Blog Post

Supplements for CrossFit: A Dietitian’s Guide

Crossfit Seminar

Last weekend I was watching The Torian Pro, which is a relatively high-level CrossFit event held in Brisbane, Australia. As I was watching, I thought to myself “I wonder if all of these athletes are taking beta-alanine?” Because that could give them a serious edge over their competition.

This thought process extended to a whole bunch of other supplements. And then obviously it extended to overall nutrition too.

As an interesting note, a large percentage of the competitors were working with a sports dietitian in the leadup. So I would wager that most of them did have a solid plan in place leading up to the comp.

Royce Dunne Crossfit

I am stoked to see that. Because I feel like for years, particularly in the early days, CrossFit had a reputation for having some wack nutrition approaches. And those approaches were sub-optimal for somebody trying to optimize their performance.

The fact that so many people have jumped on board with quality dietitians is great because it really pushes performances to the next level. It guarantees that a lot of the easy wins for performance from nutrition that a LOT of people miss, get covered.

From my end, although writing a massive blog covering all aspects of nutrition for CrossFit athletes does not seem like the best use of my time right now, I wanted to discuss the supplements that could help provide an edge.

The obvious caveat that I want to add is that supplements are not the be-all and end-all. All the top-level CrossFit athletes have incredible physiques and are on a completely different level from your average gym-goer.

If you are an average athlete and you optimise your supplementation, it will take your performance up a notch, but it won’t turn you into an incredible athlete. But the whole purpose of this article is just that, to help you take your performance up a notch, which could give you the edge you are looking for.

Supplements That Most CrossFit Athletes Will Benefit From


Creatine VPA

Creatine is easily my most frequently recommended supplement.

It is particularly beneficial for ATP regeneration. ATP is mainly relevant for the first 10 seconds of a lift/movement. So due to the improved regeneration, it allows you to get more reps here and there on repeated sets, and directly improves performance that way.

Beyond that though, I think the below image is a great representation of why I actually care about creatine for Crossfit athletes. Typically, those who take it, gain more lean mass and strength than those who do not take it.

Creatine Benefits for Strength

The following benefits have been found in the research:

  • Increased maximal power and maximal strength on single and repeat sets of muscle contractions (5–15%) found in exercises such as in bench press, squats, leg press, leg extension, chest press
  • Improved single-effort sprint performance (1–5%) i.e. decreased sprint times (15-100m)
  • Increased repetitive sprint performance (5–15%)
  • Decreased recovery times
  • Support significantly greater gains in strength, power, and body mass with no change in body fat percentage
  • Increases vertical jump height and power output, reduces the decay in performance in jumping ability in sport (ie soccer, basketball, football)
  • Increased time to exhaustion and work capacity to fatigue (i.e. you can go for longer)
  • Increased intramuscular water storage i.e improve hydration status

It helps with so many things that I do not think you need to overthink this one. It makes sense to take creatine under most circumstances.

Dosage and how to use it:

The standard dosage is 5g per day of creatine monohydrate at any time.

Arguments can be made for timing it differently, but the goal is just to have it build up in your system over time. If you supplement it consistently, it does not make any noticeable difference whether or not you use specific timing. Consistency is the key.

There is also an optional loading phase of 20g per day for 5-7 days, split over 4 dosages per day (to minimise any chance of gastrointestinal distress). This loading phase is not needed, but it helps you reach the optimal levels of creatine within the body quicker.


VPA Beta Alanine

I have been a fan of beta-alanine for quite some time. Over the last couple of years, it has become super clear to me that CrossFit is one of the best sports for beta-alanine to really shine. I think it is underrated and underutilised.

It has recently gained more popularity though because Mat Fraser mentioned it on Joe Rogan’s podcast and raved about it with quotes like “it makes me feel like I have a third lung” and “I can’t believe more people don’t take it.”

And although I was already recommending it to people, oddly enough, that moment made me double down on it even harder.

The benefits do not come from the beta-alanine directly, they more come from the increase in muscle carnosine associated with beta-alanine supplementation.

