The Supplement on Supplements

In last week's post, I offered the most recent evidence on the more popular recovery modalities.  The one area I skirted around was supplements.  There were too many options to fit into a single blurb, each with their own evidence line.  Instead, I wanted to save them for today.

I'm not a dietitian or sports scientist.  High school athletes should consult with a personal physician or dietitian when using supplements, and that's not me.  That being said, what follows comes from those in that world whom I trust, like Dr. Jeff Messer, Jennifer Giles, Dr. Laurent Bannock, Brady Holmer, the National Institute of Health, and the robust and unbiased summaries at Examine.  Hopefully I can at least offer their expertise and insights.

These are a few of the people I trust when it comes to the science of supplements.

The Biggest Takeaways on Supplements

Before discussing specific supplements, it's important to start with some key general points.  The first is that supplements are what their name suggests.  At best they are meant to supplement the core factors of training.  That certainly means the types of workouts one is doing, but it also means things like, nutrition and sleep.

That brings up the second point.  I thought about turning this post into clickbait with a title like "The Three Most Powerful Supplements for Runners".  Unwitting readers would have then been subjected to an in-depth post on sleep, hydration, and nutrition.  The most powerful complement to a runner's training is sleep and rest.  No number of bars, pills, shakes, or powders can make up for inadequate rest.  The same goes for hydration and nutrition.  Simply eating a balanced assortment of foods and drinking adequate water will do far more than any supplement.  Using supplements as a replacement for real food is not the path to peak performance.  Instead they should fill in any gaps, and for a runner eating and drinking enough, these are usually fewer and farther between than the latest influencer wants you to think.  

​Furthermore, evaluating supplements requires keeping in mind three different questions proposed by Dr. Jeff Messer.  The first is the most general:  whether supplements are advisable for high school athletes.  Some supplements are best left to adults.  Even with the rest, they should only be undertaken with parent approval and under the guidance of an athlete's primary physician and/or dietitian.  The other two are more at the heart of this post:  the strength of evidence in support of their effectiveness and their relative safety.

That last one is the most important.  Supplements aren't regulated the same way as medications.  Until a safety concern arises, no one steps in to test anything.  That leaves supplement makers with a lot more freedom to make unsupported claims and hide misleading ingredient lists behind talk proprietary blends.  The best approach here is to prioritize supplements that have been third-party tested though programs like NSF Certified for Sport or Informed Choice.

While no supplement is guaranteed to be safe, these logos are positive indicators.

Caffeine

Caffeine is one of the most popular and accessible supplements.  You can find it in coffee, tea, and even chocolate, not to mention in sodas, energy drinks, gums, chews, gels, and other artificial sources.  It works as a stimulant, impacting the nervous and cardiovascular systems.  There isn't a consensus on exactly how it would improve performance. One thought is that caffeine increases vigor while reducing perception of fatigue and pain.  There's also some suggestions that it frees up fatty acids for the body to use for energy, sparing precious glycogen in the muscles.  A third theory Holmer mentions is that it stimulates the release of calcium, an electrolyte that powers muscle contraction.  

Studies on the performance impact of caffeine are mixed.  The majority of studies do show that it gives a boost when dosed appropriately, but even then in many cases the benefit wasn't statistically significant.  Furthermore, it does pose some health risks.  Despite popular thought, it does not lead to dehydration with typical doses.  However, it can impact sleep, which as we've noted before is the most powerful supplement.  Higher amounts can also lead to cardiovascular issues such as heart arrhythmia, especially for those who metabolize it slowly or who have preexisting conditions.  For most adults, dangerous doses are well beyond levels linked to increase performance, but for teenagers it's a different story.  The American Medical Association advises that teenagers limit caffeine intake to 100 mg per day and in particular to steer clear of energy drinks.  

This is largely why Holmer rates caffeine 5/5 as a supplement and puts it on his short list for adult endurance runners while Dr. Messer isn't willing to advocate it for high school runners.  

