The significance of NAD+ supplementation depends on factors such as age, health status, desired effect, and the extent to which an individual resembles the populations examined in published studies. Rather than treating NAD+ as a universally suitable or unsuitable solution, this guide summarises the groups for which evidence from human studies is relatively stronger, weaker, or still absent.
Who has the strongest scientific basis for the use of NAD+ supplementation?
Most published randomised, placebo-controlled trials concerning NR and NMN have focused on middle-aged and older adults, typically ranging from about 40 to 70 years of age and above [1,2]. This is also the age range in which the age-related decline in NAD+ levels becomes more biologically significant.
NAD+ concentration appears to decline with age in several tissues, which is why older people have become a primary focus of research into NAD+ precursors. However, this reflects both biological interest and research priorities. It does not mean that supplementation has been proven to be beneficial for every individual in these age groups.
The evidence is most direct when a specific effect has actually been measured in human studies. Examples include physical fitness parameters such as walking speed [1], changes in lipid-related biomarkers [3], and improvements in insulin sensitivity in certain specific populations [4].
For these outcomes, there is a clearer evidence base than for broader claims regarding general „anti-ageing”, supporting longevity or improving cognitive function. These more general goals remain considerably less well supported by research in humans.
Athletes and highly active adults fall into a different category of evidence. Currently, there is no large, dedicated body of clinical research demonstrating that NAD+ precursor supplementation improves athletic performance, recovery, endurance, strength, or other sports-related parameters.
General safety data obtained from studies in healthy adults may still provide some information also for physically active individuals, but should not be interpreted as evidence of a direct benefit for athletic performance.
Groups requiring greater caution or burdened with significant evidence gaps
In several groups, there are either significant safety gaps or specific findings that make the data from general adult studies of limited application.
One example is people with a personal or family history of cancer. In one preclinical study, nicotinamide riboside supplementation was associated with an increased incidence of cancer and brain metastases in a mouse model of breast cancer [5].
This was an animal study and does not prove that NAD+ precursors increase cancer risk in humans. However, NAD+ metabolism is closely linked to cancer cell biology, and most general NAD+ studies were not designed to evaluate cancer incidence, recurrence, metastasis, or long-term oncological outcomes.
For this reason, the overall safety data in adults provide limited information for individuals with active cancer, a history of cancer, or a potentially increased cancer risk.
Pregnancy and breastfeeding represent another major evidence gap. No dedicated human safety studies have established the safety of NR, NMN, or concentrated NAD+-related products during pregnancy or breastfeeding.
Individuals with significant cardiovascular disease may also require a separate assessment, particularly if intravenous NAD+ is being considered. A retrospective real-world usage study showed that gastrointestinal and cardiac-related symptoms occurred more frequently with IV NAD+ than with intravenous nicotinamide riboside under the same clinical conditions [6].
This result relates specifically to intravenous administration and should not be automatically extrapolated to oral NR or NMN.
Children and young people were also largely absent from clinical trials. The majority of published research on NAD+ precursors has focused on adults, which is why paediatric safety, developmental impacts and dosing remain insufficiently characterised.
The use of medicines is another area of uncertainty. Formal drug interaction studies regarding NAD+ precursors are limited, and in many clinical trials the use of medicines was controlled through exclusion criteria rather than direct interaction studies.
The absence of reported interactions in such studies does not, therefore, prove that every combination of medicines is safe.
The question of age — can you be „too young”, and is there an ideal age to start?
An evidence-based „ideal age to start” NAD+ supplementation has not been established. This remains a genuine research gap.
The biological rationale for research into NAD+ precursors is largely linked to ageing, as NAD+ concentrations appear to decrease gradually over time. Proposed causes include increased activity of NAD+-consuming enzymes, such as CD38, the accumulation of cellular and DNA damage, changes in PARP activity, and disturbances in NAD+ synthesis or recovery pathways [7].
This is one of the reasons why middle-aged and older people were studied much more frequently than younger adults.
Data on healthy younger adults are considerably more limited. Many randomised trials have only recruited participants aged around 40–55 or older, and so there is relatively little direct evidence to show whether increasing NAD+ levels in healthy young adults improves physical performance, cognitive function, metabolic health or other outcomes.
