Nourishing a Healthy Immune System Before, During and After Cancer

It’s on our minds, especially as the seasons change: how to support and boost our immune systems. While the body’s natural defense system is incredibly complex, there are simple steps we can take through our daily habits to keep it in top shape to protect us from viruses and infection.

Nicole Parker, LD, RD, a registered dietitian at Dartmouth Cancer Center, shares expert insights on how a balanced diet and a few key lifestyle choices can make a big difference in keeping our immune systems healthy and strong.

Two immune systems?

We refer to the “immune system” as a single thing, but there are actually two types:

• Innate: Our first line of defense. This is our physical barrier of skin, saliva, mucus, tears, and even white blood cells.
• Adaptive: Lymphocytes (B cells and T cells) that are activated when pathogens bypass the innate immune defenses.

“Together, these systems are made up of five major types of white blood cells in many parts of our body, including lymph nodes, the appendix, bone marrow, tonsils and adenoids, thymus, spleen, ‘Peyer’s patch’ in the small intestine, and our largest organ: our skin,” explains Parker.

The immune system keeps out foreign pathogens such as viruses and bad bacteria. “Cancer cells are tricky,” Parker continues. “Because they are made from our normal cells and not an invasion of pathogens, our body doesn't always recognize them as a threat.” Immunotherapy is a cancer treatment that helps the immune system recognize and attack cancer cells.

The power of a balanced plate

When it comes to eating for immune health, Parker says the key is balance. “No single food or nutrient can offer complete protection. The most effective strategy is to eat a wide variety of foods to get a full range of nutrients. Think of your plate as a colorful, diverse team working together to keep you healthy.”

Some of the foods she recommends as particularly beneficial include:

• Yogurt: A great source of probiotics, which are the healthy bacteria that live in our digestive tracts.
• Lentils and beef: Both are excellent sources of zinc, a mineral vital for immune function.
• Red bell peppers, spinach, oranges, and strawberries: These are packed with vitamin C, a powerful antioxidant. “Just half a cup of chopped red bell pepper gives you more than 100% of your daily vitamin C needs,” says Parker.
• Walnuts and almonds: Great sources of vitamins A and E, which also play a role in supporting your immune system.
• Mushrooms: “One of the few foods that are a good natural source of vitamin D, a nutrient many of us in the Northeast may be lacking, especially during the winter months,” says Parker. Other sources include egg yolks, tuna, and fatty fish like salmon and herring.

The gut-immune connection

Our digestive systems are home to trillions of microbes, or healthy bacteria, that make up what we call the “gut microbiome.” These microbes help ward off bad bacteria and are closely linked to our immune systems. Parker explains that we can support this vital connection by incorporating probiotics and prebiotics into our diets.

• Probiotics are live healthy bacteria, found in fermented foods like yogurt, kefir, sauerkraut, pickles, and kombucha.
• Prebiotics are the food for those healthy bacteria. Good sources include beans, whole grains, garlic, bananas, onions, and asparagus.

“A great way to combine them is to create a ‘symbiotic’ snack, like Greek yogurt topped with sliced bananas,” she says.

The truth about supplements

“I get asked about supplements almost daily, and it's an important topic,” Parker says. While many claim to have "cancer-fighting benefits," the evidence shows that, unless you have a documented deficiency, supplements may not provide a benefit and can even be harmful. “For instance, high doses of antioxidants like CoQ10 or turmeric in supplement form can interfere with the effectiveness of chemotherapy. Even something as common as folic acid can be harmful with certain treatments,” Parker says.

“A couple of other things to keep in mind are that you'll absorb nutrients better from food than from supplements, and supplements aren't regulated by the U.S. Food and Drug Administration (FDA).”

Parker’s best advice is to always talk to your medical team—your provider, dietitian, or pharmacist—before starting any new supplement. They can look at the big picture of your health and help you determine what's safe and effective for you.

More than just food

Nourishing your immune system goes beyond your plate. Parker emphasizes a holistic approach to your well-being that includes:

• Hydration: Water is essential for carrying oxygen to your cells and supporting lymphatic fluid, which transports white blood cells throughout the body.
• Sleep: Chronic lack of sleep can weaken your immune system, making you more susceptible to illness and less protected by vaccines. Aim for seven to nine hours of sleep per night.
• Physical activity: Regular exercise strengthens your immune system by reducing inflammation and encouraging immune cell regeneration. The American Cancer Society recommends 150-300 minutes of moderate activity each week, or about 30-60 minutes, five days a week.
• Stress management: Chronic stress can suppress the immune system by increasing cortisol levels, which inhibits the action of white blood cells. “Find what works for you to decompress, whether it's yoga, meditation, gardening, or a good book. For me, it’s mowing the lawn. I like being outside, and it clears my mind,” Parker says.

More resources

There is a lot of information out there, and it can be overwhelming to narrow it down or even know what’s true. Here are a few of Parker’s go-tos for reliable quality information:

• The American Institute for Cancer Research: aicr.org. The AICR provides evidence-based information on use of supplements. It's also a source for recipes.
• The Family Immunity Cookbook: Written by registered dietitian Toby Amidor, this book provides more detail on cooking for immune health.
• Cancer Dietitian: cancerdietitian.com. Lifestyle tips and immune-boosting recipes.
• The American Cancer Society: cancer.org. The ACS is a wealth of information for immunotherapy, including different types, indications, and side effects.

By focusing on a balanced diet, proper hydration, quality sleep, regular physical activity, and stress management, we can give our bodies and the immune systems that protect them the best possible chance to stay healthy and strong.

For more detailed information, food lists, recipes and immune-boosting snack ideas with visual slides, watch Nicole Parker’s full webinar on Healthy Eating Ways to Boost the Immune System.