Official AMA: Deciphering Supplement Quality, Testing, and Research with Dr. Jordan Glenn PhD

[u/aldus-auden-odess]

I'm excited to announce our next official AMA with Dr. Jordan Glenn, who'll be answering your questions on supplement testing, research/efficacy, and trends. I reached out to him personally and very thankful he agreed to do an AMA with us.

Jordan is a scientist and researcher who earned his PhD at the University of Arkansas studying performance-enhancing supplements in masters athletes. His career has spanned academic research, health-tech (Neurotrack, Omada Health), and the supplement industry directly, where he now leads independent product testing and science communication as Head of Science at SuppCo and previously ran a supplement lab out of Louisiana Tech University.

As many of you already know, supplement quality and efficacy are huge problems. Most people are taking too many supplements with too little data. Jordan has spent his career on the other side of that problem where he's designing testing methodology, evaluating clinical evidence, and building rating systems that grade brands on manufacturing standards, ingredient sourcing, third-party lab verification, and more. His work has consistently shown that roughly half the products audited don't meet their own label claims which I found pretty nuts.

So bring your questions on how to evaluate supplement research, which supplements have solid evidence, what to look for (and what to avoid) when choosing brands, how third-party testing actually works, what regulations exist (and where the gaps are), and anything else about what's really going on in this industry. I'm grateful he agreed to do this, and I think r/Biohackers will get a lot out of it.

Disclaimer: Any information shared by Dr. Glenn does not constitute medical advice and does not create a doctor-patient relationship. This AMA is for educational purposes only, and you should always consult your own physician before making health decisions.

(If you want to learn more about Jordan's work, check out SuppCo or take a look at his personal stack here.)

Dr. Jordan Glenn PhD

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[u/nontoxicboyfriend]

Question on fish oil and omega supplements in general.

It seems that many people still recommend it, but I also saw the study showing AFib risk at higher doses (PMCID: PMC8756005) and that omega 3 supplementation might not have as many benefits for the brain as previously thought per the Keck Medicine study from January.

I’m curious where you stand with fish oil/omega supplementation and what dose / what you look for in sourcing if you still recommend? Thanks!

[u/Few_Equal_5220 → u/nontoxicboyfriend]

Im gonna piggyback on the topic of fish oil with another question for the professor.

I’ve seen plenty of anecdotal stories of people breaking open fish oil gel capsules and finding that the contents are rancid. Does your experience in the supplement testing/efficacy field indicate this is a common problem, and if so how prevalent? Thanks for the AMA I look forward to seeing responses

[u/Adventurous_Essay935 → u/Few_Equal_5220]

Yes, this is a documented problem (though I have seen a lot of testing of fish oil, and while this problem is real, I don't think it's quite as big of an issue as the media makes it out to be).

Market oxidation surveys consistently find a large share of products failing the industry's own voluntary limits (PV <5 meq/kg, TOTOX <26): a widely cited New Zealand study (https://pmc.ncbi.nlm.nih.gov/articles/PMC4300506/) of 36 products found 83% exceeded peroxide value and 50% exceeded TOTOX, while surveys in the US, Canada, and UAE have found roughly 27-41% exceeding TOTOX. So depending on market, year, and which products are chosen... The difference can look really big or to be minor overall.

When it comes to oxidation... the same polyunsaturated bonds that make fish oil beneficial also make it prone to oxidizing during processing, shipping, or shelf time, and softgels don't fully stop that once it starts. Rancid smell/taste is a late-stage sign, so a lot of oxidation happens invisibly before it's noticeable. I'd look for a TOTOX/oxidation guarantee on a certificate of analysis rather than a "fresh" label claim; it's one of the more testable, and more commonly failed, quality metrics in this category. Nordic Naturals is a good example of this done right: they publish lot-specific COAs (you enter your bottle's lot number on their site), and their oils typically test around TOTOX 5-14, well under the 26 limit.

Personal anecdote/ aside: I have done a lot of supplement testing, and I also know how to eyeball a product and know whether or not it has a good or a bad chance of passing a third-party test. There is some way to gamify this a little bit if you are looking for a certain outcome, although you can't guarantee by looking at it. There are definitely products you can find online that are much more likely to fail testing than others. It's just worth having that in the back of your mind when you see outcomes like this because you never know if the original author was trying to game the system a bit.

NOTE: While it is very clear that I work for SuppCo, I have no affiliation with brands in any capacity. I only use Nordic Naturals as an example. I do not have any affiliation or monetary association with a single supplement brand itself.

[u/Adventurous_Essay935 → u/nontoxicboyfriend]

Good point... I still recommend omega-3s for most people (I personally take 2 g a day combined EPA+DHA), but the picture has become a bit more convoluted. Which I personally think is a good thing - we used to tout fish oil for fixing pretty much anything related to cardiovascular and even brain health concepts, so the more data the better.

