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Supplements for endurance athletes: hype or helpful?

As an endurance athlete, you might be wondering if you should take any supplements or approved/legal ergogenic aides (substances that can enhance performance). Here is a brief overview of a few that are popular among endurance athletes.


  • Mechanism of action: Micronutrient involved in many functions including brain function, bone health and muscle recovery.

  • Athletic benefits: In some cases, supplementation may help alleviate muscle cramps, migraines and constipation, and may improve muscle recovery.

  • Recommended amount: The RDA for magnesium is 400-420mg for males and 310-320mg for females (and needs increase during pregnancy to about 350mg).

  • Important points: It is important to focus on food sources of magnesium, which include nuts, nut butters, seeds, legumes (e.g. black beans, edamame), spinach, whole grains and dark chocolate.


  • Mechanism of action: Supplemented probiotics can increase the number of beneficial bacteria in the gut, which has been associated with some health benefits including gut health and improved immune function.

  • Athletic benefits: May help strengthen immunity in endurance athletes.

  • Recommended amount: Varies based on source.

  • Important points: Adequate intake of iron, vitamin D and carbohydrates are also important to support immunity. Note that there are many strains of probiotics and each strain has specific effects. Also, the probiotic must arrive alive in the colon and in sufficient numbers to be effective (this is dependent on various factors, including storage temperature and presence of food additives).

Branched-chain amino acids (BCAAs)

  • Mechanism of action: Many actions, as they are a component of protein.

  • Athletic benefits: Suggested benefits of delaying fatigue in endurance events, decreasing protein breakdown in the muscle and muscle mass gains have not been substantiated by scientific research.

  • Recommended amount: With regards to complete protein needs, individual needs vary greatly.

  • Important points: BCAAs have no added value above complete proteins and are abundant in our food supply (both animal and plant-based protein sources). Of note, during endurance events, carbohydrates are the best source of energy for the muscles and it’s usually a lack of carbohydrate that causes protein breakdown.


  • Mechanism of action: Competes with adenosine in the central nervous system.

  • Athletic benefits: Improvement in pain tolerance and the potential to mobilize free fatty acids, sparing glycogen.

  • Recommended amount: 3-6 mg/kg about 60 minutes prior to exercise.

  • Important points: Higher doses do not lead to better results and may increase side effects (anxiety, dizziness, stomach discomfort, etc.). Also, there is variability in the beneficial effects between men and women, as well as genetic differences in caffeine metabolism from person to person.

Tart cherry juice

  • Mechanism of action: Inhibition of an enzyme that is related to inflammation.

  • Athletic benefits: Decreased muscle damage and soreness, and reduced inflammation.

  • Recommended amount: 8-12 ounces twice per day for 4-5 days prior to an event, and then 2-3 days after for recovery.

  • Important points: Tart cherry juice (100% juice) has a high carbohydrate content (from natural fruit sugar), which can aid triathletes in meeting their relatively high carbohydrate needs.

Beetroot (beets)

  • Mechanism of action: Increased nitric oxide levels.

  • Athletic benefit: Increased blood flow, improved oxygenation of the blood leading to longer time to exhaustion.

  • Recommended amount: If eating beets or drinking beet juice (as opposed to taking a supplement), there really is no specific dose. Research has shown benefits starting at 300mL (10.5 ounces) and there is evidence of high-level athletes benefiting from 600mg, but it’s best to experiment to determine the amount that is best for you. There isn’t an amount that would be harmful, other than the possibility of some GI/stomach distress.

  • Important points: Beets are packed with nutrition, so they are always a healthy addition to your diet. Also, chewing gum or using mouthwash can diminish the effectiveness of the beet/beetroot juice.

Multivitamin (MVI)

  • Mechanism of action: The individual vitamins and minerals (micronutrients) included have a variety of actions in the body. A common reason that athletes take an MVI is the belief that it will enhance performance by maximizing the function of the included nutrients in the body, but scientific evidence indicates this is not the case.

  • Athletic benefit: If it is determined that an athlete is deficient in a particular nutrient(s), then supplementation may be helpful. It is much healthier to get your nutrition from food, so a comprehensive assessment with a registered dietitian is beneficial. Endurance athletes typically do not need a general multivitamin. While it’s unlikely to be harmful to take an MVI, there is some evidence of undesirable long-term effects of high doses of certain micronutrients.

  • Recommended amount: If needed, follow dosing on product insert (typically one tablet per day).

  • Important points: It is best to check with your doctor if you believe you may be deficient in a particular micronutrient. Blood work can be done to determine deficiencies and then meeting with a registered dietitian is the best first line of treatment.

In conclusion, the sale of supplements generates billions of dollars for an industry that has an interest in making its products attractive. Even though some supplements can help athletic performance in some specific situations, it’s best to be very careful. There are hundreds of supplements that are marketed, and relatively few for which there is strong scientific evidence that supports their efficacy. A varied and balanced diet can meet the nutritional needs of most athletes. Most of the active substances contained in supplements such as vitamins, minerals, antioxidants, proteins, and branched-chain amino acids (BCAA), to name a few, can also be found in food. Also, supplements are not regulated by the FDA, which means that there is no guarantee that the product really contains what is listed on the label. To avoid consuming contaminated products, it is recommended that you choose a supplement that has been third-party tested (look for the logos NSF Certified for Sport or Informed Choice). Finally, don’t hesitate to consult with a sports dietitian to obtain personalized recommendations about which supplement regimen might be optimal for you.


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