What Supplements Actually Work for Endurance Athletes? (The Boring Truth Your Favorite Podcast Won’t Tell You)

I had a call recently with a masters athlete, a guy in his 50s who trains hard in the water almost every day. Smart, successful, deeply invested in his health. He walked me through his supplement stack and it was a full kitchen counter: mushroom powders, urolithin A, boron, collagen, creatine, a greens blend, vitamin D drops, and until recently, injectable peptides he’d heard about on a longevity podcast. BPC-157. TB-500. The stuff your Instagram feed swears will regrow your tendons.

Here’s the part that stuck with me. He told me that after all that experimenting, the thing that made the biggest difference in how he felt wasn’t the peptides. It was iron, a cheap basic supplement his blood work actually showed he needed. And then he said something I want to frame: “I can’t say a hundred percent that it wasn’t the placebo effect.”

That is the most honest sentence in sports nutrition, and almost nobody selling you supplements will say it out loud.

So let’s do what the influencers won’t: rank the supplements by what the peer-reviewed literature actually shows, for endurance athletes specifically. Fair warning, the list of things that work is short and boring. That’s exactly why nobody is yelling about it on TikTok.

The evidence hierarchy nobody promotes

In 2018, a who’s who of sports nutrition researchers (including Louise Burke, Trent Stellingwerff, and Peter Peeling, people whose work I trust and follow closely) published the IOC consensus statement on dietary supplements for high performance athletes [1]. Their conclusion, backed by decades of trials, is that only a handful of performance supplements have strong enough evidence to recommend: caffeine, creatine, nitrate (beetroot juice), beta-alanine, and sodium bicarbonate.

Five. That’s the list. Everything else is either “only useful if you’re deficient” (iron, vitamin D), “promising but early” (collagen), or “come back when there’s human data” (looking at you, peptides).

Notice what’s not driving that list: marketing budgets. Creatine and caffeine are cheap and unpatentable. Nobody gets rich selling you beetroot. The supplements with the loudest hype tend to be the ones with the thinnest evidence, because hype is what you use when you don’t have data.

Now, the fine print on those five, because “works” always comes with caveats about who it works for.

The five with real evidence (and the fine print)

Caffeine is the most reliable performance supplement we have. A 2018 systematic review and meta-analysis of 46 studies found that 3 to 6 mg per kg of body weight taken about an hour before exercise improved endurance performance by roughly 2 to 4 percent [2]. Applicability caveat: most of those studies were done on trained male cyclists in lab time trials, so if you’re a 55 year old female trail runner, your mileage may vary, and caffeine response is highly individual (some people just get jittery and need to pee). If you race in the morning and sleep poorly after evening caffeine, factor that in too. You also don’t need a fancy “pre-workout.” Coffee, caffeinated gels, or caffeine gum all work.

Creatine stopped being just a bodybuilder thing years ago. For endurance athletes, 3 to 5 grams a day supports faster glycogen resynthesis when loading carbs, better recovery between hard sessions, sprint finishes, and lean mass preservation, and a 2023 review lays out the endurance-specific case well [3]. Caveat: most creatine trials are short duration, strength-based, and done on young men, and creatine pulls a bit of water into the muscle, so expect a small amount of scale weight (usually under a kilo) that bothers some runners more than it should. I wrote a full deep-dive on this: Is creatine good for endurance athletes, not just bodybuilders?

Nitrate (beetroot juice) improves exercise economy and endurance performance at doses around 310 to 560 mg of nitrate (roughly one to two concentrated beet shots) taken 2 to 3 hours before exercise, per a 2021 meta-analysis [4]. The big caveat: the effect is most consistent in recreational and moderately trained athletes. A 2025 scoping review of randomized trials in highly trained and elite athletes found the benefit often shrinks or disappears at the pointy end of the field [5]. Translation: beetroot is more likely to help you at your local gran fondo than it helps Pogacar.

