Top 12 Strength Training Supplements Dissected

The amount of marketing BS spread about supplementation is absurd.

It makes sense – supplements are a billion dollar industry, and the craziest claims get you paid.

We’ve been dissecting supplement and nutrition claims for over two years at With over 20,000 citations now, we’ve amassed a wealth of knowledge. And we’re going to use that knowledge to reveal the truths about the 12 most popular strength training supplements.


Claim: Glutamine is touted as a muscle-building agent, and more recently it’s starting to be marketed as an intestinal-health supplement.

Reality: In a cell culture (aka a petri-dish), glutamine can cause dose-dependent increases in muscle protein synthesis. Furthermore, when given to trauma patients, there appears to be rapid recovery of muscle tissue. Unfortunately, these properties do not apply to healthy athletes who use glutamine for muscle-building purposes. This is not one of the issues where there is a lack of evidence, but instead pretty much complete consensus from repeated scientific studies in which glutamine does not outperform placebo.

It is possible that very low protein intakes (vegetarian/vegan diets) could benefit from glutamine supplementation, but supplementation could be avoiding by simply eating more protein.

The reason glutamine doesn’t work is a kinetic issue: the liver and intestines consume most glutamine, and thus little gets to your muscle tissues. Glutamine does seem to help people with intestinal disorders such as Crohn’s disease.

Notables: As glutamine’s inefficacy is a kinetic issue, it is possible that a certain variant of glutamine could bypass the issue and actually cause muscle growth. This variant is only a theory right now, and does not currently exist. However, glutamine is not likely to go away anytime soon, since the cash cow can still be milked.

> Waste of your money, unless you have serious intestinal issues.

Protein powders

Claim: Protein powders are dehydrated food supplements with the sole purpose of adding protein to the diet. The sources and flavors vary, and different forms of protein supplements come with various claims to encourage people to buy their powder rather than another. Most famously, this includes whey protein being a “faster-absorbed” protein source.

Reality: There are indeed differences in protein absorption between whey and casein, but there is not a clear relationship with muscle growth. While studies that last 24 hours do note higher protein-synthesis rates with whey over casein, studies that actually measure muscle mass over a few weeks or months note no real difference. So here we have increased muscle-protein synthesis on a technicality, but the truth for building muscle is no significant difference.

It would be safe to summarize that for an average person, the speed of digestion is irrelevant; the only benefits one source of protein would have over another would be coingested nutrients (such as calcium in whey and casein, or fiber in hemp protein).

Notables: Casein protein is known to have gel-forming properties, and with the addition of small amounts of water it can make pudding; with some ingenuity, other recipes such as ice cream or protein fluff can be made.

> A great way to get more protein into your diet, but no type of protein is significantly better than others. The speed of digestion may not be relevant.


Claim: Creatine is said to be a muscle-building and power output-enhancing supplement, with a high safety level and a plethora of evidence to support its efficacy. There are various other claims for enhancing cognition and reducing depressive symptoms.

Reality: While the cognitive benefits of creatine supplementation are sometimes reliant on a partial creatine deficiency (seen in vegetarians), supplementation of creatine is a proven way to enhance power output. There is initially some weight gain (excess water retained), but creatine does have an ability to increase muscle-protein synthesis and has been noted to increase muscle gains over time.

There is still an issue of nonresponse (some people do not respond to creatine supplementation, and do not even gain water weight from supplementation), which appears to be a kinetic issue. This does not affect enough people to call creatine unreliable in any way, but creatine nonresponse does appear to exist. You can tell if you respond to creatine by taking high doses (20g daily for 5 days) and assessing the increase in water weight gain.

Notables: Topical application of creatine might be anabolic there too, being able to permeate the skin and potently increase collagen synthesis.

> It’s safe and it works. Especially potent for vegetarians.


Claim: Beta-alanine is the amino acid precursor to carnosine, a molecule that serves as an intracellular buffer for acidity. Supplementation of beta-alanine is said to enhance work output and prevent fatigue, and due to increased work output, an increase in muscle mass is claimed to occur.

Reality: Beta-alanine does appear to be effective, although the most recent meta-analysis on the topic suggested that the benefit is 2.85% and only significant in moderate-length trials (60 to 240-second bouts of exercise). This time frame actually excludes weight lifting, and the studies assessing weight lifting and power activities below 60 seconds do not uniformly find benefit.

Oddly, the three studies that measure lean mass and fat mass do note beneficial trends of more muscle and less fat mass. It is currently not known why this occurs.

Notables: Some anecdotal reports suggest that very high (8-16 g) and chronic dosing of beta-alanine, while effective for multiday training sessions, causes severe cramping and pain. This is actually quite plausible, as beta-alanine gets into the muscles via the same transporter that the amino acid taurine uses and competitively inhibits its uptake. Transient taurine deficiencies are well known to induce muscular cramping (as commonly seen with clenbuterol usage).

