BY DALE BREDESEN, MD

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Magnesium and zinc, two essential minerals found in small amounts in the body, play a critical role in supporting brain volume and cognitive health as we age.

Most don’t know that human adults carry only about 25 grams of magnesium in their bodies— that’s about the weight of a standard AA battery.

Yet if you completely removed that mineral from our blood, bones, and other tissues, things would go very badly very quickly, especially for our brains.

Magnesium and Zinc: The Brain’s Key to Longevity

That’s because magnesium is essential for hundreds of enzymatic reactions that permit nerves to function, energy to be produced, and calcium and potassium ions to be transported across cell membranes.

What this also means is that it doesn’t take a lot of magnesium to make a big difference— just a fraction of a gram per day can pay tremendous dividends in brain health.

Indeed, when researchers imaged the brains of six thousand healthy middle-aged individuals, they discovered that those whose diets included a half gram of magnesium each day had significantly higher brain volumes—a key indicator of biological aging.

Researchers figured that this dietary habit alone equated to a full year of biological brain aging.

There’s even less zinc in the human body—about 2 grams, or the equivalent of a small sugar packet—but it plays a key role in the brain, where it has both functional and structural purposes keeping synapses firing and contributing to the ability of our brains to change the activity of those synapses in response to our ever-changing world.

Zinc is also crucial for optimal immune responses and for insulin sensitivity.

While deficiencies in zinc are rare in childhood, when this problem does occur in young people it is often associated with cognitive decline and learning struggles.

Zinc deficiency becomes much more common as we age.

Sure enough, even when we control for many other factors, deficiency in zinc is associated with cognitive decline in this stage of life as well.

This is why diets rich in oysters, shellfish, legumes, and nuts can be beneficial to lifelong brain health.

So, whether through targeted supplementation, mineral-rich foods like oysters and leafy greens, or by supporting a healthy microbiome to enhance mineral absorption, maintaining adequate levels of magnesium and zinc is a vital investment in lifelong cognitive health.

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Well Being Journal adapted the above excerpt from The Ageless Brain by Dale Bredesen, MD. Copyright © 2025 by Dale Bredesen and reprinted with permission from Flatiron Books.