What is NAD+ and what does it do in your body?
NAD+ is an indispensable molecule for energy, DNA repair and cell maintenance, and its levels measurably decline with age. Whether that decline can be corrected with supplements, and what benefit that would bring, is a separate question.
NAD+ is a molecule present in every living cell. It acts as a kind of electron shuttle: it picks up electrons from one reaction and delivers them to the next. In this way it helps cells produce energy from food. Without NAD+, the mitochondria, the power plants of your cells, run at half capacity.
Beyond energy production, NAD+ has two other important roles. It fuels a group of proteins involved in ageing, gene expression and metabolism; without sufficient NAD+ those proteins cannot do their job. At the same time, NAD+ is the raw material for enzymes that repair damaged DNA. When NAD+ is too scarce, that repair process runs poorly.
NAD+ and its related form NADPH also protect cells against harmful oxygen radicals. This is not black and white: when dysregulated, they can also contribute to the production of those radicals. In addition, signalling molecules are made from NAD+ that regulate calcium balance in cells, which in turn affects muscle contraction and nerve conduction.
As you age, NAD+ levels in tissues decline, both in animals and in humans. This decline is associated with conditions such as cognitive deterioration, muscle loss and metabolic diseases, although it has not been proven that the decline is the cause. A partly understood mechanism: ageing cells secrete inflammatory substances that prompt certain immune cells to produce an enzyme that actively breaks down NAD+, accelerating the downward spiral.
A disrupted NAD+ balance is also linked to neurodegenerative diseases and tumour formation, but whether lower NAD+ levels in humans actually cause those diseases has not yet been established. NAD+ also plays a role in immune cells and in the process by which cells stop dividing yet remain active and can fuel chronic inflammation.
This answer draws on several comprehensive review studies by established researchers in the field. The basic functions of NAD+ (energy metabolism, DNA repair, redox balance) are biochemically well established and broadly supported. The associations with ageing and disease come primarily from research that follows people or animals over many years, not from studies that can directly demonstrate cause and effect.
What does alcohol do to your cells and DNA in the long run?
Chronic alcohol use damages your DNA, disrupts how genes are read and increases the risk of several types of cancer. Drinking less, or not at all, is the only way to reduce this risk.
What does a vitamin D deficiency do to your DNA?
A vitamin D deficiency is associated with greater DNA damage, especially in people with an additional risk factor. Make sure your vitamin D level is adequate, but if you are unsure about supplementation, consult your general practitioner.
What does chronic stress do to your DNA?
Chronic stress accelerates the wear on your DNA protectors (telomeres) in a way that corresponds to years of extra cellular ageing. You cannot prevent this entirely, but limiting prolonged stress is probably one of the most direct ways to slow biological ageing.
What are free radicals and what do they do to your cells?
Free radicals arise naturally when your cells produce energy and, in small amounts, do useful work. Only when they overwhelm your body's own defence systems do they damage DNA, proteins, and fats, contributing to ageing and disease.
What does NAD+ do for your brain?
NAD+ matters for your brain and declines with age. Whether topping it up via NMN (a substance your body converts into NAD+) or other means actually helps has not yet been convincingly demonstrated in people. Wait for the results of larger studies in people before drawing firm conclusions.
What is NAD+ and why does it decline as you age?
NAD+ measurably declines with ageing, and supplements raise levels demonstrably in people. Whether that also makes you healthier has not yet been proven, and the safety of taking them for many years deserves attention.