Few if any nutritional classes are incorporated into mainstream medical education. A typical physician out of training probably learns more about eating healthfully to prevent disease from television shows, magazines, newspapers, and infomercials than from a typical medical curriculum. Public interest is high in alternative ways to ward off disease. Most physicians know little about the scientific literature surrounding nutrition and cancer. Most patients who think they know about nutrition and cancer from popular health books lack the knowledge about scientific nutrition literature.

Moreover, in comparing an oncologist and alternative nutrition specialist, neither has really extensively studied mainstream nutrition articles. There is much conflicting data about which alternative therapy does work best for which disease process. A lot of alternative therapy claims are based on anecdotal evidence rather than hard scientific evidence. Hard scientific evidence is based on data derived from comparing two therapies in two equal patient populations. The most intriguing studies are usually presented with much caution and surrounded by many legitimate countervailing findings. It is difficult for anyone to sort out the bottom line from these findings. In essence, studies done by different researchers fail to complement each other.

Critics of the alternative therapies suggest proponents offer medical advice without definite evidence. The fact is, no one knows exactly which food, in which proportions offer the best protection against any particular malignancy. Nor does anyone know which among the myriad chemicals present in an onion or a cube of tofu, can prevent a cell from becoming cancerous. Answering these questions correctly, will take decades of intensive research. Scientists are in the continuous process of discovering specific ways fruits and vegetables provide protection against cancer. It is easy to get confused by breaking news stories publicized by the media to get your attention. These stories should be placed in the proper context or big picture.

There are some mainstream recommendations about diet, nutrition, and cancer adopted by the National Academy of Sciences, National Research Council, The American Cancer Society, and The National Cancer Institute. Some Practical Guidelines from the National Academy of Science's National Research Council are:

1. High fat consumption is linked to increased incidence of certain cancers, notably breast and colon. Foods high in saturated fats such as meat, cheese, lard, and butter should be limited. These fats can promote heart disease as well. In Asia where diets are lower in saturated fat, it is not surprising that the incidence of breast and colon cancer is lower. An appropriate practical target is to reduce the intake of fat to about 30% of total calories.

2. Incorporate fruits, vegetables, and whole grain cereal products in the daily diet. In epidemiological studies, frequent consumption of these foods has been inversely correlated with the incidence of various cancers. Eat more citrus fruits, cruciferous vegetables (cauliflower, cabbage, and broccoli), and those that are carotene rich (yams, squash, and carrots).

3. Limit the consumption of salt-cured and smoked foods. i.e. salt-pickled foods, cured meats (ham and bacon), and beef jerky. High incidence of stomach and esophageal cancers have been found in countries, such as China, Japan, and Iceland, where people have diets high in these foods.

4. Intentional additives (direct and indirect) should be more extensively evaluated for carcinogenic activity before they are approved for use in the food supply.

5. Excessive consumption of alcoholic beverages, particularly combined with cigarette smoking, are associated with an increased risk of gastrointestinal and respiratory tract infections.

Some guidelines from the National Cancer Institute:

1. Reduce fat to 30% of total daily calories or less.

2. Increase fiber intake to 20 to 30 gm/day, with an upper limit of 35 gm/day.

3. Include a variety of vegetables and fruits in the daily diet.

4. Avoid obesity.

5. Consume alcoholic beverages in moderation, if at all.

6. Minimize consumption of salt-cured, salt-pickled, and smoked foods.

In the next part, we will look at how certain chemicals in specific foods can either promote or inhibit the growth of cancerous cells.

Ryan K. Lee is a physician specializing in Obstetrics and Gynecology. He is currently in private practice in Glendale and Los Angeles, California.