For decades, people thought physical exercise benefited only the body. But every year we learn how incorrect that was, and Dr. David Merrill, director of PNI’s brain health center, is one of the people pushing our knowledge forward. It turns out that exercise builds the brain by prompting the production of brain derived neurotrophic factor, or BDNF. “Trophic” compounds cause things to grow, and BDNF helps create new connections among neurons, which is how we learn. In short, BDNF is fertilizer for the brain, Dr. Merrill says. In a perfect world, we would be able to take BDNF in a pill, like a vitamin. But it’s a big, clunky molecule that doesn’t pass easily from blood to brain. Exercise gets the job done, boosting BDNF and keeping our brains nimble. That fact makes exercise crucial as we age. Pumping iron, and therefore pumping up BDNF, promotes brain plasticity: the ability to change, grow and adapt to the insults that come with growing older. Listen to this episode to hear how you can boost BDNF through exercise and stay sharp into your golden years.