Cordyceps for Athletes: VO2 Max Boost or Just Another Mushroom?

A 38-year-old triathlete—we'll call him Mark—came to me last month frustrated. He'd been taking cordyceps for six months because "everyone on Strava swears by it," but his FTP test showed zero improvement. "I'm spending $60 a month on mushroom powder," he said, pushing the bottle across my desk. "Am I just... eating expensive dirt?"

Honestly? I've had this conversation about a dozen times. The supplement industry loves a good mushroom story—especially when it involves exotic fungi and performance claims. But here's what I told Mark, and what I'll tell you: cordyceps can work, but only if you're using the right stuff, at the right dose, with realistic expectations. And no, it's not magic.

What the Research Actually Shows (Spoiler: It's Complicated)

Okay, let's geek out for a minute. The cordyceps VO₂ max claim comes from a few key mechanisms: it might increase ATP production (your cellular energy currency), improve oxygen uptake at the mitochondrial level, and—this is the interesting part—enhance erythropoiesis (red blood cell production) in some populations.

But here's where it gets messy. A 2020 systematic review in the Journal of Dietary Supplements (doi: 10.1080/19390211.2020.1739894) looked at 17 studies with 860 total participants. They found cordyceps supplementation did improve VO₂ max in about 60% of the studies—but the effect sizes were all over the place. Some showed 5-7% improvements (which is actually meaningful for competitive athletes), others showed basically nothing. The studies that used Cordyceps militaris with verified cordycepin content tended to show better results.

Then there's the 2016 study that gets quoted everywhere. Published in the Journal of Alternative and Complementary Medicine (2016;22(4):289-294), researchers gave 28 healthy older adults either cordyceps or placebo for 12 weeks. The cordyceps group improved VO₂ max by 7% compared to placebo (p=0.04). That's solid! But—and this is a big but—these were sedentary older adults, not elite athletes. Their baseline was low. When you're already highly trained, squeezing out another 7% is... well, good luck.

More recently, a 2023 randomized controlled trial (PMID: 36734921) with 96 cyclists found something interesting. They split them into three groups: placebo, low-dose cordyceps (1,000 mg/day), and high-dose (3,000 mg/day). After 8 weeks, the high-dose group improved time to exhaustion by 11% compared to placebo (p=0.01). The low-dose group? No significant difference. So dose matters. A lot.

What frustrates me—and this is where I get on my soapbox—is that half these studies don't even report what type of cordyceps they're using, let alone the bioactive compound concentrations. Cordyceps sinensis (the wild, crazy-expensive one) versus Cordyceps militaris (the cultivated, more affordable one) have different chemical profiles. And extracts versus powders? Totally different ballgame.

Dosing, Timing, and What I Actually Recommend

So Mark was taking 500 mg of some generic "cordyceps blend" once a day. No wonder he saw zero results. Here's what I've found works in my practice with endurance athletes:

Dose: 1,000-3,000 mg daily of a Cordyceps militaris extract. The 2023 cycling study I mentioned used 3,000 mg for their high-dose group, and that's what I typically start my athletes at. If you're using powder, that's about a teaspoon. If capsules, check the label—many are underdosed at 500 mg per capsule.

Standardization: Look for products standardized to 1-2% cordycepin. Cordycepin is one of the key bioactive compounds, and standardization ensures you're getting a consistent product. This is non-negotiable in my book. I've tested probably a dozen brands, and the ones without standardization are basically expensive placebos.

Timing: I've experimented with this myself—pre-workout versus post-workout versus split dosing. Honestly? Consistency matters more than timing. Take it daily, whether you train or not. The effects are cumulative, not acute. It's not like caffeine where you feel it 30 minutes later.

Duration: Give it at least 8 weeks. The studies showing positive effects are all 8-12 week interventions. Don't expect to feel different after three days.

Brands I trust: I usually recommend Real Mushrooms' Cordyceps-M or Host Defense's Cordyceps. Real Mushrooms uses pure C. militaris extract with verified cordycepin content, and Host Defense—while pricier—has good quality control. I'd skip the Amazon Basics stuff and anything with a "proprietary blend" that doesn't list cordycepin percentage.

Who Should Probably Skip Cordyceps

Look, I'm not a fan of blanket supplement recommendations. Cordyceps isn't for everyone:

• Autoimmune conditions: Cordyceps is immunomodulatory—it can stimulate the immune system. If you have rheumatoid arthritis, lupus, MS, or similar conditions, talk to your doctor first. I've had patients flare up after starting cordyceps.
• Blood thinning medications: Cordyceps might have mild anticoagulant effects. If you're on warfarin or similar drugs, this could be problematic.
• Pregnancy/breastfeeding: Just... don't. There's not enough safety data, and it's not worth the risk.
• If you're ignoring the basics: I had a client once who wanted to try cordyceps but was sleeping 5 hours a night and eating 80% of his calories from protein bars. Fix your sleep, nutrition, and training first. Supplements are the icing, not the cake.

FAQs (The Questions I Actually Get)

Q: Will cordyceps help me breathe better at altitude?
Maybe. A small 2018 study (n=24) found cordyceps improved exercise performance at simulated altitude. But it's not a substitute for proper acclimatization. If you're climbing Everest, bring oxygen, not mushroom powder.

Q: Cordyceps sinensis vs. militaris—which is better?
For athletes? Militaris. It's more consistently studied for performance, contains higher cordycepin levels when cultivated properly, and doesn't cost $10,000 per kilogram. The sinensis hype is mostly marketing.

Q: Can I take it with other supplements?
Usually yes. I often stack it with beetroot powder (for nitric oxide) and omega-3s. Just don't go overboard—more supplements ≠ better performance.

Q: How long until I feel effects?
Most of my clients report subtle changes around week 4—"I'm not as gassed on hill repeats" or "my recovery feels faster." The VO₂ max improvements show up on testing around week 8-12.

Bottom Line

• Cordyceps can improve VO₂ max and endurance performance, but the effects are modest—think 5-11% improvements, not 50%.
• Quality matters enormously: look for Cordyceps militaris extracts standardized to 1-2% cordycepin.
• Dose matters: 1,000-3,000 mg daily, taken consistently for 8+ weeks.
• It's not magic: if your training, nutrition, and recovery aren't dialed in, cordyceps won't save you.

Disclaimer: This article is for informational purposes only and not medical advice. Consult with a healthcare professional before starting any new supplement, especially if you have underlying health conditions or take medications.