Should I Take Supplements as a Runner?

Two Health Metrics I Swear By as a Runner and a Coach

I'm going to be upfront with you: I always lead with food first. A balanced, varied diet is the foundation of everything... your training, your recovery, your energy. I'm not here to sell you a supplement stack or convince you to swap meals for powders.

But I am here to tell you that sometimes, food isn't enough. And for a lot of women, especially women who run, that gap is bigger than most of us realise. I know, because I lived it for years before anyone connected the dots for me.

This is everything I wish I'd known earlier, about the two minerals I now consider non-negotiable: iron and magnesium.

Iron: the marker that changed my life (and the number no one told me to ask about)

Let me tell you a story.

After my second pregnancy, I was exhausted. Not just new-mum tired, I knew what that felt like. This was a different kind of fatigue. It sat behind my eyes. It made thinking feel like wading through fog. Running, which had always been my release, felt really hard. My legs were heavy. I was really puffed. I'd finish easy sessions feeling tired.

I got my iron tested. It came back low, but not "anaemic". My doctor at the time suggested supplements, so I did everything right... I timed them away from dairy and caffeine (more on why that matters shortly), I was diligent, I was patient. Two years later, multiple doctors, changing guidelines, natural supplments, iron supplments, dietary changes, and my ferritin was sitting at around 40. Better than it had ever been, my doctor said. But still not climbing the way it should.

It was my current doctor who finally said: we've done what we can with oral supplementation, let's try an infusion.

And the difference? Honestly, it felt like someone had turned the lights back on. The brain fog lifted. My running came back. My energy was like a different person's.

I share this not to scare you, but because I spent years thinking I was just tired from life, from motherhood, from training. And the whole time, my iron was quietly dragging everything down, even when the labs said "normal."

Why "normal" isn't always normal

Here's the problem with iron testing that doesn't get talked about nearly enough: the reference ranges women are tested against are, frankly, quite crap.

In Australia, many labs have historically used a lower cutoff for ferritin levels of around 15–20 ng/mL for women. Some labs have used thresholds as low as 12. A 2023 paper published by the American Society of Hematology called this out directly, arguing that these cutoffs were set using data from women who were already depleted, meaning the bar was set at the bottom of a broken baseline.

The research now suggests the body functions optimally with ferritin around 50 ng/mL. And for runners, a 2023 systematic review recommends targeting 40–90 ng/mL, with 50 as a foundation that accounts for natural fluctuations. Ferritin can vary by up to 27% in women between blood draws depending on training load, stress, and inflammation. If your baseline is already low, a hard training block can push you into deficiency territory fast.

There's also something called stage 2 iron deficiency, where your iron stores are depleted, but your haemoglobin is still in the normal range. Your GP's blood panel looks fine. But research, and lived experience from many runners, shows this state genuinely impairs your ability to adapt to endurance training. You're doing the work and not getting the reward, and nobody flags it.

Why runners lose iron faster

Running places specific demands on your iron stores that sedentary life simply doesn't. Your body needs iron to make haemoglobin, the protein in red blood cells that carries oxygen to your working muscles. When stores are low, your blood can't carry as much oxygen. So this means your muscles fatigue faster, your perceived effort increases, and recovery slows.

Beyond that, hard training triggers the release of a hormone called hepcidin, which actually blocks iron absorption in the hours after a workout. So your body is working harder, demanding more iron, and simultaneously making it harder to absorb what you're eating or supplementing. This is why timing your iron away from intense training matters, and why taking it with vitamin C (which enhances absorption) while avoiding dairy, coffee, and tea (which inhibit it) can make a meaningful difference. But obviously that's a really big mental load on top of life!

Who's most at risk

Iron deficiency affects up to 35% of Australian women under 50 and that's using the older, more lenient cutoffs. If you're running regularly, the risk is even higher. Needs increase significantly during menstruation (particularly heavy cycles), pregnancy, and breastfeeding, all of which can push your requirements beyond what diet alone can cover. The mental load continues!

My personal experience is a good example: I was doing everything right, eating well, supplementing correctly and my body still needed more help. An iron infusion isn't the first step, but it's worth knowing it exists. For some women, oral supplementation simply doesn't absorb efficiently enough, and an infusion can do in weeks what years of tablets couldn't.

What to actually ask your GP

Don't just ask for an iron test. Ask for your ferritin number... the specific value, not just whether it's "in range." A result of 20 can be technically "normal" and still be leaving you exhausted, and with good reason.

