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Continued from EVU News 3/’97 Part 1 of Diet for a New Century (EVU News 97/3)
Populations around the world that practice a very low fat vegetarian diet, in general, have the lowest rates of cancer. Populations that live on a rich western diet, however, have the highest rates of cancer. As a matter of fact, every fourth death in North America is due to cancer, and despite many high tech medical interventions from chemotherapy to radiation and surgery, the rates of many adult cancers are actually going up. What then shall we do? "More than 50% of cancers in Western society are directly related to overnutrition, particularly the high intake of fat."- Ernest Wynder, MD The Diet-Cancer Axis The National Cancer Institute has estimated that Americans could reduce their cancer incidence by 50 to 90% if they adopted the lifestyle and diet of low risk countries. Furthermore, the National Cancer Institute estimates that 35 to 40% of all cancer deaths, and 8 out of 10 of the most common cancers are directly related to our rich, western diet. Dr. Ernest Wynder, president of the American Health Foundation and a prominent epidemiologist, stated, “60% of female cancers and 50% of all male cancers in western society are directly related to overnutrition, particularly to the high intake of fats, grease and oil.” What are some of these factors? Let’s take a look at breast cancer. BREAST CANCER In 1960, 1 in 20 women in North America developed breast cancer. In 1980, the rate went up to 1 in 11. And now it’s estimated that 1 in 8 women will develop breast cancer. Yet the disease is virtually absent in countries where people eat differently than we do. Could we do something differently? By comparing the disease rates and diet composition of different countries, certain dietary factors have prominently emerged. In Japan, for instance, breast cancer is very rare. When Japanese women, however, move to the United States, they develop the same risk for cancer as American women – at least 500% higher than in Japan. For this reason, the cancer rate differential between the United States and Japan is obviously not related to genetics. Nor is it something in the air or in the water. Carcinogens are a concern, especially with the array of additives, preservatives, flavor enhancers, pesticides, and other chemicals used in producing and marketing food. However, only 2% of all cancers can be reliably linked to these substances. Fat and Fiber In contrast, evidence of the connection between certain adult cancers and such dietary factors as fiber and fat is growing stronger every day. While in Japan only 10 to 15% of the calories in the diet came from fat, in the United States and Canada the fat content is about three times higher, almost 40%. At the same time, the Japanese diet before World War II contained almost three times more fiber than the refined western diet. Similar trends have been observed by studying different populations within the United States. The large Adventist Health Study showed that strict vegetarians, for instance, have a much lower cancer risk than lactoovo vegetarians, and they, in turn, have a distinct advantage over meat eaters. Estrogen As the link between fat and breast cancer emerged, researchers did not have to look very far for reasons to explain it. Several possibilities presented themselves. First of all, it is known that many breast tumors are fueled and driven by estrogens, the female sex hormones. While estrogens are normal and essential hormones, the higher the estrogen levels, the greater the driving force behind some kinds of breast cancer. The main estrogen factor is estradiol, and the amount of estradiol produced by the body corresponds to the amount of fat in the diet. High fat diets increase estradiol production. Low fat diets decrease it. When women switch to very low fat diets, the estradiol levels drop noticeably, even in a very short time. Strict vegetarian women who presumably eat less fat, have considerably lower estrogen levels than meat eaters. Another problem with high fat diets is the fact that the meat, poultry, fish, and dairy products that make up those diets are usually devoid of any fiber. Fiber is the part of plantfoods that resists digestion in the intestinal tract. The evidence is fairly clear suggesting that fiber helps to reduce estrogen levels by trapping estrogen in the digestive tract. "Fat influenced high estrogen levels may hasten the onset of puberty, which increases the risk of breast cancer." In addition, soybeans, which are the mainstay of Asian diets, contain phytoestrogens. These are very weak estrogens, which can compete with and blunt the effect of normal estrogen. In the process, soybean products have been shown to reduce cancer risk. In summary then, vegetarian women have lower levels of blood estrogens which lowers the risk of breast cancer. "Vegetarians have lower levels of blood estrogens. This lower s the risk of breast cancer." Puberty Aside from estrogen, dietary factors can also affect menstrual cycles. Menstrual cycles of vegetarians are not only different from those of meat eaters, but they also begin later in life. According to the World Health Organization, the average age of puberty in girls in western countries in 1840 was about 17 years. Today, we take it as a matter of course that girls will have reached puberty at the age of 11 or 12 years. About 150 years ago, high fat diets were limited to a small, wealthy portion of the population. Today, high fat diets have spread to the entire population. At the same time, puberty has occurred earlier and earlier possibly due to the estrogen increase caused by high fat diets. Earlier puberty and higher breast cancer risks go handinhand. Later puberty, then, would be a major advantage. China Diet Study Dr. T. Colin Campbell of Cornell University in his massive China Diet Study discovered that within the country of China the lower the fat content and the stricter the vegetarian lifestyle, the lower the estrogen levels and the later the onset of puberty. In addition, he also found a virtual absence of coronary heart