The main function of interest for carnosine is that it helps to maintain the acid-base equilibrium. It helps prevent pH from dropping by buffering H+ ions, which in turn helps to reduce feelings of fatigue.

A simpler way of explaining it in a way most people would understand is to say that it helps prevent lactic acid build-up. And this is exactly why CrossFit athletes who use it love it.

It is most beneficial for exercise lasting 60-240 seconds. But it is still beneficial for exercise lasting up to 10 minutes. You can see how it is beneficial for Crossfit events.  

There are two reasons why I feel like it is underrated though. And they are both based on my interpretation of the research.

One of these reasons is that in research settings it seems to improve performance by ~3-4% under race-style conditions in events like running and cycling, for the relevant timeframes.

But the improvements in time to exhaustion (TTE) tests have been more impressive at ~13-20% improvements. I also imagine that under some circumstances the numbers would be even better than that.

TTE tests are often criticised (and ignored) due to not being as relevant as a time trial or race conditions. But I think they still have merit when it comes to Crossfit. And >10% improvements are super rare when it comes to supplements. We often are willing to do a lot more, for far less results than that.

The other aspect that I think is relevant is that supplement studies underdose and/or do not go for long enough to reap the full benefits of beta-alanine. Almost every study that uses beta-alanine, finishes while muscle carnosine levels are still increasing.

This makes me think Mat Fraser’s approach of “I take a tonne of beta-alanine” without actually knowing how much he took, might be even more effective than what has been done in the research.

My thoughts are the studies limit the dosage based on the side effect of parasthesia (a tingling feeling) that is uncomfortable at higher dosages. But arguments can be made for dosing higher than the amounts commonly used. These improvements that are seen in the research might be far less than what can actually be seen in the real world.

Dosage and how to use it:

The standard dosage is 4-6g per day at any time. Spread out over something along the lines of 4 dosages across the day if necessary to avoid uncomfortable paraesthesia.

Like creatine, it does not need to be taken pre-workout. It builds up in your system over time.

I typically do not recommend more than 6g per day, but it is something I have found curious. Particularly if you are an outlier.

I have experimented with 10g in one go without any noticeable discomfort. If parasthesia is the only concern, who is to say going higher is a bad idea? I am a cautious person when it comes to supplements, so I probably will not recommend that to anybody until I see research on it AND also see other smart people in the industry doing it. But it is an interesting area to pay attention to.

Beetroot Juice

Beetroot Juice for Endurance Athletes

Beetroot juice is particularly beneficial from an endurance perspective, but also might have some applications for improving strength performance too.

beetroot juice sys review summary

Beetroot juice is high in nitrates, which promotes vasodilation. This vasodilation improves blood flow.

To a certain degree, it is kind of like naturally mimicking some of the benefits people try to achieve via blood doping, except that this is legal in sports.

The performance benefits range from things like a 1.5% improvement in 5km time trial to 16% improvement in a TTE test. Under race conditions, there typically seems to be around a 1-2% improvement in performance.

There is one study on bench press performance with 60% of 1RM showing a 17% improvement over repeated sets. That’s a massive improvement, which contributes to why I think beetroot juice is relevant, particularly for a sport as varied as CrossFit.

Speaking of CrossFit specifically though, there is research specifically on CrossFit and beetroot juice showing improved performance. And although it is assumed it would improve performance, it is cool to see research supporting that.

Dosage and how to use it:

The ideal dosage appears to be around 5-7mmol of nitrate for most people, taken around 3hrs before training. This equates to roughly 250-300g of nitrate-rich vegetables per day.

The effects typically take 30 minutes to be noticeable, peak after 90 minutes and last for 6-8hrs.

This equates to 500ml of regular beetroot juice or 70ml of Beet It, which is a more concentrated version.

Beet-It Supplement

It is also worth noting that taking beetroot juice daily for 3-4 days actually improves its effectiveness even more than acute dosage. Arguably it would make sense to do that instead of just a once-off dose. The effects seem to plateau after about 6 days though.

The final thing to be aware of is that you must not brush your teeth or use mouthwash right after taking beetroot juice. This can block the conversion of nitrates into nitrites, which also blocks the effectiveness of the supplement.


