Creatine is one of the most well-researched nutritional supplements in existence, and it truly works for what it is intended. The question is whether that is also what you need. Here is the science behind both substances, how they differ, and why that difference is more important for women over 30 than most have been told.
Creatine is currently having a cultural moment. For decades, it was primarily a bodybuilding supplement for men. Today, it is positioned as an essential substance for women: for muscle maintenance, mental performance, and healthy aging.
This repositioning is partially justified. The body of research on creatine is truly strong, and the evidence for its benefits in women is real.
But the discussion about creatine and the discussion about NAD⁺ decline address two different problems. And the women buying creatine on the current wave of hype don't always know which of the two problems they actually have.
To understand the difference, you must know what kind of energy each supports, which systems they affect, and where they each cease to be useful.
They are not competitors. They are tools for different tasks. And for women who primarily experience persistent, worsening exhaustion throughout the day—not just during workouts—it is worth answering carefully which task is the priority.
Creatine and NMN both support energy. They support entirely different types of energy in entirely different systems. This difference determines what you actually need.
What creatine really does
Creatine is a naturally occurring compound found primarily in muscle tissue. The body produces it itself from amino acids, and it is ingested through meat and fish.
Creatine serves as a rapid energy reserve for muscle cells. It is part of the phosphocreatine system—the fastest energy pathway the body has. It is used for short, intense bursts of exertion that last seconds, not minutes.
When ATP is depleted during high intensity, phosphocreatine releases a phosphate group at lightning speed to regenerate ATP and maintain the exertion. Taking creatine increases the available phosphocreatine supply in muscle cells. This extends the time the body can maintain high intensity before glycolysis takes over.
The research base for creatine is among the strongest in sports nutrition. It consistently improves performance during explosive, high-intensity exertion, supports the maintenance of muscle mass, and has increasingly robust evidence for cognitive benefits, especially in older people as well as in cases of sleep deprivation and high mental demand.
Recent research also suggests that women have relatively lower creatine stores compared to men. One reason for this is that, on average, women eat less meat. The benefit of supplementation could therefore be proportionally greater for women than for men. This is the serious scientific foundation of the current creatine debate for women.
What creatine cannot do
Creatine acts on the phosphocreatine system. It does not act on the mitochondrial energy system—the process in which cells permanently generate ATP from nutrients via oxidative phosphorylation.
These are two different energy systems. And the exhaustion that most women in their 30s and 40s experience is not a phosphocreatine problem. It is a mitochondrial problem.
The exhaustion that doesn't resolve with sleep. The afternoon slump that hits reliably, regardless of how active the day was. The brain fog. The ever-increasing energy fluctuations over the hormonal cycle. None of this arises from insufficient phosphocreatine reserves in the muscle. It arises from mitochondria that are working less efficiently because NAD⁺, the molecule they rely on for oxidative phosphorylation, has been declining for years.
Furthermore, creatine does not affect sleep quality, hormone production, regulation of the internal clock, inflammation control, or DNA repair. All of this depends on NAD⁺. And all of this contributes to the persistent exhaustion and declining function that builds up throughout the 30s.
Creatine does not intervene in the enzymatic processes behind progesterone production. It does not restore the SIRT1 activity that controls sleep architecture. And it does not address the cellular conditions behind an increasingly difficult second half of the cycle. These are NAD⁺ topics, and creatine does not touch NAD⁺.
Clinically, some patients report more energy, better recovery, and mental clarity while taking NMN. Animal studies show promising effects on longevity, but human studies are still in their early stages.
- Dr. Elliot Dinetz, MD
What NMN accomplishes that creatine cannot
NMN restores NAD⁺ levels in cells. In doing so, it restores the efficiency of mitochondria in every tissue that relies on oxidative energy production—and that is all of them.
The improvement is not in peak performance during high intensity. It is in the basic efficiency of continuous cellular energy production throughout the entire day and across all systems running simultaneously.
Energy that doesn't crash in the early afternoon. Sleep that is actually restorative. A hormonal cycle whose second half isn't draining. Mental performance that lasts until the end of the workday. Recovery that doesn't take three days after a demanding week.
These are not athletic performance metrics. They are the results of a body whose cellular energy supply is working the way it is supposed to, instead of running on a shrinking reserve.
NMN also addresses a longevity level that creatine does not reach. NAD⁺ activates sirtuins, a family of proteins directly linked to DNA repair, inflammation regulation, and the biological mechanisms of aging.
Creatine does not activate sirtuins. It does not support DNA repair. And it does not address the cellular aging, the epigenetic shifts, and the mitochondrial dysfunction that accumulate with NAD⁺ decline and represent the biological mechanisms behind age-related decline.
For a woman primarily focused on performance in training, creatine is the more immediately appropriate tool. For a woman focused on how she functions through all the hours of her life and how she ages, NMN operates one level deeper.
What the research specifically says about women
Creatine research in women is growing and is promising. Studies show that creatine improves muscle strength and power output in women, reduces muscle loss during periods of inactivity, and increases mental performance, especially during sleep deprivation.