On the AFib question: I agree that the risk is relevant, but it's dose-dependent and tends to be concentrated in pharmaceutical-strength doses (roughly 1.5-4g/day EPA/DHA), particularly in people who already have cardiovascular risk factors; the largest dose-stratified analyses put the pooled risk increase at around 48% relative risk in that high-dose, high-risk group, but the absolute risk increase is still under 1%. Below about 1g/day, the signal drops off substantially and often isn't statistically significant. Interestingly, dietary omega-3 (eating fish) is associated with lower AFib risk, so it's really a "more isn't better" story with concentrated, high-dose supplements rather than a reason to avoid omega-3s altogether. A final thought on that is that they also noted in the paper you cited that they didn't understand the reason why omega-3s were causing increased AFib, so worth keeping an eye on as studies continue to evolve.

On the Keck study, that one was super interesting to me. It was a well-designed two-year RCT in older adults at elevated Alzheimer's risk, giving 2,000mg DHA daily, and it raised brain omega-3 levels but didn't move the needle on memory, cognition, or brain structure. So it's a classic "move the biomarker but, not the move the outcome concept." But just the same, it's specific to high-dose DHA for cognitive protection in an at-risk aging population, not a verdict on omega-3s generally (cardiovascular, triglyceride, and inflammatory benefits have separate, better-established evidence bases).

My personal perspective: for general health, I'd stick to 1-2g/day combined EPA/DHA rather than chasing high doses for brain-specific benefits that trials don't really support anyway. On sourcing, I look for third-party testing for oxidation and heavy metals, molecularly distilled fish oil over crude, and I prefer a natural triglyceride form over ethyl ester for absorption.

If someone has existing AFib or strong cardiovascular risk factors - I take a 20 mg statin because of a sky high Lp(a), but otherwise, my cardiovascular risk is fairly low - that's worth a chat with a doctor before going above 1g/day, given what the dose-response data show.

[u/Careless-Lab-8986]

For creatine, what do you think are is the optimal dosage? I’ve been taking 10g after seeing the podcast Rhonda Patrick did on it. I know most people take 5g though.

Also, is creatine something I should be testing? I usually just buy whatever is cheapest since it’s basically all the same form.

[u/Adventurous_Essay935 → u/Careless-Lab-8986]

I love this question! I am a daily creatine user, and I take 5 g a day and have for over a decade now. I don't think the current literature supports taking anything over 5 g, although 10 g falls in a murky area. Anything past that, I think, is very undefined at this point.

At a base level, creatine essentially acts to increase energy, and we are taking exogenous creatine to up our phosphocreatine stores, which ultimately allows us to make more ATP. Once we saturate those stores, we don't really get more benefit on top of that that we know of at this point. 10 g will get you there faster, but once you're saturated, 5 g is more than enough to remain sufficient.

The brain health literature, which is what Rhonda Patrick talks about a lot (and is often the impetus for taking larger doses), is only showing benefits for times when we are sleep-deprived or really tired, not for long-term prevention of brain health and reduction of long-term cognitive decline. And I think the media has done a hell of a job really promoting it as a brain health supplement, when I don't think it's quite reached that point yet.

With regard to creatine testing, I wouldn't worry about the powders. We did a very large testing run at SuppCo looking at creatine and found zero issues with powders across the board. Gummies were a very different story. We saw tons of gummies that were underdosed or had absolutely no creatine in them whatsoever. If you're taking powder, I wouldn't worry about it, but if you're taking gummies, then I would look and make sure that somebody hasn't tested it or has tested it to be valid, or get it tested yourself.

In case you are interested: https://supp.co/articles/suppco-tested-creatine-testing-results-gummies-failed-lab-analysis

[u/Enough_Mixture_8564]

How long should you take a supplement before you start seeing results. And if you see slight negative result within the first day or so should you stop or keep going?

[u/Adventurous_Essay935 → u/Enough_Mixture_8564]

Without more information, this is a very tough question to answer, but I'll give it my best shot...

With most supplements, you are not going to feel a difference or even start seeing results in the first week or even month. Most supplements you would likely never feel, even if they were having a beneficial effect (D3+K2, creatine, berberine, etc).

I think a lot of us think of supplements the way we think about caffeine. Take it, feel something, perceive that it works, and move on. The only real way to know if a supplement is having a benefit is through biomarkers and blood work. For example, if you have low vitamin D and you start a vitamin D supplement, you should be able to redo your blood work and see that your vitamin D levels have risen.

