Creatine is one of the most thoroughly researched dietary supplements available, and it genuinely delivers on its intended purpose. The question is whether that purpose aligns with your specific needs. Here's the science behind both substances, their differences, and why this distinction is more crucial for women over 30 than most have been led to believe.
Creatine is currently having its cultural moment. For decades, it was primarily a bodybuilding supplement for men. Today, it's being positioned as an essential substance for women: for muscle maintenance, cognitive performance, and healthy aging.
This repositioning is partly justified. The research on creatine is indeed strong, and the evidence for its benefits in women is real.
However, the discussion around creatine and the discussion around NAD⁺ decline address two different issues. And women who buy creatine caught up in the current hype don't always know which of these two problems they actually have.
To understand the difference, you need to know what type of energy each supports, which systems they affect, and where each ceases to be useful.
They are not competitors. They are tools for different tasks. And for women who primarily experience persistent, worsening fatigue throughout the day, not just during exercise, it's worth carefully determining which task needs attention first.
Both creatine and NMN support energy. They support entirely different types of energy in completely different systems. This difference determines what you truly need.
What Creatine Really Does
Creatine is a naturally occurring compound primarily found in muscle tissue. The body produces it from amino acids, and it's also obtained through meat and fish.
Creatine serves as a rapid energy reserve for muscle cells. It's part of the phosphocreatine system – the body's fastest energy pathway. It's used for short, intense bursts of activity lasting seconds, not minutes.
When ATP is depleted during high-intensity activity, phosphocreatine rapidly donates a phosphate group to regenerate ATP, allowing the activity to continue. Creatine supplementation increases the available phosphocreatine stores 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 in explosive, high-intensity activities, supports muscle mass retention, and has increasingly robust evidence for cognitive benefits, especially in older adults, as well as during sleep deprivation and high mental strain.
Newer research also suggests that women have relatively lower creatine stores compared to men. One reason for this is that women generally consume less meat. Therefore, the benefit of supplementation might be proportionally greater for women than for men. This is the solid scientific basis for the current creatine discussion concerning women.
What Creatine Cannot Do
Creatine acts on the phosphocreatine system. It does not act on the mitochondrial energy system, which is the process by which cells continuously produce ATP from nutrients via oxidative phosphorylation.
These are two different energy systems. And the fatigue most women in their 30s and 40s experience is not a phosphocreatine problem. It's a mitochondrial problem.
The fatigue that doesn't resolve with sleep. The afternoon slump that reliably arrives, regardless of how active the day has been. Brain fog. The increasingly severe energy fluctuations throughout the hormonal cycle. None of this arises from insufficient phosphocreatine reserves in the muscle. It stems from mitochondria working less efficiently because NAD⁺, the molecule they rely on for oxidative phosphorylation, has been declining for years.
Creatine also does not affect sleep quality, hormone production, regulation of the internal clock, inflammation control, or DNA repair. All of these depend on NAD⁺. And all of these contribute to the persistent fatigue and declining function that build up throughout one's 30s.
Creatine does not interfere with the enzymatic processes behind progesterone production. It does not restore SIRT1 activity, which controls sleep architecture. And it does not address the cellular conditions behind the worsening second half of the menstrual cycle. These are NAD⁺ issues, and creatine does not touch NAD⁺.
Clinically, some patients report increased energy, better recovery, and mental clarity with NMN. Animal studies show promising effects on longevity, but human studies are still in their early stages.
- Dr. Elliot Dinetz, MD
What NMN Achieves That Creatine Cannot
NMN restores NAD⁺ levels in cells. By doing so, it restores the efficiency of mitochondria in every tissue that relies on oxidative energy production, which is all of them.
The improvement is not in peak performance at high intensity. It is in the fundamental efficiency of continuous cellular energy production throughout the day and across all systems running simultaneously.
Energy that doesn't crash in the early afternoon. Sleep that is actually restorative. A hormone cycle whose second half doesn't drain you. Mental acuity 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 as it should, instead of running on a shrinking reserve.
NMN also addresses a longevity aspect 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 cellular aging, epigenetic shifts, and mitochondrial dysfunction that accumulate with NAD⁺ decline and represent the biological mechanisms behind age-related deterioration.
For a woman primarily concerned with athletic performance, creatine is the more immediately suitable tool. For a woman concerned with how she functions through all hours of her life and how she ages, NMN intervenes at a deeper level.
What the Research Specifically Says About Women
Creatine research in women is growing and promising. Studies show that creatine improves muscle strength and power output in women, reduces muscle loss during periods of inactivity, and enhances cognitive performance, especially during sleep deprivation.
The cognitive effects, in particular, are relevant for women in perimenopause, as cognitive changes are among the most frequently reported and least treated symptoms. At doses of 3 to 5 grams daily, creatine is well tolerated by women, and the research supporting its applications is solid.
NMN research in women primarily draws 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 supplementation.
This is the most cited human study on NMN. It was conducted exclusively with women and measured outcomes directly relevant to the metabolic and hormonal changes occurring from age 30 onwards. Further 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 basis is deeper, and the areas NMN addresses are broader.
Creatine has stronger study evidence for training performance. NMN addresses a deeper and broader set of cellular mechanisms. Both are true, and neither cancels out the other.
Why Dr. Stacy Sims Changed the Creatine Debate for Women
Dr. Stacy Sims is a sports 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 of the field.
Her argument for creatine in women specifically addresses the lower baseline stores compared to men and women's particular susceptibility to muscle loss and cognitive decline during the perimenopausal 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 aligns perfectly with the case for NMN. Because NMN acts precisely on those cellular and hormonal mechanisms that Sims identifies as crucial for women's health between 35 and 55.
Creatine covers a part of physical performance. NMN addresses the cellular energy environment that determines how well the body can even respond to training, nutrition, and recovery—in other words, precisely what creatine supports. The two truly complement each other rather than competing.
What First and Can You Take Both?
There is no reason against taking creatine and NMN simultaneously, no documented negative interaction, and a plausible scientific rationale for them addressing complementary aspects of the same goal: maintaining energy, function, and health throughout the aging process.
If your primary concern is training performance, muscle retention, and mental sharpness under stress, creatine is the more immediately suitable tool.
If you're dealing with persistent, worsening fatigue 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 broader picture of how your cells age and function, then NMN addresses these mechanisms, and creatine does not.
For most women over 35 experiencing the typical symptoms of NAD⁺ decline, the more urgent measure is one that addresses the root cause. Creatine can be 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 legitimate. But working well for a specific purpose doesn't make it the right tool for every energy problem.
The fatigue that has been building since the mid-30s. Sleep that doesn't restore. A cycle that gets harder. Brain fog that sets in even before physical exhaustion. These are not phosphocreatine problems. These are NAD⁺ problems. And a supplement designed for training won't fix them—no matter how good the evidence may be for what it's 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, 16. Oktober). 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.