Can This Gene Protect Against Respiratory Infections? (IL2)

Exercise

A study in 10 elite Taekwondo athletes suggests that exercise may increase IL-2 levels [R].

We know that exercise and physical fitness improve the immune response and reduce rates of illness [R].

Moderate to vigorous exercise improved the immune function of the respiratory tract (measured as higher production of IgA antibodies, which fight off respiratory infections) and reduced the incidence of upper respiratory tract infections in several studies [R, R, R, R, R].

However, for the purposes of immunity and preventing infections, it’s important to stay within your comfort zone; periods of intense physical training have been linked to windows of reduced immunity that predispose to upper respiratory tract infections [R, R].

Indeed, strenuous exercise reduced IgA production and increased the incidence of upper respiratory tract infections in multiple studies [R, R, R, R, R, R, R, R, R, R, R, R]. 

One study, for example, found increased production of IL-2, together with anti-inflammatory cytokines IL-4, and IL-10 after intense exercise, which could partly explain the increased rate of infections [R].

This is in line with the theory that low/moderate levels of IL-2 may boost the immune response but high levels act to suppress it [R, R, R].

In simple terms, getting and staying physically fit but not overtaxing yourself could help improve defenses against infections [R].

Moderate exercise helps boost the immune system and this may partially be due to an increase in IL-2. However, both strenuous exercise and higher IL-2 levels may suppress the immune response in excess. 

Getting Enough Sleep

Human studies suggest that IL-2 is produced during sleep and that sleep deprivation decreases the production of IL-2 and NK cells, which are important for combating viral infections [R].

Sleep deprivation, disrupted circadian rhythms, and insomnia are well-known triggers of poor immune function and increased susceptibility to infections, including those of the respiratory tract [R, R].

Two studies on over 1,300 people associated suboptimal sleeping with an increased incidence of respiratory tract infections [R, R]. 

Try to go to sleep at the same time each night and sleep for eight hours whenever possible to help with the prevention and recovery of respiratory infections [R, R].

Sleep is important for IL-2 production. Studies suggest that sleep deprivation may decrease IL-2 levels.

Zinc

Zinc is crucial for good immune defense. Even a mild deficiency can impair immune function and increase the risk of bacterial, viral, and parasitic infections [R, R].

Studies in cells show that zinc enhances the effect of IL-2 on immune cells and also increases the production of IL-2 by immune cells [R].

Humans with mild zinc deficiency have lower IL-2 levels and they have lower levels of immune cells needed to combat viral infections. Supplementing immune cells with zinc boosts IL-2 production in laboratory [R].

Zinc supplementation was shown to improve the immune response and increase IL-2 production in pigs [R].

In malnourished infants and children, zinc administration reduced the duration, severity, and incidence of respiratory infections [R, R, R].

Zinc may help improve health outcomes in severe forms of pneumonia. Zinc deficiency, which is common in older people, reduces immune defense and increases the risk of walking pneumonia and other infections [R, R, R, R].

According to some estimates, zinc deficiency contributes to about 16% of lower respiratory infections [R].

Zinc-rich foods include seafood (especially oysters), beef, pork, beans, and pumpkin seeds [R, R, R].

Studies suggest that zinc is important for both IL-2 production and IL-2 function. People with mild zinc deficiency tend to have lower IL-2 levels and may have a higher risk of respiratory infections.

Garlic

In cell studies, garlic and its compound allicin boost the immune response by increasing IL-2 production [R, R, R]. Clinical studies are needed to confirm this effect in humans.

In a study of 120 people, aged garlic extract reduced the severity of colds and the flu. It increased the number of immune cells (T cells and NK cells), thus boosting the immune system while lowering inflammatory proteins (cytokines) [R, R].

Another clinical trial on 146 healthy volunteers found that taking an allicin-containing garlic supplement every day helped prevent the common cold and reduce its duration [R].

The latest analysis, however, failed to find any other studies with good quality. Overall, the evidence is insufficient to claim that garlic can prevent or fight the cold and flu [R].

In one study on 52 healthy volunteers, garlic powder extract with a cellulose-containing nose spray (Nasaleze Travel) prevented airborne infections better than the spray alone [R].

However, garlic extract had little or no effect in a clinical trial on 26 people with a bacterial lung infection [R].

Importantly, have in mind that cooked garlic is less potent than raw garlic because its main active compound (allicin) is broken down by heat [R, R, R]. 

Cell studies suggest that garlic helps boost the immune response by increasing IL-2 levels. Clinical studies are needed to confirm this in humans.

Licorice Root

Licorice root may enhance antiviral immunity by boosting IL-2 and IFN-gamma. In test tubes, it has shown promising effects against different respiratory viruses [R, R, R, R].

In a trial of 28 patients, maoto (an herbal product that contains licorice root) was as effective as antiviral drugs for treating flu symptoms and reducing viral activity [R].

A study of 46 children with respiratory tract infections found that an herbal mixture containing licorice root may be able to reduce coughing and awakenings during the night [R].

According to another study of 70 patients with a chronic cough, licorice pastille (a type of candy) was able to significantly reduce coughing compared to placebo [R].

Licorice root may enhance antiviral immunity by boosting IL-2 and help prevent respiratory infections.

Asian Ginseng

In mouse studies, ginseng enhances both innate and adaptive immunity and these effects include an increase in IL-2 production [R, R].

Ginseng also helped increase IL-2 levels in a study with 97 lung cancer patients [R].

In a trial of 227 people, those who took 100 mg of a ginseng extract (G115) were less likely to catch a cold or flu. The ginseng group also had higher levels of NK cell activity [R].

In another trial on 100 people, Korean red ginseng reduced the incidence and severity of upper respiratory infections [R].

In mice, Asian ginseng, its fermented extracts, and compounds (saponins and polysaccharides) increased survival after infection with different influenza viruses [R, R, R, R, R] and enhanced the effectiveness of the vaccines against them [R, R, R].

Small-scale human and animal studies suggest that ginseng enhances immunity by increasing IL-2 levels.