Immune-supportive foods to prevent colds & flu

18th Oct 2024

To avoid colds and flu, build a strong immune foundation by eating nutrient-rich whole foods. Here's our top list for colder months, including spices, probiotics and prebiotics.

How can diet support the immune system?

We’re learning a lot more about how food components—such as fibre, vitamins, minerals and plant polyphenols—support the immune system and lower the risk of infections. A well-balanced diet provides:

• Fuel for the immune system to function, supplying energy and building blocks for the production of proteins (antibodies, cytokines, etc) and immune cells.
• Stronger defence by regulating immune cells and having specific antibacterial or antiviral functions (e.g., vitamin D, zinc).
• Protection from oxidative stress and inflammation (e.g., vitamins C, E, zinc, selenium, omega-3 fatty acids, polyphenols).
• Substrates for gut microbes, which strengthens the gut barrier and supports immune responses (e.g. plant-derived fibres).

So while there’s no such thing as an instant "immune booster," we’ve compiled a shortlist of key foods rich in important nutrients and antioxidant compounds for immune function.

5 foods to support immune health

1. Leafy greens

Broccoli, kale, cabbage, Brussels sprouts, spinach

They are a rich source of fibre, vitamins C and K, minerals (calcium, potassium, iron) and polyphenols, such as carotenoids, with strong antioxidant and anti-inflammatory properties. A higher intake of Brassica vegetables, including broccoli, kale, Brussels sprouts and collard greens, is tied to lower levels of inflammatory markers, suggesting they could protect the body from excessive inflammatory response when infected.

Add to your meals: 1 to 2 portions a day of various greens. One portion is about a small bowl of mixed salad leaves or 4 heaped tablespoons of cooked greens like kale or spinach.

2. Colourful fruits

Oranges, lemons, mandarins, kiwis, berries, apples

They provide fibre, vitamin C and flavonoids, a group of plant polyphenols with antiviral and antioxidant effects. Studies suggest that higher flavonoid intake (0.2 to 1.2 g/day) can lower the risk of upper respiratory infections by 33% and sick days by 40%.

Add to your meals: Citrus, kiwi, berries and apples. To get around 1 gram per day, eat 2–3 handfuls of berries (~100g), 1–2 oranges, 2–3 kiwis or an apple.

3. Fermented foods

Kefir, live yoghurt, sauerkraut, kimchi

They provide probiotics, which help increase the diversity of gut microbes and support immune function. Daily probiotics are linked to a lower risk of upper respiratory infections like the common cold and quicker recovery.

How much? Most trials used 100 to 250 mL of fermented milk or yoghurt with at least 109 CFU of probiotics. We recommend regular, smaller servings over large amounts once in a while.

Add to your meals: 1-2 portions a day of fermented foods, such as a cup of kefir, live yoghurt, or a few spoonfuls of sauerkraut or kimchi.

4. Warming spices

Turmeric, cinnamon, cloves, ginger, oregano, fennel, star anise

They are easy to overlook but spices contain high concentrations of different active plant compounds with antiviral and antioxidant properties. Growing research shows that daily doses of spices can protect against excessive inflammation, lower pain and possibly improve the gut microbiota.

• Ginger contains gingerols that give it its pungent fragrance and unique aroma. But it also contains other major polyphenols, such as shogaols and paradols.
• Cinnamon contains cinnamaldehyde and cinnamic acid from the bark of cinnamon trees.
• Turmeric or “the golden spice” contains curcuminoids, such as curcumin.

Add to your meals: A few teaspoons of various warming spices, including turmeric, cinnamon, cloves, ginger, oregano, fennel and star anise. They are great in broths, soups, stews and herbal infusions like fresh ginger and cinnamon tea.

5. Prebiotic foods

Beans, peas, lentils, garlic, onions, leeks, seaweed

Prebiotics are specific food components that cannot be digested and instead pass through the upper gut to “feed” gut microbes, improving the gut microbiota. In turn, gut microbes can influence immune function by strengthening the gut barrier and stimulating immune responses.

Add to your meals: Different sources of prebiotic-rich foods, including garlic, onions, leeks, seaweed and legumes like soybeans, lentils, chickpeas, white beans, black-eyed peas and red kidney beans.

Other immune-supportive foods

• Mushrooms: They are a source of beta-glucans, known for their immune-modulating effects by activating immune cells in the gut and improving the gut microbiome, though more human studies are needed. Mushrooms exposed to UV can also provide vitamin D.
• Oily fish and shellfish, such as herring, mackerel, sardines, trout, salmon and oysters. They provide omega-3 fatty acids, zinc and vitamin D. Aim for 2-3 portions a week.
• Nuts and seeds, such as sunflower seeds, flaxseeds, almonds, cashews and pumpkin seeds. They add fibre, zinc, magnesium, vitamin E and healthy monounsaturated and polyunsaturated fats. Aim for a handful a day.
  

Key habits to help prevent colds

• Stay hydrated by drinking plenty of water and warm liquids like broths, infusions, and herbal teas. It’s essential for nutrient absorption and gut function, influencing defences against pathogens.
• Regular exercise: Muscles play a key role in immune function, so regular strength training to increase muscle mass could improve our ability to handle viral infections.
• Improve indoor air quality: We spend a lot of time indoors, especially in winter, where the air can be more polluted than outside, affecting immune cell function. To help, open windows when cooking, avoid candles that release particulates and wet dust regularly.
• Vitamin D+K2: Taking 400–1000 IU of vitamin D daily has been linked to a lower risk of acute respiratory infections, including colds and flu.

Plus, sauna sessions? Emerging research suggests they may improve immunity by increasing heat shock proteins. A small trial in young men found benefits with 3 sessions a week, each including three 15-minute exposures and 2-minute cooldowns in between.

In daily life

Our favourite ways to eat more immune-supportive foods:

1. Greens with every meal, like a side salad, roasted vegetables or tossed into soups, pasta sauces and stews.
2. Fruit as a dessert or snack like 2-3 kiwis, an orange, an apple or frozen berries in yoghurt.
3. Probiotic breakfast: Try yoghurt or kefir with some berries, nuts, and seeds or mix things up with a bit of kimchi or sauerkraut with eggs or beans on toast.

For recipe inspiration, check out our Winter Warmers. We have a treasure trove of recipes—both free and subscription-based—using hearty, seasonal ingredients that are perfect for cosy soups and stews.