Beta-carotene, a rather amazing nutrient, is found in carrots, spinach and other common foods. And it just may prevent some cancers.
VOLUNTEERS WANTED: 200,000 doctors needed to further test beta-carotene as a protection against cancer. Doctors, you have only to take a 30-milligram beta-carotene capsule every other day: a small price to pay for cancer prevention.
Why have the researchers at Harvard Medical School made this request? Because the evidence continues to mount and continues to impress. There is something very healthful in beta-carotene, a rather amazing nutrient found naturally in certain vegetables and fruits. Beta-carotene is a cancer fighter or inhibitor, and the ramifications of this fact are beginning to cause excitement throughout the world of American medicine.
Indeed, there currently are 324 research studies on file with the National Cancer Institute at Bethesda, Md. These establish, rather clearly, that when most people follow diets rich in beta carotene a chemical found in carrots, dark green leafy vegetables, deep orange winter squash and yams, apricots, cantaloupes and peaches there is a blocking or inhibition of certain types of cancer, including lung cancer and even in people who smoke cigarettes.
This is especially good news to oncologists, doctors who treat cancer victims. For in 1982 alone, lung cancer will kill more than 110,000. This is the most virulent of all cancers; more than 90 percent of those who contract it are dead within five years. Currently, lung cancer is the No. 1 killer of men, and the speculation is that, sometime in the 1980’s, it will become the No. 1 killer of women as well. The reason? More women are smoking, and with the introduction of low-tar cigarettes, they are smoking more.
Now, in a major new research effort, scientists at Harvard are asking 200,000 male doctors to take part in a federally funded, $3.7 million, five-year study that may help to determine whether the risk of some cancers can be effectively thwarted by beta-carotene. The project’s principal investigator, Dr. Charles H. Hennekens, said the call went out to physicians “because of their ability to assess medical evidence and, provide reliable information on any illness [complication] that may develop.”
Some doctors already are getting their beta-carotene. Dr. Lewis Clayton, medical director of the American Lung Association, says, “I eat so many vegetables, especially carrots, I keep looking at my skin to see if it has turned yellow.”
Dr. Clayton is not a vegetarian; he is merely following good health habits, and for him that also means being a nonsmoker. He adds: “We don’t know how beta-carotene helps protect the body against lung cancer. There are many questions that need to be answered by further research. However, there is sufficient evidence to recommend that everyone, especially cigarette smokers, increase consumption of foods rich in beta-carotene.”
For the people so hooked on nicotine that they can’t quit, increasing the intake of carotene, according to Dr. Clayton, may be a simple, inexpensive way of perhaps offsetting one of the many serious risks of cigarettes.
WHAT IS BETA-CAROTENE?
Just what is this nutrient, beta-carotene? It is the most common and powerful form of carotene, the name given several hydrocarbon pigments. Further, carotene got its name because it was first identified in carrots. A chemical action in the body converts it into vitamin A.
Vitamin A., then, has naturally figured into the research and debate over beta-carotene and cancer, but it does not belong to the group of chemicals known as carotenoids, as do carotene and betacarotene. Vitamin A found in some fruits and vegetables and also in animal products such as milk, eggs and liver-is essential for the health of tissues called the epithelium, the cells that coat the body’s inner and outer surfaces.
CAROTENE & CANCER RESEARCH
Several recent studies have dealt with carotene and lung cancer. A notable one was headed by Dr. Richard Shekelle, director of epidemiology and bio-statistics at Rush-Presbyterian-St. Luke’s Medical Center in Chicago. He and his colleagues took data gathered about the dietary habits of almost 2,000 middle-aged male employees of Western Electric Company in Chicago and related eating patterns to medical histories over a 19-year period. Of 488 men whose diets were high in carotene, only two developed lung cancers compared with 14 in the low-carotene group.
Other research would seem co substantiate the Western Electric investigation. The largest study to date involved 8,000 Norwegian men who responded to questionnaires about their smoking and dietary habits over a five-year period. Dr. Eric Bjelke, the principal investigator, of the Norwegian Cancer Registry in Oslo, found that low consumption of vegetables was linked with a high rate of lung cancer.
And in a study of the dietary habits of over a quarter-million Japanese, Dr. Takeshi Hirayama found that risk of lung cancer was reduced by half in subjects who ate green or yellow vegetables daily, compared with those who ate them less frequently. Dr. Hirayama is chief epidemiologist of the Nation Cancer Research Center in Tokyo.
