First it was cranberries. Then blueberries. Then pomegranates. Then acai berries, whatever they are. Now there's more. ``Fight flu with the wonder fruit!!!'' says the ad by the New Zealand Blackcurrant Research Headquarters touting the antioxidant power of its dark-purple fruit. It's just one more antioxidant-rich ``superfood'' claimed to be a natural defense this flu season.

Reality, we're learning now, is more complicated.

Fruits packed with antioxidants are great, and good for us, health experts say. But they won't, by themselves, bulletproof our immune systems and save us from the H1N1 influenza virus. Or anything else.

Today's expert advice sounds discouragingly like what our mothers always told us.

``A well-balanced diet minus too many sweets and artificial ingredients, with an adequate amount of protein, fruits and vegetables and vitamins is what we need,'' says Dr. Tracie Miller, a professor of pediatrics at the University of Miami Miller School of Medicine.

It's not that antioxidants won't give you a little extra boost, experts say.

``Antioxidants as a class have specific effects in enhancing the immune system,'' says professor Jeffrey Blumberg of the Friedman School of Nutrition Science at Tufts University. ``But it's a complex system. You also need a lot of other things to have good nutrition.''

``The bottom line is that to have good immunity, you have to eat a variety of foods,'' says Sherry Mahoney, director of nutrition for the Mayo Clinic, Florida. ``Chronic dieters who omit a food group omit needed vitamins and minerals.''

Mahoney suggests five servings of fruits and five of vegetables per day for women; seven of each per day for men.

Dr. Michael Kolber, assistant chief of infectious diseases at the UM Med School, says our bodies' immune systems are strongest if we eat a normal, healthy diet that is not deficient in important nutrients.

``Malnourished people have poorer immunity. You need to keep your organs healthy, and your immune system is just another organ.''

Still, what's the single best thing we can do to avoid swine flu?

``Get your flu shot,'' Kolber says. Get shots against the regular seasonal flu and also the H1N1 swine flu.

And don't be discouraged.

There may not be 10 superfoods that will turbocharge your immune system and help you blast through disease. But there is a nifty list of things that will help your immune system be all it can be.

• Eat a healthy, balanced diet: This includes such antioxidant-rich foods as dark-colored berries, apples, cherries, red beans, artichokes, broccoli, green tea, red wine, almonds, ground cloves, oat-based products and, for dessert, dark chocolate, the Mayo Clinic says. Antioxidants neutralize free radicals that otherwise can damage body cells, fighting cancer and heart disease and boosting the immune system, the clinic says.

Oily fish like tuna, salmon and sardines provide omega-3 fatty acids, which boost general health and help fight heart disease, macular degeneration and other maladies.

• Take a one-a-day multivitamin. Even well-balanced diets can leave deficiencies in vitamins A, D and E, selenium, zinc and other nutrients, Miller says.

``As we understand more about diet and health, we see that nutrition can be helped by a multivitamin.'' But don't overdo it. ``Don't overdose on one specific vitamin.''

• Lose weight if you need to: ``Fat creates a lot of inflammatory chemicals. Obese people are immuno-suppressed. Their immune systems don't work as well as people with lean body mass,'' Miller says.

• Exercise: Both aerobic exercise such as walking and weight training, if your doctor permits, also improve lean body mass, Miller says. ``Half an hour a day is excellent.''

• Stop smoking: ``If you smoke, get help to quit; smoking hurts your immune system,'' says Lillian Rivera, administrator of the Miami-Dade Health Department.

• Avoid stress: Stress creates harmful oxidants in the system, decreasing the overall good health that maximizes your immune system, Miller says. How to fight it? Sing. Pet your dog. Get a hobby. Take up yoga. Whatever relaxes you.

• Get enough sleep. ``Scientists have documented that when we are sleep-deprived our immune system suffers,'' says the Mayo Clinic web page on fighting stress.

• Practice good hygiene: You've heard it a thousand times: Wash your hands, cough into your elbow, stay home if you're sick.

All these ways of boosting your immune system are particularly important to fighting the H1N1 strain of influenza, says the U.S. Centers for Disease Control and Prevention.

Asked how contagious swine flu is, CDC officials cite a University of Maryland experiment with ferrets that found the H1N1 swine flu virus was twice as contagious as regular seasonal flu. Not more virulent, just easier to catch.

So is the bottom line that no matter how many healthy habits we follow, if we're directly exposed to swine flu, we're likely to catch it?

``Absolutely,'' Miller says. ``But you may have a milder course.''