The Runner's Stack: What High Mileage Actually Takes Out of You

Most pages written for runners are performance pages. This one is not. Nothing in a capsule is going to move your 10K time the way a well-built training block does, and a page that implies otherwise is selling you something. What supplements can do for a runner is narrower and more useful: replace what consistent mileage costs you, and support the recovery that lets you show up for the next session instead of limping through it.

Running is a depletion sport with a long tail. You lose minerals in sweat, session after session, at a volume most other training does not touch. Iron losses run higher than in the general population through sweat, gut losses, and the mechanical destruction of red cells under repeated foot strike — and training-induced inflammation raises hepcidin, the hormone that clamps down on how much iron you absorb, so a runner can be losing more and absorbing less at the same time. Connective tissue takes a loading dose every time you run and adapts on a slower clock than muscle does. And the recovery window between hard days is where the actual adaptation happens.

So this hub is built around those four pressures rather than around a finish line. One row on it — iron — is different in kind from everything else on this site, because it is the one compound where taking it on a hunch carries a real downside. Read the iron paragraph and the cautions before you read the doses. The rest of this page will still be here.

How we build this stack

Iron first, and iron carefully. Runners are one of the groups genuinely likely to be running low on stored iron, and female runners most of all — recommended intake is 18 mg a day for menstruating women against 8 mg for men, and endurance training pushes losses up on top of that. But the body has no efficient way to excrete a surplus, so the responsible move is a ferritin level and a blood count ordered by your clinician, read in context, and a dose they set. Not a bottle bought on the strength of feeling tired. Ferritin also rises with inflammation, which is exactly what hard training produces, so the number needs interpreting rather than eyeballing. If a clinician confirms low stores, the studied approach is smaller than most people expect — 18–30 mg of elemental iron, often alternate-day rather than daily, with a retest at 8 to 12 weeks and a stop when stores are restored. Iron is a course of correction, not a permanent habit.

Sweat losses, told honestly. Magnesium goes out in sweat, and high-volume training raises your requirement — that part is real. What is oversold is the picture of a runner sweating out their entire mineral reserve on a long run. The bigger driver is that most adults' baseline magnesium intake already sits under the recommended 400–420 mg for men and 310–320 mg for women, and mileage widens a gap that was already there. Magnesium glycinate at 200–400 mg elemental in the evening covers it and doubles as the best sleep move on this page. The electrolyte you actually lose in meaningful quantity is sodium, and that is a drink-and-food problem, not a capsule problem — salt your food, and use a sodium-containing drink on long or hot runs rather than looking for it in a pill.

Connective tissue and inflammation, on a longer clock. Vitamin C is the row that touches connective tissue directly — it is the cofactor your body requires to build collagen at all, and it is also the cheapest way to make plant-source iron absorb better, which is why it earns a slot on a runner's page twice over. Omega-3 at 1–2 g combined EPA and DHA daily is the year-round inflammation row — it changes the fatty acids your body builds signaling molecules from, which is slow and judged over months rather than weeks. Curcumin is the situational row: 500–1,000 mg of curcuminoids from an enhanced-absorption form during a peak block, a race week, or a stretch where the ache from Sunday is still there on Thursday.

Two things we deliberately left off. There is no stimulant, no pump ingredient, and no ergogenic aid on this list, because that is a different page and mostly a different conversation. And creatine is not here either — not because it does not work, but because its evidence is strongest for repeated hard efforts and the strength work around your running, not for steady-state distance. If you lift, creatine at 5 g daily is a reasonable addition for that reason; it is just not something distance running takes out of you. The largest levers remain unglamorous: sleep, enough carbohydrate to support your training load, and mileage that climbs gradually. The stack sits alongside those, never in place of them.

The stack

What to expect

• Iron is the sharpest before-and-after on this page, and only in one direction. Where a clinician has confirmed low stores, repletion runs on an 8 to 12 week clock, and the fatigue and training-tolerance changes people describe are the handbrake coming off — not a performance effect. Where stores were already normal, trials in athletes show nothing, and you have taken on the downside for no upside. That asymmetry is the whole argument for testing.
• Magnesium is quick if your intake was genuinely low: easier sleep onset and fewer 3 a.m. wakeups inside the first week or two. If your diet was already at the recommended intake, expect the honest answer, which is not much.
• Omega-3 is measured in months. Red blood cell membranes turn over across three to four months, so your omega-3 index reflects the last season of eating and supplementing, not last week's doses. This is the row we would never cycle and never judge in a fortnight.
• Curcumin's fastest read is the 24 to 72 hour window after hard downhill or eccentric work, where trials reported lower soreness ratings. Joint comfort is the slower job — the trials showing better comfort and function scores ran 8 to 12 weeks at 500–1,000 mg of curcuminoids per day.
• The metric that matters is not a personal best. It is how many weeks in a row you complete the sessions you planned. Nothing here compresses the 8 to 12 week horizon connective tissue needs to adapt to loading, and nothing here substitutes for sleep or for eating enough to support the mileage you are running.