As a runner, new guidelines are recommending:

• Testing ferritin every 6 months

• Aiming for 50+ ng/mL as a working target

• Knowing your number, not just your flag

Magnesium: the mineral the modern world is quietly stealing from us

Okay, I'll start with the personal bit here too, because it's the simplest story I have: if I don't take magnesium, I get muscle cramps overnight. Calves, feet, the kind that wake you up at 2am doing an involuntary standing stretch and cursing the world. The first time I connected the dots, missed a few nights, cramps returned, I no longer forget this one.

But there's a much bigger picture here, and it starts in the soil.

The soil depletion problem

Here's something that doesn't get nearly enough airtime in nutrition conversations: even if you're eating a genuinely good diet full of leafy greens, whole grains, nuts, and legumes (the foods that are supposed to be rich in magnesium) you may be getting significantly less than you think.

Intensive modern farming practices have progressively depleted the magnesium content of our soils. Research has found that crops grown on depleted soils can contain up to 40% less magnesium than those grown on nutrient-rich soil. The magnesium content of wheat, vegetables, dairy, and meat have all dropped.

The same food, less nutrition. You can do everything right and still fall short, through no fault of your own.

This is one of the key reasons that 1 in 3 Australians don't meet their daily magnesium requirements, according to Australian Bureau of Statistics data. You can eat well and still land in that statistic.

Why runners need to pay extra attention

Magnesium is involved in over 300 enzymatic reactions in the body including energy production, nerve function, blood sugar regulation, and crucially for runners: muscle contraction and recovery.

When you sweat, you lose magnesium. The more you train, the more you sweat, the more you lose. In the Australian heat, this compounds quickly. It's not just about cramps in the night, low magnesium can show up as persistent muscle soreness, slower recovery between sessions, disrupted sleep, and a general flatness that's hard to pin down.

The sleep piece is particularly important for runners, and it's why I take mine at night. Magnesium supports muscle relaxation and plays a role in nervous system regulation. It literally helps your body wind down. Sleep is when adaptation happens. If you're training hard but sleeping poorly and recovering slowly, your magnesium status is worth investigating.

The form you take actually matters

This is where a lot of people get tripped up, and where the supplement industry has genuinely done people a disservice. Look at the shelves in the chemist these days and you'll get very confused by the differing types of mangesium being offered for apparently different reasons.

Let's break it down for you in to simple differentiations...

Most cheap, widely available magnesium supplements, the ones you'll find at the supermarket, use magnesium oxide. It's inexpensive to produce, which is why it's everywhere. But it's poorly absorbed. The body doesn't take much of it up, it sits in the gut, draws in water, and you get the classic side effect: a definite pre-run poop.

This is why a lot of people try magnesium, feel nothing positive, and conclude it doesn't work for them. It's not that magnesium doesn't work, it's that they weren't absorbing it efficiently.

Magnesium citrate is an organic form that's significantly better absorbed. Multiple randomised studies have confirmed it produces measurably higher magnesium levels in the blood than oxide. The basic logic is simple: more gets absorbed, more reaches the cells that need it, more impact on muscle recovery and sleep.

Magnesium glycinate is another option, particularly if you have a sensitive gut... it tends to be even gentler while maintaining good absorption.

There are also some great magnesium drinks on the market now that make it an easy evening habit. Switch Nutrition makes a hot chocolate version (genuinely delicious) that uses a bioavailable form, something like this is a far cry from choking down tablets, and if a nicer format means you're actually consistent with it, that matters.

When you're looking at labels: look for citrate or glycinate. If it just says "magnesium" without specifying the form, or if oxide is listed, you can probably do better.

The bottom line

Food first. Always. I cannot stress this enough. No supplement replaces the foundation of a varied, whole-food diet. These minerals are found in real food for a reason, and that's always where we should start.

But we also live in the real world. Our physiology and lifestyle creates windows where needs outpace what diet can provide. Running adds another layer of demand on top.

Iron and magnesium are not miracle markers for perfect health or trendy "superfoods"... But when they're low, the impact is profound and often invisible, quietly expressed as fatigue, brain fog, cramps, slow recovery, sluggish training. And when they're optimised? The difference can be remarkable.

Ask for your ferritin number. Choose the right form of magnesium. And if something feels off with your training or your energy, please push for answers, even when the labs say you're fine.

This blog is for educational and informational purposes only and reflects my personal experience. It is not medical advice. Please work with your GP or a sports dietitian for personalised guidance.