By most people's 50s, NAD+ levels have fallen to roughly half of what they were in their 20s. That is not a minor decline. This coenzyme is involved in more than 500 enzymatic reactions across every living cell in the body, and when it drops, a lot of things drop with it.
What NAD+ Does in the Body
NAD+ has a central role in mitochondrial energy production, DNA damage repair, and the activation of sirtuin proteins. Sirtuins are the class of proteins most consistently linked to longevity in ageing research, and their activity is directly coupled to NAD+ availability. When NAD+ is abundant, they work. When it declines, sirtuin activity falls with it. Most of the biological processes the body uses to stay healthy and repair itself sit downstream of this relationship.
The Age-Related Decline of NAD+
Published studies put the decline at roughly 50% between a person's 20s and 50s. That number is not controversial. The longevity research community has been working with it long enough that it functions as a baseline assumption rather than a finding still needing defence. The consequences show up in mitochondrial efficiency first. Then in how well the body repairs DNA. Then in sirtuin activity. None of these decline in isolation. They pull each other down, and the cumulative effect is what most people recognise as getting older: the energy that used to recover overnight but now needs a weekend, the mental clarity that has become unreliable rather than just occasionally off.
What Is the Best Way to Boost NAD+ Naturally?
Eating your way to higher NAD+ does not work. NAD+ itself does not survive digestion in any meaningful quantity. Precursors do. NMN and NR are absorbed, transported into cells, and converted into NAD+ through the biosynthesis pathway. Of all the precursors studied in humans, those two have the most published trial data behind them. NMN (nicotinamide mononucleotide) enters the pathway one step closer to NAD+ than NR (nicotinamide riboside) does. Whether that translates to a practical advantage is still being worked out in the research.
Outside supplementation, certain behaviours reliably support NAD+ metabolism: consistent sleep, high-intensity exercise, intermittent fasting, and regular heat exposure such as sauna use all show up in the research with meaningful effect.
Which Works Better, NR or NMN?
The research does not yet clearly favour one over the other. NR has a longer published trial history with more human studies. NMN has attracted more recent attention and the mechanistic argument for its pathway efficiency is reasonable, but head-to-head clinical data remains limited. Both raise NAD+ levels. If you are deciding between them, the more practical question is which you will take consistently, because duration of supplementation matters more than the precursor choice.
Feel Supreme's range includes both NMN Capsules with Astaxanthin and NR Capsules with Astaxanthin, each paired with an antioxidant to support cellular protection alongside NAD+ replenishment.
Spermidine and Autophagy
NAD+ supplementation addresses one side of cellular ageing. The other is autophagy.
Autophagy is the process by which the body breaks down and recycles damaged or dysfunctional cellular components. It declines significantly with age, and that decline contributes to a build-up of cellular debris that accelerates ageing processes independently of NAD+ levels. The two pathways are separate problems that compound each other.
Spermidine is a naturally occurring polyamine and one of the most studied autophagy activators outside of caloric restriction itself. It occurs in wheat germ at the highest concentrations found in any food, and in smaller amounts in aged cheeses and mushrooms. Studies show it can stimulate autophagy in a way that mimics some of the effects of fasting. Feel Supreme's Spermidine Capsules with Astaxanthin combine it with antioxidant support for a complementary approach to cellular longevity alongside NAD+ precursor supplementation.
