 There's accumulating evidence that brain-derived neurotrophic factor may be playing a role in human depression. BDNF controls the growth of new nerve cells, and so low levels may explain the atrophy of specific brain errors you see among depressed patients. That may be one of the reasons exercise is so good for our brains. Starting our day exercise regimen, within three months you can get a quadrupling of BDNF reliefs from your brain. This makes sense. I mean, anytime we were desperate to catch prey, or desperate not to become prey ourselves, we needed to be cognitively sharp. And so when we're fasting, or exercising, or in a negative calorie balance, our brain starts churning out BDNF to make sure we're firing on all cylinders. So of course, big pharma is eager to get drugs to mimic this effect, but is there any way to boost BDNF naturally? Yes, I just said it, fasting and exercise. Okay, okay, but is there anything we can add to our diet to boost BDNF? Well, higher intakes of dietary flavonoids appear to be protectively associated with symptoms of depression. The Harvard Nurses study followed tens of thousands of women for years and found that those who were eating the most appeared to reduce the risk of coming down with depression. Flavonoids occur naturally in plants, so there's a substantial amount in a variety of healthy foods, but wait, how do we know the benefits are from the flavonoids and not just from eating healthier in general? You don't know until you put it to the test. See, some fruits and vegetables have more than others. Apples have more than apricots, plums more than peaches, red cabbage more than white, kale more than cucumbers. So if you randomize people into one of three groups, more high flavonoid fruits and vegetables, more low flavonoid fruits and vegetables, or no extra fruits and vegetables at all, after 18 weeks only the high flavonoid group got a significant boost in BDNF levels, which corresponded to an improvement in cognitive performance. The BDNF boost may help explain why each additional daily serving of fruits and vegetables is associated with a 3% decrease in the risk of depression. A teaspoon a day of the spiced turmeric may boost BDNF levels more than 50% within a month, consistent with the other randomized controlled trials that have so far been done. Nuts may help too. In the Predomet study where people were randomized to be sent weekly batches of nuts or extra virgin olive oil, the nut group lowered their risk of having low BDNF levels by 78%. And brain-derived neurotrophic factor is not just implicated in depression, but schizophrenia as well. Have those with schizophrenia undergo a 12-week exercise program and they get a significant boost in BDNF levels, leading the researchers to suggest that exercise-induced modulation of BDNF may play an important role in developing non-pharmacological treatment for chronic schizophrenia patients. Okay, but what actually happened to their schizophrenia symptoms? Let's find out. 30 individuals with schizophrenia were randomized to ramp up to 40 minutes of aerobic exercise three times a week or not. And there did appear to be an improvement in psychiatric symptoms, such as hallucinations, as well as increasing their quality of life. In fact, you can actually visualize what happened in their brains. Loss of brain volume in a certain region appears to be a feature of schizophrenia, but 30 minutes of exercise three times a week and you can get up to a 20% increase in size of that region within three months. Calorie restriction may also increase BDNF levels in schizophrenia, but they didn't just have them eat less, but eat healthier, less saturated fat and sugar and more fruits and veggies. It's like the Soviet fasting trials for schizophrenia. They reported these truly unbelievable results, supposedly restoring people to function. Fasting described as an unparalleled achievement in the treatment of schizophrenia. Okay, but part of the problem is that the diagnostic system the Soviets used is completely different, making any results hard to interpret, but they do have a subgroup that does seem to correspond to the Western definition and they still report between 40 and 60% improvement rates from fasting. But that's not all they did after being fasted for up to a month. They report on a meat and egg-free diet, so when they report these remarkable effects even years later, that's for those who stuck with the diet. Those who broke the diet evidently relapsed, and the closer the diet was followed, the better the effect. They note that not all patients were able to remain vegetarian, but they tried to keep meat to a minimum. And look, we know from randomized controlled trials that just removing meat and eggs can improve mental states with even just two weeks, and so it's hard to know what role the fasting itself played in the reported improvements. A single high-fat meal can drop BDNF levels within hours, and you can prove it's the fat itself by seeing the same thing injecting fat straight into their veins. Perhaps that helps explain why increased consumption of saturated fats in a high-fat diet may contribute to brain dysfunction, neurodegenerative diseases, long-term memory loss, cognitive impairment. Maybe that helps explain why the standard American diet has been linked to a higher risk of depression, dietary factors modulating the levels of brain-derived neurotrophic factor.