January 31, 2026 - Behnaz Atree, MD
During the winter months, shorter daylight hours, leading to decreased vitamin D and reduced physical activity, more time spent indoors, and exposure to colder temperatures place additional demands on the immune system. Because of this, it becomes more important to support our immune system, keeping in mind that rather than “boosting” immunity with a food or supplement, providing the body with consistent nourishment allows the immune system to respond appropriately – both to daily demands and to illness when it occurs.
Foods rich in vitamin D, vitamin C, zinc, omega-3 fatty acids, and fiber are particularly recommended for immune support during winter, when respiratory infections peak and sunlight exposure decreases. These nutrients contribute to the normal function of the immune system, immune response through oxidative properties, regulation of inflammatory responses and antibody production and are important for the synthesis and function of immune cells. They are the foundation of immune health – supporting immune defenses, reducing inflammation, and helping the body recover more efficiently when illness does strike.
- Vitamin D-rich foods are extremely important during winter months as reduced sunlight exposure can lead to lower levels in the body. Food sources of vitamin D include fatty fish (salmon, sardines), egg yolks, fortified dairy products and plant-based milk alternatives. A vitamin D supplement may be necessary if levels are very low.
- Foods containing vitamin C help reduce cold duration and severity if they are consumed regularly. Food sources of vitamin C include citrus fruits (oranges, lemon, lime, grapefruit), bell peppers, broccoli, cauliflower, tomatoes, brussels sprouts, tropical fruits (kiwi, pineapple, mango) and berries (strawberry, blueberry, raspberry).
- Zinc-rich foods may shorten the duration of colds by approximately 33% when adequate intake is maintained. Good sources of zinc include legumes and beans (lentils, chickpeas), nuts (cashews, almonds, pine nuts), seeds (especially pumpkin seeds), poultry, oysters and shellfish, and whole grains.
- Omega-3 rich fatty acid sources (particularly EPA and DHA), have anti-inflammatory properties that support immune function. The best sources are fatty fish (salmon, mackerel, herring, sardines) consumed 2-3 times weekly. Plant -based sources like walnuts, flaxseeds and chia seeds provide ALA with some benefits.
- Approximately 70% of our immune system is located in the gut, which makes it imperative to keep it healthy. Probiotics (fermented foods) enhance beneficial gut microbiota composition and fiber-rich prebiotics feed the bacteria increasing the production of short-chain fatty acids, which stimulate immune cell activity. These foods include whole grains, oats, legumes, apple, garlic, onions and fermented foods (yogurt, kefir, kimchi).
- Additional beneficial foods include those rich in vitamin A (sweet potatoes, carrots, dark leafy greens), vitamin E (nuts, seeds), and selenium (Brazil nuts, seafood, whole grains).
Overall, a Mediterranean-style diet rich in fruits, vegetables, whole grains, olive oil and fish has been shown to help maintain optimal immune function. Evidence also shows that whole foods sources of these nutrients may be more effective than supplementation for baseline immune support. Targeted supplementation with vitamin D, zinc, probiotics, and catechins (green tea) may be helpful for preventing or treating acute respiratory infections.
Nutrition When You’re Sick: What to focus on
If illness hits, your nutrition needs may change as appetite may be low, and energy demands increase. Below are a few tips:
- Hydration comes first – Fever, congestion, and reduced intake increases fluid needs. Try to prioritize water, herbal teas (ginger, chamomile, peppermint), broth and soups.
- Eat foods you can tolerate even if the appetite is low – Meals may be smaller or less balanced temporarily. Options include soups and broths with added proteins, toast, rice, yogurt, smoothies with fruit and protein, soft fruits and cooked vegetables.
- Try adding protein even if in small amounts – Protein supports immune cell activity and recovery. Try adding beans or lentils to soup, Greek yogurt or cottage cheese, eggs, protein-containing smoothies.
- Minimize high fiber and heavy foods – Fiber is important long term, but very high fiber or heavy meals may worsen nausea, bloating and fatigue during acute illness. Gradually add in a variety of cooked vegetables, whole grains and legumes.
- Foods to limit if you have a Cold or Flu – Foods that may worsen inflammation or digestion include highly processed foods, excess added sugar, alcohol, and greasy or heavy meals. It is best to avoid these during acute illness.
Nutrition as Part of the Big Picture – Finally, nutrition does not stand on its own. It works best alongside – quality sleep, stress management, and regular physical activity. Together, these lifestyle medicine pillars create a resilient immune system. It is also not a substitute for prescribed medications to treat acute infections, but it plays a pivotal role in strengthening the immune system.
Consistent nutrition can make a meaningful difference for long term immune health. By focusing on whole foods, key nutrients and gut health, you can support your immune system naturally this winter and beyond.
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