Your Brain On... Nutrition (with Dr. Walter Willett)

Ayesha Sherzai (0:00)

Everyone eats, but how and what we eat has become one of the most divisive conversations in modern life, and most people seem to be a little confused. Every week brings a new diet trend on social media, a headline that contradicts the last one, and a flood of confident voices. Amid all the noise, the science, the real, rigorous, evolving science, often gets drowned out. But here's the truth. Nutrition science actually holds far more consensus than confusion. We actually have a good idea of what supports our brain and body health long term. And those core principles, like eating more fruits and vegetables, and whole grains, and nuts and seeds, etc. haven't really changed much, as much as the headlines suggest. Still, it's deeply refreshing to hear world-renowned scientists, like Dr. Walter Willett, to say things like, we don't know everything. Because that humility is the scientific method at work. It's not hesitation. It's not weakness. It's integrity. The willingness to follow the evidence, not ideology. Or, as Dean and I often say, to never extrapolate beyond the data. We rarely give our podcast episodes sweeping titles. Most are focused on single, specific questions. But this conversation with Dr. Walter Willett was so rich and so panoramic, it earned the first letter in our neuroacronym. N for nutrition. Dr. Willett, who is a physician and an epidemiologist, is among the most influential nutrition scientists of our time. His decades of Harvard-led research has reshaped how the world understands diet, chronic disease, and planetary health. With more than 2,000 scientific papers to his name, he has helped define what we know about healthy fats, the Mediterranean diet, and how our food choices impact both our human and environmental well-being. In this episode, we talk about his life's work, the importance of nuance, and how culture and context shape what healthy truly means. We also explore why the best diets aren't about restriction, but about quality, diversity, and balance. In a world obsessed with shortcuts and quick fixes, Dr. Willett reminds us that real progress in nutrition, like science itself, comes from taking the long view. Carefully, thoughtfully, and with open eyes. This is Your Brain On Nutrition with Dr. Walter Willett.

Dr. Willett, it's such an honor to speak with you. Thank you so much for your time today. As I was telling you earlier, I feel like I know you because you are the most cited nutritional scientist in the world, and your work, your scientific research, and your papers have guided us to better understand what types of nutritional patterns are associated with better health. I am grateful for your work and this opportunity to speak with you.

Walter Willett (3:03)

Well, it's my pleasure, and I'm greatly appreciative that you're taking on this challenge of providing information because there's so much confusion out there.

Ayesha Sherzai (3:12)

Yes, and it can be quite confusing being exposed to so much noise in nutrition. If you could speak with someone who is not in the field of medicine or science and is wondering what kind of nutritional pattern is associated with better health, whether it's brain health or heart health, how would you start that conversation with them? What would you tell them?

Walter Willett (3:33)

Well, we know a lot, although we're still in the process of additional learning, especially about a lot of the details. But I think we do know a lot about the big picture of how diet influences health. I did have the privilege recently of chairing an international committee to look at this question. We started off by looking at the major food groups one at a time. We learned it's really whole grains we should be eating, not processed, refined grains.

We looked at tubers, like potatoes. Well, not quite as good as whole grains. Sure, we could have some modest amounts, but we favor whole grains. We looked at fruits and vegetables, major protein sources, types of fat, and added fats, say butter versus plant oils like olive oil or soy bean oil, and of course, sodium as well. And when we put all those pieces together, we ended up with something that is very much consistent with a traditional Mediterranean diet, which is quite convenient because we and other investigators have looked at the Mediterranean diet as a whole package and seen that it's very healthy. This time we sort of started from the ground up, looked at all the building blocks and we ended up in the same place. Now, we're still doing work on what's the optimal mix of types of fat, what's the optimal intake of whole grains versus healthy fats. It looks like there's a lot of flexibility, actually. Something like the traditional Mediterranean diet is, overall, a good way to go and we're digging down again looking at more details. But also, because we've taken this bottom up approach, we can understand that we can put this dietary pattern together in many different ways using the flavors and foods of, say, a traditional Latin American diet, African diet, or Southeast Asian diet. This can be implemented around the world and end up with a very healthy diet with different foods and different flavors. There's still nuances and details, but the big picture seems pretty clear.