Triathletes How-To Guide to Sports Supplements

Your Guide to understanding the risks and benefits of dietary supplements for endurance athletes and triathletes.

our 2022 Guide to understanding the risks and benefits of dietary supplements for endurance athletes and triathletes.

Energy drinks, protein shakes and other supplements often make promises of quick fixes to your athletic performance. Many athletes believe that dietary supplements are needed to perform their best. Sure, some supplements can be helpful in certain circumstances, but people can regularly overestimate their benefits and safety. 

It’s important to be an informed consumer and understand the benefits and the risks before deciding to use any dietary supplement. 

Note: this information is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment.

Do you need a dietary supplement?

A dietary supplement does not serve as a substitute for a healthy diet. Focus first on your diet as the benefits are far greater when you get your nutrition through food. 

For situations where there’s a nutrient deficiency that can’t be reversed through diet alone, talk with your dietitian or qualified healthcare provider about a supplement. 

Do your homework

Despite the claims a supplement may make in its marketing, in the U.S. there are no regulatory or enforcement agencies to check to make sure the claims are accurate. It’s for this reason that athletes should ignore marketing claims, investigate the supplement company and review the product’s ingredients. 

A good place to start is to make sure the supplement you’re considering is third-party tested, such as NSF Certified for Sport or Informed Choice for Sport. 

Next is to evaluate the benefit the supplement would offer, as well as any risks. It’s helpful to consult with a dietitian, pharmacist or other qualified healthcare provider to help provide that guidance. Another resource includes the U.S. Anti-Doping Agency (USADA). 

The following supplements are commonly used, so let’s walk through the benefits and the risks. 

Multivitamin & multimineral 

Benefits – Can provide the needed vitamins and minerals that were missing in the diet.

Risks – Mega-doses can cause toxicity which can lead to vomiting, nausea, organ damage or more. 

Protein powder 

Benefits – It’s an easy way to consume more protein during the day. Consuming adequate protein will aid in supporting muscle development. 

Risks – High doses can cause bloating, gas, reduced appetite, fatigue and thirst. 


Benefits – Can delay muscle fatigue in high-intensity training. When taking appropriate dosing, it’s generally recognized as safe. The performance benefits are seen typically in high-intensity, short-interval-type training. Little benefit is provided in endurance-style training. 

Risks – High doses can lead to kidney damage, diarrhea, cramping and nausea. 

Fish oil 

Benefits – Offers anti-inflammatory properties. It has been shown to reduce triglyceride levels. Research shows a modest reduction in blood pressure. 

Risks – Should be taken with caution if you’re on blood-thinning medication. 


Benefits – It can offer improvements in strength and endurance performance as it gives the perception that you’re less fatigued. 

Risks – May cause GI issues in certain athletes. It can impact your sleep if taken too close to bedtime. It can have a negative impact on blood pressure and acid reflux (heartburn). 

Beetroot juice

Benefits – The results are mixed regarding athlete performance benefits. 

Risks – It has been linked to sudden GI distress after consumption. The vasodilation can cause a drop in blood pressure, dizziness and lightheadedness. 

Talk to your healthcare providers (including doctors, pharmacists, and dietitians) about any dietary supplements you’re taking. They can help you determine which supplements, if any, might be valuable for you. If you think that you have had a bad reaction to a dietary supplement, let your healthcare provider know.

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Alex Larson, MS, RDN, LD is a registered dietitian and age-group triathlete and runner. She works virtually with endurance athletes to improve performance and body composition through a flexible eating style. Alex lives near Duluth, Minnesota with her husband, two young boys and golden retrievers. You can find Alex at and on social channels @alexlarsonnutrition.