Only a person in a bubble has 100% protection against the germs that cause winter colds. The rest of us have to rely on the infection-fighting immune cells that patrol the bloodstream, destroying germs before they can trigger a dry, hacking cough or head-pounding cold.

Most of the time, your body does a decent-enough job keeping you well, but sometimes there are breakdowns (that's why most guys end up getting sick at least once every winter).

Working out and staying well rested can help you avoid illness, but if you really want to stop a cold before it starts, you also need to eat right. Start by piling your plate high with these proven immunity boosters. Tonight's dinner could mean the difference between fighting a few sniffles and suffering for a week in bed.

EDIBLE Rx NO. 1: BAKED sweet potatoes
Your skin and nasal mucous membranes form the first line of defense against viral invaders bent on sneaking into your bloodstream and making you sick. To keep that tissue healthy, your body needs huge amounts of beta-carotene, a vitamin found in brightly colored orange and yellow fruits and vegetables (especially sweet potatoes). Once swallowed, beta-carotene enhances the terminating action of structures called macrophages, large immune-system cells that surround foreign viruses and bacteria and destroy them, according to data from the Memorial Sloan-Kettering Cancer Center. Opt for raw taters you prepare and cook yourself, rather than those canned in high-calorie "syrup" (i.e., sugar water).

EDIBLE Rx No. 2: Tea
All liquids are beneficial when you're trying to recover from a cold, but if you want to stop an oncoming illness in its tracks, you need to bag the bug with large amounts of tea. Researchers at Boston's Brigham and Women's Hospital found that sipping 20 ounces of tea daily can spur on the immune system's infantry (your army of T cells) to pump out extra-large doses of interferon. This cold- and flu-fighting compound helps coat your cells and thereby defend them against attacking germs that can make you sick.

EDIBLE Rx No. 3: Turkey
Most good sources of protein -- including beef, eggs, seafood, and dairy -- help pump up the body's immunity by providing a hefty dose of needed amino acids, which aid in the production of T cells and other immunity boosters.

Turkey's got a leg up over other protein sources, though, because it's also one of the very best sources of glutamine, an amino acid gobbled for energy by white blood cells and those killer macrophages. Since colds and infections can deplete muscle glutamine stores -- leaving you vulnerable to illness -- eating turkey often during cold season will help keep your body's cold-fighting powers at their peak. (And you thought you were done with turkey after finally polishing off all those holiday leftovers.)

EDIBLE Rx No. 4: Salmon
Yet another reason to go fish: Adding omega-3 fatty acids to your diet can help to balance out your intake of the inflammation-promoting, immunity-destroying omega-6 fats found in such foods as sunflower, safflower, and corn oils, says William Boisvert, Ph.D., a professor of medicine at Harvard Medical School. Eating fatty fish such as salmon, sardines, mackerel, and bluefish at least twice a week is a good way to reduce your chances of getting sick, he says. If that's not possible, you can reap some of the same immunity-boosting benefits from walnuts, canola oil, green leafy vegetables, wheat germ, flaxseed, and flaxseed oil. To work these foods into your diet, dress salads with canola or olive oil, top salads with wheat germ or ground flaxseed, grab a handful of walnuts for a snack instead of noshing on cookies or chips, or add one to three teaspoons of flaxseed oil to your morning fruit and yogurt smoothie or pre- or post-workout protein shake.

EDIBLE Rx No. 5: Garlic
Forget the flakes and powders. The best way to get your garlic is raw, advises James Duke, Ph.D., an herbal-medicine guru and author of The Green Pharmacy. "There are at least 13 compounds in raw garlic that help boost immunity," he says. During cold season, Duke swears by a garlic cocktail (water, raw garlic, carrots, celery, and red and black pepper), which he liquifies in a blender and then chugs to ward off illness. If you can't stomach raw garlic, add as much as possible to the foods you cook, whether it's stir-fry, meat loaf, pasta, or soup.

EDIBLE Rx No. 6: Almonds
If almonds were music, they'd rock out loud, because they're heavy in metal -- the tasty seeds have an unusually high magnesium content. According to a European Journal of Clinical Nutrition review article, magnesium-rich foods help strengthen cells and bolster immunity in a number of ways, especially in athletes. Unfortunately, four out of five men don't get enough of the mineral. Magnesium is prevalent in green leafy vegetables, whole grains, and fish, but it is particularly concentrated in seeds and nuts, including almonds. Two ounces of almonds -- or a single handful -- provide nearly half your daily magnesium requirement of 420 milligrams, so go nuts!

EDIBLE Rx No. 7: Raisin Bran
Zinc lozenges might help lessen existing cold symptoms, but they're often too little, too late in terms of strengthening the immune system. It's much more important to have high-quality sources of zinc in your regular diet, says Boisvert. "Zinc helps keep your thymus gland running at its peak," he says. "That's important because the thymus is responsible for converting ordinary white blood cells into the specialized T cells that recognize and destroy invading germs." Whole grains are naturally high in zinc, and most breakfast cereals are fortified with even more of the hard-to-get mineral. A half-cup of Total Raisin Bran, for example, boasts about eight milligrams of zinc -- enough to satisfy even the biggest guy's daily zinc requirement.

EDIBLE Rx No. 8: Vitamin-E capsules
When it's not busy fighting cancer and slowing the signs of aging, vitamin E spends its time earning the title of the "most potent cold fighter" around. And for good reason: A new USDAstudy reports that taking vitamin E may help reduce both the severity of your cold as well as the length of time you're sick by up to 20%.

And, according to a study in the Journal of the American Medical Association, adding a little E to your diet might even keep you from getting sick in the first place. The study's author, Simin Nikbin Meydani, Ph.D., reports that swallowing just 200 additional units of vitamin E each day could help most people significantly reduce their risk of colds and upper-respiratory infections.