Best supplements for runners: what helps and what to skip.

What a supplement is actually for

A supplement is a lever you pull when food, sleep, and training are already working, and one specific thing is still missing. That is the whole job. It is not a shortcut around a bad diet, and it is not a replacement for the training. If your easy days are too fast and you are sleeping six hours, no pill is going to fix your season.

In 15 years of coaching I have watched runners spend hundreds of dollars a month on stacks of powders and capsules while under-eating carbs on a Tuesday and skipping the strides on a Friday. The order of operations is fixed: training, food, sleep, then supplements. If you have not honestly done the first three, do not spend money on the fourth. If you have, this list is short and worth reading.

The short list that earns a spot

Five things clear the bar for most runners I coach. Each one solves a specific problem the training itself creates or exposes. Everything else in the aisle is either optional at best or a lottery ticket at worst.

1. Iron, when a blood test says so
2. Vitamin D, from October through March in most of the northern half of the country
3. Protein powder, if you cannot hit around 1.6 grams per kilogram of bodyweight from food
4. Creatine monohydrate, for the strength work that supports your running
5. Beetroot or dietary nitrate, in the two weeks before a target race

Notice what is not on that list. Not BCAAs. Not glutamine. Not turmeric. Not any of the "recovery blends" whose ingredient list reads like a search-engine keyword file. Those get their own section further down.

Iron, and the one blood test I ask new athletes to run

Iron is the supplement I am most careful about, in both directions. Low iron is the single most common thing I see quietly ruining a training block. Runners lose iron through footstrike hemolysis, sweat, and, for women, menstruation. When ferritin drops below roughly 30 to 40 ng/mL, easy runs start feeling like tempos, workouts fall apart, heart rate drifts up at the same paces, and the athlete is convinced they are overtrained. They are not. They are running on a broken oxygen delivery system.

Before I put an athlete on iron, I want a blood panel. Ferritin, hemoglobin, transferrin saturation. Guessing is how people end up over-supplementing, which is its own problem because excess iron is stored in the liver and is not benign. I ask every new distance athlete to get a baseline panel at intake and to repeat it once a year, or sooner if the training data goes sideways for no obvious reason.

If the panel says low, the fix is straightforward: a targeted iron supplement, taken with vitamin C, on an empty stomach or with a small non-dairy snack, ideally not on the same day as a hard workout. Recheck at eight to twelve weeks. If the panel is fine, do not take iron "just in case." The pattern I watch for in athletes who confuse low iron with something else is buried in the recovery-data signals that show up before you feel it.

One more thing about iron. The first line of defense is food, not capsules. Red meat, liver, dark leafy greens cooked in a cast-iron pan, lentils, oysters, fortified oats. Athletes who eat these consistently need supplemental iron much less often than the internet suggests. Cook a steak on Sunday and you have done real training work.

Vitamin D and the winter tax on training

Vitamin D is the most under-appreciated supplement for runners who live above 35 degrees latitude, which is most of the United States. From roughly October to March, the sun is too low in the sky to make meaningful vitamin D in your skin, and endogenous production stops even if you are outside every day. If you are training through the winter and racing in the spring, low vitamin D quietly compromises bone remodeling, immune function, and muscle recovery.

The evidence for D3 supplementation in athletes with low serum levels is strong. The evidence for taking it when your levels are already fine is weak. So the same rule applies: test, do not guess. A serum 25-hydroxyvitamin D reading below about 30 ng/mL is a signal to supplement through the dark half of the year. In the summer, if you get regular sun on your forearms and legs, you can often stop. I have coached athletes whose stress-fracture history disappeared the year they got their D level into a healthy range and kept it there.

Protein, creatine, and beetroot: legit but oversold

These three are supported by real endurance-sport research, and I recommend all of them in specific situations. What I do not recommend is treating them as magic.

Protein powder. Endurance athletes need more protein than the general recommendation, in the range of 1.4 to 1.8 grams per kilogram of bodyweight per day, split across the day rather than banked at dinner. Most runners I coach hit this from food if they think about it. The ones who cannot, usually because their appetite drops during a heavy build, benefit from a whey or plant protein shake after the hardest session of the day. The shake is a delivery mechanism, not a magic recovery agent. If your diet already hits the number, adding a scoop mostly just costs money.

Creatine monohydrate. The best-studied supplement in sports nutrition. For runners, the value is not sprint output. It is in the twice-a-week strength work that supports your running. Creatine lets you do slightly more work in the weight room, which over months means better hip and posterior-chain strength, which shows up as durability and late-race economy. Standard dose is 3 to 5 grams a day, no loading phase needed. It also holds about a pound of water, which is worth knowing before you weigh yourself the day after starting it.

Beetroot or dietary nitrate. The nitrate in beetroot juice or concentrate has been shown to modestly improve endurance-exercise economy in the two to three hours after ingestion. In practice, I use it for the last two weeks before a target race, plus race morning, and only for events of 5K to marathon distance. It is not something to take year-round. And it is the kind of small edge that only matters if the foundational work is already done.

The long list of things I would not spend money on

The supplements aisle is a business. Its incentives are not aligned with your training. Here are the categories I tell my athletes to stop buying, and why.

• BCAAs and amino acid blends. Whole protein already contains everything BCAAs offer, in better ratios, for less money.
• Glutamine. Promoted for immune support and gut health. The endurance data is unconvincing at real training loads.
• "Recovery" and "greens" blends. Marketing-driven ingredient piles at doses too low to matter. A real meal does more.
• Testosterone or hormone "support" for men under 50. If something is off, that is a doctor's conversation and a blood panel, not a supplement.
• Fat burners. Not for runners. Not for anyone in a training block. Undereating during a build is how injuries happen.
• Anything with a proprietary blend that does not list per-ingredient doses. If the label is hiding the numbers, the numbers are not impressive.

One more thing. Race-day fueling is a separate category from supplements. Carbohydrate drinks, gels, and chews are not supplements, they are food you eat while running. The rules for how to use them are in the fueling protocol, and they matter more than any capsule on this list.

How I would stack it for a runner starting today

If you are a healthy adult runner training 30 to 60 miles a week and you want a reasonable protocol, here is the sequence I use with new athletes.

That is the whole plan. Six lines. Nothing on this list is going to make you faster the way a good 12-week block of consistent training will. But it can quietly stop a good block from getting derailed by something small and fixable, which over a career is worth more than any single workout you might have done differently.

If you want an honest read on whether a supplement belongs in your plan, or whether something in your training is what is actually holding you back, that is the kind of thing I sort through on an intro call. Coaching is a lot of these small calls made in the right order.

Written by

Coach Johnny Crain

2:12 marathoner. 4× US Olympic Marathon Trials qualifier. 4× NCAA national champion and 4× NCAA runner-up. Spoke at the RRCA National Convention. Founder and head coach at RunFitCoach, where he coaches every athlete personally.