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Supplements and Sports Performance

Content by: Nancy Clark MS RD CSSD

Understanding supplements and nutritional needs for athletes. Learn a few basics.

Supplements and Sports Performance





A consistent training program combined with an effective sports diet—right foods at the right times—is fundamental for athletic success. For athletes who are not eating well, supplements can help fill a few dietary holes. But that said, no amount of supplements will compensate for a poor sports diet.

Supplements are used for many reasons:

• Prevent/treat nutrient deficiency.
Nutrients of concern for athletes include iron (to prevent anemia), and calcium plus vitamin D (for bone health). Any athlete who is deficient should make dietary changes to resolve the issue.

• Provide energy.
Commercial sports drinks, gels, electrolyte replacements, protein supplements, energy bars, energy drinks and liquid meals are often used to help fuel athletes before, during and after exercise. They are a convenient alternative to common foods.

• Support health and limit illness.
“Immune support” supplements with research to support health claims include probiotics, vitamin D and zinc. Promising supplements include vitamin C, fish oil, curcumin and tart cherry juice. Supplements lacking strong support from research include BCAA, HMB, magnesium and prebiotics.

• Improve performance.
The very few performance enhancing supplements that have solid research showing they “work” include caffeine, creatine monohydrate, dietary nitrate, sodium bicarbonate and beta-alanine. If you choose to use them, buy a brand that is NSF Certified for Sport, to minimize the risk of consuming harmful drugs. Every year, athletes get suspended for failing a drug test after they unknowingly took a supplement with an illegal ingredient.

Consulting with a registered dietitian (RD) who is board certified as a specialist in sports dietetics (CSSD) is a winning plan. This nutrition professional can assess your diet and guide your food and supplement options.

Quick Tips!

• Varied responses.
Even among supplements that “work,” the response varies greatly from person to person due to genetics, biology, the placebo effect, adequate fuel and enough sleep. Hence, a positive response may be due not to the supplement, but rather to the athletes taking better care of their bodies, eating wisely and getting enough sleep.

• Adverse effects.
Some supplements have been linked to liver toxicity, heart problems, seizures and anxiety.

NOTE: Manufacturers are not required to show safety or assure quality of a supplement. That’s why you want to use only safe supplements that are NSF Certified for Sport (as is visible on the supplement’s label).

• Other Resources.

Next Steps:

Where to learn more? Educate yourself about supplements before consuming.

• NSF Certified for Sport ( is an independent organization that evaluates products and assures athletes and coaches of the quality, purity and safety of ingredients found in the reviewed product. Product companies voluntarily submit products for testing. Look for the certified emblem.

• Operation Supplement Safety ( offers abundant information, including:
- 28 unsafe sports supplements to avoid.
- Questions to help determine if a supplement is safe.
- An A-Z index with info about specific supplements.
- Information on unusual reactions and adverse effects (nausea, headaches, shakiness, elevated heat rate, mood change, etc.).
- How to report an adverse event to the FDA and the National Institutes of Health (NIH).

• The Australian Institute for Sport’s ABCD Classification System ( ranks sports foods & supplements into 4 groups:
1. Group A includes products with strong evidence for benefits in specific events, including sports drinks, gels, iron, caffeine, beta-alanine, bicarbonate, beet root/nitrate, and creatine, among others.

2. Group B deserves further research. It includes food compounds with antioxidant and anti-inflammatory properties (i.e., tart cherry juice, curcumin), vitamin C, and collagen, to name just a few.

3. Group C lacks scientific evidence to support use. These include (and are not limited to) magnesium, alpha lipoic acid, HMB, BCAAs, leucine, vitamin E, plus more.

4. Group D includes products with a high risk of leading to a positive doping test: ephedrine, DMAA, herbal stimulants, pro-hormones, hormone boosters (such as DHEA, androstenedione, Tribulus terrestris) and others.

• IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete
This science-based article offers all you should know about supplements.

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