Beta-alanine works, but for a narrower job than the marketing suggests. The best meta-analysis we have (Saunders and colleagues, 40 studies) shows benefits mainly in high intensity efforts lasting about 30 seconds to 10 minutes [6]. That’s track racing, criteriums, hill attacks, and finishing kicks, not steady state marathon pacing. It requires weeks of daily loading (typically 3.2 to 6.4 g per day), and the tingly skin (paresthesia) is harmless but real. If your event is long and steady, this one is probably not worth your money.

Sodium bicarbonate buffers acidosis in short, hard efforts. Useful for some racers, but the gastrointestinal roulette is famous, and if you’ve ever had GI distress mid-race you know that trade is not free. Practice in training or skip it.

The “only if you’re actually low” tier

Iron is where my client’s story gets its second lesson. Iron deficiency is common in endurance athletes, especially menstruating women, because of sweat, gastrointestinal, and footstrike losses plus hepcidin, an inflammation-driven hormone that blunts iron absorption for hours after hard training [7]. If your ferritin is low, repletion can change your life. But here’s the moment from that same call that I keep coming back to: he’d been taking iron since a blood test flagged him as low, his levels had since come back to normal, and he was still taking it, just on autopilot. Iron is exactly the supplement you do not want to take on autopilot, because the body has no good way to dump an excess. Test, supplement to a target (for endurance athletes I like ferritin comfortably in the 60 to 100 range), then reassess. Never blind-supplement iron.

Vitamin D follows the same logic. Meaningful if you’re deficient (common if you train indoors or live at northern latitudes), not a performance booster if you’re already replete. Test, don’t guess.

The promising middle: collagen

For tendon and ligament support, there’s an interesting study from Keith Baar’s lab: 15 grams of gelatin with vitamin C taken about an hour before loading exercise roughly doubled markers of collagen synthesis [8]. Applicability caveat in bold: that study had eight participants, all young men, doing jump rope. It’s a mechanism study, not proof your Achilles heals faster. I still use collagen protocols with injured athletes because the cost-benefit is favorable, and I covered the full injury stack in Supplements for Healing Sports Injuries: What Actually Works (and What Is Just Expensive Hope).

The hype tier: peptides and the stuff with zero controlled human trials

Back to those podcast peptides. BPC-157 is the one my athletes ask about most, and here’s the score: the evidence base is almost entirely rodent studies. To be fully fair, a few human data points exist: a 16 person retrospective knee pain case series with no control group and purely subjective outcomes [11], and some early 2000s inflammatory bowel disease trials whose results were never fully published. That’s it. A 2025 narrative review of BPC-157 for musculoskeletal healing found no published human randomized controlled trials supporting the injury-healing claims [9]. Not one controlled trial in humans for muscle, tendon, or ligament healing. WADA added it to the prohibited list, and USADA has publicly warned athletes that it’s an unapproved, experimental substance with real anti-doping and safety risk [10].

The point my client repeated from a podcast, and the reason I’m writing this post, is worth restating: creatine has literally hundreds of peer-reviewed human trials and costs pennies a day. BPC-157 has rodent data plus one tiny uncontrolled case series, a banned-substance listing, and a sketchy gray-market supply chain, and it costs more per month than most people’s entire grocery supplement budget. When the evidence is that lopsided and the hype runs the other direction, somebody is making money off the confusion. That’s the injustice in this corner of sports nutrition: the athletes taking the biggest risks are usually the ones being sold the least-proven products.

Same logic applies, gentler version, to greens powders and mushroom blends. Fine foods, no endurance performance data worth building a stack around.

Audit your stack (the part nobody sells)

Here’s how we actually handle supplements with my athletes: we pull their real food intake, run a nutrient report, and compare it to what their stack provides. You would be amazed how often someone is paying for a vitamin D supplement that puts them at several thousand percent of their needs, while an actual gap (iron, omega-3s, total energy) goes unaddressed. Then we downgrade the stack. Fewer pills, better targets, blood work to confirm. Supplements are the last 2 percent, layered on top of fueling, and an under-fueled athlete with a perfect stack is still an under-fueled athlete.

