The weakening of the body’s immune defenses is a common phenomenon. This results in persistent fatigue and an increased susceptibility to infections, illnesses, and allergies. It most often affects adults, the elderly, and pregnant women.
As with many other functions of the human body, nutrition plays a crucial role. Indeed, some foods contain nutrients and active compounds that can stimulate our defenses and protect the body in cases of immune deficiency.
Here is our selection of the 6 best foods to boost immunity. Read on after the list to understand the mechanisms at work in the immune system and, in particular, the role of vitamin D.
Note: Integrating these foods into your diet is a good way to strengthen your natural defenses. However, in the case of a significant immune deficiency, we recommend that you consult a doctor for appropriate care.
1. Camu camu
The camu camu, a small acidic fruit native to the Amazon, stands out for its exceptional content of vitamin C (or ascorbic acid). In fact, it contains 16 times more than an orange and 20 times more than a kiwi!
Vitamin C actively contributes to boosting our immune system. To do this, it supports various cellular functions, strengthens the barrier function against pathogens, and promotes the production of lymphocytes (white blood cells) as shown by this study.
Also read | Which is the best vitamin D on the market?
How to consume it : because fresh fruits have a bitter taste, camu camu is most often consumed as juice or powder (to mix into a smoothie, yogurt, milkshake…). It can also be used as a substitute for lemon because it is acidic.
2. Ginger
Riche en gingérol, le rhizome de gingembre exerce une action antioxydante, anti-infectieuse, anti-microbienne et anti-virale. Il protège ainsi l’organisme contre les radicaux libres, qui altèrent les défenses naturelles, et contre de nombreux agents pathogènes. Le gingembre est un aliment très intéressant dans la prévention des infections : rhumes, états grippaux, bronchites…
How to consume it : delicious as an infusion, ginger can also be consumed fresh, as juice or as a powder. Ginger powder is brewed as a tea or used to season dishes savory or sweet.
3. Shiitake
A medicinal brown-capped mushroom, also delicious to cook. Shiitake is the second most cultivated mushroom in the world. Native to the Far East, it has many health benefits and specifically for immunity, thanks to a polysaccharide it contains, lentinan. It is also richly endowed with vitamin D and minerals that stimulate the immune system.
In Asia, it is used as an extract as a medicine to help patients undergoing chemotherapy or people living with HIV, in order to strengthen their immune system. This study shows the effectiveness of shiitake on immune system markers (levels of inflammation…).
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How to consume it : favor organic shiitakes, because mushrooms absorb everything! When fresh, eat them sautéed or grilled, with other vegetables. In dietary supplements, you will find liquid extracts or capsules containing dried shiitake powder.
4. Green tea
Green tea acts beneficially on the immune system. It particularly promotes the production of cytokines, hormones secreted by T lymphocytes and involved in the body’s immune response.
Green tea contains theanine, an amino acid that, in addition to promoting mental well-being, improves immune system performance as shown by this review.
How to consume it: Green tea is generally prepared as an infusion and can be flavored with lemon, mint, ginger… try matcha, a fine powder made from grinding green tea leaves and traditionally consumed in Japan.
5. Turmeric
The turmeric has an ideal nutritional composition to strengthen the immune system. Packed with vitamins and minerals, it is very rich in vitamin C (25.9 mg per 100 g). It also contains curcumin, a yellow-orange pigment with antioxidant and antiviral properties.
As shown by this study, curcumin increases lysozyme levels, a molecule involved in defense against bacterial infections, and immunoglobulins that help defend the body against microbes.
Comment le consommer : râpé ou coupé en morceaux, le curcuma aromatisera vos plats de légumes, soupes, salades… Vous pouvez aussi utiliser du curcuma en poudre à ajouter dans vos smoothies, infusions et boissons santé.
Also read | Buying guide: the best curcumin
6. Kefir
The kefir is a fermented beverage originating from the Caucasus. Primarily known as an excellent natural probiotic, it is also very useful for strengthening the immune system as shown by this study.
It notably increases the production of interleukin 5 (IL-5) and immunoglobulins. Finally, kefir activates immunity by stimulating macrophages (white blood cells) and increasing phagocytosis (the process of destroying pathogenic microorganisms).
How to consume it : people generally distinguish milk kefir, which tastes similar to yogurt, fruit kefir, with a more tangy flavor, and coconut water kefir. This drink is enjoyed throughout the day.
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What are the mechanisms of immunity?
A complex network
The immune system works thanks to different “ body defenders ”: organs, tissues, and cells work together to fight pathogens. The proper functioning of the immune system is governed by a complex network:
- primary and secondary organs: liver, bone marrow, thymus, lymph nodes, spleen…
- tissues including lymphoid tissue
- specialized cells : leukocytes and lymphocytes (white blood cells), phagocytes, NK cells…
Each of these components plays a specific role and contributes to the immune response throughout the body. They are able to distinguish foreign substances (viruses, bacteria, microbes, fungi…) from ‘self-antigens’, which belong to us. When an external organism is detected, our defense mechanisms activate and come into place.
Unfortunately, many internal and external factors can slow down this well-oiled mechanism, weaken our immune system, and impair the activity of our natural defenses.
Poor diet, physical inactivity, lack of sleep, stress, and pollution are among the main culprits. That’s where certain foods, rich in beneficial vitamins and minerals, come into play…
Nutrients and immunity: example of the role of vitamin D
If vitamin C is the quintessential immunity vitamin, vitamin D (or calciferol) also plays an important role in the defense system of our body.
On the one hand, it stimulates the production of macrophages and dendritic cells that enable the initiation of the immune response. On the other hand, vitamin D helps destroy pathogens by increasing the production of antimicrobial peptides. Finally, it has an immunomodulatory effect, meaning that it regulates the immune response and prevents excessive reactions.
As shown in this study, vitamin D also has the advantage of acting during the 2 types of immune response : during the innate immune response, which is activated immediately, and during the adaptive immune response that occurs 4 days after detection of the pathogen. Vitamin D therefore acts broadly and over the long term to support our natural defenses.
It is found in good amounts in cod liver oil, fatty fish, eggs, dairy products, and mushrooms. In winter, we synthesize less of it because sun exposure stimulates its production. Furthermore, our defenses are weakened. Supplementation may then be necessary.
Also read | Everything you need to know before buying vitamin D
