In one of my recent blog articles, “My Top 5 Most Commonly Recommended Dietary Supplements,” I discussed supplements that may benefit certain clients including omega-3 fish oil, vitamin D, GABA, vitamin B-12, and BCAAs. Although it is best to get nutrients from the diet, there are some cases in which this is not possible, and supplements can help to fill in the gaps. Situations that may require the addition of a supplement may include dietary deficiencies, certain disease states, and some demanding training regimens.  When purchasing a dietary supplement, it’s important to remember that the FDA does not regulate vitamins, minerals, herbals, or sports supplements. For this reason, looking for a third-party seal can ensure quality, purity, and potency of the product.  Examples of third-party seals include USP, Informed Choice, NSF, and GMP. The image below shows an example of a vitamin supplement with a USP seal.

Figure 2 image source: https://www.quality-supplements.org/

Often, a product’s marketing or testimonials will promise superior effects. Because these products are not regulated by the FDA, the evidence for these statements is often lacking. Additionally, unregulated products often have added hidden ingredients that may be harmful.

This article will discuss five supplements that I do not recomend for sports performance in particular. If you have questions about other supplements not listed here, feel free to leave me a comment or send me an email!

Before taking any supplement, consult with a sports dietitian or other health-care professional. 

 

1. Vitamin C and Vitamin E

This first one might surprise you! While vitamin C and vitamin E are antioxidants (which protect our body from cellular damage), taking them immediately before or after exercise could interfere with progress. The reason for this is that while intense exercise does cause some cellular damage, this also triggers the release of proteins and enzymes that initiate muscle repair and recovery. Taking antioxidants before your workout can thus limit muscle recovery and performance adaptations. You can read more about antioxidants and performance in my blog post here. Does Taking Antioxidants During Your Workout Improve Exercise Recovery?

Supplement Claims:

• Minimize free-radical damage to skeletal muscle
• Reduce muscle fatigue and soreness

Clinical Studies:

• Only small numbers of studies on sports performance
• Findings do not show associated improved performance
• Supplementation appears to hinder body’s physiological and exercise-induced adaptations (3)
• Vitamin E: Several studies have shown supplementation is detrimental to health and may increase oxidative stress (2)

Summary:

• Taking antioxidants such as vitamin E and vitamin C before a workout may limit the body’s ability to initiate muscle repair and recovery
• Most individuals get enough vitamin E and vitamin C from a balanced diet and don’t require supplementation
• High dose vitamin E supplements should only be consumed if recommended by a qualified healthcare professional to treat a deficiency or other health-related issue

 

2. Citrulline

Citrulline is a non-essential amino acid. It enlarges blood vessels to increase the amount of oxygen and nutrients that reach the muscles. Athletes that take citrulline supplements hope to enhance exercise performance from citrulline’s effects on the cardiovascular system that enhance blood flow. The body can make its own citrulline, and it can be found in some common foods including watermelon, pumpkin, and cucumbers.

Supplement Claims:

• Supports production of protein
• Reduces muscle soreness
• Supports the immune system
• Assists body with muscle building

Clinical Studies:

• Clinical trials show conflicting results:
  • A 2010 study in 41 men doing barbell bench presses showed a single dose of citrulline resulted in a 59% increase in number of repetitions performed and a 40% decrease in muscle soreness after exercise. The researchers concluded that citrulline may be useful to increase athletic performance in high-intensity anaerobic exercises with short rest times and to help with post-exercise muscle soreness. (4)
  • A study in 2017 in older adults showed that citrulline demonstrated a modest increase in blood flow during submaximal exercise in men but not women. (4)

Summary:

• Only a couple of studies that show enhanced sports performance
• Conflicting results with men vs. women in submaximal exercise
• Not enough evidence to show that supplementation is beneficial

 

3. Beta-alanine

Athletes take beta-alanine supplements to delay the onset of muscle fatigue and enhance performance. However, most people can get enough beta-alanine from the diet by eating meat, poultry, and fish. Vegetarians may have less beta-alanine in their bodies(5)

Supplement Claims:

• Supports muscle endurance
• Supports muscle output
• Benefits athletic performance
• Enhances high-intensity exercise

Clinical Studies:

• Inconsistent data from studies that examined if consumption increases performance in sports that require bursts of high intensity (i.e., team sports).
• Little to no performance benefit in activities lasting more than 10 minutes
• May help with high-intensity and short-duration exercise lasting one to several minutes

Side effects:

• Some people report tingling in the face, neck, and hands
• Itchy skin

Summary:

• Doses up to 6.4g/day appear to be safe
• Benefit questionable regarding increasing performance in events requiring high-intensity effort over a short period of time
• Little to no benefit in increasing performance in events lasting more than 10 minutes

 

4. DHEA

DHEA is short for dehydroepiandrosterone. It is a steroid hormone made by the adrenal glands. The body converts DHEA into other hormones, testosterone, and estradiol. DHEA production in the body declines rapidly after early adulthood. (2). For this reason, DHEA supplements are often referred to as a “fountain of youth.” DHEA in supplements is made from a substance found in soy and wild yams. However, the National Institute of Health issued a warning about DHEA that the body cannot convert the substance from wild yams to DHEA on its own. Athletes that take DHEA hope to improve muscle strength and enhance energy levels and athletic performance.

