Hundreds of products promise to "strengthen your defenses" or "boost your immune system" … But what do these expressions really mean? Is our immunity really something that a given food can muscle, develop, stimulate? And if such a thing is possible, is it really safe? While the common sense advice would be to avoid deficiencies through a healthy diet, the traders pseudo-remedies have invented a concept as misleading as effective …
By Florian Gouthière
Our natural defenses
What are these "immune defenses" that we would like to "boost" against cash and hard cash?
Part of our immunity, called innately, corresponds to general reactions against all aggressions (our defenders are called macrophages, neutrophils, natural killer cells, but also … fever !). We also have immunity acquired (sometimes called "adaptive"), which allows a more specific defense against infectious agents, including unknowns of the body, thanks to the action of B and T lymphocytes.
In an article published in 2009, Dr. Marc Crislip(1) observed that "most people apparently think that the immune system is a kind of muscle, and that by doing it, by giving it dietary supplements and vitamins, it will become stronger, bigger, more impressive, the way the biceps of Mister Universe. "
In fact, as its name suggests, our immune system is a set of cell and of protein, very varied. Produced by our organization, they recognize elements belonging to this organism (the "self") and those that are foreign to it (the "non-self"), in insulating – even in eliminating – these latter.
In the simplest situations, specific antibodies will clump on foreign bodies, attracting to them white blood cells that will proceed to their elimination.
But the "system" is much more complex. Some proteins have the effect of modulating the rate of detection of infection or elimination activity. Some of our cells can self-destruct in case of infection, to protect the rest of the body … The list of defense mechanisms available to living organisms in general, and the man in particular, is particularly rich!
Finally, it should be noted that other independent agents of the immune system contribute to prevent infections. For example, our nose hair and others cellular eyelashes that act as filters and limit the entry of bacteria into our body, or blood platelets that can quickly close our cuts …
These armies of antibodies, globules and hair constitute the complex contingent of our natural defenses.
When a merchant declares that a product "boosts our natural defenses"What part of this impressive system is it supposed to stimulate? The production of certain antibodies? The amount of this or that family of white blood cells? The length of our nose hairs?
And if such a phenomenon occurs, can we know in what proportions?
(1) Dr. Marc Alden Crislip, a specialist in infectious diseases, is one of the co-founders of theInstitute for Science in Medicine and some Society for Science-Based Medicine.
Train the army
The expression "boost immunity"is attractive, because it refers to a vision a little magic of our health.In this imaginary, the human is endowed witha kind of magic shield against diseases it would be possible and desirable to increase density and strength.
Shields exist: our skin, the walls of our cells. To reinforce them, we wear clothes, avoid cutting ourselves, and try to feed ourselves properly to avoid nutrient deficiencies essential for the formation of healthy cells.
Beyond these considerations, the immune system proper is, as we have seen, a much more complex thing. As simple as it is, the metaphor of a contingent of soldiers coordinated, withadapted weapons at every infection situation, is much more realistic from a biological point of view than that of the shield.
Biology students are familiar with the following metaphor: it is useless for soldiers to be more numerous and more heavily armed if they do not have the only poison that can kill the enemy, or if she can not know how to locate the enemy. Each virus or bacterium must be identified by specific antibodies, or recognized by infected cells.
It is quite possible – and desirable – to strengthen this acquired immunity (see box) That's what we do through the vaccination. But, as we can see, this is a very specific actionin the sense that we offer here to the army a radar and a precise means of struggle for a given invader.
Other ways to stimulate all or part of the system?
In the scientific medical literature, almost all the articles which evoke a "stimulation" or a "reinforcement" of the immunity speak either of vaccination … or pathologies or serious clinical situations, in which the organism is strongly immunodepressed ( leukemia, AIDS …). A person who no longer produces this or that family of functional lymphocytes is in serious danger, and any process to reactivate this production (marrow donation …) can save his life.
And the plants?
An article from the Harvard Medical School summarizes the state of current knowledge about the effects of plants on the immune system. He recalls that no serious clinical trial has been able to demonstrate that thealoe vera, theastragle, theEchinacea, the ginseng or the licorice can modulate in any way the immune response. For Echinacea, large studies show that it does not affect the rate of infection, progression and severity of colds. For ginseng, the authors note that NCCAM (the US Center for Complementary and Alternative Medicine) itself finds insufficient scientific evidence to support the existence of a protective effect of this root. About thegarlic, they note that tests in vitro show an antibacterial and antiviral effect, which has not yet been validated in humans.
But winter capsules retailers do not cater to those seriously ill people, and well to the average consumer who fears to catch a cold, get a gastroenteritis or a flu …
What do clinical trials say?
There are scientific studies which reveal phenomena of stimulation of a function of the immune system by the supply of foreign substances. But when researchers observe something other than banal inflammatory reaction, their experiments consist in introducing the tested products in phenomenal proportions at the very heart of the cells(2).