> Works, but the benefits are small.

“Testosterone Boosters”

Claim: Testosterone-boosting supplements are cocktails of various herbs or extracts that are said to increase testosterone production in the human body. Marketed to male weight lifters, the claims found on the label are the stereotypical claims associated with steroid usage.

Reality: Testosterone boosters are in an odd position. There are numerous herbs (fenugreek, Bulbine Natalensis) or molecules (D-Aspartic Acid, vitamin D, DHEA) that do appear to work, but the increases are quite small relative to testosterone injections, and these studies do not actually measure muscle mass gain over time.

More importantly, there are an astounding number of things marketed to increase testosterone with no apparent consistency in what works and what doesn’t. Even then, libido enhancers (sole purpose is to make you hornier) are very commonly put into testosterone boosters to make you feel like they’re working; the most popular T-booster, Tribulus terrestris, is evidence of this. People often confuse increased libido with an increase in testosterone, but the two can be independent of each other.

Notables: The most promising test booster of late is Bulbine Natalensis. Currently, there is no human evidence on its testosterone-boosting properties (it will apparently be published soon) but it appears to be quite respectable in rodents. While D-Aspartic acid is known to increase testosterone by 42%, Bulbine has been cited at 346%. Usage of Bulbine is limited by its known toxicity in rats (kidneys and liver), and the state of research on this topic is somewhat odd (all toxicity reports come from one research group in Africa, which appears to be the only group who really cared about it up until recently).

> There are promising ones on the horizon, but the current batch are mostly useless. Many of the T-boosters increase your libido without increasing your testosterone levels enough to appreciably build muscle

Branched chain amino acids, aka BCAAs

Claim: Branched chain amino acids (three amino acids known as leucine, valine, and isoleucine) are said to be muscle-building amino acids. This is technically true, and the BCAAs (especially leucine) are prime regulators of how food can increase muscle-protein synthesis. The leucine content of protein powders is even a marketing point, with “leucine-enriched proteins” being claimed to be more anabolic.

Reality: BCAAs do work, and they are anabolic. To be specific, they are anabolic relative to nothing. While this means that the marketing claims do reflect the state of the science, there are some practical limitations. BCAAs are in all protein-containing foods, and the studies that measure protein versus protein with added BCAAs do not uniformly note increased muscle-protein synthesis.

In short, if you follow a protein-rich diet, then you likely get enough BCAAs already, and consuming BCAAs separately will have little impact in increasing muscle mass.

Notables: Isoleucine is quite interesting due to it increasing glucose uptake into muscle cells quite potently, and by a relatively unique mechanism to boot. Leucine can do this as well, but due to inducing muscle-protein synthesis it eventually shoots itself in the foot (the same mechanism also reduces glucose uptake). Due to this, isoleucine supplements have a potential role for being antidiabetic or used on carbohydrate refeeds.

> If you are getting ample protein via your diet/supplementation, BCAAs likely have little benefit. They are a low-caloric source of protein.

Fish oil

Claim: Fish oil, for athletes, is most frequently used to reduce joint pain and inflammation and to allow for faster recovery. It is commonly followed up by studies showing that NSAIDs (the other choice for reducing soreness) hinder muscle growth in youth, while fish oil can theoretically increase glucose uptake and enhance leucine signaling in muscle tissue.

Reality: The joint health and inflammation issue is well known and researched, and does appear to exist. Fish oil dose-dependently reduces soreness and inflammation, and this appears to be secondary to a slight immunosuppressive effect.

Although there is not as much evidence for the muscle-building claim, it is potentially true as well. Relative to people without dietary fish oil, those with inclusion of fish oil appear to have enhanced leucine signaling (and muscle-protein synthesis from amino acids) and increased glucose uptake into muscle cells. There are no current studies that assess actual muscle growth (rather, they measure fractional synthesis rates over a few hours) so while it cannot be claimed that fish oil builds muscle, it does seem possible.

Notables: Fish oil exerts many of its benefits in an omega 3:6 ratio, with the desired ratio being around 1:1.

> Mostly useful in helping you achieve a 1:1 omega 3:6 ratio (or close enough). If you eat ample amounts of fatty fish and not too much omega-6, you likely do not need it. It can help with inflammation and joint pain.


Claim: L-Carnitine is touted to be a fat-burning agent, as a carnitine-dependent enzyme (carnitine palmitoyltransferase) is the rate-limiting step of transporting fatty acids into the mitochondria for their subsequent oxidation (the “burning” of the fat). Beyond that, carnitine is also said to enhance recovery from exercise.

Reality: L-Carnitine provision does not inherently increase the rate of fatty-acid oxidation, although it seems to under a few instances. For those deficient in carnitine, usually elderly individuals (65+) and vegetarians, supplementation can help burn fat. In otherwise healthy and young omnivores, carnitine has not been demonstrated to have fat-burning properties.

