A guide to supplementation and longevity: why personalization matters more than trends, and a specialist’s take on rhodiola, ashwagandha, vitamin D, omega-3, CoQ10, and NAC.
Quick answer
No supplement has human trials showing that it extends life; their real usefulness lies in correcting deficiencies and in specific uses. Vitamin D, for example, did not reduce cancer or cardiovascular events in the VITAL trial (25,871 adults, 2,000 IU/day, 5.3 years). Ashwagandha has liver-safety warnings and is restricted in Denmark; NMN is not authorized as a supplement in the EU.
We are experiencing a genuine craze for supplements. Omega-3, vitamin D, vitamin C, ashwagandha, turmeric, melatonin—these names crop up repeatedly on social media, in podcasts, and in everyday conversations, as if they were magic formulas for longevity. But amidst all these promises, how much is based on science, and how much is just a trend?
For Dr. Estela Lladó-Carbó—a specialist in neurophysiology, longevity, and neuroscience, and the Director of Longevity at Monarka Clinic—the issue is not supplementation itself, but the context in which it takes place. “When it comes to supplements and longevity, there is a lot of information overload but little actual knowledge. I prefer that people take just a few things—but that they actually take them,” she explains.
Before taking supplements: diagnosis, context, and personalization
The key lies in one word: personalization. As Dr. Lladó emphasizes, “not every drug is bad, and supplementation is beneficial if it targets the root of the problem; we shouldn’t just treat the symptom.”
In practice, this means analyzing key biomarkers before making any recommendations. Conventional medicine relies on a set of standardized analytical markers—such as a complete blood count, biochemical profile, liver and kidney function tests, lipid profile, and inflammation markers—as a baseline reference. In longevity medicine, the focus is broader, encompassing markers such as homocysteine, lipoprotein(a), glycated hemoglobin, HOMA index, fructosamine, hormone profiles, and 24-hour cortisol levels.
“Before taking supplements, we need a diagnosis, context, and personalization to avoid unnecessary risks,” the doctor insists. The goal is not to accumulate tests, but to understand what each body needs—and what it does not.
Rhodiola or ashwagandha: which one does a longevity specialist recommend?
Ashwagandha is currently one of the most popular supplements on social media. However, Dr. Lladó-Carbó takes a cautious approach to it:
Ashwagandha is very popular, but I find rhodiola more suitable, as it has a more reasonable safety profile at standard doses.
— Dra. Estela Lladó-Carbó, Monarka Clinic
This is precisely one of the areas where there is the most “information overload”: the idea that a popular supplement is automatically the most suitable one for everyone.
Ashwagandha: what is known about its safety
In 2023 Denmark banned ashwagandha in food supplements. In June 2024, a working group of EU food safety agencies recommended prioritizing it for an evaluation procedure (Article 8 of Regulation 1925/2006) because of possible effects on reproduction, thyroid hormones, acetylcholinesterase and the immune system, and because of liver toxicity. France (ANSES) and the Netherlands (RIVM) advise against its use in pregnant women and other vulnerable groups, and cases of liver injury have been described. Reviews of trials with standardized root extracts have not found serious adverse events (Pharmaceuticals, 2026), but those trials are short and enrolled selected participants.
Before taking ashwagandha
Today it can still be sold as a food supplement in the EU, but talk to your doctor, especially if you are pregnant or planning to be, if you have thyroid or liver problems, or if you take thyroid medication, sedatives or immunosuppressants.
Vitamins D and K2: When It Makes Sense to Take Them
Vitamin D is another compound experiencing a sustained surge in popularity. Here, the doctor’s recommendation is clear: “We should take it if there is a deficiency, as an excess can have significant adverse effects on the body, and I advise taking D3 and K2 in synergy if supplementation is needed.”
This combination is no coincidence: vitamin K2 helps direct the calcium mobilized by vitamin D toward the bones, rather than allowing it to be deposited in soft tissues. Once again, the underlying message remains the same: taking vitamin D “just because”—without prior blood work confirming a deficiency—is not without risk.
What does the evidence say? In the VITAL trial (N Engl J Med, 2019), 25,871 adults (men aged 50 or older and women aged 55 or older) received 2,000 IU/day of vitamin D3 for a median of 5.3 years: supplementation did not reduce the incidence of invasive cancer or cardiovascular events compared with placebo. That is why its use makes sense for a confirmed deficiency, not as a “longevity” supplement for everyone.
Omega-3: Beyond the Generic Capsule
The same applies to other popular compounds like melatonin, which is not a universal supplement suitable for everyone either. As the specialist summarizes, “the evidence exists, but the key lies in dosage, bioavailability, and context. A young, healthy person will not have the same needs as someone with chronic inflammation, high stress, or accelerated cellular aging.”
