SCIENCE 101

Selenium is an essential dietary mineral and antioxidant (an agent that helps quench or neutralize free-radical chemicals that cause cell damage and can lead to chronic diseases, such as cancer). A selenium deficiency can make you more vulnerable to viruses, cancer, even "down" moods and low energy. But it's poisonous in high doses.

TAKE A PILL?

As insurance against deficiency, some experts, such as Donald J. Lisk of Cornell University, have long taken 100-200 micrograms of selenium daily. There is no downside, Lisk says, and there could be a lot of benefit.

HOW TOXIC?

Lisk puts the toxic dose at 2,500mcg daily. Symptoms linked to poisoning: nausea, garlicky breath, flulike symptoms, loss of hair, neurological problems, respiratory failure and liver damage. Stick to 200mcg daily; there's no reason to take more.

SUPER SOURCES

-- Brazil nuts: For a super source of selenium, you can't beat Brazil nuts, especially those bought in the shell. One unshelled Brazil nut, which you crack yourself, averages 100mcg, says Cornell's Donald J. Lisk. A shelled nut, found in health food stores, averages 12-25mcg.

-- Garlic: Some researchers suspect a prime reason garlic blocks cancer in animals is its high selenium content. Cornell's Lisk finds that high-selenium garlic (grown in selenium-rich soil) is 60 percent more effective against cancer in animals than low-selenium garlic.

4 WAYS SELENIUM MAY PROTECT YOU

Prevents cancer: After several years of tantalizing evidence that selenium might prevent cancer, a groundbreaking new study seems to confirm it. Physician Larry Clark, of the University of Arizona, found that a modest dose of a selenium supplement reduced overall cancer incidence by a remarkable 42 percent. Further, taking selenium slashed cancer death rates in half.

Clark's randomized double-blind study (the "gold standard" in medical research) followed 1,312 older people with common skin cancer an average of seven years. Half took 200 micrograms of selenium daily; the others took a placebo (inactive pill).

Clark had expected selenium to block the recurrence of skin cancers. Oddly, it did not. But to his surprise, he began to notice a striking drop in other cancers. His final analysis shows taking selenium slashed the occurrence of prostate cancer by 69 percent, colorectal cancer by 64 percent and lung cancer by 39 percent. The new finding is unprecedented -- the first real scientific proof of any nutrient's power to prevent cancer in humans.

Note: Clark saw no signs of toxicity from the selenium supplement, a type readily available in drugstores and health food stores called selenomethionine, derived from yeast. The daily dose of 200mcg is about three times the recommended daily value and five times what most Americans consume. Whether selenium is effective against women's cancers (breast or ovarian) is unknown, because few women were in the study. Clark now plans a larger study of mostly women.

Polices viruses: A lack of selenium may allow viruses to run rampant in your body, according to recent research at the U.S. Department of Agriculture. In mice raised on diets deficient in selenium, a normally harmless virus mutated into a virulent one, inflicting serious damage on heart muscle. "It was a viral transformation from Dr. Jekyll to Mr. Hyde," says the USDA's Orville A. Levander. Selenium may help curb various viruses, from colds to AIDS. Some researchers believe a selenium deficiency helps trigger the spread of the AIDS virus in the body.

Lifts mood: A lack of selenium can sap your energy, feed your anxiety and put you in the doldrums, says USDA psychologist James G. Penland. Penland found that men who boosted their intake of dietary selenium to 220mcg daily felt less anxious and more energetic, confident and agreeable. Those with the most selenium in their red blood cells felt the best. Men who initially felt the worst improved the most. Welsh researchers documented the same mood lift in a double-blind study of men and women after taking 100mcg of a selenium supplement daily.

Interestingly, Penland found selenium triggered dramatic improvement in men who showed no signs of selenium deficiency. His conclusion: Many Americans are not getting enough selenium for peak well-being, but don't know it.

Boosts Immunity: In a double-blind study of elderly people, researchers at the University of Brussels in Belgium found that taking 100mcg of selenium a day improved certain factors in immune functioning by 79 percent. One reason: The body needs selenium in order to produce a critical antioxidant enzyme, glutathione peroxidase. The enzyme helps detoxify cellular fats that otherwise lower immunity, foster cancer and destroy arteries.

Whether selenium helps prevent heart disease is unclear. Some studies suggest that it does, but a recent Harvard University study found no link between blood levels of selenium and heart attacks in men.

TO GET THE MOST

At the Supermarket: Foods high in selenium are whole grains, sunflower seeds, nuts, garlic, meat and seafood, especially swordfish, tuna and oysters.

Nutty, Garlicky Spaghetti

4 ounces spaghetti

3 Tbs. extra virgin olive oil or macadamia nut oil

2 large garlic cloves, crushed or minced

1/2 cup chopped parsley

1/2 cup sliced black olives

2 Tbs. capers (optional)

2 1/2 ounces Brazil nuts, coarsely ground in a blender

Salt and freshly ground pepper, to taste

While pasta is cooking, brown garlic in oil over medium heat. Add warm oil to drained pasta. Stir in parsley, olives, capers, half the ground nuts, salt and pepper. Transfer to plates and top with remaining ground nuts. (Note: The ground nuts have the appearance and texture of grated Parmesan cheese.) Serves 4 as an appetizer.

Per serving: 336 calories, 6.5g protein, 25.7g carbohydrates, 3.7g fiber, 24.5g fat (4.5g saturated, 13g monounsaturated), 152mg sodium.

Swordfish Sandwich

1 swordfish steak (4-5 ounces)

4 slices whole-wheat bread

2 Tbs. low-fat mayonnaise mixed with 1/2 tsp. cumin

1/2 medium avocado, sliced

2 thin slices red onion

2 large pieces Romaine lettuce, washed and trimmed

2 slices tomato

Cut steak in half; from flesh side, slice each half horizontally, folding it over into a butterfly shape. Saute fish in hot non-stick skillet sprayed with canola or olive oil for 2 minutes on each side or until done. Cut away fish skin and discard. Spread bread with mayonnaise. Add fish and other ingredients. Makes 2 sandwiches.