Besides coffee and energy drinks, caffeine can be found in many products for runners. None of them are recommended for high school athletes.

Protein Powder

Protein powder is also one of the most popular supplements among athletes, including runners.  Obviously protein is found naturally in a wide variety of food sources, but it can also be found in powders sourced from a number of ingredients.  The easiest for the body to absorb and use would be whey, with pea being a decent vegan option.  There's really zero debate to protein's benefits.  The body uses it to build new muscle and to repair what was broken down during exercise.  Without adequate protein, athletes will see a gradual decrease in available strength and will end up far more susceptible to injury.

There are really no risks with consuming protein in of itself.  Contrary to popular belief, it does not pose a risk to kidney health.  The only real concerns are focusing on protein to the exclusion of other key nutrients.  For runners, this would most importantly be carbohydrates.  We can typically only stomach so much food, and so the risk would be shoving too much protein into that and not getting the carbs necessary to replenish glycogen stores. 

A lot of the current talk in popular channels (especially the "bro science" world) is riding higher on protein than ever before.  Some are more than willing to convince you that your cereal, your potato chips, and maybe even your toothpaste needs to be fortified with protein.  That's probably not true as long as someone's eating enough protein-based foods:  meat, fish, eggs, dairy, lentils. 

​For growing teenage athletes, that might mean some supplementation with protein powders.  Here the main concern is quality.  As mentioned before, many supplements haven't been third-party tested.  This is true with protein powders that claim massively inflated protein levels.  Furthermore, untested protein powders come with a heavy risk of contamination.  On one hand that could mean banned substances like steroids meant to secretly boost the effect of the product.  In other cases, it's the presence of heavy metals.  A recent study by the Clean Label Project of 160 protein powders revealed that nearly half of them exceeded safety thresholds for toxic metals like lead, cadmium, arsenic, and mercury.  

Many flavored protein powders are primarily marketed to body builders with a low-carb priority and therefore contain artificial sweeteners like sucralose, acesulfame potassium, and erythritol.   These have all been linked to gastrointestinal distress of varying forms, none of which are ideal for runners.  The same is often true of the common thickeners and binding agents like xanthan gum and lecithin from sunflower or soy.  

For these reasons, individuals like Dr. Messer aren't opposed to protein powders, they just recommend putting real foods on the plate first.

This protein powder ingredient list might be fine for a gym bro looking to add muscle, but for a runner, it could definitely spell an upset stomach.

Creatine

Another supplement with extensive research is creatine.  Creatine's primary role has long been understood for activities with short, high-burst energy demands, as it supplies key ingredients to the body's phosphocreatine energy system.  Because this system maxes out after about 10 seconds, its benefits haven't typically been of interest to endurance runners so much as to sprinters and football players.  

This was Dr. Messer's primary reservation.  And if a cross country runner maintained a steady 5K pace throughout an entire race, this assessment would make sense.  But anyone who's been to a meet knows that both the start and finish of races include bursts above race-pace, not to mention the occasional mid-race surge.  Quite often a few seconds is the difference between gold and silver, or a new PR.  Studies have repeatedly shown creatine's ability to improve force production. 

There have been no documented health risks with creatine monohydrate, the most common form.  There has been some evidence that creatine might slightly reduce VO2 Max, the body's maximum capacity for using oxygen during exercise.  Creatine does also often lead to weight gain via additional water retention, which some might see as a negative for endurance running.  However, that also means increased hydration.  Individuals like Holmer still see creatine as a net positive for endurance runners.  He rates it a 5/5.  

It is important to note that despite studies showing no short-term effects of creatine use on youth, lack of research into long-term effects has led the American Academy of Pediatrics not to recommend creatine use for those under 18.  Athletes and parents should always consult with a pediatrician or dietitian before turning to creatine.