Cup of coffee and coffee beans on wooden table

Most people think of caffeine as something that helps hype you up. But it actually does improve performance beyond that.

For resistance exercise performance improvement the research-based dosage is 5-6mg/kg, which is a pretty high dosage, 30-60 minutes prior to training/competition can help improve power output slightly.

The majority of studies done on short-duration activity following this type of dosage have shown noticeable improvements in performance.

The research is even stronger for endurance performance, with 3-6mg/kg consistently providing benefits.

When it comes to caffeine tolerance, it is a surprisingly complex topic. Some research shows that it matters, others show no difference. My thoughts are that it is probably a good idea at minimum to have caffeine-free days here and there and ideally also save it for situations where you feel it would be most beneficial.

Beyond literally improving performance, it also has benefits for reducing the perceived effort/pain. This is particularly relevant for CrossFit. If it feels easier, it might make it possible to push even harder.  

Dosage and how to use it:

3-6mg/kg 30-60 minutes before activity. If using something quickly absorbable like caffeinated gum, I would drop that timeframe down to 15-30 minutes before activity.

Although a lot of people prefer caffeine through sources like coffee, it is hard to accurately dose that. Caffeine intake through coffee is surprisingly inconsistent. One study from the Gold Coast identified that an espresso from different coffee shops could range from 25-214mg of caffeine.

While caffeine is beneficial, it is often used poorly. A lot of people use it in a way that impacts their sleep. Throughout training over the course of a year, the benefits of getting good sleep far outweigh the benefits of caffeine usage. I strongly encourage not having caffeine late in the day.

Supplements That CrossFit Athletes Might Benefit from Under Specific Circumstances

Citrulline Malate

Citrulline Malate

Citrulline Malate has merit for Crossfit, but I am not as sold on it as other supplements. The way I view it is that if you take pre-workout and it happens to be in there, that’s great. But I’m not sure I recommend going out of your way to purchase it individually.

Citrulline improves blood flow through nitric oxide, similarly to beetroot juice. It can also help clear ammonia, which is associated with muscular fatigue.

Malate plays a role in the Krebs cycle, improving energy production. It also reduces the rate of lactic acid buildup.

These theoretical mechanisms sound awesome. But I care more about outcomes than mechanisms. A meta-analysis on the topic concluded that Citrulline Malate likely does improve performance slightly, but not by a lot.

If you want to take it, go for it, there is no downside. But it seems like the least impactful supplement mentioned in this article so far.

Dosage and how to use it:

8g of Citrulline Malate ~60 minutes pre-workout. Unlike some of the other supplements, it does not build up in your system over time. It has more of an acute effect.

Protein Powder

Protein Powder

Protein powder is something that in my opinion, should be viewed as a convenient source of high-quality protein.

If you do not meet your protein needs through food, it makes sense to supplement with protein powder.

That can be interpreted in many ways though.

If you struggle to meet your total protein intake for the day, it would be beneficial to have whenever, to help meet that need.

If you want some protein post-workout, but do not have easy access/ability to consume food, it makes sense to have it then.

If you want to improve the distribution of your protein across the day, protein powder can make it easier, since for example you could have it in a gap in the afternoon, or add it into your breakfast.

It is not necessary or magical. When total protein needs are met, there is typically no difference between protein powder and food. But that does not mean it does not have the benefit of being convenient.

Dosage and how to use it:

30-60g when needed.

Vitamin D3

Vitamin D3

While there are no magical supplements, vitamin D3 is about as close as you can get for somebody who is either deficient in vitamin D, or on the low end of the healthy range.

It does not have any additional benefit if you are already at the high end of the healthy range. But I encourage every athlete to get a blood test to see where they are at.

Vitamin D3 has the potential to help improve bone mineral density, immune function, balance, mood, insulin sensitivity and more. Vitamin D deficiency is quite common as well.

In older adults, there is evidence that addressing a deficiency can significantly improve muscle strength as well.

Unfortunately, there is a lack of data on younger subjects. I would be hesitant to speculate that it is going to make a significant impact on strength for those already lifting at a high level.

