Does NAD+ decline with age? What a new study really tells us

NAD+ is seen by many as the gold molecule for healthy ageing. This is based on the well-documented role of NAD+ in supporting cellular energy and the assumption that NAD+ levels decline as we age. As a consequence, longevity science is turning to NAD+ supplementation as a promising alternative to increase energy and vitality in people’s old age.

But we can’t deny that research around NAD+ is still evolving, especially when it comes to understanding its real impact on ageing. A recent study published in Nature Metabolism last week has sparked a new debate, spreading online alongside claims that NAD+ is not effective for healthy ageing. 

To distinguish interpretation from evidence, we have dissected the controversial study in this article, so you understand:

• What’s the evidence behind NAD+ and ageing

• How was the new study designed, and do its results challenge NAD+ reduction with age

• What are the limitations of this study

• And whether NAD+ supplements are still worth it

TL;DR

• A new Nature Metabolism study finds that blood NAD+ levels stay surprisingly stable across age, lifestyle and fitness, so blood NAD+ alone may not be a good biomarker of ageing.

• This does not contradict evidence that NAD+ can decline in energy‑hungry tissues like muscle and brain, where lower NAD+ has been linked to age‑related decline.

• The study confirms that NAD+ precursors can raise blood NAD+, supporting the biological rationale behind NAD+ supplements even if the benefits are not captured by a single blood test.

• Overall, the paper reshapes how scientists study NAD+ and ageing, but it does not deny the benefits of NAD+ supplements; instead, it highlights the need for better tissue measurements and larger, well‑controlled trials.

Why are NAD+ and ageing linked?

Over the last decade, different studies have shown an age-related decline in NAD+ levels in blood and tissues like muscle and brain. Scientists are interested in studying this further, as NAD+ is directly linked to energy production and cellular damage repair, two processes that become increasingly important to maintain as we age.

But among these studies, there are some contradictions, especially in blood tests: some studies show NAD+ blood levels decline the older we get, while others do not. This variability comes from differences in how NAD+ was measured, how samples were handled, and the small number of people included in many studies.

Those are the exact challenges that a new paper in Nature Metabolism wanted to address. To do so, they analysed different groups of people using a single, optimised measurement method. Their goal was to answer this question: if NAD+ blood levels vary as we age, could we measure NAD+ to track healthy ageing? 

The Nature Metabolism study combined several groups—from young adults to seniors, athletes and twins on an NAD+ supplement—to test how blood NAD+ behaves across ages and lifestyles

How this new study measured blood NAD+ and ageing

Their approach was straightforward: analyze blood samples from adults of different ages to test NAD+ levels, using a method optimized to detect NAD+ even at very low quantities. They compared healthy younger adults up to 30 years old with people over 60, and they also studied another group of adults from their late twenties to early seventies who were at higher risk of heart problems.

The results were clear: there was no significant difference in NAD+ blood levels between younger and older adults in both groups. Still, the authors wondered if NAD+ might only start to drop at very old ages, so they looked at NAD+ blood levels in people in their early sixties untill their late eighties. Again, they didn’t find any clear relation between age and reduced levels of NAD+ levels in blood. 

However, ageing is not only about the number on your ID card or what researchers call chronological age. You can be 50 but follow a lifestyle that makes your body function and feel more like you were 30. The actual state of your body is called biological age, and it’s an essential factor when studying NAD+ and ageing.  

Are there ways to increase NAD+ levels naturally?

To study whether training and diet influence NAD+ blood levels, the authors analyzed samples from elite endurance athletes. When they compared NAD+ blood levels with those of people following normal training routines, they found no differences regardless of age. 

Similar results were observed when diet was taken into account. They selected a group of older adults who were physically vulnerable and who received different combinations of training, a protein-rich diet, and nutritional supplements. They didn’t find any differences in NAD+ levels in blood after 3 and 6 months of following this lifestyle. 

Lifestyle highly influences how energetic we feel as we age,  which is why longevity research looks at NAD+ and ageing alongside different lifestyle programmes 

Are NAD+ supplements still worth it?

NAD+ supplements are still worth it as this research analyzed only a specific aspect of NAD+: its levels in the blood. However, the study didn’t look at NAD+ in tissues such as muscles or the brain. These organs consume high amounts of energy and thus rely heavily on NAD+, which fits with evidence that NAD+ in these tissues declines with age, just when people start to notice a drop in energy.

NAD+ in tissues and ageing: key human and animal studies showing where NAD+ was measured, how it changes over time, and what these shifts in muscle and brain mean for healthy ageing.