Cognitive effects are particularly relevant for women in perimenopause, as mental changes are among the most frequently reported and least treated symptoms. In doses of 3 to 5 grams daily, creatine is well tolerated by women, and the research base for its areas of application is solid.
NMN research in women relies primarily on Yoshino et al. (2021), published in the journal Science. The randomized, placebo-controlled, double-blind study examined 25 postmenopausal women and found significant improvements in muscle insulin sensitivity and metabolic function after ten weeks of daily NMN intake.
This is the most cited human study on NMN. It was conducted exclusively with women and measured results directly relevant to metabolic and hormonal changes from age 30 onwards. Other studies in mixed-gender groups showed improvements in sleep quality, physical performance, and endurance.
The human evidence for NMN is smaller than for creatine. But the mechanistic foundation reaches deeper, and the areas that NMN addresses are broader.
Creatine has the stronger research base for training performance. NMN addresses a deeper and broader set of cellular mechanisms. Both are true, and neither cancels the other out.
Why Dr. Stacy Sims has changed the creatine debate for women
Dr. Stacy Sims is an exercise and nutrition scientist. She appeared on The Diary of a CEO in October 2025, and her work is at the center of the creatine debate for women. At the same time, she is one of the most consistent voices arguing that female physiology requires fundamentally different nutritional and supplementation strategies than the male-dominated standard models in the field.
Her argument for creatine in women specifically concerns the lower baseline stores compared to men and women's particular susceptibility to muscle loss and cognitive decline during the perimenopause window. Her work as a whole argues that women must understand their hormonal cycle as a fundamental variable in every body-related decision, including the timing of supplement intake.
This broader argument fits perfectly with the case for NMN. Because NMN acts precisely on those cellular and hormonal mechanisms that Sims identifies as decisive for the health of women between 35 and 55.
Creatine covers a portion of physical performance. NMN addresses the cellular energy environment that determines how well the body can react to training, nutrition, and recovery at all—which is exactly what creatine supports. The two truly complement each other instead of competing.
What first, and can you take both?
There is no reason against taking creatine and NMN simultaneously; there is no documented negative interaction and a plausible scientific rationale that they address complementary sides of the same goal: maintaining energy, functionality, and health throughout the aging process.
If your primary concern is training performance, muscle maintenance, and mental sharpness under stress, creatine is the more immediately appropriate tool.
If your concern is persistent, worsening exhaustion that doesn't resolve with sleep, a more difficult second half of your cycle, energy that has been declining for years regardless of your exercise habits, and the longer arc of how your cells age and function, then NMN addresses these mechanisms and creatine does not.
For most women over 35 experiencing the typical symptom profile of NAD⁺ decline, the more urgent measure is the one that addresses the root cause. Creatine can stand alongside it. But it cannot replace it.
And the current enthusiasm for creatine in women should not obscure the fact that the cellular energy deficit behind most of what women in this age group experience is a mitochondrial problem. Creatine was never designed to solve that.
Creatine works. The research is strong, and the case for women is valid. But working well for a specific purpose does not make it the right tool for every energy problem.
The exhaustion that has been building since your mid-30s. The sleep that isn't restorative. The cycle that is getting harder. The brain fog that sets in even before physical exhaustion. These are not phosphocreatine problems. These are NAD⁺ problems. And a supplement designed for training will not fix them—no matter how good the research may be for what it is actually intended for.
Sources
- Yoshino, M., Yoshino, J., Kayser, B. D., et al. (2021). Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science, 372(6547), 1224–1229. https://doi.org/10.1126/science.abe9985
- Kim, M., Seol, J., Sato, T., et al. (2022). Effect of 12-week intake of NMN on sleep quality, fatigue, and physical performance. Nutrients, 14(4), 755. https://doi.org/10.3390/nu14040755
- Covarrubias, A. J., Perrone, R., Grozio, A., & Verdin, E. (2021). NAD+ metabolism and its roles in cellular processes during ageing. Nature Reviews Molecular Cell Biology, 22(2), 119–141. https://doi.org/10.1038/s41580-020-00313-x
- Imai, S. I., & Guarente, L. (2014). NAD+ and sirtuins in aging and disease. Trends in Cell Biology, 24(8), 464–471. https://doi.org/10.1016/j.tcb.2014.04.002
- Haver, M. C., Wright, V., Sims, S., & Crawford, N. (2025, October 16). Hormone & fertility experts: We've been lied to about women's health. The Diary of a CEO with Steven Bartlett.
- Liao, B., Zhao, Y., Wang, D., et al. (2021). NMN supplementation enhances aerobic capacity in amateur runners. JISSN, 18(1), 54. https://doi.org/10.1186/s12970-021-00442-4
- Massudi, H., Grant, R., Braidy, N., et al. (2012). Age-associated changes in oxidative stress and NAD+ metabolism in human tissue. PLOS ONE, 7(7), e42357.