Food for Life: How the New Four Food Groups Can Save Your Life (13 page)

Foods are indicted in even more cancer cases than tobacco. The National Cancer Institute estimates that at least 35 percent of cancers are linked to foods, and some estimates are as high as 60 percent. Foods increase the amount of certain hormones in the body—hormones that can increase the risk of cancer. For example, several of the most common forms of cancer are linked to sex hormones. This is true of cancer of the breast, uterus, ovary, prostate, and perhaps other sites. The amount of hormones in our bodies and their actions are determined, in large part, by the foods we eat. Foods can help calm our hormonal storms and can also shore up our immunity.

Some foods also contain carcinogens, and others can increase the production of free radicals. On the other hand, some foods are protective. They help the body neutralize free radicals, eliminate carcinogens, and help the immune system knock out cancer cells.

Other factors, including radiation, pollution, genetics, and viruses, also play roles in certain forms of cancer. (See
Table 5
.) Sometimes factors work together to cause cancer. For example, tobacco and asbestos exposure can both contribute to lung cancer risk.

In this chapter, we learn about the dietary friends and enemies of cancer that we put on our plates every day.

Ask any doctor what women can do to prevent breast cancer, and the response will probably be to get an annual mammogram after age fifty, or perhaps after age forty. Mammograms help, but they do not prevent cancer. They
find
cancer. Biopsy, surgery, radiation, and chemotherapy then follow.

In the late 1970s, breast cancer attacked one in every eleven women. In the 1980s, the rate went up to one in ten. And in 1992, the rate was one in eight. In the sixteen years from 1973 to 1988, the annual number of new cases went from 73,000 to 135,000.
¹

Table 5     
Estimated Percentages of Cancer Due to Selected Factors

Source: National Cancer Institute,
Cancer Rates and Risks
(Washington, D.C.: 1985); also & Doll and R. Peto, “The Causes of Cancer: Quantitative Estimates of Avoidable Risks of Cancer in the United States Today,”
Journal of the National Cancer Institute
1981;66: 1191–1308.

Increasing scientific evidence shows that breast cancer is often preventable. In 1982, the National Research Council published a report called
Diet, Nutrition, and Cancer
,
²
showing the mountain of evidence already available at that time linking specific dietary factors to cancer of the breast and other organs. But brochures with watered-down recommendations have sat collecting dust at cancer research centers. There has never been an organized effort to give women the information they need to make decisions about cancer prevention.

As I mentioned earlier, when I was a medical student, the first room on the left on the hospital ward was occupied by a thirty-five-year-old woman whose breast cancer had spread to her bones. And in the very next room was another woman in her early forties with the same disease. This epidemic sent victims to every hospital in America. The only difference today is that the number of victims is higher than ever.

The link between diet and cancer is not new. An article in
Scientific American
in January 1892 printed an observation that “cancer is most frequent among those branches of the human race where carnivorous habits prevail.” Asian countries, such as Japan, have low rates of breast cancer while Western countries have cancer rates that are many times higher. These differences are not due to genetics. Nor is it something in the air or water.
Many scientific studies have suggested that an important factor is the food we eat.
^3
,
4

When Japanese women Westernize their diets, as has been happening since the 1950s, particularly among the affluent populations of Tokyo, Osaka, and other major cities, the rate of breast cancer has increased dramatically. And when Japanese families move to the United States, the daughters have the same risk of cancer as the American women around them—many times higher than that in Japan.

Researchers have found that fat in the diet, especially animal fat, increases the risk of breast cancer. Although scientists continue to debate the role of fat in cancer, substantial evidence shows that the more fat there is in the diet, the greater the risk of breast cancer, as we will see. Alcohol also increases risk. And fiber, vitamins, and the mineral selenium help protect the body. As we look at these factors individually, it is important to remember that each one alone is just part of the puzzle. It is not fat alone that causes cancer, nor vegetables alone that prevent it, but rather the combined effect of the nutrients and poisons we put on our plate three times a day.

In Japan in the late 1940s, when breast cancer was particularly rare, only about 7 percent of the calories in the Japanese diet came from fat.
⁵
The American diet, of course, is quite different. Animal products are at the center of the menu, and there is no chicken or beef that is 7 percent fat as a percentage of calories. These products are all at least three times higher in fat, and the fat content on the average American plate is in the range of 37 to 40 percent of calories.

Countries with a higher intake of fat, especially animal fat, have a higher incidence of breast cancer.
^3
,
6
,
7
This has been found not just once or twice but repeatedly in very carefully conducted studies. Even within Japan, affluent women who eat meat daily have 8.5 times higher risk of breast cancer compared to poorer women who rarely or never eat meat.
⁴
The Surgeon General’s
Report on Nutrition and Health
stated: “Indeed, a comparison of populations indicates that death rates for cancers of the breast, colon, and prostate are direcdy proportional to estimated dietary fat intakes.”
⁸

When the link between fat and cancer was found, researchers did not have to look far to explain it. There are many ways that fatty foods affect the body.
First, as we saw in
Chapter 1
, high-fat diets increase the level of estrogens, the female sex hormones, in the blood. It is known that many breast tumors are fueled by estrogens. Estrogens are normal and essential hormones for both women and men. But the more estrogen there is, the greater the driving force behind some kinds of breast cancer. On high-fat diets, estrogen levels increase; on low-fat diets, they decrease.
^9–
11
When women begin low-fat diets, their estrogen levels drop noticeably in a very short time. Vegetarians have significantly lower estrogen levels than nonvegetarians, in part because of the lower fat content of their diet, and they have more of the carrier molecules,
sex hormone binding globulins
, which have the job of holding onto the hormone until it is needed. Fatty foods do the reverse. They increase estrogens and reduce the amount of the carrier molecule that is supposed to keep the estrogens in check. And every minute, the breast cells are exposed to a little more estrogen than is normal.