If immunity is improved that means there will be might be less time spent off from training due to illness.

Increased bone mineral density can potentially reduce the likelihood of certain injuries. It has also been speculated that higher bone mineral density makes it easier to gain more muscle.

Balance can potentially play a role in some assistance exercises. For example, improved Bulgarian Split Squats, which could carry over to improved hypertrophy and strength overall. Arguably it could directly improve certain CrossFit specific movements such as walking handstands.

Improved insulin sensitivity can potentially play a role from a nutrition perspective, but that is a very complex topic beyond the scope of this article.

Dosage and how to use it:

The standard dosage is 1000IU per day, taken at any time. But it is not uncommon to take higher dosages (ideally under the guidance of a professional) to address a deficiency quicker.


Collagne Supplementation for Rehab

Collagen supplementation has the potential to be a game-changer for injury recovery. If you have any musculoskeletal injuries that you are rehabbing, collagen could potentially speed up the process.

To be clear though, for it to be effective, you need to have a sufficient dosage, appropriate timing and also have it near some vitamin C (either food or supplemental form).

Since we cannot just “direct” collagen where we want it to go, timing is important.

The amino acids and peptides from collagen supplementation peak in the blood 40-60 minutes after consumption, so if you align that timeframe alongside your rehab, it significantly increases collagen synthesis in the injured area.

One study even showed a doubling in the rate of collagen synthesis in comparison to placebo.

This is huge because it means you could significantly speed up rehab timeframes. This means you could get back to training and full performance quicker.

Dosage and how to use it:

15-25g of gelatin or hydrolysed collagen, with 50mg of vitamin C, 40-60 minutes before training/rehab.


Multivitamin + Immune Function Blackmores

I do not recommend multivitamins to my clients very often. I have a food-first approach whenever practical. And whenever there is a specific nutrient that is lacking, I will identify that and address that with more specific supplementation.

If your overall diet is going to be consistently lacking in multiple nutrients though, it makes sense to address that with a multivitamin. It is a bit of a coverall-all solution.

Another aspect to consider is for people who are in a calorie deficit and looking to get leaner.

The way I view it, it typically takes ~80% of your maintenance calories to meet your micronutrient needs. This would require around 80% of your maintenance calories coming from nutritious foods.

This is a debatable statement. There are a lot of gaps and areas to address with that statement. It would take excessively long to go through every point. But if we accept that statement as somewhere in the ballpark of being relatively accurate, it raises an interesting question.

If it takes ~80% of our maintenance calories to meet our nutrient needs, what if we are in a large calorie deficit. If you are in a 20% calorie deficit, which is not even aggressive, it means you would need pretty much 100% of your food to come from micronutrient-rich foods to meet these needs.

Using that logic, you could argue that if you are going through a fat loss phase, it might be worth considering whether or not a multivitamin would be beneficial.

It is not a go-to recommendation for me, but it is worth considering as an option under specific circumstances.

Dosage and how to use it:

1x serving of whatever the company has listed as a serving.  

What About Supplements Not Listed Here?

I am far more focused on what will help improve your performance than what is not going to be beneficial. If I tried to go through and list what supplements I do not think are worth taking, it would be an endless list.

That does not mean that EVERY supplement not listed here does not have the potential to be beneficial. If you have questions or anything like that, feel free to get in contact and ask. Or obviously, if you want an entire plan put together, I encourage booking in properly.

Hopefully, this post helps you in some way though, because even adding in one useful thing can make a difference to your overall performance.

By Aidan Muir

Aidan is a Brisbane based dietitian who prides himself on staying up-to-date with evidence-based approaches to dietetic intervention. He has long been interested in all things nutrition, particularly the effects of different dietary approaches on body composition and sports performance. Due to this passion, he has built up an extensive knowledge base and experience in multiple areas of nutrition and is able to help clients with a variety of conditions. One of Aidan’s main strengths is his ability to adapt plans based on the client's desires. By having such a thorough understanding of optimal nutrition for different situations he is able to develop detailed meal plans and guidance for clients that can contribute to improving the clients overall quality of life and performance. He offers services both in-person and online.