The CDC reports that more than 1 in 9 Americans over age 12 take an antidepressant – and 60% will be on it for 2 years or more. Yet, several studies have shown that moderate exercise can be as effective as taking an antidepressant for mild to moderate depression.
You don’t have to be a fitness guru – just walking for 35 minutes, 6 days each week lowered mild to moderate depression by 47%.
Why? A recent study in the New England Journal of Medicine (Dec 11, 2014) may have the answer: kynurenine.
In the absence of exercise, stress greatly increases production of kynurenine in the liver, spleen and monocytes (a type of white blood cell). Kynurenine finds its way into the bloodstream and brain, resulting in inflammation and free radicals that influence brain metabolism and behavior that leads to depression.
When you are stressed and you exercise, your muscles produce enzymes called KATs or kynurenine aminotransferases that metabolize the kynurenine. The byproduct (kynurenic acid) can’t get from the blood stream into the brain. That creates resilience to stress.
This is of particular importance in menopausal women and those with type 2 diabetes, when kynurenine levels are typically higher.