Scientists know that phytochemicals increase our resistance to disease and boost immunity. What scientists don't know is why phytochemicals seem to lose their disease-fighting powers when they are isolated from the 'host" plant. Maybe it's their interaction that gives them power, Or maybe "squashing" a serving of broccoli into a pill results in some phytochemical destruction. Regardless, it has become clear that "whole foods" contain the protective power; phytochemical pills do not

So, until we know more about supplemental phytochemicals, let's go with whole foods. Here's a fist of the best and brightest fruits and vegetables, complete with the phytochemicals that make them so essential to our good health.

CABBAGE

A close relative of broccoli, cabbage contains a long list of phytochemicals. Among the most beneficial are the indoles. These show promise as cancer- fighters because they block the conversion of the sex hormones into a more potent cancer-causing form. Since indoles aren't damaged by cooking, chop up a bunch of cabbage with other vegetables for a tasty, phytochemical-filled stew. Use cabbage raw in coleslaw (with fat- free mayonnaise, of course) or as a grated topping for tacos.

CELERY

This lowly vegetable has suffered from bad PR for years. Okay, we knew it contained fiber and potassium, and we occasionally threw some peanut butter on it. But isn't it always the last vegetable left whenever there's a vegetable-dip platter?

Time for a reassessment: Celery is packed with phytochemicals, most notably 3-n-butyl phthalide. Following treatment with this potent phytochemical, blood pressure dropped over 10 percent in hypertensive laboratory animals. Researchers theorize that this phytochemical may help regulate those hormones in the body that trigger high blood pressure in some people. Which is not to say you should replace your blood pressure medication with several stalks of celery each day. Instead, get in the habit of cutting up a stalk or two every time you stir- fry vegetables or heat some soup. Or, what the heck, where's the peanut butter?

FLAXSEED

The tiny, flat, brown-black seed of the flax plant is one of the world' s richest sources of lignin. So what you say? Simply this: After it is modified slightly by intestinal bacteria, lignin goes into the bloodstream. There it interferes with estrogen synthesis, which in turn may reduce the risk of breast and ovarian cancer. You can buy flaxseed in bulk at your local health food store. Use it as a topping for cereals, casseroles and thick soups. However you use it, you'll also be getting an excellent source of fiber and heart-healthy omega- 3 fatty acids.

HOT PEPPERS

They're loaded with vitamin C, yet hot peppers also contain the phytochemical capsaicin, which is what puts the "hot' in hot peppers. Better yet, capsaicin shows promise as a neutralizer of known carcinogenic bad guys such as nitrosamines. These form in the stomach from nitrates found in processed meats. Capsaicin also protect us against stomach ulcers by killing the bacteria partly responsible for ulcer formation.

Time for a hot 'n' healthy "phyto-salsa" chip dip? Blend together fresh tomatoes, onions and hot peppers--and it's yours.

KALE

A true phytochemical heavyweight, leafy green kale contains lutein and zeaxanthin, two carotenoids with Powerful antioxidant properties. Lutein and zeaxanthin also happen to be the main pigments in part of the eye called the macula. Research shows that people with diets rich in lutein and zeaxanthin are at a lower risk for degeneration of the macula, which is the leading cause of blindness in older adults. Kale also contains sulforaphane, a phytochemical (also found in large amounts in broccoli) with known cancer-fighting properties. Some people find raw kale too bitter, but you'll like it in soups and stir-fries or as a cooked side dish. Note: Cooking destroys very little of the carotenoids and leaves sulforaphane completely intact.

LEMONS

Like limes and other citrus fruits, lemons contain monoterpenes. These phytochemicals do some fancy (and fortunate) footwork against carcinogens, or cancer-causing agents. When a carcinogen (typically from food, air or smoke) invades a cell, monoterpenes essentially take that carcinogen back out of the cell before the cell can become cancerous. Lemons come with many other phytochemicals besides, so this summer be sure to squeeze your own tart and, tangy lemonade, or add some real lemon to the store-bought kind. Or use the zest (grated skin) of the lemon in salads, seafood and stir-fries.

ONIONS

Onions contain some 50 different phytochemicals. The best of the lot may be the allylic sulfides, a group of cancer-fighting phytochemicals. These substances bolster a cell's defense system so the cell can more readily detoxify incoming carcinogens. The proof comes from research in China, where high onion consumption is linked with lower stomach cancer rates. And don't worry, you don't have to eat them raw to get their disease-fighting benefits. Cooking does not destroy allylic sulfides.

SOYBEANS

Studies show that a soybean-rich diet may Protect You against cardiovascular disease and cancer. The soybean secret? Isoflavones. Chemically very similar to the female and male hormones estrogen and testosterone, isoflavones bind to sites on cells. There they block the action of estrogen and testosterone in the development of cancer. (Breast and prostate cancer are both considered "hormone sensitive"; estrogen, for example, is known to promote the growth of breast cancer.) Population studies from Asia clearly show that diets high in soybeans can virtually wipe out the threat of certain cancers.

Isoflavones also help lower total cholesterol while raising "good" HDL levels. And because of their estrogenlike activity, isoflavones slow the bone-mineral loss that occurs in postmenopausal women. Isoflavones also help lessen menopausal symptoms such as hot flashes and mood swings caused by declining estrogen levels. A caveat: researchers know that soybeans benefit those who eat low-fat diets, but they don' t know if these benefits hold for those who eat high-fat diets.

STRAWBERRIES

This delicious fruit contains ellagic acid, a proven cancer-fighter. Through several mechanisms, this phytochemical protects the body's genetic material from damage by carcinogens. As we know, strawberries make great toppings for cereal and yogurt and are excellent as the main ingredient in a refreshing smoothie. Since ellagic acid is highly resistant to extreme temperature changes, it won't break down when you freeze or cook strawberries.

TOMATOES

Men, this one's for you. According to a new study from Harvard Medical School, regular intake of tomatoes and tomato-based products may cut your risk of prostate cancer. Lycopene, the phytochemical that gives tomatoes their red color, appears responsible for this cancer protection. Lycopene is a carotenoid. Carotenoids are present in the blood and tissues throughout the body, where they act as antioxidants. And here' s the point lycopene happens to be the most abundant carotenoid in the prostate. Considering that one in nine men will get prostate cancer, I'd say it's time to boost your intake of tomatoes. Fresh. Cooked. On pizza. In spaghetti sauce. Tomato dishes are tasty, fun and possibly life-extending as well.

WATERCRESS

This delicate, leafy green vegetable may not be familiar to you, but maybe this'll help: it's the green that comes in those little whitebread tea sandwiches without the crust. Watercress may be delicate, but its dietary impact is anything but. It contains a powerful phytochemical called isothiocyanate. Studies show that when animals are fed watercress- rich diets, their risk of developing lung tumors when exposed to tobacco carcinogens is cut in half. Whether watercress benefits human smokers in the same way is not clear, but studies are underway. We can reasonably conclude that isothiocyanate will provide some degree of cancer protection. Use fresh watercress in salads or broth soups. Or go ahead and make yourself a crustless watercress sandwich.

COPYRIGHT 1996 Rodale Press Inc.