactly how fiber protects
against digestive tract disorders, there are several possibilities.
By definition, fiber cannot be digested by humans early in the digestive
process. It moves food more quickly through the intestines, helping
to eliminate carcinogens. It also draws water into the digestive
tract. The water and fiber make fecal matter bulkier, so carcinogens
are diluted.
Bile acids are secreted into the intestine to
help digest fat; there, bacteria can change the acids into chemicals
which promote colon cancer. Fiber may bind with these bile acids
and evict them from the intestines.
Also, bacteria in the colon ferment the fiber creating a more acidic
environment which may make bile acids less toxic.
Fiber is also protective against other forms of
cancer. Studies have shown that stomach cancer and breast cancer
are less common on high-fiber diets.
Fiber affects levels of estrogens in the body. Estrogens are normally
secreted into the intestine, where the fiber binds with the hormone
and moves it out of the body.4 Without adequate fiber, the estrogen
can be reabsorbed from the intestine into the bloodstream. High
levels of estrogen are linked to a higher risk of breast cancer.
In the U.S., the average daily fiber intake is 10 to 20 grams per
day. Experts recommend 30 to 40 grams per day. The best sources
of fiber are whole grains, beans, peas, lentils, vegetables, and
fruits. Foods that are closest to their natural state, unrefined
and unpeeled, are highest in fiber.
Fat Raises Cancer Risks
Cross-cultural studies have revealed that the
populations with the highest levels of fat consumption are also
the ones with the highest death rates from breast and colon cancer.
The lowest rates are in groups with the lowest consumption of fats.Migration studies help to rule out the influence of genetics.
Many studies indicate that fat in foods increases
one’s risk for cancer, and it may also adversely affect breast
cancer survival rates for those who have cancer.
Although the total amount of fat one eats is of
concern, there is evidence that animal fat is much more harmful
than vegetable fat. One study noted a 200 per cent increase in breast
cancer among those who consume beef or pork five to six times per
week. Dr. Sheila Bingham, a prominent cancer researcher form the
University of Cambridge, notes that meat is more closely associated
with colon cancer than any other factor.
Meat and milk are also linked to both prostate and ovarian cancers.
How Fat Affects Cancer Risks
Fat has many effects within the body. It increases
hormone production and thus raises breast cancer risks. It also
stimulates the production of bile acids which have been linked to
colon cancer.
The average diet in the U.S. is about 37 per cent
fat. The National Cancer Institute suggests that people lower that
percentage down to 30 percent; however, studies have shown that
fat intake should be well below 30 per cent to have an anti-cancer
affect. Ten to 15 per cent is more likely to be helpful.
The Importance of Vegetables
Not only are vegetables low in fat and high in
fiber, they also contain many cancer-fighting substances. Carotenoids,
the pigment that gives fruits and vegetables their dark colors,
have been shown to help prevent cancer. Beta-carotene, present in
dark green and yellow vegetables, helps protect against lung cancer
and may help prevent cancers of the bladder, mouth, larynx, esophagus,
breast, and other sites.
Vegetables such as cabbage, broccoli, kale, turnips,
cauliflower, and Brussels sprouts contain flavones and indoles which
are thought to have anti-cancer activities.
Vitamin C, found in citrus fruits and many vegetables,
may lower risks for cancers of the esophagus and stomach. Vitamin
C acts as an antioxidant, neutralizing cancer-causing chemicals
that form in the body. It also blocks the conversion of nitrates
to cancer-causing nitrosamines in the stomach.
Selenium is found in whole grains and has the
same antioxidant effects as vitamin C and beta-carotene. Vitamin
E also has this effect. Caution is advised in supplementing selenium,
which is toxic in large doses.
Alcohol
Excessive intake of alcohol raises one’s
risks for cancers of the breast, mouth, pharynx, and esophagus.
When combined with smoking, these risks skyrocket. It also raises
risks for stomach, liver, and colon cancers.
Vegetarians Are Better Off
All the evidence points to a low-fat, high-fiber
diet that includes a variety of fruits, vegetables, whole grains,
and beans, as being the best for cancer prevention. Not surprisingly,
vegetarians, whose diets easily meet these requirements, are at
the lowest risk for cancer. Vegetarians have about half the cancer
risk of meat-eaters.
Vegetarians have higher blood levels of beta-carotene.
They consume more vitamin C, beta-carotene, indoles, and fiber than
meat-eaters. Vegetarians also have stronger immune systems. German
researchers recently discovered that vegetarians have more than
twice the natural killer cell activity of meat-eaters.
Natural killer cells are specialized white blood cells that attack
and neutralize cancer cells. Also, vegetarians tend to eat more
soy products than meat-eaters. Soybeans contain many substances
that are anticarcinogens, including lignans and phytoestrogens.
A diet that is rich in soybeans may be one reason for the lower
incidence of breast cancer in Asia.
Conclusion
A cancer prevention diet is one that is high in
fiber, low in fat (especially animal fat), and includes generous
portions of fruits and vegetables. It also minimizes or excludes
alcohol. The best diets are pure vegetarian diets.
References
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dietary fiber in breast cancer etiology: a case control study. J
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