These reactions, observed in vitro, can they have a measurable effect at the level of the whole human body, for reasonable amounts of ingested food?
For now, no study Epidemiological evidence has yet to prove that a diet rich in antioxidants significantly reduce the rate of infections to a particular bacterium. No work corroborated by the scientific community has, more generally, shown that the consumption of a given product, by healthy people and without deficiency, would statistically decrease the rate of contracted diseases. The only exception, so far, is perhaps that of probiotics (live micro-organisms added to certain food products).
(2) For example, there are chemicals in the diet that, if they enter certain cells, can increase the expression of a gene encoding a protein having selective antimicrobial action. See for example: doi: 10.1002 / mnfr.201300266
The controversial interest of probiotics
The consumption of certain probiotics has probable effects on the duration to several pathologies digestive system (without, however, reducing the risk of occurrence). But can probiotics significantly affect the frequency or duration of other diseases?
The people allergic (whose immunity is excessively activated against agents that are harmless to others) and those suffering from autoimmune diseases (whose immunity targets not only "self-talk", but also "self") know how unhealthy the immune system is. Over-the-counter substances that "activate immunity" could potentially be dangerous poisons for these people … if they had the slightest effect!
Small studies have suggested that the consumption of some lactobacilli selectively reduces the risk of skin allergies. In some people, it would also reduce the average duration of respiratory infections (The number of infections, on the other hand, does not decrease). Some of these results appear significant. However, the amount of available data is considered insufficient by European health authorities to allow "health" trade claims to be allowed around probiotics(2).
The mechanism involved would be the following: in the presence of bacteria ingested (and / or degraded(4)), the immune system reacts against the invader ; and this inflammatory reaction has many positive effects. In the article previously mentioned, Dr. Marc Crislip explains that regular users of probiotics who are vaccinated against influenza, produce more specific antibodies than others, because their body is already on the war foot against the inflammation related to bacteria.
Inflammatory reactions with shovel
To assimilate an inflammatory reaction against an infection to a stimulation of the defenses is rather devious. Admittedly, repeated aggression keeps our personal army awake, but is it really desirable?
Crislip recalls that chronic inflammations have particularly deleterious side effects, including the flexibility of our arteries. The doctor issues thehypothesis that repeated consumption of probiotics could lead to the same vascular effects as chronic periodontitis.(5)
Titill the production of white blood cells on the pretext of maintaining its immunity in perpetual alert appears, as such, a very bad idea. Note also that the activity of innate immunity is rarely silent: fever, runny nose … A booster of the immune system would essentially maintain these symptoms!
If you get a winter sickness, you will definitely look for reduce the innate immune reaction(6) by reducing these symptoms (while allowing the acquired immunity to overcome the disease). Again, avoid throwing your money out the window: few drugs effectively reduce pain and fever.
(3) The European Food Safety Authority (EFSA) not allowed the commercial use of many health claims for probiotics. Since the beginning of the decade, these products can no longer claim to "contribute to the proper functioning of the immune system and enhance resistance to infections" or "reduce the sensitivity of the immune system to allergens". Danone counterattacked in 2014 by adding vitamins her Actimel® yogurt, she can now legally declare that her consumption "participates in normal running of the immune system ".
(4) Recent experiments on the mouse have shown that the degradation of the walls of innocuous bacteria of our intestinal flora causes a continuous reaction of our immune system against them; an inflammatory reaction that allows the mouse to have a "rolling stock" of leukocyte killers of bacteria, beneficial in case of serious infection. See doi: 10.1038 / nm.2087
(5) He also points out that recent inflammations significantly increase the risk of thrombosis (clots), stroke and heart attacks.
(6) One recent tribune published by the magazine online Slate This point is made very clear by referring to the difference between innate and acquired immunity.
Effective solutions for a valiant immune system
Do you want your immune system to react to a quarter turn in case of infection? No need to give your money to magic food sellers or fantastic capsules to achieve this. The following tips have nothing metaphysical secrets inherited from a mystical knowledge, and do not cost much to be remembered:
- Avoid vitamin and nutrient deficiencies. The confusion between reduction of deficiencies and "strengthening of natural defenses" is cleverly maintained by marketing. Warning: it is useless, even dangerous, to take vitamin supplements if you are not deficient!
- Try to spend restful nights.
- Avoid stressful situations as much as possible.
- Avoid smoking and drinking too much alcohol.
- Cover well when leaving. (Yes mom)
- To reduce the risk of contracting a particular pathology, vaccinate yourself.
- Wash your hands when coming back from the outside and before cooking.
Any practitioner or trader who claims to stimulate your immune system while you are in good health, who claims to be able to strengthen your shield (with the help of metaphors "energetic"), just trying to make you lower your guard to tap into your wallet . It is also an excellent method to distinguish an honest doctor and pharmacist from charlatans. They are usually the same ones who, after the holidays, try to convince you of the need for a detox cure.
Sponsored by Ligatus