This does not mean that NAD+ precursors are harmful to younger adults. It simply means that the rationale based on counteracting the age-related decline in NAD+ is less directly applicable if a significant decline has not yet occurred.
Children and adolescents represent an even greater evidence gap. No paediatric starting age, standardised dosing regimen or sufficient safety data have been established for NAD+ precursor supplementation in this population.
Current clinical trials therefore do not provide a basis for treating NAD+ supplementation as an established intervention in healthy children or adolescents.
Special circumstances: liver disease, the menopause and medicines being taken
NAD+ metabolism is closely linked to liver function, as the liver plays a key role in nutrient metabolism, lipid processing, detoxification and the metabolism of several NAD+ precursors and related metabolites.
Some human studies have reported results significant for metabolic markers associated with liver health. A meta-analysis of 40 studies showed that interventions with NAD+ precursors significantly reduced the levels of triglycerides, total cholesterol, and LDL cholesterol [3].
These results relate to circulating lipid markers, rather than direct measurements of liver disease. They do not prove that NAD+ precursors reduce liver fat, improve fibrosis, normalise liver enzymes or treat conditions such as non-alcoholic fatty liver disease, hepatitis or other diagnosed liver diseases.
No specific human trial has been identified that would confirm the use of NAD+ precursors as a treatment for a diagnosed liver disease. The findings relating to lipids should therefore not be interpreted as direct evidence of a therapeutic effect on the liver.
The menopause is another area where there are limited data from human studies. In one open-label pilot study, 40 women aged over 35 were given a combination of 250 mg of nicotinamide riboside and 50 mg of pterostilbene for 7 days [8].
Among the 32 participants who initially reported symptoms associated with the menopause, a reduction of at least 50% in the frequency and severity of hot flushes, bloating and sleep disturbances was observed. The study also noted a change in the ratio of oestradiol to oestrone, two forms of oestrogen [8].
These results are still preliminary. The study was short, lasting only 7 days; it was an open-label trial and did not include a placebo group.
The research team also included employees of the company that manufactures and sells the supplement under investigation. These limitations make it difficult to distinguish intervention-specific effects from the placebo effect, expectations, natural fluctuations in symptoms or other sources of systematic error.
The findings therefore need to be confirmed in larger, independent, randomised, placebo-controlled trials before any effect relating to the menopause can be considered proven.
The use of medicines remains another area where data are incomplete. Formal studies of the interactions between NAD+ precursors and commonly prescribed medicines are limited.
In human studies, changes in glucose regulation, insulin sensitivity, lipid metabolism, vascular function, and parameters associated with blood pressure have been observed, although the results have not been consistent across all studies.
This may be relevant for medicines used to treat diabetes, hypertension, cardiovascular diseases and other chronic conditions. However, the current literature does not provide a complete or validated map of interactions for NR, NMN and other NAD+-related compounds.
How does the evidence vary depending on the population and the objective?
The significance of NAD+ supplementation depends to a large extent on whether the specific population and the expected effect have actually been studied.
The evidence is stronger when the question concerns a clearly defined biological or clinical outcome assessed in controlled human trials. Examples include changes in NAD+ biomarkers, lipid markers, selected parameters of physical fitness and insulin sensitivity in specific populations [1,3,4].
The evidence becomes weaker when the expected effect is broad or poorly defined. Terms such as „wellness”, „anti-ageing”, „brain restoration”, „mental clarity” or „support for longevity” often encompass a wide range of biological or subjective effects that have not been validated as individual clinical endpoints.
Age also influences how directly available data can be applied. Middle-aged and older adults have a significantly larger body of research, as these are the populations that most frequently participated in studies on NAD+ precursors [1,2].
There is significantly less direct data on outcomes for healthy young adults, whilst for children, adolescents, pregnant women and breastfeeding women, dedicated safety data is very limited or completely lacking.
Health status constitutes a further layer of assessment. Findings obtained in generally healthy, middle-aged individuals cannot automatically be generalised to people with active cancer, serious cardiovascular disease, diagnosed liver disease, diabetes requiring medication, or other complex medical conditions.