Other supplements: CoQ10 and NAC
Beyond trendy supplements, there are compounds that have been studied more widely, although with very uneven results depending on the compound and the goal: vitamin C, coenzyme Q10, NAC, creatine and glycine are among the most studied. The same caution applies to products that promise to “activate autophagy”: in people there is still no validated way to measure it. We explain why in what autophagy is.
The difference between a useful supplement and a superfluous one, the specialist insists, “lies not in the product label, but in the clinical judgment behind it.”
Summary table: evidence, legal status and precautions
| Supplement | Evidence in humans | Status in the EU | Precautions |
|---|---|---|---|
| Vitamin D | Useful if there is a deficiency. VITAL: no reduction in cancer or cardiovascular events in the general population. | EFSA health claims (bone, muscle, immunity). | Do not supplement without a confirmed deficiency; excess can be harmful. |
| Omega-3 (EPA and DHA) | Widely studied; the benefit depends on the dose and the goal. | EFSA claim on normal heart function. | Some high-dose trials have observed more atrial fibrillation; ask your doctor if you take anticoagulants. |
| Creatine | Supported for physical performance together with strength training. | EFSA claim on high-intensity exercise performance. | Check with your doctor if you have kidney disease. |
| Rhodiola | Small trials on fatigue and stress; limited evidence. | Supplement; no EFSA-authorized health claim. | Possible interactions with antidepressants and stimulants; ask before combining it. |
| Ashwagandha | Short trials with root extracts without serious events; cases of liver injury described. | Banned in supplements in Denmark (2023); under review by EU authorities. | Avoid in pregnancy; ask your doctor if you have liver or thyroid problems, or related medication. |
| CoQ10 and NAC | Weak evidence for longevity. | NAC may be regulated as a medicine depending on the dose. | Check with your doctor or pharmacist. |
| NMN | Small human trials; no evidence of an effect on longevity. | Not authorized as a supplement in the EU (novel food). In 2026 EFSA issued a favorable safety opinion on one specific product, pending a European Commission decision. | Do not buy NMN products without guarantees; even if authorized, an anti-aging effect could not be claimed. |
Regulatory situation as of October 7, 2026; it may change. No supplement replaces medical diagnosis or treatment.
Frequently Asked Questions About Supplements and Longevity
Is ashwagandha or rhodiola better?
According to Dr. Lladó-Carbó, rhodiola offers a more reasonable safety profile at standard doses, although the final choice depends on each person's context.
Should you take vitamin D all year round?
Only if a deficiency is confirmed by blood tests. An excess can have adverse effects, so it is recommended to combine it with vitamin K2 when necessary.
Will any omega-3 do?
No. The quality and actual dosage of EPA and DHA vary significantly between products, so ideally, one should assess each person's fatty acid profile before choosing a dosage.
Can you take several supplements at the same time?
Only upon professional assessment. Combining supplements without clinical judgment can lead to interactions or prove unnecessary if there is no actual deficiency to correct.
Is ashwagandha legal in Spain?
It can still be sold as a food supplement in the EU, but it is under safety review by European authorities and Denmark bans it. Talk to your doctor before taking it.
Can you buy NMN in Spain?
NMN is not authorized as a food supplement in the EU. In 2026 EFSA issued a favorable safety opinion on one specific product, pending the decision of the European Commission.
Does vitamin D help you live longer?
There is no evidence that vitamin D prolongs life in the general population: the VITAL trial did not reduce cancer or cardiovascular events. It makes sense if there is a confirmed deficiency.
Sources and references
- Manson JE et al. Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL). N Engl J Med 2019;380:33-44.
- Ashwagandha: monitoring by food safety authorities. NutritionInsight · Nutraceuticals World
- Ashwagandha: is it safe? Phytotherapy Research, 2025. Link
- Safety profile of Withania somnifera. SEFIT
- Review of trials with ashwagandha root extracts. Pharmaceuticals, 2026. Link
- EFSA: favorable safety opinion on NMN (May 2026). NutraIngredients
- Regulations (EC) 1924/2006 (health claims), 1925/2006 and (EU) 2015/2283 (novel foods).
Informational content based on the opinion of Dr. Estela Lladó-Carbó and on the cited sources (updated on October 7, 2026). It is not a purchase recommendation and does not replace an individual medical assessment.
Do you want to know which supplements make sense for you? At Monarka Clinic, we have a team specializing in longevity medicine that evaluates your biomarkers before making any recommendations.
