An old folk remedy, extract from these dark berries appears to block flu viruses in test tube studies. And a few small studies done in people show it may help you recover more quickly from flu. But scientists caution that further study is needed. The fruit itself is rich in antioxidants and may also have the ability to fight inflammation.

Button Mushrooms

Don't dismiss the lowly mushroom as nutrient poor: It has the mineral selenium and antioxidants. Low levels of selenium have been linked to increased risk of developing more severe flu. And the B vitamins riboflavin and niacin, found in these mushrooms, play a role in a healthy immune system. Animal studies have also shown mushrooms to have antiviral, antibacterial, and anti-tumor effects.

Acai Berry

Hawked as a "super food" along with produce like blueberries, the little acai berry's dark color signals that it is high in antioxidants called anthocyanins. While the acai is not scientifically linked to specific disease- or illness-fighting ability, antioxidants may help your body fight aging and disease. Acai berries can be found most often in juice or smoothie form, or dried and mixed with granola.

Oysters

Aphrodisiac? Immune boosters? Maybe both, thanks to the mineral zinc that's found in oysters. Low zinc levels have been associated