disease, osteoporosis, obesity and very low rates of western adult cancers among those population groups that lived on a very simple, very low fat diet with meat being used only on special feast days. Simple diets seem to keep the blood estrogen levels lower and with that puberty is not accelerated. In addition, research has shown that the menstrual cycle can be changed in its length. In Asian countries, for instance, women have longer menstrual cycles; this means more days elapse between periods. Those longer menstrual cycles in turn are important in that a woman over her lifetime will be exposed to less estrogen, which is linked to lower breast cancer risk. In short: the higher the fat intake, the shorter the menstrual cycle, the higher the estrogen exposure, the higher the risk for breast cancer. COLON CANCER Dietary changes can reduce the risk of colon cancer. The famous Irish surgeon, Dr. Denis Burkitt, with whom I worked for 5 years, observed that the type and number of bacteria in the colon was influenced by the type of food eaten, This, in turn, greatly influenced the stool volume. He found that high fat diets not only increased the amount of certain bile salts in the intestinal tract, but they also increased the number of intestinal bacteria, which in turn, converted these bile salts into cocarcinogenic substances in the colon. On the other hand, the less fat eaten, the fewer bile salts were produced and the fewer were converted into carcinogens. In addition, Dr. Burkitt noticed that diets high in fiber not only created larger stool volumes, which diluted the concentration of bile salts and carcinogens in the colon, but high fiber diets also drastically reduced the transit time of the stool and thus the contact time of the carcinogens with the colon membranes. In his experiments in Africa Dr. Burkitt noticed that the high fiber foods eaten in Africa would take some 20 to 30 hours to pass through the intestinal tract. But when he repeated his experiment with people in England, he found that on an English diet – very low in fiber and high in fat – the food actually needed 80 to 100 hours to pass through the intestinal tract. It seems obvious now: High concentrations of cocarcinogenic bile salts, largely due to high fat diets, sitting for several days in the colon, largely due to a low fiber diet, may have an irritating effect on the colon membranes. This may be involved in the initiation or promotion of colon cancer. In 1971, Dr. Denis Burkitt proposed that very idea. He suggested that the enormous difference in colon cancer rates in various geographic areas may largely be explained by critical differences in the intake of fat and fiber. Diets high in fat and low in fiber promote cancer of the colon; diets low in fat and high in fiber protect against it. If a very low fat, high fiber vegetarian diet – which is also very high in protective substances such as phytoestrogens and phytochemicals – could protect against certain cancers, could such a diet also affect the survival of patients who already have cancer? While the evidence is somewhat sketchy, there’s good reason to believe that foods may play a favorable role in the outcome. It has to do with the immune system. Substantial scientific evidence shows that certain foods can enhance the immune function while other foods can impair it. For instance, natural killer cells are specialized white blood cells that seek out and destroy cancer cells in the body. Vegetarians, according to a recent German study, have more than twice the natural killer cell activity than is found in meat eaters. This suggests that vegetarians may have much more power to kill cancer or to keep cancer in check. The greater immune strength of a vegetarian diet probably comes directly from its usually low fat content and from its richness in phytochemicals and other nutrients that enhance the immune system. Recently, a study of 122,000 American nurses found that those women who ate meat daily were 25 times more likely to develop colorectal cancer than those women who ate meat less than once a month! "Diets high in fat and low in fiber promote colon cancer. Diets low in fat and high in fiber protect against it." – Plantbased diets are rich in a variety of fibers, while animalbased diets have none; – In the China Diet Study: the more fiber eaten, the lower the rates of bowel cancer. PROSTATE CANCER Similar relationships exist with prostate cancer. Interestingly enough, early prostate cancer is just as common in Japan as it is in the United States. However, prostate cancer in Japanese men grows much slower so that it rarely poses a lifethreatening event. Their tumors are much less likely to grow into full blown cancer - and once again, diet may play the big role in that high fiber intakes decrease the risk of prostate cancer while high fat intakes increase the risk. This is particularly true for animal fats. "Prostate Cancers in Japan grow so slowly that they rarely pose a lifethreatening event." Optimal Anti-Cancer Diet Asound anticancer diet should be very low in fat and contain little, if any, animal protein. At the same time, an optimal anticancer diet should be high in fiber and phytochemicals. These are compounds in plants that have no nutritional value but they can have important biological effects that may lower the risk for cancer, heart disease and other diseases. Hundreds of these phytochemicals have only been discovered during the last 10 years. Since they’re only found in plantfoods, vegetarians have much higher intakes of these compounds than meat eaters. Many plant pigments, for instance, that give fruits and vegetables their bright colors, are phytochemicals that also give protection against cancer. More than 100 studies of eating habits throughout the world show that fruits and vegetables decrease cancer risk. That’s why the National Cancer Institute has advised Americans to eat more fruits and vegetables, at least five servings a day. "Fruits and vegetables decrease cancer risk." Will be continued
Contact: Hans Diehl, Lifestyle Medicine, Institute, P.O. Box 474, Loma Linda, CA 92354-0474.
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