Episode 19 – Evidence Based Supplements for Athletes Part 2

Key Topics Covered

Evidence-based supplements that support athletic performance. We’ll explain who they help, how they work, and the dose recommended for:

  • Beta-Alanine
  • Vitamin D
  • Iron
  • Probiotics
  • Pre-Workout
  • Glycerol
  • Beetroot Juice


Who: Individuals who do short intense spurts of exercise lasting between 60-240 seconds, but can support up to 10 minutes. Eg. Crossfit

How: Increases carnosine in the body, which helps prevent pH from dropping. In turn, this helps decrease feelings of fatigue and lactic acid build-up.

Recommend: 4-6.4g/day. However, this can cause paresthesia (tingly/itchy feeling). The issue with the research is that even taking up to 6.4g daily for 6 months still does not reach optimal carnosine levels. Therefore, take as much as you can handle.

Vitamin D

Who: If you’re vitamin D deficient it’s likely to be beneficial.

  • It assists with calcium absorption for bone health.
  • Potentially improves muscle strength (if deficient).
  • Assists with atrophy of type 2 muscle fibres.
  • Potentially improve VO2 max (if deficient).
  • Improved immune function and reduced inflammatory markers.

There’s a difference between being vitamin D deficient and having optimum vitamin D stores. Even if you’re at the lower end of the range, you can benefit from increasing those stores to the higher end.

  • 30% of individuals are deficient
  • 20-30% would be sub-optimal

Supplementing with vitamin D is an easy win!


Who: Anyone who is deficient.

How: Those who are deficient experience:

  • Fatigue
  • Issues with oxygen transportation
  • Reduced VO2 max and exercise capacity
  • Lower volume of red blood cells

Iron losses are higher in athletes and the breakdown of red blood cells occur (especially with running).

Recommend: Speak to your doctor about iron infusions (a quick way to boost) compared to a supplement that can take up to 6 months to replete.


Who: Can support immune function, especially for elite endurance athletes.

How: Probiotic consumption could decrease the risk of upper respiratory tract infection in athletes. However, it is very strain-specific (see useful resources for further detail). The International Society of Sports Nutrition position stand also mentions probiotics’ ability to improve upper-gastrointestinal issues (runners gut) and reduce delayed onset muscle soreness (DOMS).


A concoction of usually caffeine, beta-alanine, creatine and citrulline malate.

  • Citrulline malate supports that acute phase of training and increases the ‘pump’ phase. Unclear whether it increases muscle mass
  • Beta-alanine is required to build up in your system over time, to decrease fatigue and lactic acid build-up feeling. This is often used so that people physically feel the results of pre-workout (slight placebo effect)
  • Creatine increases the phosphate availability of ATP (energy) production

Each of these products assist athletic performance

Non-stimulating Pre-workouts typically contain:

  • Citrulline malate to assist with the ‘pump’ phase. Unclear whether it increases muscle mass
  • May have AAKG
  • May have nitric oxide to increase blood flow

Overall, if you like it take it. Each individual supplement increases performance, however, it is not guaranteed whether the quantities used in this concoction improve performance.


Who: Assists those who are doing endurance exercise. Especially when experiencing GI upset when consuming too much fluid or when fluid is not available.

How: It allows you to be hyperhydrated, by increasing fluid in your system up to 1L of water. It’s usually combined with sodium to improve that hyperhydration.

  • Individuals are able to retain up to 72% more water and sodium alone.
  • We want to avoid losing more than 2% of our body weight (due to fluid loss) when training to keep performance high.
  • Sweat rates are higher when you are hyperhydrated, which can assist with cooling of the body. This can potentially delay fatigue.

It can also be helpful for:

  • Weight lifters to help get a ‘pump’, however, it’s unclear whether this improves performance.
  • Bodybuilders this might be useful to increase the ‘pump’ on show day.

Recommend: 1.2g kg BW glycerol + 26mL/kg BW of fluid. Over an hour, around 30min before exercise. It can be found at the chemist. It has a sweet taste and because of this, it is quite high in calories.

  • Eg. 75kg athlete = 90g of glycerol + 2L fluid. This equates to 500 calories, this can be a logistical challenge for those trying to preserve calories. It’s also unclear whether this can cause gastric upset.

Beetroot Juice

  • Who: For an endurance athlete completing a 5km run, it improves performance by 1.5%. The better-trained athlete, the less of an effect it will elicit. Likely due to their body already experiencing those adaptations.
  • For lifters, a study showed that they experienced increased bench press performance by 19%. They looked at 60% of 1 rep max, training to failure for 3 sets. The group who took beetroot juice completed 17% more reps than the group who did not. This can help with a better muscle pump, but does it relay to increased muscle mass?

How: Beetroot juice is a great source of nitrates which convert to nitric oxide, this leads to vasodilation and thus improved blood flow.

Recommend: 1kg of beetroot, 500mL juice or 70mL concentrated 30min before training. There are greater benefits for those who take it consistently for 6 days. It is expensive, one shot is $4-5.

Relevant Links/ Resources

Studies mentioned

Ingestion of Nitric Oxide Enhancing Supplement Improves Resistant Exercise Performance

Useful resources

International Society of Sports Nutrition Position Stand: Probiotics

Blog Posts

Beta-Alanine: A Dietitian’s Guide

Vitamin D Supplements and Fractures

Probiotics for Immunity in Athletes

Glycerol for Athletes: Everything you need to know

Beetroot Juice for Bodybuilders and Powerlifters