Mother, Naturally, Was Right : Diet: What we eat provides a first line of defense against many cancers. Fear not the’killer broccoli.’

The “Revenge of the Killer Tomatoes” may sound like the name of a cult, but it’s really a specter haunting our supermarkets today. Deadly cabbage? Poisonous broccoli?

Poppycock! Sure, some naturally occurring compounds extracted from cabbage and broccoli cause cancer in test animals. But people do not eat these extracts alone. Rather, we eat whole foods that contain lots of good things that fight cancer--anti-carcinogens.

No one would dispute the fact that what our species has ingested is what we beget. We have been eating as long as we have been evolving. Lactose tolerance is greatest in people living in regions that have consumed dairy products for the longest time. Several million years of evolution from our omnivorous hominid ancestors may well have conferred upon us some resistance to longstanding, naturally occurring carcinogens, such as those studied in broccoli. We have no such genetic experience with new synthetic organic materials.

What people eat provides a first line of defense against many cancers. Beta-carotene, the stuff that makes carrots orange and is the precursor for vitamin A, protects against lung cancer, caused mostly by smoking. Recent studies have found that smokers have lower levels of beta-carotene in their blood, even if their consumption is the same as a nonsmoker’s, suggesting that smoking itself may reduce blood carotene.

Orangeness is not the only trait of food that may protect against cancer, according to several recent studies. People of China’s Shanxi Province who routinely eat garlic and onions have much lower rates of stomach cancer. In Hawaii, those whose diets include lots of vegetables have significantly lower rates of lung cancer, while in Japan green-tea drinkers have lowerstomach cancer rates.

Studies with some naturally occurring compounds demonstrate the wisdom of eating your fruits and vegetables. Far from being a harbinger of destruction, broccoli contains lots of good materials, including anti-oxidant vitamins, fiber and a compound called phenethylisothiocyanate (PEITC). It prevents the most toxic material ever found in tobacco smoke from attacking DNA, and can snuff out or reverse the growth of tumors in animals. Ellagic acid, found in many fruits, such as strawberries, also inhibits cancer growth by blocking nasty compounds within cells.

Numerous foods and condiments inhibit the growth of tumors in animals and are linked with lower risks for some human cancers. Parsley, sage, rosemary and thyme not only made a great song, but they prevent some toxic molds from growing. Mice on a diet deficient in vitamin E contracted more colon tumors when exposed to a cancer-causing compound than did those on a diet high in this vitamin. Garlic and onions, turmeric (a common spice in Indian cooking), capsaicin (extracted from hot peppers), cumin, clove, caraway and seafood all contain substances shown to reduce the effect of cancer-causing agents and provide a number of other health benefits.

The long list of good things in vegetables and fruit may well explain why vegetarians have lower overall rates of cancer. As populations change their eating habits to include more foods that contain anti-carcinogens, their patterns of cancer may change. In the United States, Britain, West Germany and most of the other industrialized countries, stomach cancer rates are dropping rapidly. This decline may reflect improved handling and preservation of food, reduced use of salts and year-round consumption of green and yellow vegetables and fruits that contain potent anti-carcinogenic compounds and fiber.

In many industrial countries, this continuing decline in stomach cancer is accompanied by increases in a number of cancers not associated with cigarette smoking, including bone and brain cancer. From 1950 to 1986, according to the National Cancer Institute, new cancer cases (minus lung cancer and adjusted for aging of the population) rose by 27%. New cases of childhood cancer rose more than 20% during this same time, despite impressive improvements in treatment for this disease. The causes of these troubling trends are not likely to rest with killer broccoli and its ilk, or with major changes in our food patterns or changes in methods of diagnosis. Cancers that have continued to increase over the past two decades are likely to reflect changes in our modern life that have not been adequately studied or identified.