The importance of NAD+ supplementation depends on factors such as age, health status, desired effect, and how closely a given individual resembles the populations examined in published studies. Rather than treating NAD+ as a universally suitable or unsuitable solution, this guide summarizes the groups in which evidence from human studies is relatively stronger, weaker, or still absent.
Who has the strongest scientific basis for using NAD+ supplementation?
Most published randomized, placebo-controlled trials on NR and NMN have focused on middle-aged and older individuals, typically ranging from about 40 to 70 years of age and above [1,2]. This is also the age range where the age-related decline in NAD+ levels becomes more biologically significant.
NAD+ concentration appears to decrease with age in several tissues, which is why older adults have become a primary focus of research on 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.
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-aging,” longevity support, or cognitive enhancement. These more general goals remain significantly less supported by human studies.
Athletes and highly active adults belong to another category of evidence. Currently, there is no large, dedicated base of clinical studies showing that NAD+ precursor supplementation improves athletic performance, recovery, endurance, strength, or other sport-related parameters.
General safety data obtained from studies in healthy adults may still provide some information for physically active individuals as well, but they should not be interpreted as evidence of a direct benefit to 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 data from general adult studies of limited applicability.
One example is individuals 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 assess cancer incidence, recurrence, metastasis, or long-term oncological outcomes.
For this reason, general 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 evaluation, particularly if intravenous NAD+ is being considered. A retrospective real-world 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 applies specifically to intravenous administration and should not be automatically extrapolated to oral NR or NMN.
Children and adolescents were also largely absent from clinical trials. Most published studies on NAD+ precursors have focused on adults, which is why pediatric safety, developmental effects, and dosing remain insufficiently characterized.
Medication use is another area of uncertainty. Formal drug interaction studies regarding NAD+ precursors are limited, and in many clinical trials, medication use was controlled through exclusion criteria rather than direct interaction studies.
The absence of reported interactions in such studies therefore does not prove that every combination of drugs is safe.
The issue of age — can one be „too young” and is there an ideal starting age?
An evidence-based „ideal starting age” for NAD+ supplementation has not been established. This remains a real research gap.
The biological rationale for research on NAD+ precursors is largely related to aging, as NAD+ concentrations appear to gradually decrease over time. Proposed causes include increased activity of NAD+-consuming enzymes such as CD38, accumulation of cellular and DNA damage, changes in PARP activity, and disruptions in NAD+ synthesis or salvage pathways [7].
This is one of the reasons why middle-aged and older individuals were tested much more frequently than younger adults.
Data on healthy younger adults are much more limited. Many randomized trials have recruited participants only from about 40–55 years of age or older, which is why there is relatively little direct evidence showing whether increasing NAD+ 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 only means that the rationale based on correcting the age-related decline in NAD+ has less direct applicability if a significant decline has not yet occurred.
Children and adolescents represent an even greater evidence gap. A pediatric starting age, standardized dosing regimen, or sufficient safety data for NAD+ precursor supplementation have not been established 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 cases: liver diseases, menopause, and concomitant medications
NAD+ metabolism is closely linked to liver function, as this organ 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 triglyceride, total cholesterol, and LDL cholesterol levels [3].
These results pertain to circulating lipid markers rather than direct measurements of liver disease. They do not prove that NAD+ precursors reduce liver fat, improve fibrosis, normalize liver enzymes, or treat conditions such as metabolic dysfunction-associated steatotic liver disease, hepatitis, or other diagnosed diseases of this organ.
No dedicated human study has been identified that confirms NAD+ precursor supplementation as a treatment method for a diagnosed liver disease. Therefore, lipid-related results should not be interpreted as direct evidence of a therapeutic effect on the liver.
Menopause is another area where there is limited human trial data. In one open-label pilot study, 40 women over the age of 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 menopausal symptoms, there was a reduction of at least 50% in the frequency and severity of hot flashes, bloating, and sleep disturbances. The study also noted a change in the ratio of estradiol to estrone, two forms of estrogen [8].
These results remain preliminary. The study was short, lasting only 7 days, was open-label, and did not include a placebo group.
