"These little blue berries are called elderberries, and they have one of the highest antioxidant contents of any berry in the world," said author and nutritionist Dr. Jonny Bowden.
Bowden is a big fan of the hard-to-find elderberry. He says the berries' extract can be found in products that might make a difference during flu season.
"Studies in Israel on this, where they gave people with the flu Sambucol and other people did not get it," said Bowden. "And the people who got it had only one to two days of downtime, as opposed to six to seven days."
Bowden is a consultant for the company that makes Sambucol. He also says there are foods and compounds studied that offer properties that may minimize symptoms.
"No cure yet but a lot of things you can do to shorten the time that you're down," said Bowden.
Chicken soup and green tea have both been extensively studied.
Chicken soup inhibits the way white blood cells amass when there's infection or inflammation, which may help with a respiratory infection. Homemade is better but even store-bought can help put a damper on discomfort.
Green tea contains the amino acid L-theanine, a known immunity-booster.
Plus both chicken soup and green tea have another helpful boost: the hot fluids also help open stuffy nasal passages. So does Alkalol, a medicated oil.
"It's been around 100 years, but it's now in Walgreens and CVS, and what it basically is is a supercharged kind of 'Neti pot': nasal irrigation," said Bowden. "You just put the product in there and you inhale it through here and it really is very, very pleasant."
Despite the urban legend that high doses of vitamin C stave off colds, the National Institutes of Health says with the data of more than 30 clinical trials, they've found no reduction of risk.
But there's no harm in keeping vitamin-C-rich foods like peppers, strawberries, kiwi and citrus as part of your diet.
Nutrients coming from whole foods themselves appear to impact immunity well beyond supplements.
What about over-the-counter medications? The Center for Science in the Public Interest studied a handful of them. They found, for example, that zinc lozenges like Cold-Eeze only reduce symptoms by about a day. There was little or no reduction with Airborne. Echinacea was found to be no more effective than a placebo.