Supplement Claims: 

• Helps immune cell function
• Supports a healthy lean muscle mass to fat ratio (testosterone increases muscle mass by increasing protein synthesis and reducing fat mass)
• Provides higher energy levels (fatigue is a common effect of low testosterone and estrogen.)
• Supports bone and joint strength. (low levels of DHEA have been found in some people with osteoporosis.)

Clinical Studies:

• Some studies show a short-term rise in testosterone concentrations however this short-term rise does not affect muscle size, strength, or power. (2)
• Studies with older adults also confirmed that there is no evidence that DHEA increase strength in this population. (2)

 

Summary: 

• Unknown safety profile
• Not effective as a performance enhancer
• No evidence of increase in lean body mass
• No evidence of increase in testosterone levels in men
• Should only be used under supervision of qualified health-care professional
• Use is banned by many sports organizations

 

5. Glutamine

Glutamine provides nitrogen for the body in many biochemical reactions. The body uses glutamine in metabolism and energy production. Glutamine is stored in muscles and released into the bloodstream during times of intense physical exercise. Athletes take glutamine supplements to try and prevent muscle breakdown and improve immune function. In general, however, the body stores enough glutamine to protect against deficiencies during endurance exercise. (4).

Supplement Claims:

• Aids in muscle repair
• Promotes cellular energy
• Supports immune function (the immune system uses glutamine during times of stress and intense prolonged exercise)

Clinical Studies:

• Only a few studies examining the enhancement of athletic performance
• Studies show no effect on muscle performance in weight lifters
• No effects on body composition
• May help with recovery of muscle strength or reducing muscle soreness

Summary:

• The body can normally supply enough glutamine to protect against deficiencies
• More studies are needed to determine effects on sports performance
• Not effective as an immune enhancer
• May help with recovery of muscle strength or reducing muscle soreness

Summary

In summary, although I routinely recommend some supplements for certain clients, there are many supplements that I do not recommend.  The FDA does not regulate supplements so many products do not have clinical evidence of safety or effectiveness. When choosing a supplement, check for a third party seal on the bottle such as Informed Choice or USP.

Two proven ways to increase sports performance are with optimal nutrition and hydration. A sports dietitian can help develop a personalized nutrition and hydration plan for you that supports performance, recovery, and good health. If you feel like you need some direction in taking your health or performance to the next level, leave a message on the contact page!

 

References

1. Thomas, D. T., Erdman, K. A., & Burke, L. M. (2015, December). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Retrieved January 27, 2021, from https://pubmed.ncbi.nlm.nih.gov/26920240/
2. Dunford, M., & Doyle, J. A. (2019). Chapter 10 Dietary Supplements and Ergogenic Aids. In Nutrition for sport and exercise (pp. 365-366). Boston, MA: Cengage.
3. Office of Dietary Supplements – Dietary Supplements for Exercise and Athletic Performance. (n.d.). Retrieved January 26, 2021, from https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance
4. Leal, D. (2020, July 13). Do Pre-Workout Supplements Improve Your Strength and Performance? Retrieved January 28, 2021, from https://www.verywellfit.com/can-a-pre-workout-product-improve-physical-fitness-4154378
5. Semeco, A. (2018, December 07). Beta-Alanine-A Beginner’s Guide. Retrieved January 27, 2021, from https://www.healthline.com/nutrition/beta-alanine-101
6. Mayo Clinic Staff. (2020, November 13). Vitamin E. Retrieved January 28, 2021, from https://www.mayoclinic.org/drugs-supplements-vitamin-e/art-20364144
7. Contraindications for Ascorbic Acid (Vitamin C) Oral. (n.d.). Retrieved January 28, 2021, from https://www.webmd.com/drugs/2/drug-322/ascorbic-acid-vitamin-c-oral/details/list-contraindications
8. Vitamin E: Uses, Side Effects, Interactions, Dosage, and Warning. (n.d.). Retrieved January 28, 2021, from https://www.webmd.com/vitamins/ai/ingredientmono-954/vitamin-e