These epidemiological studies that is, studies of the incidence and distribution of disease in a population are, by their very nature, open to criticism. There are just too many factors beyond the control of researchers. In contrast, variables are easily controlled in animal experiments. To clear up some of the, unavoidably murky conclusions, there have been to date a number of studies testing beta-carotene on cancers induced by chemicals in laboratory animals. In
every instance, a protective effect was found.
Still, many question the carotene-cancer connection. For example, Dr. Philip White, director of the Department of Food and Nutrition of the American Medical Association, concedes that the carotene research is promising. But he insists that “it is premature to jump to the conclusion that increasing carotene consumption will prevent cancer.” His statement serves to underline others’ belief that the procarotene evidence needs further substantiation.
Asked if he eats lots of carotene-rich vegetables, Dr. White replied, “I always have.” His reason is that they are essential to a well-balanced diet, not that he hopes to fend off cancer.
Excessive amounts of carotene can cause carotendermia, an otherwise harmless condition characterized by yellowing skin. Fortunately, the yellow color soon disappears when carotene intake is curtailed. Toxicity tests on laboratory animals and humans show that, even in large doses, carotene has no serious adverse side effects. This is because it is converted to vitamin A only as the body requires it and, unlike vitamin A, doesn’t accumulate in the liver. In large doses, vitamin A can be highly toxic, causing, among other things, severe liver damage.
Because beta-carotene has shown evidence of being a cancer inhibitor, scientists are also seeking to determine whether vitamin A might help halt cancer. In the opinion of Dr. Michael B. Sporn, chief of the Laboratory of Chemoprevention at the National Cancer Institute: “People should not rush out and buy vitamin A in the hope of preventing cancer. The vitamin A available over-the-counter is not effective in this way.”
Involved in intensive research on vitamin A and synthetic substances that are similar, Dr. Sporn has recently reported considerable success in preventing as well as arresting or reversing the development of malignant cells in animals. He has observed that, conversely, experimental animals deficient in vitamin A have an increased susceptibility to chemically induced cancers. Still, he points out that his research “… is not like proving that a vaccine works. It is much more complicated.”
The doctors in the Harvard study will be taking large doses of beta-carotene in capsules. The nutrient has been available in this form for a while, for use in treating a rare disorder involving sensitivity to sunlight. Does this mean we should all run out and buy betacarotene pills*?
Dr. James Moore of Purdue University predicts that there may indeed be a rush to market the nutrient as a “cancer preventive” in drug and health-food stores. However, most doctors advise those who want to increase their intake of beta-carotene to turn to natural food sources instead.
Until medicine has a fuller understanding of the disease, the average consumer will persist in looking for ways to minimize the cancer risk. The question becomes: How can anyone be sure that he or she is eating enough carotene to stay healthy? Dr. Shekelle recommends that everyone eat one or two servings of fruits and vegetables high in carotene. Each serving (of one-third to one-half cup) ideally should be eaten with a little butter or with a meal otherwise containing some animal oil, which aids in absorption of the nutrient.
Even if carotene doesn’t turn out to be the “miracle nutrient” researchers and
inveterate cigarette smokers hope for, there are other good reasons for eating fruits and vegetables rich in carotene:
- They supply minerals and other vitamins, especially C and B-complex indispensable to maintaining health and fending off infection and disease.
- Along with other foods high in fiber, they act as “nature’s broom,” aiding in digestion and elimination. Recent medical research; suggests they may also reduce the risk of colon and rectal cancer and may lower cholesterol levels.
- They aid in weight loss, as they are low in calories and high in nutrients.
- They are vital as a source of vitamin A. In adults, the most common sign of vitamin A deficiency is a strong reaction to glare along with night blindness. Without adequate vitamin A, nails peel, split or become ridged; hair loses its luster and becomes dry and brittle; skin becomes blemished, dry or prematurely wrinkled. In children, vitamin A deficiency shows up in retarded growth, impaired development of bones and teeth, mucous membrane disorders, increased susceptibility to infection and, in severe deficiencies, xerophthalmia a disease that, unchecked, leads to blindness.
While further confirmation of the anti-cancer effect of carotene is required, a carotene-rich diet can’t hurt. It possibly could help a great deal.
*Reprinted from Family Circle, July 1982