How an apple a day can keep pneumonia away

The Vitamin C boost found in fruits such as apples can boost anti-bacterial immunity and help protect people from pneumonia, suggests new research. The researchers found that to weaken the immune system and cause pneumonia, bacteria use hydrogen peroxide, also known as a bleaching agent that is used to whiten teeth or hair, as a stain remover, as well as for cleaning surfaces and disinfecting wounds. "By using hydrogen peroxide to defeat the immune system, you could say that the bacteria are fighting fire with fire. The body itself also produces hydrogen peroxide as a defence against the bacteria," said research leader Nelson Gekara from Umea University in Sweden.

"Therefore, it was surprising to see that many types of bacteria actually use the same substance to overcome the body´s defences," he said. "One of the best known substances with the ability to neutralise hydrogen peroxide and that could hence boost anti-bacterial immunity are vitamins such as Vitamin C found in fruits. Perhaps the old adage `an apple a day keeps the doctor away` is not off the mark," Gekara added.

The researchers mainly focused their studies on Streptococcus pneumoniae. This bacterium, often called pneumococcus, is the most common bacterium causing pneumonia but can also cause, among other illnesses, meningitis or severe sepsis. The ultimate goal of any invading microbe is to reside peacefully within our bodies without evoking a strong inflammatory reaction that may result in the elimination of the microbe. 

The researchers have found that pneumococcus and other bacteria accomplish this by targeting a key component of the immune system - the inflammasomes. Inflammasomes are protein complexes, which upon recognising foreign molecules, for example those found in microbes or damaged cells, initiate reactions to kill microbes and to clear diseased cells. 

The researchers found that bacteria such as pneumococci release large quantities of hydrogen peroxide, and that this causes inactivation of inflammasomes thereby weakening the immune system. In mice models, the researchers observed that bacteria manipulated to produce less hydrogen peroxide were unable to inactivate inflammasomes and therefore elicited a faster inflammatory response that effectively cleared the bacteria from mouse lungs. 

The researchers also found that by innoculating the mice with a special enzyme, catalase, which breaks down hydrogen peroxide, one could increase the inflammation and inflammatory symptoms, leading to faster elimination of pneumococci from the lung. The study was published in the journal Nature Communications.