FLIGHTFUD

Infrequent sleep and traveling across time zones disrupts the circadian rhythm, causing jet lag.

Research shows this disrupts the gene expression that influences aging and the immune system.

When circulation is impaired, blood pools in your legs, contributing to foot swelling by forcing fluids out of the blood and into the surrounding tissue.

More serious problems like varicose veins or blood clots can also result.

The blood in your digestive tract is rerouted to support vital functions so there is less energy to digest the food you eat.

Your under-functioning digestive system will have a harder time digesting the unhealthy, nutrient-depleted plane food, and the air pressure changes cause build-ups of gas. It's clear why we feel bloated and experience all sorts of digestive disturbances while we fly.

Not only are you exposed to tons of germs being in close quarters with hundreds of strangers, but the fatigue from reduced oxygen levels and jet lag can switch off immune system response. 

The dry cabin air also causes swelling of the mucous membranes, compromising their ability to protect you.

Cosmic radiation is radiation from the sun, which can cause damage to tissues and DNA.

At ground level this isn’t a problem, because the atmosphere provides somewhat of a protective barrier. But once you put yourself into a metal tube and fly to altitudes of 30,000-40,000 feet this can become a big problem over time. 

Cabin air is typically drier than the Sahara desert.

Dehydration can cause headaches, parched skin and lips, and fatigue.

Having dehydrated mucous membranes (especially in the nose) leaves us more vulnerable to viruses.