The creators of The Truth About Food found 10 London cab drivers who said they were stressed out. Before changing their diets for the experiment, researchers monitored their heart rates for 24 hours and checked their levels of cortisol, which is known as the stress hormone.
Then, unbeknownst to the cab drivers, an actor posed as a demanding client and stressed them out on purpose. Mission accomplished—after a 15-minute cab ride with the actor, each driver's heart was racing and their cortisol levels skyrocketed!
After they were put to the test, the cab drivers changed their diet. Four times a week for three months, each cabbie ate mackerel, haddock, sardines, salmon, kippers and tuna. These types of oily fish contain certain omega-3 acids thought to have a calming effect on the body.