Andrographis»

Also known as Indian echinacea, andrographis is a bitter annual plant native to Asia with antiviral, antibacte- rial, and immune-stimulating qualities that help the body fight off cold and flu viruses. A controlled study of Russian children found that those who took andrographis at the start of a cold had significantly less congestion, faster recovery times, and fewer instances of taking supplemental medication. Another study of Russian workers found that those who took the herb missed fewer days of work and had fewer complications as a result of the flu. Dose» Take 1,200 mg a day for four days at the start of a cold or flu. Cautions» Andrographis can interfere with prescription drugs; be sure to check with your doctor before using if you are currently on any medication.

Elderberry»

The sugars of the berry of this flowering plant promote the production of infection-fighting immune cells and are particularly effective in mitigating the flu. A study of Norwegian adults found that those who took an elderberry syrup four times a day within 48 hours of developing flu symptoms recovered four days faster than flu sufferers who didn’t. And a 2009 study found that elderberry inhibited H1N1 swine-flu virus proliferation in laboratory tests. Dose» Take elderberry syrup orally as directed on the package at the first sign of flu. Cautions» None when using the flowers and berries of the elder plant (which is what reputable herbalists and herb companies use to create syrups); however, the bark, roots, leaves, and stems are toxic.

North American ginseng»

Although both Panax ginseng (Asian) and Panax quinquefolius (North American) have been used to boost stamina and immunity, the North American form of ginseng is particularly known for its ability to ward off upper-respiratory infections, especially colds. It was shown to reduce severity of colds in a 2005 study and the number and severity of colds in a 2006 study. Dose» Take two 200-mg capsules a day for the duration of cold and flu season. Cautions» May increase blood pressure and is not advised during pregnancy.

Vitamin D»

The direct role this vitamin plays on immune function is still unclear, but studies have found that people with low levels of vitamin D miss significantly more days of work due to respiratory illnesses (according to a 2007 study of young Finnish men) and are more likely to have recent respiratory infections (per a 2009 review conducted by doctors at Massachusetts General Hospital in Boston). Dose» Kris Somol, ND, suggests taking a total of 1,000–2,000 IU a day; the darker your climate and the farther north you live, the higher the dose, because the body manufactures D on its own when exposed to sunlight. Cautions» None.