 Next, everyone feel for your pulse. Stick your hand out, thumbs up. Feel for the knobby bone at the top of your wrist. Then if you slide your hand down across the front of your wrist, you'll feel these like strands of spaghetti. Those are the tendons in your wrist. If you lightly feel between the knobby bone and that first tendon, you should feel your pulse. Got it? Okay, now we're going to feel what happens to our pulse when we take a deep breath. We're going to try it twice. Try to feel what happens to your pulse when you inhale and when you exhale. All right, here we go. Slow inhale, slow exhale, one more time. What happened when you breathed in and breathed out? You should have felt your pulse speed up when you breathe in and slowed down when you breathe out. That's called heart rate variability, and it's a very good thing. That's a measure of the control our nerves have over our heart. This is the survival curve for people after a heart attack. With good heart rate variability, 9 out of 10 people are still alive four years later. But with bad heart rate variability, in that time period, half drop dead from sudden cardiac death. So is there anything we can do to improve our neurological control over our heart? A landmark article this year in the American Journal of Clinical Nutrition found that there was only one type of food that could significantly improve our heart rate variability. Is it citrus fruits, omega-3s, or dark green leafy vegetables? Let's look at the graph. Here's the level at which statistical significance is reached. Let's see which one makes it. Eating just a half serving of greens every day significantly improved neuronal heart control, which may be why studies in the past have suggested a quarter cup of greens a day could cut our risk of having a heart attack by 67%. So control your heart by any greens necessary.