When we get a bad cold or just feel run down, we often like to blame it on our immune system. It’s easy to think of our immune system as being separate from the other functions in our body. Like border guards or traffic cops, we expect our bodies’ defenses to work 24 hours a day, 7 days a week, regardless of what else is going on in our lives. The reality is somewhat more complicated.

While our immune systems are indeed amazing (they keep us alive, after all), they are not separate from the rest of our body. We may not be able to control our immune systems directly, but, we can control many of the factors that influence our ability to fight illness. For example, by learning how to control your stress level, exercising more and improving our diet, you can boost your immune system naturally.

The power of nutrition to strengthen our immune system isn’t fully understood and you should definitely check with your doctor before making changes in your diet. That said, here are a few healthy foods that are suspected to be able to boost your immune system naturally.

Sweet Potato

You may not think of skin as being part of your immune system, but skin is the first line of defense that helps keep bacteria and viruses from getting into your body. Our skin needs vitamin A to stay healthy, and one of the best ways to get vitamin A into your diet is from foods containing beta-carotene (like sweet potatoes), which your body turns into vitamin A. Other foods that are rich in beta-carotene include: carrots, squash, pumpkin, and cantaloupe.

Avocado

Many people who want a diet to lower cholesterol and lose weight often pursue a “low fat diet.” But, not all fats are bad for you. For example, avocados contain 18 of the 22 amino acids used by people. They also have plenty of fiber.

In addition to avocados and avocado oil, other examples of “good fats” include dark chocolate, coconut and coconut oil, oily fish (especially anchovies), nuts and nut oils (especially hazelnuts, macadamias and walnuts), and olive oil. Avocados really are one of the best immune system boosting foods.

Tea

Tea is wonderful for relaxing and re-focusing in the midst of a busy day, but, did you know that the ingredients in tea have been also shown to have beneficial health effects? According to a Harvard study, people who drank 5 cups a day of tea for 4 weeks had 5 times more virus-fighting interferon in their blood than others who drank coffee.

The amino acid that’s responsible for this immune boost, L-theanine, is in both black and green tea. (Read more here about how green tea can boost your health!)

Yogurt

Just like there are “good fats,” there are also “healthy bacteria.” Our bodies are full of billions of bacteria, most of which help keep us healthy. Probiotics, or the “live active cultures” found in yogurt, are healthy bacteria that keep the gut and intestinal tract free of disease-causing germs. Any yogurt with a “Live and Active Cultures” seal contains some beneficial bugs.

Garlic

Garlic is a popular ingredient in many recipes and in many global cuisines – but did you know that garlic can also help fight infections? Garlic has been used as a medicine for thousands of years, dating back to the time of the building of the Egyptian pyramids.

Garlic may help to lower cholesterol and prevent hardening of arteries. Its immune-boosting properties come from heavy concentration of sulphur-containing compounds, such as allicin.

Spinach

Smoothies are one of my favorite new healthy snack ideas – but did you know you can make a “green smoothie” with Spinach and other vegetables? Spinach is high in vitamins A and C and folate, and is also a good source of magnesium. The plant compounds in spinach may boost your immune system, and spinach’s beta carotene, lutein and zeaxanthin protect against age-related vision diseases, such as macular degeneration and night blindness. Spinach may also help protect against heart disease and certain cancers.

Which of these healthy foods for your immune system would you like to include as a more regular part of your diet? Can you recommend any favorite recipes that use these foods? Please join the conversation.

Want to learn more about the immune-boosting benefits of green tea? Watch my interview with Jesse Jacobs, owner of the Samovar Tea Lounge, in San Francisco.