These changes at the tissue level also make sense with other mechanisms where NAD+ is involved. Our cells use NAD+ to repair DNA damage, which tends to build up as we get older. The more repair is needed, the more NAD+ is consumed locally, which could increase the need for NAD+ in particular tissues without necessarily causing a big drop in blood levels. 

NAD+ supplements could help support these local NAD+ demands. In fact, in this study, the authors also measured NAD+ levels after people received an NAD+ supplement and found a clear increase in blood NAD+. This adds to the evidence that NAD+ precursors are effective at boosting NAD+ pools, which explains why people experience increased energy and better recovery after supplementing with NAD+. 

In other words, this article doesn’t represent the whole picture of NAD+ in ageing. It mainly shows that blood NAD+ might not be a reliable indicator of how we age or of what happens in specific tissues. Still, we need to be cautious when interpreting these results, as the study comes with different limitations that should not be ignored.

The science behind NAD+ supplements and ageing supports the energy and recovery benefits people notice. NEU+ brings that science into everyday life with an easy‑to‑drink daily shot.

Limits and blind spots of this study

The first limitation comes down to the people involved in the study. The researchers did not follow one large group over time but worked with samples from previous clinical trials, meaning that each group was analyzed independently. 

So while the total number of participants sounds high, each comparison was based on at most 70 people, which is relatively modest for drawing broad conclusions. On top of that, individuals came from different countries, and this can also introduce bias. 

Another limitation has to do with how variable NAD+ levels were. In fact, the authors examined how different methods of processing blood samples influenced NAD+ levels, finding that freezing, a very common procedure, can strongly affect NAD+ stability. This means that detecting more subtle changes in NAD+ levels can be hard, which may be the case as we age. 

In short, this article doesn’t deny the effects of NAD+ supplements on ageing, it just show scientists new ways NAD+ should be studied, by accounting for NAD+ degradation in samples, increasing the number of people involved, and measuring NAD+ in different parts of the body. 

Curious to know more about the science behind the benefits of NAD+ supplements? Explore our article about it here.

FAQs

1. Does this new study mean NAD+ doesn’t decline with age?

Not exactly. The study shows that whole‑blood NAD+ levels are remarkably stable across different ages and lifestyles, but it doesn’t measure NAD+ inside organs such as muscle or brain. Those are the tissues where several human and animal studies have reported NAD+ declines with age, and where NAD+ is specially important as they consume high amounts of energy. So the paper mainly questions blood NAD+ as a marker of ageing.

2. If blood NAD+ doesn’t change much, are NAD+ supplements pointless?

The study was not designed to evaluate clinical benefits of NAD+ supplements; it focused on whether blood NAD+ tracks ageing. In fact, the researchers saw a clear rise in blood NAD+ after people took a nicotinamide riboside supplement, supporting previous work showing that NAD+ precursors can boost NAD+ levels in blood and cells. What the paper tells us is that blood NAD+ alone is probably not a good indicator of how we age, not that NAD+ supplementation has no biological effect.

3. Can lifestyle changes like exercise and diet still affect NAD+?

 In the Nature Metabolism paper, blood NAD+ stayed stable in endurance athletes and in older adults following structured exercise and nutrition programmes. That suggests blood NAD+ is quite robust to lifestyle changes. But other research has shown that regular exercise can increase NAD+ in muscle, and that tissue‑level NAD+ is linked to better function. The take‑home message is that lifestyle could reshape NAD+ even if that doesn’t show up clearly in blood tests, and we need more evidence to support this. 

4. What are the main limitations of the new NAD+ study?

There are several. The researchers analysed samples from multiple existing clinical cohorts rather than one large, unified study, so each comparison involved at most 70 people. That limits the ability to detect small age‑related changes. Handling and storage of blood samples also turned out to have a strong impact on measured NAD+ levels, especially freezing, which can degrade NAD+. All of this means subtle effects with age could be missed, and the results need to be seen as an important piece of the puzzle, not the final word.

5. How should we think about NAD+ testing and supplements after this?

This study suggests that using a single blood NAD+ measurement as a “biological age test” is premature. Blood NAD+ appears too stable, and too sensitive to sample handling, to serve as a reliable ageing biomarker on its own. For supplements, the picture is different: the biology still supports a key role for NAD+ in tissues, and this study adds to the evidence that precursors can raise NAD+ in blood and cells. The next step is better‑designed trials that control sample handling, look directly at NAD+ in tissues, and link changes in NAD+ to meaningful outcomes like energy, recovery, and long‑term health.