If you’re like most parents, you want your kids to be healthy. And if your kids are like most kids, that isn’t always the case. The most frequent illness of childhood is the common cold, and children — especially those in daycare — can get several of these infections per year. While cold viruses rarely result in significant complications, they certainly cause their share of discomfort, lost sleep, and time away from work and school. Because illnesses like the common cold are so common, there’s no shortage of people looking for ways to prevent them — or of Internet sites offering “natural” ways to boost your immune system (often by clicking the link at the top of the page to purchase a variety of supplements).

Over the years, there have been a variety of “immune-boosting” supplements that have been marketed as nothing short of miraculous. But when we look for evidence to support these claims, they break down quickly. Large doses of vitamin C have been promoted for this purpose for years, but well-designed trials don’t show any benefit. Vitamin D doesn’t seem to do much, either. Echinacea doesn’t help. There was one very small trial that showed a possible benefit from garlic, but didn’t provide enough data to say for sure. Oscillococcinum doesn’t do anything (but you shouldn’t expect it to, because homeopathy doesn’t make sense). Zinc might help to shorten the duration of cold symptoms by a day or so, but it doesn’t prevent the infections. It can also cause nausea, or possibly — if used in a nasal spray — a permanent loss of smell.

It’s not just supplements, though; there’s a wide array of “superfoods” that some people claim will improve the immune system in one way or another. But the term “superfood” is nothing more than a marketing strategy. Sure, some foods are more nutritious than others, but there’s no single food that you just have to eat. Obviously, your body needs an adequate supply of nutrients to fight infections — but no more than you can get from eating a diet consisting of a variety of real foods (like things that actually grew in the dirt). You’ll also see sleep and stress reduction mentioned as ways to improve your immune system. But choosing nutritious foods, getting sufficient sleep, and minimizing stress aren’t immune system boosters; they’re just good life decisions.

So if supplements and superfoods aren’t going to help, what else can we do? Well, before we can know how to help the immune system do its job, it helps to understand a little bit about how it works:

Every day, our bodies are exposed to a constant barrage of viruses, bacteria, fungi and parasites. The vast majority of these germs (or pathogens) never make it into the body because they are kept out by the skin barrier or destroyed in stomach acid. Ironically, another factor that protects us from infections is bacteria; there are trillions of beneficial bacteria* living on our skin and inside the GI tract that help to prevent infections by competing for nutrients and space with organisms that would cause disease. These initial layers of defense are very effective, but those few germs that do sneak through have to be taken out before things get out of control.

The immune system — just like an army — is made up of a variety of components, each of which plays a unique role in protecting the body from enemy assaults. There are several varieties of white blood cells that travel through the bloodstream, then migrate out into the body’s tissues to do their jobs. When these cells find bacteria or viruses, they send out chemical signals known as cytokines. These chemicals recruit other white blood cells to join the fight, and they control other aspects of the immune response — like fever and increased blood flow to the area. (They’re also what makes you feel bad when you’re sick.)

Some white blood cells make antibodies — proteins that bind to a specific part of a specific pathogen, labeling it for destruction. When the immune system fights off a new infection, it creates antibodies against that particular pathogen. After the infection is over, the immune system typically continues producing those antibodies for years or decades in the future. It’s this “memory” function that prevents reinfections with things like chickenpox or measles. Some other infections stimulate a response that is more short-lived. And some pathogens have multiple strains, each of which is different enough that immunity to one strain doesn’t protect against the others (think about influenza, or cold viruses).

Just like any well-equipped army, human cells wear uniforms that help to distinguish them from invaders. There are proteins on the outer surfaces of our cells that help the immune system to know the difference between our own cells and pathogens that need to be destroyed. When this process goes wrong, we end up with autoimmune diseases — conditions in which the immune system attacks the body’s own cells as if they were foreign, leading to a wide array of symptoms. This phenomenon is responsible for many diseases, including type 1 diabetes, thyroid disease, lupus, and rheumatoid arthritis.

Another way the immune system can wreak havoc is by over-reacting to environmental exposures that don’t present any real threat. This process is the cause of diseases like allergic reactions, asthma, and eczema. There’s no great reason that anyone needs to have an immune response to, say, cat dander or ragweed. But sometimes the system runs amok, creating antibodies to all sorts of non-threatening substances. For most people, these conditions are simply uncomfortable or inconvenient. But for some, the reactions can be deadly. In any case, it’s not something I’d want to boost.

On the other end of the spectrum are people whose immune systems don’t function as well as they should — because of genetic problems, chemotherapy treatments, or disorders acquired later in life. Many of these people actually do need an immune system “boost” — using methods like infusing antibodies produced by other people, giving growth factors to stimulate white blood cell production, or performing bone marrow transplants. For those with a true immunodeficiency, it would be dangerous — and potentially fatal — to rely on supplements or “superfoods” instead of addressing the root cause.

People with normal immune systems have the capacity to respond to a wide variety of pathogens. For the vast majority of childhood illnesses, a minimalist approach works well. Colds, stomach viruses, and other mild infections tend to resolve on their own after a few days. Many bacterial infections like ear infections or strep throat will get better without our help as well. But sometimes, the immune system gets overwhelmed. And in those cases, a little “unnatural” assistance for the immune system can be quite helpful. For many bacterial infections, treatment with antibiotics can be beneficial, or even lifesaving. (If you were really tracking with my military metaphor, think of antibiotics as close air support.)

Another option, if you’re willing to give it a shot, is immunizing your child. It’s a great way to boost the immune system — not in a vague, buy-my-supplements kind of way, but in a very specific and effective way. Vaccines work by exposing the body to either a portion of the pathogen or a weakened version of it, promoting a specific immune response that is also active against the actual virus or bacteria. Some people argue that the immunity provided by vaccines isn’t as long-lasting as “natural” immunity. In many cases, that is true. But it’s also a terrible argument, because acquiring immunity naturally requires one to get sick. And although most cases of measles or rotavirus resolve without complication,some don’t. Immunizations are some of the safest and most effective tools we have to reduce a child’s risk for certain infections, many of which can be life-threatening.

Chances are, your child’s immune system is working just fine — reacting as it should to infections, and taking well-deserved breaks when there’s no work to be done. The most common cause for frequent illnesses in childhood is frequent exposures (like in school or daycare). If you’re concerned that your child has a true problem with his immune system, talk to your pediatrician. Otherwise, focus on the simple things — like hand-washing, good nutrition, and quality sleep. Be sure to stay up-to-date with immunizations to prevent a lot of serious infections. Aside from those steps, it’s probably best to stop worrying about it and just accept the fact that — no matter how hard we try — kids are going to get sick.

* With regard to probiotics: because these beneficial bacteria play a role in the immune system (as well as so may other bodily functions), they have recently become popular as supplements, known as probiotics. These live bacteria have shown benefits for a wide variety of conditions. In fact, of all the supplements out there, the best evidence of any benefit for the immune system seems to be for probiotics. We still need some bigger and better-designed studies to say for sure, but it makes sense that probiotics may actually be beneficial, at least for some people.

Chad Hayes is a pediatrician who blogs at his self-titled site, Chad Hayes, MD.

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