Animal fats are apparently a bigger problem than vegetable oils. Paulo Toniolo, of the New York University Center, compared the diets of 250 women with breast cancer to 499 women without cancer from the same province in northwestern Italy. The two groups ate about the same amount of olive oil and carbohydrates. But what made the cancer patients different was that they had habitually eaten more meat, cheese, butter, and milk. The women who consumed more animal products had as much as three times the cancer risk of other women.
¹²

Vegetarian diets based on grains, vegetables, fruits, and legumes are the most powerful diets for health, but their power erodes if milk and cheese and other dairy products are added. Some studies of lacto-ovo-vegetarians have found that their cancer risk is almost as high as meat-eaters.
^13
,
14
These vegetarians were avoiding meat but eating considerable amounts of dairy products that, like meat, contain animal fat and not a speck of fiber.

Even though cross-cultural comparisons have pointed a finger at animal fat as the principal problem, vegetable oil is also under some suspicion. Vegetable oils can probably affect estrogen levels and, as we will see below, increase the production of cancer-causing free radicals. So it is no good just replacing fried chicken with fried onion rings. The best diet not only eliminates animal products but keeps vegetable oils to a minimum as well.

Certain foods have special actions. As we saw in
Chapter 1
, soybeans contain natural compounds called
phytoestrogens
. These are very weak estrogens that can occupy the estrogen receptors on breast cells, displacing normal estrogens. The result is less estrogen stimulation of each cell. Soybeans
are a mainstay of Asian diets, and may be an additional reason why these countries have low cancer rates.
¹⁵

If a woman begins a low-fat vegetarian diet, can estrogen levels drop? The answer is yes, with measurable changes usually occurring within a few weeks of beginning a new diet.

The results are often dramatic. A patient once called me asking for Demerol, a narcotic painkiller. She was having intense menstrual cramps, and she had found that milder analgesics would not ease the pain. I agreed to prescribe pain medication, but asked her to modify her diet during the next month: no animal products of any kind, and no vegetable oil. This meant a vegan diet, and no potato chips, salad dressings, and the like. At the end of the next month, she called again. For the first time in years, her period had been essentially pain-free. The pain she had assumed to be simply part of “the curse” was actually gone.

If you or anyone you know has the same problem, try this dietary experiment. You may be surprised with the results.

Will the 30 percent fat diet of lean meat, poultry, fish, and vegetables, long recommended by the National Cancer Institute, prevent cancer in the American population? I strongly doubt it. It is just too weak. In the 1950s, when Japan’s cancer rates were very low, fat intake was about 7 percent of calories. In China, average fat intake is now about 15 percent of calories. The China Health Study looked at provinces with fat intakes ranging from 6 to 24 percent of calories, and found that breast cancer was more common in those provinces at the higher part of this range. Thirty percent is too high to be of any significant benefit.

A study at Harvard University suggested the same thing. Walter Willett and his colleagues followed a large group of nurses for an eight-year period, tracking their diets and their cancer rates. The nurses ate standard American diets; and those who had a bit less fat, about 27 percent of calories from fat, were not any better off against cancer than those consuming more fat.
¹⁶
Some have interpreted this to mean that diet has nothing to do with breast cancer. A more reasonable conclusion is that the diets these women followed
were still high-risk diets. No groups with low fat intakes were tested in the study. A diet including regular consumption of animal products and drawing nearly 30 percent of calories from fat is much higher in fat than the Asian diets associated with low cancer risk. Just as reducing cigarette smoking from two packs a day to one pack a day will not lower your cancer risk much, minor changes in diet cannot be expected to, either.

The bottom line is that the National Cancer Institute’s guideline—that fat be no more than 30 percent of calories—is far too high. Fat intake should probably be approximately 10 percent of calories.

But here is a key point: As important as it is to get the fat off your plate, that is only the beginning. Fat is not all there is to it. Other parts of the diet play important roles in your risk of cancer. Vegetables, fruits, grains, and beans are not just low in fat. They also provide fiber, vitamins, and minerals. Fiber, of course, is only found in plants and, as noted above, fiber is vital for helping the body to rid itself of estrogen. And the vitamin C and beta-carotene in vegetables and fruits are also linked to lower cancer risk. Numerous researchers have found that the more high-fiber, vitamin-packed foods women consume, the lower their risk of cancer.
¹⁷

Selenium also has a protective effect. As we’ve seen, selenium is an essential element in the antioxidant system that works within the cells. It comes from grains, and women with higher amounts of selenium in the blood are less likely to develop breast cancer than women with lower amounts.
¹⁸

Alcohol increases cancer risk. Although some have promoted modest alcohol consumption, hoping to lower risk of heart disease, even one drink a day can increase breast cancer risk by more than 50 percent, compared to nondrinkers.
¹⁹
That does not mean that your cancer risk is 50 percent. It means that it is half again higher than it was before. The effect of alcohol is mainly seen in younger women.

Aside from diet, other factors have been identified that increase breast cancer risk

•
Hormones
. Oral contraceptives appear to increase risk. Although newer birth control pills contain less estrogen and progesterone than older versions, evidence suggests some increase in risk from oral contraceptives.
²⁰
The same may be true of supplemental hormones given to women after menopause.
²¹
In both cases, it
makes sense for women to discuss the risks and benefits with their personal physicians.