While studies estimate that as many as 25% of high school athletes use creatine, this flies in the face of the recommendations of many professional medical organizations, especially without the supervision of a sports physician or dietitian.

Probiotics

Probiotics are microorganisms believed to improve gut health.  They occur naturally in fermented foods like yogurt, but the market for capsules, powders, and gummies claiming to offer the same effect in concentrated doses has exploded in recent years.  The simplest train of thought is that replacing bad bacteria in the gut and reloading good bacteria improves the microbiome inside an individual and should lead to fewer illnesses and gastrointestinal issues that could derail training or races.

Preliminary research has supported some benefit to these supplements, but the pile of evidence is still limited, partly because there are various strains to evaluate and no consensus on whether the microbiome in each person's gut should ideally be the same.  Delivery methods are also of concern, as questions persist as to whether the microorganisms in some forms can survive the journey through manufacturing to a shelf in someone's cabinet and then through the acid in their stomach to their intestines.  

For all of these reasons, Giles compares taking probiotics indiscriminately to throwing spaghetti at the wall.  She offers the option of using stool tests to make more informed choices in consultation with a dietitian.  But unless someone is experiencing significant gastrointestinal issues, this might be an extreme measure.  Holmer gave them a general rating of 2/5, and I haven't seen them advocated by any of the other individuals I trust.

Sodium Bicarbonate

The next two supplements both fall into the category of buffering agents.  The first--sodium bicarbonate--is one of the oldest supplements in the books.  The average person probably knows of it as baking soda, but there were studies on it at Harvard all the way back in the 1930s.  The theory is quite simple.  During exercise, hydrogen ions accumulate in muscle cells, lowering the pH and causing acidosis, which compromises the muscle's ability to contract.  As a base, sodium bicarbonate neutralizes these ions and keeps acidosis at bay, allowing athletes to push harder for longer.  

After some initial uncertainty from research, more recent data is quite clear on the performance benefits.  Messer, Giles, and Holmer (who gave it a 4/5) all recognize this.  The impact isn't the issue.  It's the side effects, which include all the things probiotics would want to eliminate:  nausea, stomach pain, bloating, cramps, diarrhea.  In a race setting these easily outweigh any performance gains and make it mostly impractical as a supplement, especially for the most sensitive.  

There is some hope of late.  Recognizing that the digestive distress of sodium bicarbonate was the result of its interactions with stomach acids, developers at Swedish gel company Maurten worked on a method of sealing it within a hydrogel that would prevent any interactions prior to the intestine.  The recent studies have shown a drastic reduction in negative side effects despite a maintained boost in performance.  But with all of this happening in the last year, further studies will need to solidify the early results.

In the meantime, four servings of the Maurten version retails for $70, and the typical meet doesn't have enough porta potties for anyone to recommend taking a spoon to a box of Arm and Hammer as part of one's pre-race regiment.

If Arm & Hammer and Dippin' Dots had a baby, the result would look something like Maurten's bicarb system.

Beta-Alanine

The story for beta-alanine is similar to bicarbonate, as it also works as a buffer by increasing carnosine levels in muscles.  Carnosine has the ability to absorb the free hydrogen ions and limit acidosis.  

Studies are a little less conclusive than with bicarbonate, though in middle-distance events beta-alanine has shown some benefits.  In the end, highly regarded organizations like the Australian Institute of Sport have given it a thumbs up, and like bicarbonate, Holmer rates it as 5/5.  

And like bicarbonate, the main concern is with the side effects.  Rather than digestive issues, the primary side effect is paresthesia, tingling and burning sensations in the face, neck, hands, and torso.  While this isn't harmful, it is troubling enough to many athletes that they shy away.  It's also why Dr. Messer discourages it for high school athletes.  

Nitrates

Nitrates are another popular supplement, most commonly sourced from beet roots.  In fact, many athletes simply drink beet roots juice itself, though powders and capsules exist as well.  The common explanation of its effect is that by dilating blood vessels, nitrates allow for increased delivery of oxygen and other nutrients.  This allows the aerobic energy system to be pushed harder without maxing out its capacity.

