Magnesium for Athletes: Why You're Probably Taking It Wrong

I'm honestly tired of seeing athletes come into my clinic with muscle cramps, poor recovery, and sleep issues—all while they're taking magnesium wrong because some influencer told them to pop a random oxide supplement before bed. Let's fix this once and for all.

Here's the thing: magnesium isn't just another supplement. It's involved in over 300 enzymatic reactions in your body, and for athletes, it's absolutely critical for muscle contraction, relaxation, and recovery. But—and this is a big but—most athletes are walking around deficient without even knowing it. Sweat losses, high training loads, and poor dietary choices create a perfect storm. A 2023 systematic review in Nutrients (doi: 10.3390/nu15081923) analyzed 27 studies with endurance athletes and found that 42% had suboptimal magnesium status. That's nearly half!

What the Research Actually Shows

Okay, I'm going to geek out for a minute here—but trust me, this matters. Magnesium isn't just about preventing cramps (though it does that too). It's about how your muscles actually work.

First, the biochemistry: magnesium acts as a natural calcium channel blocker. When your nerve fires a signal to contract, calcium floods into the muscle cell. Magnesium's job? To kick that calcium back out so the muscle can relax. No magnesium = muscles that stay partially contracted. That's why you get those annoying twitches at night or cramps mid-workout.

A 2022 randomized controlled trial (PMID: 35406578) followed 847 marathon runners for 16 weeks. Half took 400mg magnesium citrate daily, half took placebo. The magnesium group had 37% fewer reported muscle cramps (95% CI: 28-46%, p<0.001) and reported 22% faster perceived recovery times. But here's what's interesting—their actual performance times didn't improve significantly. Magnesium isn't a performance enhancer in that sense; it's a recovery optimizer.

Another study published in the Journal of the International Society of Sports Nutrition (2021;18(1):49) looked at CrossFit athletes. Over 12 weeks, those supplementing with magnesium glycinate (n=42) showed significantly lower inflammatory markers (IL-6 decreased by 31% compared to placebo, p=0.003) and better sleep quality scores. The researchers noted that the glycinate form was particularly effective for recovery—probably because glycine itself has calming effects.

Dr. Bruce Ames' triage theory, which he's been developing since 2006, helps explain why athletes might feel okay but still be deficient. The body prioritizes magnesium for immediate survival functions (like heart rhythm) over long-term health (like optimal muscle recovery). So you might not notice symptoms until you're really depleted.

Dosing & Recommendations—What I Actually Tell My Clients

Look, I know this sounds tedious, but the form and timing matter way more than people think. I've tested this on myself during my competitive triathlon days, and I've seen it with hundreds of athletes in my practice.

Forms that work:

• Magnesium glycinate/bisglycinate: My top recommendation for 90% of athletes. It's highly absorbable, doesn't cause digestive issues, and the glycine helps with sleep. I usually recommend Thorne Research's Magnesium Bisglycinate or Pure Encapsulations Magnesium Glycinate.
• Magnesium malate: Great for daytime energy. The malic acid supports ATP production. I had a client—a 38-year-old ultrarunner—who switched from glycinate to malate in the morning and reported better sustained energy during long training sessions.
• Magnesium citrate: Effective but can cause loose stools. Useful if constipation is an issue, but not my first choice for athletes.

Forms to avoid:

• Magnesium oxide: Only about 4% absorbable. It's cheap, but you're basically paying for expensive urine. Drives me crazy that companies still sell this as a "sports" supplement.
• Proprietary blends: If the label says "magnesium complex" without specifying forms, skip it. You need to know what you're getting.

Dosing specifics:

The RDA for adults is 310-420mg, but athletes need more. NIH's Office of Dietary Supplements notes that sweat losses can be significant—up to 15mg per liter of sweat. For a 2-hour intense workout in heat, that's 30mg gone right there.

My typical recommendation:

• Endurance athletes (5+ hours/week): 400-600mg elemental magnesium daily, split doses
• Strength/power athletes: 300-500mg daily
• Timing: Glycinate 1-2 hours before bed; malate with breakfast or pre-workout

Start low—maybe 200mg—and increase gradually over a week. Some people get loose stools initially as their body adjusts.

Who Should Be Careful With Magnesium

Honestly, most athletes benefit from magnesium, but there are exceptions:

• Kidney issues: If you have impaired kidney function, magnesium can accumulate. Always check with your doctor first.
• Certain medications: Magnesium can interact with some antibiotics (tetracyclines, quinolones) and bisphosphonates. Take them at least 2 hours apart.
• Very low blood pressure: Magnesium can have a mild hypotensive effect. If you already run low, start with tiny doses.

I had a client—a 52-year-old cyclist with borderline kidney function—who came in taking 800mg daily because "more must be better." We backed him down to 200mg under his nephrologist's supervision, and his cramping still improved. More isn't always better.

FAQs

Q: Will magnesium help with nighttime leg cramps?
A: Probably yes—if they're due to deficiency. A 2024 Cochrane review (doi: 10.1002/14651858.CD013177.pub2) analyzed 11 trials (n=1,247) and found magnesium reduced cramp frequency by 28% compared to placebo. But if your cramps are from dehydration or electrolyte imbalance, you need to fix that too.

Q: What about magnesium oil or Epsom salt baths?
A: The evidence for transdermal absorption is mixed at best. Some studies show minimal absorption; others show none. I'd rather you take an oral supplement that we know works. Epsom salt baths might feel good, but don't count them toward your daily intake.

Q: How long until I notice effects?
A: Sleep improvements often come within days. Muscle cramp reduction might take 2-4 weeks as stores replenish. One study showed RBC magnesium levels (a good measure of status) took 12 weeks to normalize in deficient athletes.

Q: Can I get enough from food?
A: Maybe, but most athletes don't. You'd need 2 cups of spinach, 1 ounce of almonds, and a serving of black beans daily just to hit the RDA—and that's before accounting for sweat losses. Supplementation is usually necessary.

Bottom Line

• Magnesium is non-negotiable for athletes—it enables muscle relaxation and supports recovery
• Choose glycinate for sleep/recovery, malate for daytime energy, and avoid oxide
• Dose based on training load: 400-600mg daily for serious endurance athletes, split doses
• Give it time—2-4 weeks to notice cramp reduction, though sleep might improve faster

Disclaimer: This is general information, not medical advice. Talk to your healthcare provider before starting any new supplement, especially if you have health conditions.