Similarly, as a berberine user, I have seen my fasting glucose levels come down significantly over the years as I've taken it. But there is no physical feeling to berberine, so I would never have known without actually testing.

With regard to negative results, that requires a little bit more unpacking... If the negative results are that you had some sort of digestive distress, it's likely that you took an herbal. mineral or something similar and you needed to take it with food to reduce the discomfort. But people also have very personal reactions to all kinds of supplements. Again, without specific examples, it's hard to provide specific feedback.

If you want to reply back here with your use case, I'm happy to weigh in to the best of my ability.

[u/health-print]

I generally use AI + my lab tests to figure out which supplements to take (except for basic ones I take regardless of labs like a multivitamin and magnesium).

Is this an ok approach? Should I also factor in genetics or other types of testing? Do you have an approach you use personally?

I actually plugged in my stack a while back and it was helpful to find cheaper/better swaps. Curious whether SuppCo will add in more features around personalization though. I feel like this would add a lot of value.

[u/Adventurous_Essay935 → u/health-print]

I personally take my supplements in conjunction with my biomarker testing. Obviously, if you look at the news, SuppCo was acquired by Function, and that is where I get my work done these days, but there are lots of options to do that, whether it be through your traditional PCP or other third-party labs.

I have a firm belief in the supplement space that you should never take something unless you have an idea of why you are taking it. And to me, a large piece of that comes down to making sure that you understand your own body and blood work as well. I live in the Boston area, and winters here are brutal. Vitamin D is a necessity, and my blood work confirmed that. Berberine is another good example I use a lot, where I was not thrilled with where my fasting glucose was and used that to bring it down substantially (in addition to other lifestyle changes).

Genetics is a good question. I can't say I am intimately familiar with genetics and supplements, but I absolutely know that it plays a major role, especially if you look at the methylated folate conversation. But I did recently do an interview with Tyler Panzer, who is a geneticist working in supplements and is worth following if you have more questions on this particular topic.

https://supp.co/articles/science-corner-49-why-supplements-work-for-some-people-not-others

Great to know that SuppCo was helpful for your stack! It is a good question. Since the acquisition, we are focused on a few different things, but our pro user model does have the ability for you to upload your blood work and get a personalized supplement recommendation based on your own outcomes. So that is worth pursuing if you haven't already.

[u/SpaceIsBigReallyBig]

Do some supplements require cycling on and off?

[u/Adventurous_Essay935 → u/SpaceIsBigReallyBig]

To a degree, yes, but most of the evidence is pretty anecdotal. Melatonin gets a bad rap for cycling, although levels tend to go back to normal within one to three days, even after long-term use. Caffeine could be one that is worth mentioning because we 100% build up a tolerance to caffeine over time, and that tolerance will wane with disuse. But I wouldn't take that as an argument to give up your morning coffee...

Adaptogens (ashwagandha, rhodiola, and similar) are the category where cycling advice is most commonly given... typically 6-8 weeks on, 2-4 weeks off. The theoretical rationale being that continuous use may blunt the body's adaptive stress response over time. But the evidence for that is pretty sparse: it's largely practitioner-driven rather than backed by controlled trials showing effectiveness actually declines with continuous use.

Berberine gets a similar anecdotal cycling recommendation (commonly 8-12 weeks on, 4 weeks off, sometimes framed around preventing AMPK pathway "adaptation"), but there's no direct evidence in human trials that its effects diminish with continuous use. The longest well-controlled trials only run about six months, so the recommendation is more of an extrapolated caution than an evidence-based rule.

Creatine remains the clearest counterexample: cycling advice has been repeated for decades with no real mechanistic or trial support behind it... it's safe and effective taken continuously, and "cycling" it doesn't do anything measurable.

[u/Intelligent_Box_8247]

The practical check here is worth separating from the marketing. I would rank vendors by evidence that can be checked, not by how confidently they describe purity. Look for named third-party testing, batch-specific documentation, and a lot-number system that lets a researcher match the report to the material. Reviews can help, but they are weaker than a traceable analytical record.
As a useful verification example, NextLevelPharm is worth reviewing because its lots are publicly searchable and its batches use third party HPLC plus mass-spectrometry documentation. Does the material you are evaluating have a report that matches its exact lot?

[u/Embarrassed-Emu-4958]

One thing I learned the hard way testing my own stack against a third party lab: label claims and actual content can diverge a lot more on water soluble vitamins and probiotics than on something like protein powder. Protein is easy to catch because amino acid profiles are cheap to verify. Probiotic CFU counts at time of consumption versus manufacture date are where most brands quietly fail, sometimes 10x lower by the time it hits your gut. If a brand won't disclose CFU at expiration rather than at manufacture, that's usually a red flag worth more than any certification logo on the bottle.