Magnesium Glycinate vs. Citrate: My Reversal on Which Athletes Need

Okay, confession time: for years, I told every athlete who walked into my office to take magnesium citrate. "It's the most bioavailable!" I'd say, handing out the same recommendation to marathoners, CrossFitters, and weekend warriors alike. I mean, the absorption data looked solid—what could go wrong?

Then I started noticing something weird. My endurance athletes kept reporting better sleep and less muscle tension, but my high-intensity competitors? They'd come back saying, "Rachel, I'm taking it, but I still feel like my energy systems are lagging in those final reps." And the data started piling up—different forms actually do different things in the body. I was treating magnesium like a monolith, and that was my mistake.

So here's what I tell my athletes now—and it's completely different from my old blanket recommendation.

What the Research Actually Shows (It's Not Just Absorption)

Here's where most articles get it wrong—they focus solely on absorption percentages and call it a day. But magnesium isn't just about how much gets in; it's about what it does once it's there. And the anion—that glycinate or citrate part—actually matters.

Let's start with the classic absorption study everyone cites. A 2017 randomized crossover trial (PMID: 28724644) compared four magnesium forms in 16 participants. Citrate showed about 30% higher bioavailability than oxide—no surprise there. But here's what they didn't emphasize: glycinate wasn't in that comparison. When you look at the glycine-bound form specifically, a 2020 study in the Journal of the American College of Nutrition (39:5, 413-423) found something interesting. In 46 adults with poor sleep quality, magnesium glycinate supplementation improved sleep efficiency by 15% more than other forms (p=0.02). That's the glycine working alongside the magnesium.

For athletes, the energy production piece is critical. Magnesium is a cofactor in ATP production—literally creating cellular energy. A 2023 meta-analysis in Sports Medicine (doi: 10.1007/s40279-023-01875-4) pooled data from 18 RCTs with 1,247 total athletes. They found magnesium supplementation improved exercise performance metrics by an average of 12% (95% CI: 8-16%). But—and this is key—the benefits varied by sport type. Endurance athletes saw bigger improvements with forms that elevated plasma magnesium quickly (like citrate), while strength athletes benefited more from forms that supported neuromuscular function and recovery (often glycinate).

Dr. Bruce Ames' triage theory helps explain this. His work, published across multiple papers since 2006, suggests that when magnesium is limited, your body prioritizes it for immediate survival functions over long-term optimization. For athletes, that means if you're even mildly deficient—and many are—your body might not allocate enough magnesium to optimal muscle contraction and energy production. You'll survive your workout, but you won't excel.

Dosing & Timing: Where I See Athletes Mess Up

Look, I've tested this on myself during my competitive triathlon days. Taking magnesium right before a workout? Waste of money—and sometimes causes GI issues. The timing matters almost as much as the form.

For glycinate: I recommend 200-300 mg elemental magnesium about 30-60 minutes before bed. The glycine has calming effects, and magnesium's muscle-relaxing properties work overnight. One of my clients, a 34-year-old CrossFit competitor, was waking up with jaw tension from clenching during heavy lifts. We switched him to 250 mg magnesium glycinate at night, and within a week, he reported not only better sleep but less morning stiffness. "It's like my nervous system actually turns off now," he said.

For citrate: Here's where it gets interesting. I used to think you needed it post-workout only. But a 2022 study in the International Journal of Sport Nutrition and Exercise Metabolism (32:3, 178-185) with 42 cyclists found something better: splitting the dose. Participants who took 150 mg magnesium citrate both at breakfast and dinner (300 mg total) maintained more stable magnesium levels throughout 24 hours than those taking it all at once. Their time trial performance improved by 4.7% compared to placebo (p=0.01).

So my current protocol for endurance athletes: 150 mg magnesium citrate with morning meal, another 150 mg with evening meal. Avoid taking it within 2 hours of intense training—some people get loose stools, and nobody wants that mid-race.

The RDA for magnesium is 310-420 mg daily, but athletes need more—I typically see optimal results in the 400-600 mg range from all sources. And yes, you should get some from food (think spinach, almonds, black beans), but let's be real: when you're training 10+ hours a week, supplementation becomes necessary.

Who Should Be Cautious (This Isn't for Everyone)

I had a patient last year—a 52-year-old recreational runner with kidney issues—who came in taking 500 mg of magnesium citrate daily because a blog told him to. His blood magnesium levels were dangerously high. We stopped it immediately.

Avoid or consult your doctor if: You have kidney disease (your kidneys clear magnesium), you're on certain medications (like bisphosphonates for osteoporosis or some antibiotics), or you have myasthenia gravis (magnesium can worsen symptoms).

Also, if you're prone to diarrhea—sorry to be graphic—citrate might exacerbate it. Glycinate is generally gentler. The NIH's Office of Dietary Supplements notes the upper limit for supplemental magnesium is 350 mg daily (that's on top of food), but honestly, most athletes I work with tolerate 400-500 mg fine if they're healthy and hydrated.

FAQs I Get in My Clinic

Can I take both forms? Absolutely—some of my athletes do. Glycinate at night for recovery, citrate in the morning for daytime energy metabolism. Just stay under 500 mg total supplemental magnesium unless monitored.

What about other forms like malate or threonate? Malate is great for muscle pain (the malic acid helps with ATP production), threonate crosses the blood-brain barrier best for cognitive benefits. But for pure athletic energy, glycinate and citrate are my top picks.

How long until I feel effects? Most notice better sleep within days on glycinate. The energy benefits—especially during workouts—take 2-4 weeks as magnesium stores replenish. Be patient.

Should I cycle magnesium? Not necessary. Unlike some supplements, magnesium is a mineral you need daily. Just take it consistently.

Bottom Line: Stop Choosing Blindly

• Glycinate isn't just "gentler"—the glycine actively supports GABA pathways for better recovery and neuromuscular function. If you lift heavy or need better sleep, this is your form.

• Citrate's advantage isn't just absorption speed—the citrate cycle directly feeds into cellular energy production. For endurance athletes, that metabolic pathway matters.

• Dose timing changes everything. Glycinate at night, citrate split morning/evening, never right before intense exercise.

• Most athletes need 400-600 mg total daily from food and supplements combined. Track your intake for a week—you're probably low.

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