Supplements for Athletes: What Works?

Published by Garret Rock on

The world of endurance sports is inundated with supplements manufactured with the endurance athlete in mind. It’s easy to get wrapped up in supplements. Before you know it you’re taking a handful of pills in the morning, a special powder for your water bottles, and another handful of pills in the afternoon.   So let’s talk about what supplements are supported by research, and what may not be worth the money for endurance athletes.

supplements for athlete

Athletes should focus on food

First: one important concept:  although it is sometimes difficult to get all of the nutrients needed through diet, it is almost always better to try to meet your nutrient needs through foods than supplements.   At Athlete Blood Test, we like to say that supplementation generally isn’t a great long-term strategy.  Foods, especially fruits and vegetables, have enzymes that optimize bioavailability (how much you absorb) of nutrients within the food. When nutrients are isolated to be made into supplements some of those enzymes are lost.

Absorption of supplements

Bioavailability of supplements varies depending on many factors, including the supplement quality, how the supplement is manufactured, what the supplement is, time of day you take it, what you take it with, and on and on. Some popular supplements have been shown to have absorption rates of less than 5%!  It is because of the variables above that you should strive to get the majority of your nutrients through an ultra-healthy diet. In short: put the same emphasis on diet as you do training.

Athlete Supplements Backed by Science

Of course, there are supplements for athletes that appear to benefit endurance athletes in well-designed, double-blind studies. Below is a summary of well-researched supplements. This isn’t a comprehensive list: there are more supplements that may be effective. This list is simply a list of those that research consistently shows to be effective.

The following supplements have consistently shown through quality, peer-reviewed research to be effective for endurance athletes.

*Note – we have no affiliation with and obtain no commission for any vitamin or supplement linked in below.


Although multivitamin supplements do not appear to improve performance in endurance athletes, they are a generally-accepted health strategy. Endurance athletes burn through a lot of nutrients during and after workouts, which can lead to depleted micronutrients. Even if these depletions are marginal, they can affect performance, recovery, and immune function.

To be clear, there is a debate about whether multivitamins are actually beneficial for athletes.  In our experience at Athlete Blood Test, when we find deficiencies in intracellular micronutrient tests with professional and elite amateur athletes, and then correct for those deficiencies, we typically get positive feedback from the athlete about improved performance and quicker recovery.   Be warned, however, that Athlete Blood Test’s recent data show that some athletes are getting an excess of certain vitamins, which can also have detrimental consequences.  Thus, it is important to look at your individualized blood biomarker levels and then choose a multivitamin that makes sense for you.    

Fish Oils/Omega 3’s

Fish oils should be an essential supplement for every endurance athlete. These super-powered anti-inflammatory and antioxidant supplements are one of the most well-researched and supported supplements. They fight free radicals and oxidative stress and reduce post-exercise inflammation. *Processing makes a difference. Omega 3’s in the triglyceride form have shown to be superior. The huge majority of omega 3/fish oil supplements out there are in the ethyl ester form because this form is easier and cheaper to produce. One over-the-counter brand is in the triglyceride form and can easily be found in Nordic Naturals. The ideal EPA to DHA ratio for athletes is 4:1. Most supplements are 2:1. This ratio is fine, but if you can find a 4:1 supplement (such as Nordic Naturals ProEPA) that is ideal. I recommend 1200-1800 mg per day with food. My top pick is Nordic Naturals ProEPA, which can be found online or in many health food stores and pharmacies.


Strenuous exercise increases the production of free radicals, which can damage muscle tissue, increase muscle soreness, and create inflammation. Vitamin C is an effective antioxidant, and can be taken safely, easily, and cheaply. Antioxidants fight the production of free radicals. Vitamin C is also an immune booster and high intensity training decreases immune function. Most professional triathletes and ultramarathoners we see at Athlete Blood Test show reduced white blood cells, which are associated with immunity, throughout the peak of their training. There are well-run studies that show vitamin C does reduce post-exercise muscle pain and speed recovery, then there are well-run studies that conclude it likely does not. Ultimately, vitamin C is easy to take, is cheap, boosts the immune system, and probably helps with recovery, so for athletes with heavy training schedules, we often recommend it through peak training season.

Iron (only when indicated!)

Don’t try to guess at iron supplementation yourself.  Iron should be taken under the guidance of an expert or physician.  The need for iron supplementation should be shown through blood testing and analysis.  There are hundreds of thousands of endurance athletes blindly taking iron. When iron is indicated, this supplement can be essential to your well-being and ability to train and race. It can boost performance WHEN NEEDED. When taken in excess, it can be hard on the liver, cause gastrointestinal problems, inhibit zinc absorption (an important nutrient for athletes), and cause fatigue. There are several different forms of iron. Our top choice is iron carbonyl.

B12 (only when indicated!)

B12 for athletes

When used correctly and at the appropriate time, B12 can help ward off anemia and pre-anemia. If you are monitoring your blood work during your training, a sudden change in the MPV (which indicates the shape of the red blood cells) and a slight drop in hemoglobin and hematocrit suggest that it may be time to supplement B12 or increase your folate intake. That said, B12 is often high in the bloodwork of high-performing endurance athletes, but deficient intracellular (within the cell) micronutrient tests.


Research shows magnesium can increase lactic acid clearance, decrease muscle aches and cramping, and possibly improve power output and performance. Magnesium is plentiful in foods, but some studies show that in endurance athletes magnesium levels are very slow to rebuild once depleted by prolonged muscle use or training in hot, humid weather. In addition, alcohol, coffee, refined sugar, and high salt intake can deplete magnesium.  Endurance athletes may consider supplementation during peak training, especially if in hot, humid weather. Magnesium also is linked to potassium and calcium. When magnesium levels drop, potassium and calcium will soon follow. Drops in potassium result in severe muscle cramps. Drops beyond certain levels can be dangerous—it can end your race and possibly send you on a ride to the hospital.

Categories: Supplements


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