Elements of this approach will sound familiar–science has vindicated your mother’s views on eating well and getting enough sleep–but other aspects will sound exotic. For example, I advise patients to take two 600mg capsules of NAC (N-acetyl cysteine) daily whenever they feel an infection coming on. And I take one capsule a day as a prophylactic. NAC, a special form of the amino acid cysteine, boosts levels of glutathione, an antioxidant produced by the body that is essential for healthy immune function. In a large, six-month study of NAC, Italian researchers found that while the supplement did not prevent infection with the flu virus, it dramatically reduced the severity and duration of illness. Only 25 percent of the flu-stricken volunteers taking 600mg twice daily reported feeling sick, versus 79 percent of the placebo users. In my experience, NAC also helps ease colds, allergies and sinus infections. Like the other supplements I recommend, it’s available without a prescription at selected health-food stores, supermarkets, discount chains and online pharmacies–and it is not known to cause side effects or drug interactions. NAC costs roughly 25 cents per capsule.

For adults or children who are plagued by frequent infections, I recommend an herb called astragalus. Test-tube and animal studies suggest that this staple of Chinese medicine boosts the activity of two types of immune cells (T cells and natural killer cells). And researchers at the University of Texas Medical Center have found that it helps counter the immunosuppressive effects of cancer chemotherapy. (If you’re on chemotherapy, don’t take any herb or medicine without consulting your physician.) A bottle of 60 to 90 astragalus capsules (500mg each) costs $6 to $15. My infection-prone patients take two capsules daily.

If your child suffers from ear infections, you might consider giving her Western larch, a nutrient-rich pine extract. Its immune fighting ingredient is a natural sugar called arabinogalactan, which is also found in astragalus and echinacea. A study conducted at the Southwest Research Institute, in Tempe, Ariz., found that 1,500mg of larch sugar, administered daily, raised immune cell counts in adult volunteers. No one has yet conducted a controlled clinical trial in children, but many physicians have found it useful, and researchers are now launching a major study of kids’ recurrent ear infections. Larch comes in capsules or in a powder that can be mixed in juice, and it’s very safe. In fact larch powder has been approved as a thickening agent for powdered puddings. For a daily immune boost, children should take 1 teaspoon of powder daily; adults should take 1 tablespoon (or three 500mg capsules). For acute infections, take the same doses three times a day, with meals. Western larch is sold as “larch arabinogalactan” or “larch extract” and is very inexpensive.

The list goes on. Beta glucan, a natural sugar found in baker’s yeast, has a powerful effect on immune cells known as macrophages, but at $70 a month it’s a bit costly to use as a tonic. Olive leaf extract is more affordable ($25 to $40 for four months’ worth of 500mg capsules). And because its active ingredient, oleuropein, kills a wide range of viruses and bacteria, it’s a good safeguard for schoolteachers, physicians and other people who are constantly exposed. I take one capsule with breakfast each morning.

Not all supplements work equally well for everyone. I recommend starting with an inexpensive one (larch or astragalus) and adding olive leaf or beta glucan if you still need a boost. And keep NAC around for those nasty colds and flus. Though none of these supplements have known hazards, you should avoid them if you’re taking antirejection drugs. And because some products contain less active ingredient than their labels suggest, talk to a pharmacist or herbalist about which brands are most reputable. You may not banish colds and flu from your life, but you’ll give your body an advantage. As I tell my patients, take care of your immune system and it will take care of you.