Frequently asked questions

What supplements should runners actually take?

In priority order: iron, but only after a clinician has checked your ferritin; magnesium glycinate at 200–400 mg elemental in the evening for sweat losses and sleep; omega-3 at 1–2 g combined EPA+DHA daily for the inflammation side of recovery between sessions; vitamin C both as a collagen cofactor and to make plant-source iron absorb better; vitamin D3 with K2 for bone and muscle maintenance, tested rather than assumed; and curcumin situationally during hard blocks. That is a list built around what mileage costs you, not around going faster — no capsule on it competes with sleep, adequate carbohydrate, or a sensibly progressed training plan.

Do runners need iron supplements?

Some do, and more runners than non-runners — but the honest answer is that you cannot know without a blood test. Endurance training raises iron losses through sweat, gut losses, and red cells destroyed under repeated foot strike, and training inflammation raises hepcidin, which blunts how much you absorb. Menstruating women need 18 mg a day against 8 mg for men, so female runners sit at the sharp end of both effects. The problem is that your body has no efficient route to excrete a surplus, and genetic iron overload is more common than most people assume. So the sequence is not negotiable: ask your clinician for ferritin alongside a blood count, let them interpret it in the context of your training, dose from that, and retest at 8 to 12 weeks.

Does magnesium help with running cramps?

This is the place where popular belief has run well ahead of the evidence, so we will say it plainly: controlled work in athletes has not shown that magnesium supplementation reliably changes how often exercise-associated cramps happen. Cramps look far more like a neuromuscular fatigue phenomenon — muscle worked past what it is currently trained for, often late in a race at a pace above what you practised — than like a mineral running out mid-run. Magnesium is still worth taking if you run high mileage, because training raises your requirement and most adults start below the recommended intake, and because the evening dose supports sleep. Buy it for those reasons and you will not be disappointed. Buy it as cramp insurance and you probably will be.

Should runners take creatine, or does it just add water weight?

Creatine has the most robust evidence base of any performance supplement, but that evidence is built on repeated short hard efforts and strength work, not on steady-state distance. It is a fair addition for a runner who lifts, does hill repeats and track sessions, or is trying to hold lean mass through a heavy block — 5 g daily, timing irrelevant. The water-weight concern is real but usually overstated: the early gain is typically 1–2 kg of water pulled inside the muscle cell rather than under the skin, and it plateaus rather than keeps climbing. We left it off the core stack because it is not something running depletes. It is an addition you might choose, not a gap you need to fill.

Do antioxidant supplements blunt endurance training adaptations?

There is a real signal worth knowing about. Some human work suggests that large antioxidant doses taken around every session may dampen part of the oxidative stress signal that training adaptation is built on — the same logic as not taking a maximum anti-inflammatory dose after every hard run. That is why curcumin is a situational row here rather than a daily maximum, and why vitamin C sits on this page for its collagen-cofactor and iron-absorption roles rather than as an antioxidant megadose. While we are here: the belief that daily vitamin C keeps colds away does not hold up in the controlled trials, where adults taking it caught colds at essentially the same rate. The one group that stands apart is people under short bursts of extreme physical stress — endurance racing, heavy cold exposure — whose demand on vitamin C status is genuinely higher. That is a claim about status, not about catching fewer colds, and most runners in most weeks are not in it. The better reasons to take vitamin C are still the collagen-cofactor and iron-absorption roles above.

What about electrolyte drinks — are they worth it?

For long or hot runs, yes, and specifically for sodium. Sodium is the electrolyte you lose in quantities that actually matter over a couple of hours of sweating, and it is the one most worth replacing during the run rather than after it. Read the label for the sodium figure per serving, because a lot of products are built around a flattering ingredient list rather than a useful amount. The magnesium, potassium, and trace minerals on those labels are usually present in token quantities — pleasant marketing, not a meaningful contribution to your daily total. Get magnesium from a real evening dose, and treat the drink as what it is: fluid and sodium, which is enough of a job on its own.

Written for adults aged 18 and over. This content is for education only and is not medical advice. Supplements are not intended to diagnose, treat, cure, or prevent any disease. Talk with your clinician before starting any supplement, especially if you are pregnant, nursing, taking medication, or managing a health condition. Supplements for children are a pediatric clinician's decision — keep all supplements out of reach of children.

Our medical advisor is Dr. Garrett Wdowin, NMD, ABAAHP, FAARM, naturopathic doctor. This page has not been medically reviewed.