1. Probiotics

Fermented foods such as yogurt, kefir, kimchi, kombucha, tempeh, and even wine are the best sources of probiotics.

These fermented foods are most commonly regarded for supporting a healthy balance of gut bacteria and aiding in digestion and absorption. One of the more commonly recognized, yet overlooked benefits of probiotics are that they may help support a healthy immune system. So, probiotics are considered premium immune system boosting foods by helping support a healthy inflammatory response, enhancing intestinal barrier function, and more.

2. Vitamin C

Ask anyone about the immune system boosting foods, and vitamin C is probably the first nutrient that comes to mind. Indeed, certain cells of the immune system need vitamin C to perform their functions…

And a deficiency in vitamin C results in reduced resistance to pathogens.

However, there’s no need to go overboard, as super-doses of vitamin C are unlikely to prevent the common cold or reduce its severity. Having said that, vitamin C can enhance the immune system.

So, make sure you’re eating plenty of citrus fruits (e.g., oranges, grapefruit, clementine, and tangerines), bell peppers, broccoli, Brussels sprouts, strawberries, pineapple, kiwifruit, and dark leafy greens, which are all good sources of vitamin C.

3. Vitamin D

The traditional view is that vitamin D, often referred to as the “sunshine vitamin,” plays an important role in building and maintaining healthy bones. But now we know it does much, much more. This is because the human body is laced with vitamin D receptors throughout, including the cells of the immune system.

Vitamin D influences both the innate and adaptive immune responses. While sun exposure is the best way to increase levels of vitamin D, it can also be found in oily fish (e.g., wild salmon, sardines, mackerel), egg yolks, and mushrooms.

4. Prebiotics

Certain types of fiber (such as oligosaccharides, gums, some hemicelluloses, and resistant starches) serve as “food” for the good bacteria in the large intestine.
Prebiotics support immunity by promoting a healthy balance of gut microbes.

When prebiotic fibers are fermented by bacteria, it leads to the production of short-chain fatty acids (SFCA). These serve as fuel for the immune system (among a variety of other health properties).

Prebiotics occur naturally in foods such as leeks, asparagus, chicory, Jerusalem artichokes, garlic, onions, whole grains (e.g., oats, wheat, corn), and soybeans.

Resistant starch can be found in green unripe bananas, uncooked oats, and cooked-then-cooled potatoes, rice, beans, and lentils.