A dietitian’s advice on eating to support immunity

Immune health is one of the core foundations of overall health. Whether trying to avoid catching colds, protect themselves from COVID, or manage chronic conditions, people often ask me what they can eat to prevent getting sick. Recently, one client told me that she felt like her immune system was constantly under attack, sparking a conversation about how our bodies defend themselves.

Understanding the basics of immune function is empowering. It helps us make informed nutrition and lifestyle choices that keep our bodies strong. Read on to discover how the immune system works and what you can do nutritionally to keep it functioning at its best.

What is the immune system?

The immune system is your body’s defense against harmful invaders. It has two main parts: innate and adaptive (or acquired). The innate immune system is the first line of defense. Skin and mucous membranes serve as physical barriers, while immune cells like macrophages and neutrophils identify and attack invaders. The adaptive immune system then produces a specialized response. Lymphocytes, including T cells and B cells, produce antibodies and remember previous pathogens for targeted future responses.

Inflammation often takes the role of villain in health discussions, but it is a crucial component of immunity. Short-term inflammation helps to remove pathogens and facilitates tissue healing. However, chronic inflammation can increase the risk of various health issues, including diabetes, cardiovascular disease, and cancer. 

When it come to diet, we want to eat in a way that reduces long-term inflammation and helps facilitate all the vital reactions that need to take place for your immune system to function.

Nutrition strategies to support immune health

Maintain a healthy gut

Gut health is intertwined with immune health, with approximately 70% of immune cells found in the digestive tract. Good bacteria in the gut produce beneficial compounds, such as antimicrobial agents and short-chain fatty acids, that regulate inflammation and support intestinal and immune health. The gut barrier acts as a selective gatekeeper between the gut and the rest of the body. When this barrier is weakened, foreign substances and pathogens can leak into the bloodstream and cause an inflammatory response that may raise your risk for a variety of adverse health conditions.

Consuming fiber-rich foods like fruits, vegetables, and legumes supports a healthy and diverse microbiome. Probiotic foods, such as sauerkraut, kefir, and miso, introduce beneficial live bacteria (watch out for added sugar in some common probiotic foods like yogurt and kombucha). Prebiotic foods, like garlic, onions, and Jerusalem artichokes, provide essential nutrients that feed these good bacteria. Staying hydrated and limiting processed foods, alcohol, and refined carbohydrates can prevent gut inflammation and dysbiosis.

Load up on phytonutrients

Phytonutrients are compounds found in plants that have anti-inflammatory and antioxidant properties. They are invaluable to the immune response. For example, flavonoids, found in berries and green tea, have been shown to support immune cells such as T-cells and macrophages. Carotenoids from carrots boost the activity of natural killer cells. Cruciferous vegetables like broccoli and Brussels sprouts are high in glucosinolates, which help facilitate detoxification processes in the body.

Different colors usually mean different types of phytonutrients. Red and purple fruits like plums and cabbage are packed with anthocyanins, while leafy greens such as spinach and kale are great sources of lutein and zeaxanthin. Snack on nuts and seeds, which add lignans and phytosterols to your diet, and flavor your food with spices such as turmeric and ginger for valuable polyphenols like curcumin and gingerol.

Variety is key. Personally, I start off my day with a green smoothie or veggie scramble, enjoy a salad at lunch, and have high-quality protein with a mix of steamed or sautéed veggies for dinner. My clients often find that incorporating more colorful plant-based foods not only enhances their immune health but also helps with satiety, gastrointestinal regularity, and weight management.

Balance blood glucose

Balanced blood sugar helps keep your immune system strong. High blood sugar levels can interfere with the functioning of immune cells like neutrophils, macrophages, and natural killer cells, making it harder for the body to fight infections. When glucose levels are elevated, glycation occurs—a process in which sugar molecules bind to proteins without the help of enzymes. This reaction forms advanced glycation end products (AGEs). AGEs change the structure and function of immune proteins, weakening the body’s defenses. High blood sugar also creates an inflammatory environment.

A continuous glucose monitor (CGM) provides real-time insights into how different foods and activities affect your blood sugar. This personalized data allows you to make informed dietary and lifestyle choices to maintain blood sugar stable.

Eat enough protein

To keep your immune system functioning optimally, you need to eat enough protein. Amino acids serve as the building blocks of immune cells like antibodies, cytokines, and enzymes. Certain amino acids are particularly important. Arginine is a precursor to nitric oxide, which enhances blood flow and supports immune cell activity. Glutamine feeds rapidly dividing cells, facilitating immune cell growth. Ensuring adequate protein intake for healthy skeletal muscle also supports immune function, as muscles release myokines that have anti-inflammatory effects.

The amount of protein you need depends on certain factors such as your age, activity level, and health status. The recommended daily amount (RDA) of 0.8 g/kg should be viewed as a minimum rather than a goal. I like to have my clients aim for 1.2 – 2 g/kg, with older and very active adults needing more to preserve lean body mass. You can get high-quality protein from animal sources such as grass-fed meat, free-range poultry and eggs, and wild caught-fish, as well as complete plant-based sources such as soy and hemp. Clean protein powders are also an option. Try to include at least 30 grams of high-quality protein in your first meal of the day to stimulate muscle protein synthesis, the process in which your body builds and repairs muscle tissue by creating new proteins.

Include key vitamins and minerals

Aim for high diet variety to provide your immune system with the vitamins and minerals it needs to do its job. Vitamin C, found in oranges, bell pepper, and broccoli, is a powerful antioxidant that also enhances the function of white blood cells. Vitamin D, which you can get from fatty fish, liver, and certain fortified foods, regulates T cell production and stimulates your body to produce antimicrobial peptides. Vitamin A from carrots and spinach supports the cells in your skin, respiratory tract, and gut. Don’t forget healthy fats, such as omega-3’s, which are important for the absorption of fat-soluble vitamins and also help to regulate inflammation and support immune function in their own right.

I love pumpkin seeds and hemp seeds for zinc, which supports neutrophils and natural killer cells. Brazil nuts are a great source of selenium, a powerful antioxidant. Iron helps transport oxygen, promote the proliferation of immune cells, and stimulate the production of reactive oxygen species that destroy pathogens. It is abundant in red meat, poultry, and beans. I teach my clients to get creative in the kitchen to incorporate these vitamins and minerals into their meals.

Lifestyle strategies to support immune health

Diet isn’t everything—you can also strengthen your immune function with lifestyle practices. Adequate sleep allows the body time to regenerate immune cells. Proper hydration helps transport nutrients and remove waste, while excessive alcohol consumption alters the gut microbiome and reduces the effectiveness of natural killer cells. Regular exercise regulates inflammation and improves circulation of macrophages throughout the body. Managing stress is also critical. Chronic stress leads to persistently elevated cortisol levels, which have detrimental metabolic effects. I encourage my clients to practice mindful eating and prioritize social connection, which may improve health by supporting immune, cardiovascular, and neuroendocrine function.

Conclusion

Understanding how the immune system functions allows you to make informed decisions to protect it. I help my clients develop healthy eating plans that prioritize high-quality protein, healthy fats, and a variety of colorful fruits and vegetables while limiting processed foods, alcohol, and excessive sugar. I also emphasize stress management, regular exercise, and strong social support networks as key components of a healthy lifestyle. Embracing these strategies will not only help you ward off illness, but will also help you improve your day-to-day well-being.