The 1 food you should eat for brain health — and why you can't replace it with supplements

• A neurologist says there's a lot you can do for your brain health through small dietary changes.
• The first tip he recommends is eating more leafy greens, like spinach and kale.
• The nutrients that help plants grow up healthy and green are also good for our brains.

Dean Sherzai, a neurologist and dementia researcher, has a favorite study.

Published in 2018, and funded by the National Institute on Aging, the blockbuster study — which examined the eating patterns of over 900 older adults living around Chicago — showed that those who ate about one or two cupfuls of salad greens a day, including spinach, kale, collards, and lettuce, had brains that performed about 11 years younger than their lettuce-less peers of the same age.

"Just add green," Sherzai, half of the husband-and-wife team who call themselves "The Brain Docs," told me when I asked what single change I could make today to stave off neurodegenerative diseases.

"If you have to start one place, because there's only so much space in your stomach, add two servings of greens to your diet," he told Business Insider. With that, "you've significantly reduced inflammation, oxidation, glucose dysregulation, and lipid dysregulation," which are all hallmarks of many age-related diseases.

Sherzai knows it's tempting to reach for a novel, quick-fix potion that promises to boost brain health, like a fancy supplement, an expensive gummy, or a new smoothie powder. But what he's discovered, after decades of research, is that some of the "most profound" ways we can influence our own cognitive health are the most old-school.

Our thirst for novelty may be steering us in the wrong direction, away from seeing the truly phenomenal chemical properties of greens. If there is anything like a silver bullet ingredient for your brain, it's more likely to be the cocktail of nutrients quietly sitting inside bright green leaves, helping them grow.

Why chlorophyll from plants is more powerful than green juices and supplements

When we eat green plants, we are consuming a green pigment molecule called chlorophyll, which helps plants photosynthesize — capturing solar rays and converting them into energy to grow.

Chlorophyll is green because red and blue light from the sun gets taken in and absorbed by the plant for energy. Green light is what's left over, and what gets reflected back to us visually. And it turns out that those green chlorophyll molecules are packed with a rich bounty of nutrients including iron, magnesium, and nitrogen — ingredients that are fundamental for life, whether it's a plant's or a person's.

Wellness brands have tried to harness this natural dream team combo by putting it in supplements and things like chlorophyll water. But because chlorophyll is so unstable, they often have to take out the magnesium and add in other elements like copper or zinc instead. Experts say it's unclear whether those industrial versions of chlorophyll could have much of a health benefit at all. What we do know is that you can get the health benefits if you consume chlorophyll in its original packaging. In other words: eat more leaves.

"The chlorophyll itself is maybe not that useful," Troy Magney, an associate professor focused on plant optics at the University of California, Davis, told Business Insider, reflecting the fact that there is no solid research to support chlorophyll supplementation.

Rather, it's the chemical "building blocks" of chlorophyll molecules in the leaves we eat that likely help us humans thrive, Magney said. Crack open that dusty chemistry textbook, and you'll discover many of the various atomic components of the chlorophyll molecule, as well as other ingredients necessary for proper plant metabolism and growth, are great human health boosters.

"Things like iron and magnesium and nitrogen and these nutrients that all are necessary for chlorophyll," Magney explained.

Magnesium is an essential element for our muscles, nerves, bones, and blood sugar — and roughly half of us aren't getting enough of it. Iron plays a key role in carting fresh oxygen around our body, while nitrogen helps us grow, and keeps our brain and immune system strong.

People who eat more leafy greens also take in decent amounts of other nutrients including vitamin K, folate, lutein, and beta-carotene. Experts think these nutrients — all present thanks to the bright pigments in the leaves — may work together synergistically in ways that can protect our brains. We know already that they're great for curbing inflammation, improving eyesight, and protecting DNA.

Darker leaves have more nutrients in each bite

Sherzai recommends incorporating more of the darkest green plants like spinach and kale into your diet when you can.

"The darker the better," he said.

That's because darker greens have, by default, more chlorophyll packed inside of them, and thus more nutrition in every bite.

"There's more nutrients required to produce more chlorophyll," Magney said. "So there's a higher density of these compounds in the leaf itself."

It's also a good idea to consume your plants as fresh as possible. When leafy greens start to go bad and turn yellow in your fridge, that's good evidence that they're losing some of the green chlorophyll they created while they were growing.

"Those yellow pigments are always there, but we can't actually see them because the chlorophylls are so intense, they kind of overwhelm the yellow pigments," Amber Flores, a Ph.D. candidate in plant biology at UC Davis, told BI. "Once the chlorophyll starts to degrade as the leaf begins to senesce, or to die, we start to see the yellows come out."

There may still be some beneficial carotenoid pigments tucked into those yellowing leaves (and they are great for eye health) but in general, a wilting leaf is becoming less and less nutritious than it used to be.

So look for the very freshest lettuce you can find, and if you like olive oil, drizzle a little on top — the fat will help your body better absorb nutrients inside the plant too. If you happen to prefer a less colorful green leaf, like a pale iceberg or romaine, don't be ashamed. Go for it.

"I know people think that lettuce is kind of like crunchy water, especially iceberg lettuce, but that is definitely diminishing the other things that lettuce can bring to the table," Flores said. While it's true that lettuce growing inside a protective ball like a lettuce head won't be able to absorb as much sunlight as something like a floppy stock of spinach, and therefore won't be bright green and chlorophyll-rich, it still has a decent amount of other minerals and fiber packed inside.

"It's not as pigmented as some of the other leafy greens, but again, still very much worthwhile to eat and also easier to incorporate into a lot of meals," Flores said. "Just keep eating vegetables," she said, however you like them.