safe as you think: Cooked ones can make you sick, too.

The dangers of raw oysters are well known. They may carry dangerous bacteria that only cooking will kill.

But now health experts are learning that bacteria are not the only problem.

Oysters also can shelter viruses that cause the stomach flu. And ordinary cooking does not kill them.

Testing oysters for bacteria, as is commonly done in coastal states, is no guarantee, because viruses do not show up in these tests.

"There is no way of telling whether oysters are infected,'' said Dr. Kathy Kirkland of Duke University.

Kirkland and Dr. Sharon McDonnell of the Centers for Disease Control and Prevention presented separate reports on recent outbreaks of digestive ills caused by cooked oysters. They spoke Wednesday at an infectious-disease conference sponsored by the American Society for Microbiology.

The culprit is a class of microbes called Norwalk-like viruses. They are spread through fecal contamination and cause vomiting and other intestinal ills. These viruses are the leading cause of shellfish-associated illness in the United States. Just how many get sick is not known.

Health experts blame boaters for the problem. They say people dump their waste over the side, and the shellfish absorb it.

Clare Vanderbeek of the National Fisheries Institute said the problem is rare but real.

"There will be areas where these kinds of things happen,'' she said. "The industry is working with government to strengthen testing and regulation of waters. Consumers just have to be very, very careful. If they are concerned, they should not eat the product.'' McDonnell investigated outbreaks of oyster-related illness in northern Florida and Georgia last New Year's. She found 140 people who got sick after eating oysters at 38 holiday parties. Symptoms typically lasted two days, but some people were ill for up to two weeks.

The illness was traced to oysters harvested in Apalachicola Bay on Florida's Gulf coast. Victims were asked how their oysters were prepared on a scale ranging from raw to wet and slippery to tough and dried-out. Half of those who ate cooked oysters got sick, compared with just under three-quarters of people who had them raw. Cooking oysters until they were the consistency of rubber bands did not significantly reduce the risk.

"Steaming a little until the shell opens is definitely not sufficient,'' McDonnell said.

*** Vitamins and minerals will help you grow.

Nobody knows that better than Walter S. Borisenok, the entrepreneur behind the nutrient list on some of America's favourite brands of cereal, snack bars and baby formulas. For the last three years, his company, Fortitech Inc. has made Inc. Magazine's list of the nation's 500 fastest-growing companies.

Fortitech isn't a household name, but its products are likely to be found in just about every kitchen in the country.

Read the "vitamins and minerals'' list on a box of bran flakes or fruit-filled breakfast bars. There's a good chance the mixture of niacinamide, zinc oxide, iron, pyridoxine hydrochloride, riboflavin and other chemicals came from Fortitech.

"We have 1,500 different formulas for products made by about 300 companies,'' said Borisenok, Fortitech's president and one of four co-founders and stockholders. "We do about 350,000 pounds a month.'' Those formulas fortify all kinds of foods: cereal, baby food, tube-feeding liquid for hospitals, sports drinks and bars, peanut butter, potato chips, breakfast drink powders, fruit juice, diet foods and processed meats.

Borisenok asked that the brand names remain confidential.

"We just got a $150,000 contract from a Brazilian company for a mix for meatballs, hot dogs and sausage,'' said Sam Sylvestsky, Fortitech's marketing director and one of the four partners.

Sales have grown from $127,000 in 1987 to $18 million in 1994 and are projected at around $20 million this year.

"In seven years, we've gone from 5,000 square feet and four employees to doing business in most parts of the world,'' Borisenok said. Fortitech now has 45 employees, recently opened a branch in Brazil and plans facilities in Europe and the Philippines.

Borisenok talked about the nutrition business in an interview at Fortitech's plant in an industrial park in Rotterdam, about 15 miles west of Albany.

The tanned and muscular microbiologist, wearing faded jeans and a polo shirt, said he got the idea for Fortitech when he worked for Milupa Corp., a German firm making baby formula and medical foods.

"We'd buy the vitamins one place, the minerals someplace else,'' he said.

"We couldn't buy a complete package anywhere.'' "So I came up with the idea of putting together complete nutrient systems to fortify food products. Sort of one-stop shopping.'' Borisenok developed the business with Sylvestsky, food scientist Ram Chaudhari, and Borisenok's father, Walter A. Borisenok, who worked for 30 years as a researcher for Sterling Drug Co.

When a food manufacturer comes to Fortitech, it doesn't simply buy a sack of vitamins and minerals. Fortitech scientists develop custom-made mixes, testing and fine-tuning to ensure that the final product -- say, a breakfast bar -- has the specified levels of each nutrient and also tastes good.

A lot goes into choosing the right form of a nutrient for a product.

"There are 20 forms of iron you could use,'' Borisenok said. "The one we choose depends on the other ingredients in a product, how it's processed, how it's packaged, what the shelf life is.'' "Copper gluconate, a typical form of copper, has a metallic taste like pennies,'' Borisenok said. "So we coat the particles to mask the taste.'' Borisenok walked through a storeroom where small plastic bags of powder were stacked on hundreds of shelves. They were samples of batches, to be kept for three years in case of questions about their composition.

In an adjacent warehouse were sacks and drums of raw materials from chemical companies in Germany and Japan: black iron, orange vitamin B2, blue copper sulfate, emerald green chromium chloride, dark orange beta carotene, white vitamin C.

Technicians measure the powders and crystals into steel blenders ranging from table size to taller than two men.

Several food trends are helping Fortitech's business. One is publicity about health benefits of certain nutrients. The anti-oxidant vitamins, A, E and C, have been touted as cancer fighters. Women are often advised to add iron and calcium to their diets.

"The trend toward low fat drives business for us, because companies are reformulating,'' Borisenok said. "Foods lose some nutrient value when you take out the fat. We put it back.'' Fortified foods are best used as part of a varied diet, not as a replacement for fruits, vegetables and other nutritious foods, said Gerald Combs, a nutritionist at Cornell University. Borisenok agreed, but said diets often fall short of the ideal.

"The reality is, what people know they should eat and what they actually do eat is two different worlds,'' Borisenok said. "Fortification kind of fills the gap.'' *** At Silver Diner restaurants, the veggie chili, herb chicken sandwich, "world's lightest sundae'' and a dozen other dishes get red heart symbols on the menu to let patrons know what's good for them.

A fact sheet on the table provides data on the fat, cholesterol, calories and salt content of every menu selection.

Could this be the future of dining out in America? The National Restaurant Association hopes so.

The trade group is urging its 15,000 members -- mostly small, independent restaurants -- to overhaul their bills of fare in anticipation of government requirements to standardise health claims on menus. It suggests that restaurants have a dietician or nutritionist review menus, use computer programs to analyse recipes or hire a lab to do it.