If you want that kind of audit for your own training, that’s exactly what we do inside one-on-one coaching. And if you want the self-serve version first, grab the free guides and cheat sheets on our free downloads page.

Where to buy the ones that earn their spot

If you and your blood work decide a supplement deserves a place, quality matters more than brand loyalty. Third-party tested products (NSF Certified for Sport or Informed Sport) are non-negotiable for tested athletes and a good idea for everyone.

We carry practitioner grade brands like Thorne, Momentous, Pure Encapsulations, Metagenics, Nordic Naturals and others through our Fullscript dispensary, and readers get 20 percent off anything in the Fullscript database through our portal: shop the NR Fullscript dispensary. That covers the workhorses from this post: creatine (Thorne or Momentous), iron bisglycinate (Thorne, only if your labs say so), vitamin D (Thorne or Pure Encapsulations), and omega-3s (Nordic Naturals).

For beetroot, the concentrated nitrate shots used in most of the actual studies are easiest to find on Amazon: Beet It Sport nitrate shots. Caffeine you already own; it’s called coffee.

The boring truth wins again: five proven supplements, two “test first” minerals, one promising tendon protocol, and a whole lot of expensive hope you can skip.

References

1. Maughan RJ, Burke LM, Dvorak J, Larson-Meyer DE, Peeling P, Phillips SM, Rawson ES, Walsh NP, Garthe I, Geyer H, Meeusen R, van Loon LJC, Shirreffs SM, Spriet LL, Stuart M, Vernec A, Currell K, Ali VM, Budgett RG, Ljungqvist A, Mountjoy M, Pitsiladis YP, Soligard T, Erdener U, Engebretsen L. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439-455.
2. Southward K, Rutherfurd-Markwick KJ, Ali A. The effect of acute caffeine ingestion on endurance performance: a systematic review and meta-analysis. Sports Med. 2018;48(8):1913-1928.
3. Forbes SC, Candow DG, Neto JHF, Kennedy MD, Forbes JL, Machado M, Bustillo E, Gomez-Lopez J, Zapata A, Antonio J. Creatine supplementation and endurance performance: surges and sprints to win the race. J Int Soc Sports Nutr. 2023;20(1):2204071.
4. Gao C, Gupta S, Adli T, Hou W, Coolsaet R, Hayes A, Kim K, Pandey A, Gordon J, Chahil G, Belley-Cote EP, Whitlock RP. The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: a systematic review and meta-analysis. J Int Soc Sports Nutr. 2021;18(1):55.
5. Effects of beetroot-derived nitrate supplementation in highly trained and elite athletes: a scoping review of randomized controlled trials on performance, recovery, and physiological outcomes. 2025. Available via PubMed Central (PMC13468440).
6. Saunders B, Elliott-Sale K, Artioli GG, Swinton PA, Dolan E, Roschel H, Sale C, Gualano B. Beta-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis. Br J Sports Med. 2017;51(8):658-669.
7. Sim M, Garvican-Lewis LA, Cox GR, Govus A, McKay AKA, Stellingwerff T, Peeling P. Iron considerations for the athlete: a narrative review. Eur J Appl Physiol. 2019;119(7):1463-1478.
8. Shaw G, Lee-Barthel A, Ross ML, Wang B, Baar K. Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr. 2017;105(1):136-143.
9. Regeneration or risk? A narrative review of BPC-157 for musculoskeletal healing. 2025. Available via PubMed Central (PMC12446177).
10. US Anti-Doping Agency. BPC-157: experimental peptide creates risk for athletes. usada.org/spirit-of-sport/bpc-157-peptide-prohibited/.
11. Lee E, Padgett B. Intra-articular injection of BPC 157 for multiple types of knee pain. Altern Ther Health Med. 2021;27(4):8-13.