Beet juice hasn't been on the scene quite as long as some other supplements, so the research is moderate but still somewhat limited.  Some studies have shown benefit, whereas others have been more mixed.  Nonetheless, a meta-analysis of existing research does indicate improvements to power output and time to exhaustion.  

There also don't appear to be any dangerous side effects.  Some have expressed concerns about the ingestion of nitrates and links to cancer, but the levels typically consumed in supplements are far below recommended limits.  Furthermore, recent medical opinion is that naturally occurring nitrates like those found in beetroot juice are less problematic ones than those added to foods because the accompanying presence of antioxidants prevents the nitrates from breaking into the nitrosamines that seem to be the real danger.  Otherwise, the only real noted side effect is that early in use it can often cause urine to turn red or pink.  

For these reasons, Dr. Messer, who generally opposes the use of supplements in high school runners outside of the common vitamins and minerals, said that if forced to pick one popular supplement for athletes, it would be beet root juice.  Holmer likewise rates it a 4/5.  Outside of caffeine, it was the only supplement endorsed to improve performance in cross country athletes by the International Association of Athletics Federations in their 2019 consensus statement on nutrition for athletics.

Tart Cherry Juice

Moving from one red juice to another, tart cherry juice is another widely touted supplement, even available now as gummies and powders.  The thought is that a type of antioxidant called anthocyanins in the cherries can reduce inflammation if consumed post-exercise.  

The evidence isn't always consistent.  Some studies have shown improved performance and decreased perceived muscle soreness.  Meta-analysis showed a small impact on soreness but a moderate impact on recovery of muscle strength and power.  One thing worth noting is that many of the existing studies have been funded by the cherry industry.

Despite the mixed evidence on performance, there don't appear to be any negative side effects.  For that reason, Holmer is willing to rate it as a 2/5, more open to its impact on recovery than on performance.  

Ketones

The next two supplements are relatively recent ones on the scene.  That largely means their effectiveness and safety hasn't been fully tested.  That should immediately mark a note of caution.  

Ketones are produced naturally by the body in states when carbohydrate stores are low, either due to fasting or extended exercise.  The liver breaks down fat into ketones, which the body uses to produce energy.  However, ketones can also be ingested in liquid form, and the thought is that this can trigger the body's use of fat for fuel before carbohydrate depletion occurs, thus preserving precious glycogen and glucose stores.  Even if this theory is correct, that would seem to suggest that exogenous ketones (those consumed) would only benefit athletes in exercise long enough to deplete carbohydrate stores.  For a high school cross country runner, that could possibly be a factor in the long runs of exceptional athletes, but it isn't going to become a factor for a 5K.

While initial studies yielded promising results regarding performance, subsequent research has failed to repeat those findings.  There are some studies examining a potential boost to recovery, but no agreed upon explanation for how has been found.  There's also some evidence to indicate mental improvement with ketone use, particularly alertness and reaction time.  However, the research here is preliminary and has mostly focused on ultra-endurance events.

With regards to side effects, there have been many reports of gastrointestinal issues like nausea, cramping, and diarrhea.  Because of their newness, long-term side effects are also unclear.  Until further evidence emerges, Holmer rates ketones as a 2/5, though he was more convinced of its impact on mood and cognition.

N-Acetylcysteine

N-Acetylcysteine (NAC) is another relatively new player in the running supplement world.  It functions as an antioxidant, and to the thought is that it would reduce damage from exercise, limiting fatigue and inflammation.

A 2017 meta-analysis found no evidence of benefit to performance, and a 2023 review concluded that more research was needed as to its effectiveness and safety.  No significant side effects have been documented so far, but the jury is very much still out on this one.  

NAC might work as a treatment for cystic fibrosis or COPD, but at present there is little to no evidence supporting performance enhancement.