The research team also included employees of the company that manufactures and sells the studied supplement. These limitations make it difficult to separate intervention-specific effects from the placebo effect, expectations, natural symptom fluctuations, or other sources of systematic error.
The results therefore require confirmation in larger, independent, randomized, placebo-controlled trials before any action related to menopause can be considered confirmed.
Drug use remains another area with incomplete data. Formal studies on the interactions of NAD+ precursors with commonly prescribed drugs are limited.
In human studies, changes in glucose regulation, insulin sensitivity, lipid metabolism, vascular function, and blood pressure-related parameters have been observed, although the results were not consistent across all studies.
This may be relevant for medications used in diabetes, hypertension, cardiovascular diseases, and other chronic conditions. However, the current literature does not provide a complete or validated interaction map for NR, NMN, and other NAD+-related compounds.
How do evidence vary by population and purpose?
The importance of NAD+ supplementation largely depends on whether a 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 evaluated in controlled human studies. Examples include changes in NAD+ biomarkers, lipid markers, selected physical fitness parameters, and insulin sensitivity in specific populations [1,3,4].
Evidence becomes weaker when the expected effect is broad or poorly defined. Terms such as wellness, anti-aging, brain repair, mental clarity, or longevity support often combine many different biological or subjective effects that have not been validated as single clinical endpoints.
Age also affects how directly the available data can be applied. Middle-aged and older adults have a much larger body of research, as these are the populations that have most frequently participated in studies on NAD+ precursors [1,2].
Healthy younger adults have significantly fewer direct outcome data, whereas children, adolescents, and pregnant and breastfeeding individuals have very limited or completely absent dedicated safety data.
Health status constitutes another layer of assessment. Results obtained in generally healthy middle-aged individuals cannot be automatically generalized to people with active cancer, severe cardiovascular disease, diagnosed liver disease, diabetes requiring pharmacological treatment, or other complex medical problems.
The route of administration also matters. Oral NR and NMN currently have the largest base of randomized human trials among commonly discussed NAD+-related products.
Evidence regarding NAD+ patches, subcutaneous injections, and intramuscular and intravenous administration is much more limited. Therefore, the results of studies on oral precursors should 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 characterized with continuous multi-year use.
Publicly available literature supports a population- and expected-effect-dependent interpretation rather than a universal conclusion regarding who „should” use NAD+.
In the case of 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 studies on NAD+ precursors have involved middle-aged and older individuals. Data regarding 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.
- There is no established evidence-based „ideal starting age” for NAD+ supplementation.
- The age-related decline in NAD+ provides a biological rationale for research in older adults, but it does not prove that supplementation confers clinically significant benefits simply because a person has reached a certain age [7].
- Pediatric safety, developmental impact, and dosage have not been adequately established.
- Safety data regarding pregnancy and breastfeeding remain insufficient.
- The findings on menopause discussed in this article are derived from a small, short-term, 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, randomized, placebo-controlled trials are needed before the effect related to menopause can be considered confirmed.
- No dedicated human study has been identified confirming NAD+ precursors as a treatment for diagnosed liver disease.
- Improvement in triglyceride, total cholesterol, or LDL cholesterol levels should not be interpreted as evidence of a reduction in hepatic steatosis, fibrosis, inflammation, or other liver-specific parameters [3].
- The discussed cancer risk comes 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 evaluate cancer incidence, recurrence, metastasis, or cancer-related mortality.
- Formal drug interaction studies remain limited, therefore general adult safety data do not confirm the safety of every combination with medications.
- Evidence varies significantly depending on the route of administration. Oral NR and NMN have significantly more controlled human clinical trial data than intravenous, intramuscular, subcutaneous, or transdermal NAD+-related products.
- Short- and medium-term tolerance data should not be treated as equivalent to confirmed long-term safety.
- Increasing NAD+ levels in 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 summarizes 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 aging, menopause symptoms, liver diseases, cancer, metabolic disorders, cardiovascular diseases, cognitive disorders, improvement 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 evaluated clinical outcome.
The strongest human research data concern selected biomarkers and specific outcomes studied primarily 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-aging effects. Short- and medium-term safety results in the general adult population do not establish suitability for every group, and NAD+ biomarker changes in themselves do not prove clinical benefit.
References
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