The route of administration is also significant. Oral NR and NMN currently have the largest body of randomised human trials of any of the commonly discussed NAD+-related products.
The evidence regarding patches, subcutaneous injections, intramuscular and intravenous administration of NAD+ is considerably more limited. The results of studies on oral precursors should therefore not be automatically extrapolated to other routes of administration.
Another significant limitation is the duration of the studies. Many of them lasted only a few weeks or months, rather than many years.
An intervention that appears well tolerated in the short or medium term does not necessarily have to be equally well characterised with continuous multi-year use.
The available literature supports a population-specific interpretation depending on the expected effect, rather than a universal conclusion regarding who „should” use NAD+.
For some middle-aged and older adults, human studies provide relatively significant evidence that oral NR or NMN can increase NAD+ biomarkers and affect selected metabolic or functional parameters.
For many other proposed uses, the evidence remains preliminary, inconsistent, indirect or entirely absent.
This distinction is important because proof that a given compound is relatively well tolerated in a clinical trial is not the same as proof that it provides a significant clinical benefit for a specific purpose.
Limitations of current evidence
- Most clinical trials regarding NAD+ precursors have involved middle-aged and older adults. Data on healthy younger adults remain relatively limited [1,2].
- Dedicated research involving athletes or participants selected specifically for athletic performance, recovery, strength or other physical activity-related goals is limited.
- No evidence-based „ideal starting age” for NAD+ supplementation has been established.
- The age-related decline in NAD+ provides a biological rationale for studies in older adults, but it does not prove that supplementation confers clinically significant benefits simply because a person has reached a certain age [7].
- Paediatric safety, effects on development and dosage have not been adequately established.
- Data regarding safety during pregnancy and breastfeeding remain insufficient.
- The menopause results discussed in this article are from a small, short, open-label study without a placebo group [8].
- Researchers employed by the company manufacturing the tested product also participated in the menopause study, which represents an additional potential source of systematic error [8].
- Independent, randomised, placebo-controlled trials are needed before any effect related to the menopause can be considered confirmed.
- No dedicated human study has been identified confirming NAD+ precursors as a treatment for diagnosed liver disease.
- Improvements in triglyceride levels, total cholesterol or LDL cholesterol should not be interpreted as evidence of a reduction in hepatic steatosis, fibrosis, inflammation or other liver-specific parameters [3].
- The discussed cancer risk originates from a single animal study and has not been confirmed as a comparable risk in humans [5].
- Most general NAD+ studies were not designed to assess cancer incidence, recurrence, metastasis, or cancer-related mortality.
- Formal drug interaction studies remain limited, therefore general safety data in adults do not confirm the safety of every combination with medicines.
- Evidence varies significantly depending on the route of administration. Oral NR and NMN have by far more controlled human trial data than intravenous, intramuscular, subcutaneous or transdermal NAD+-related products.
- Data regarding short-term and medium-term tolerance should not be treated as equivalent to confirmed long-term safety.
- Increasing the level of NAD+ in the blood or tissues does not automatically mean an improvement in physical performance, cognitive function, metabolic health, biological age, healthspan or lifespan.
Disclaimer
The article is purely educational and summarises scientific research. It does not constitute medical advice or an individual recommendation for or against NAD+ supplementation.
NAD+ and its precursors should not be presented as FDA- or EMA-approved treatments for ageing, menopausal symptoms, liver disease, cancer, metabolic disorders, cardiovascular disease, cognitive impairment, the enhancement of athletic performance, or any other diseases or medical uses, unless referring to a specific approved medicinal product and indication.
Available evidence varies significantly depending on age, health status, study population, specific NAD+ precursor, route of administration, dose, duration of use and the clinical outcome assessed.
The strongest human clinical data relate to selected biomarkers and specific outcomes studied mainly in middle-aged and older adults. Evidence is more limited or entirely absent for healthy younger adults, children, adolescents, pregnancy, breastfeeding, many medically complex populations, and numerous commonly promoted wellness and anti-ageing effects. Short- and medium-term safety findings in the general adult population do not establish suitability for every group, and NAD+ biomarker changes on their own do not prove clinical benefit.
References
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