by Elyse M. Rogers
Diet, Nutrition and Cancer
In June 1980, The National Cancer Institute (NCI) com-missioned the National Research Council (NRC) to study the relationship of diet and cancer. As interesting background information, the National Research Council was established by the prestigious National Academy of Science way back in 1916 “. . . to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and of advising the federal government.”
Just recently, the printed report, Diet, Nutrition and Cancer, was published—a tome of more than 300 pages—and I bought a copy. The report contains a great deal of valuable information about the relationship between diet and cancer.
What is perhaps as significant as the research data is that the researchers made some recommendations, despite the fact that the scientific evidence is sometimes more suggested than actual. Specific cause/ effect relationships are seldom seen, mostly because it’s scientifically impossible to document aspects of diet. An average diet is composed of a myriad of substances that are combined in different ways during different days and weeks.
As if that didn’t make it difficult enough, there are individual physiological variances that obviously affect the role that any substance plays on body cells and functions. But despite all this, there is solid evidence that different overall diets do affect cancer rates. As I mentioned previously, the most startling evidence that diet (and other lifestyle measures) influences cancer rates is shown by studies with the Seventh Day Adventists. This religious group doesn’t drink, smoke, use beverages containing caffeine and promotes a vegetarian-type diet. Their rates for all types of cancer is significantly lower than other members of the American community.
One interesting part of the introduction of the report is the explanation as to why specific recommendations are included— “. . . the public often demands certain kinds of information before such information can be provided with complete certainty.” It goes on — “… scientists must be especially careful in their choice of words whenever they are not totally confident about their conclusions.”
As a medical and science writer, I know only too well how cautious one must be of saying that any evidence is “absolute.” For instance, even though there is significant evidence that a diet high in cholesterol contributes to coronary artery disease, as a writer I must be careful to explain that “scientific evidence suggests,” or that “some cause/ effect relationship has been discovered.”
In support of their giving recommendations prior to scientific certainty, the report refers to the unhappy experience of the smoking/cancer link. “. . . it has become absolutely clear that cigarettes are the cause of approximately one-quarter of all the fatal cancers in the United States. If the population had been persuaded to stop smoking when the association with lung cancer was first reported, these cancer deaths would not now be occurring.”
The message is clear—scientists have an obligation to suggest measures even when total proof is lacking; an individual has the option of deciding for himself with those facts or “almost facts.” There are still heavy smokers around, despite all the scientific data available.
I’ll be covering specific aspects of the report in month detail in future columns, but-right now I’d like to share with you the six general recommendations of the National Research Council. Remember, these are only guidelines, as the evidence is still not “for sure.” Many of the dietary suggestions will be “old news” to some of you, but they remain important. Some may hold a surprise or two. I’m condensing them, but will keep the wording and context whenever possible.
- “There is sufficient evidence that high fat consumption is linked to increased incidence of certain common cancers (notably breast and colon cancer). . . .” The recommendation is for the reduction of fat intake from the current 40% of the diet “to 30% or less.”
- “The committee emphasizes the importance of including fruits, vegetables and whole grain cereal products in the daily diet.”
- “In some parts of the world, especially China, Japan and Iceland, populations that frequently consume salt-cured (including salt-pickled) or smoked foods have a greater incidence of cancers at some sites, especially the esophagus and the stomach.” (Remember, we’ve discussed watching total salt intake in the diet.)
- “Certain non-nutritive constituents of foods, whether naturally occurring or introduced inadvertently (as contaminents) . . . pose a potential risk of cancer to humans.” The committee also suggests that all intentional additives continue to be evaluated before being approved for use.
- Supports “. . . further efforts to identify mutagens in food and . . . for identifying carcinogens.”
- Notes that “. . . Excessive consumption of alcoholic beverages, particularly combined with cigarette smoking, has been associated with an increased risk of cancer of the upper gastrointestinal and respiratory tracts.” The committee suggests that if you drink, you do so in moderation.