Iron

The final supplements included are different from the previous in that we ingest them all regularly as part of our everyday diet.  The question is whether a runner would need to intake more of them for optimal health and performance.  The answer to all of these is going to be that it depends on the runner, their current diet, and other conditions.

Iron would be at the top of the list of this "it depends category", which is why Holmer rates it anywhere from a 1 to a 5 out of 5.  Iron plays a crucial role in oxygen transport and storage driving the aerobic energy system.  The clearest indicator of the body's iron stores is its ferritin level, which I wrote a post about last year.  Runners, especially females, are at a much greater risk of low iron.  In cases where diet can't close the gap, a supplement might be necessary, as low iron poses threats not only to performance but to a runner's overall health.

Iron supplements come in a variety of liquid and pill forms, some of which can cause gastrointestinal issues in runners.  For those with conditions like hemochromatosis, an iron supplement could cause major complications.  As the post linked above suggests, athletes should get their ferritin, hemoglobin, and total iron counts tested and then meet with a doctor who understands adequate levels for endurance athletes before starting on an iron supplement.

Ferrous sulfate is the iron supplement Dr. Messer recommends.

Electrolytes

Electrolytes are another big variable as a supplement.  Different products are quite the rage at the moment.  And the body does need electrolytes.  They play a vital role in fluid balance and muscle contraction.  As athletes sweat, their bodies lose some of these electrolytes, especially sodium and chloride but to some degree potassium, magnesium, and calcium as well.  The exact quantities depend on the intensity of the exercise and the weather conditions.  It also depends on the person, as every individual has a unique sweat rate as well as a particular saltiness to their sweat.

That means on an easy run in December, an individual might not lose many electrolytes.  But during a long run in July or an afternoon cross country race in August, the levels lost will be much more significant.  But even in the same conditions, variation in losses is significant across athletes.  The only way to know definitively for where someone falls is through a sweat test.

That's going to determine when and to what degree electrolytes are beneficial.  In some cases, a well-balanced diet can provide adequate levels, especially of potassium and magnesium.  Calcium is a little trickier for growing teens, not because it is lost in large quantities during exercise but because it is used during growth to build bone mass. When calcium blood levels drop too low, the body will actually break down bone to replenish stores.  This makes bones more susceptible to fracture, and for a sport like running where bone injuries are common, this is especially important.  Plenty of foods either naturally contain or are fortified with calcium.  This is preferred, but supplements are an option if food alone can't get to recommended levels.

As for electrolyte supplements, a daily dose probably isn't necessary absent of exercise.  Excess sodium does pose its own set of health concerns.  However, for heavy/salty sweaters, in warm conditions, or before or after strenuous workouts, they might have a place.

Ratios vary widely in electrolyte supplements. Liquid IV has half the sodium of LMNT but nearly twice the potassium.

Vitamin D

Vitamin D is our last topic.  Its primary role seems to be helping the body with the absorption of calcium.  As just mentioned above, that could be pivotal for runners.  

Vitamin D is hard to consume in large quantities through food.  Fatty fish and egg yolks are the best sources, though in the average person will prove insufficient.  Ultraviolet light can also stimulate the production of Vitamin D in the body.  That's an advantage in sunnier places, but in the winter months somewhere like Missouri might keep athletes inside too much for adequate production levels.  All the more so in Seattle or Scandinavia.  This is where Vitamin D supplements are often most heavily marketed.  

There is some room for pause.  Holmer points to a 2022 study that showed no decrease in bone fracture incidents among those who supplemented with Vitamin D versus those who didn't.  This held true regardless of the initial Vitamin D levels of participants.  And it wasn't a small study.  It included more than 25,000 participants.

There are other potential benefits to Vitamin D, so Holmer wasn't willing to write it off entirely.  However, for improving performance in runners, he only rated it as a 1/5.

Getting Vitamin D from a number of sources is important. It just might not directly improve athletic performance.