What does NAD+ do for your brain?

NAD+ is present in all your cells, including your brain cells. It is indispensable for energy production, DNA repair, healthy mitochondria (the powerhouses of your cells), and the resilience of neurons under stress. Several NAD+-dependent enzymes also play a role in synaptic plasticity, the ability of your brain to strengthen or weaken connections. That is the foundation of learning and memory¹.

As you age, your NAD+ levels decline, including in your brain. This is seen as a possible explanation for why older brains are more susceptible to decline and disease. It remains a hypothesis for now: the precise cause and effect in humans has not yet been firmly established².

In Alzheimer's disease, the link with NAD+ has been studied most extensively, but almost everything comes from mouse studies. Mice with advanced Alzheimer's showed, after restoration of NAD+ metabolism, less accumulation of harmful proteins, less inflammation and oxidative damage, and a restored blood-brain barrier. Their cognition improved completely. Separate mouse studies show that NAD+ supplementation reduces neuroinflammation and senescence, the process by which damaged cells continue to release harmful substances³,⁴. Impressive, but whether this also works in humans is still unknown.

NAD+ supplements, such as NMN, are available as a supplement. In cell and mouse studies they raise NAD+ levels and inhibit age-related processes such as DNA damage. One mouse study showed that NMN counteracts leakage of the blood-brain barrier by restoring NAD+ levels in the brain's blood vessels⁵. Human studies to date are small or still ongoing. The same effect seen in mice has not yet been demonstrated².

There is also a broader story: your body produces NAD+ via a pathway that starts with tryptophan, an amino acid from food. Some intermediates in that pathway protect brain cells, while others are actually toxic. Dysregulation of this pathway is associated in mouse studies with depression-like behaviour and cognitive problems. In humans there is a link with psychiatric conditions during inflammation⁶. It is therefore not only about how much NAD+ you produce, but also which intermediates are released along the way.