Preloading exercise with carnitine supplements (either tartrate or GPLC) does appear to have a muscle-protection effect, as increases of biomarkers of damage measured the next day appear to be reduced. Carnitine does not appear to have 100% reliability in actually increasing performance, although it has been associated with it at some times, and although this could lead to increased muscle mass over time (by allowing more work to be conducted) this has not yet been shown with carnitine supplements.

Notables: A variant of carnitine known as Acetyl-L-Carnitine (ALCAR) is commonly used in nootropic communities for its cognition-enhancing effects, which are said to be stimulatory but “cleaner” than caffeine. This may be related to an increase in neural glucose consumption, and would be an added benefit for elderly persons who might be partially deficient.

> Ineffective as a fat burner. Only helpful if you are deficient in it.

Conjugated Linoleic Acid (CLA)

Claim: CLA is touted to be a fat-burner, and is said to work on a novel method of fat burning (whereas the mitochondria mediates beta-oxidation of fatty acids, the system that CLA activates is known as the peroxisomal system and its receptors are called PPARs; peroxisomes can burn fat independently of the mitochondria). At times, CLA is also claimed to build muscle mass.

Reality: CLA is a prime example of how animal research differs from human research. In rats and in mice, CLA supplementation results in significant fat loss (and eventually fatty liver in mice) via the above mechanisms. There is ample human evidence to suggest that CLA has no such potency in humans.

Now, it would be incorrect to conclude that CLA is ineffective; if you cherry-pick evidence you can find studies to support the role of CLA in fat loss. The problem is that CLA is highly unreliable (with one study actually supporting an increase in fat mass) and the reason for this unreliability is not yet known.

Notables: CLA was one of the first molecules to be found to be a ligand for PPARs, and in the past few decades (partly due to research on CLA) studies on PPARs in general have exploded. PPARs are already the target of some drugs (thiazolidinediones) and supplements (tetradecyl thioacetic acid) and their established benefits are probably set to be the next things abused by supplement companies in marketing

> Great example of something that was very promising in rats/mice, but did not translate to humans. Highly unreliable results, and thus can be stated as being ineffective in fat burning.

Nitric-oxide boosters

Claim: Nitric-oxide boosters are a category of supplements that are all collectively said to increase bodily production of nitric oxide (aka give you “the pump”). Nitric oxide is not actually supplemented (it has a half-life of a few seconds), but instead supplements that stimulate the enzyme that makes nitric oxide are used.

The most popular supplement in this category is L-Arginine (the amino acid that nitric oxide is actually made from) and recently L-Citrulline has been gaining popularity (being a better absorbed version of L-Arginine), as have Agmatine and Beetroot (via nitrates). These supplements are said to enhance pumps in the gym, muscle growth, and be cardioprotective.

Reality: Nitric oxide itself is very important in the body, and there is evidence for most nitric-oxide boosters. Unfortunately though, the first bout of nitric-oxide supplements (which were all based on arginine) appear to be quite unreliable in their benefits. This unreliability is similar to CLA in the sense that we cannot say they are useless but it limits how much they can be recommended.

Also based on the aforementioned unreliability with arginine, a lot of studies in humans with the statement of “I wonder how nitric oxide does something in the body” could not properly assess the question. Nitric oxide is indeed involved in building muscle, but it isn’t confirmed if the increase in nitric oxide seen with supplementation is sufficient to actually induce benefits.

Beetroot and supplemental nitrates appear to be more reliable, and agmatine is set to get more studies to confirm its benefits (or lack thereof). However, the research is still at a “preliminary and promising” stage.

Notables: Arginine is a somewhat interesting supplement, as although it is the amino acid that nitric oxide is made from, this fact is completely irrelevant and a complete misdirection. The enzyme that makes nitric oxide from arginine is fully saturated even in a fasted state, and adding in more substrate would not work in the desired way. It has recently been noted that arginine can act on a receptor (alpha-2 adrenergic) to induce nitric-oxide production, but it appears to need really high concentrations to do this (which is hard to do with arginine supplementation due to the intestinal issues). Agmatine is more potent at the same issue, citrulline acts vicariously through arginine, and beetroot is a completely different (perhaps complementary) mechanism.

> While L-arginine is the common choice, L-citrulline works better (on a per-dosage basis). Beet roots are a great food-source for nitric oxide, and agmatine holds a lot of potential.


Claim: Caffeine is the worlds most popular cognitive enhancer, and is known to be both stimulatory and “antisleep” to non-users; while tolerance develops to the stimulatory effects, the antisleep properties are retained. It is marketed to athletes to increase power output and to prevent fatigue from setting in during workouts.

Reality: Caffeine definitely does have an ability to increase training volume and power output, but requires dosages of around 600 mg in people who are not caffeine tolerant. Such a dosing protocol, while effective, is likely to cause some hyperstimulation issues.

The increase in power output and training volume is mostly lost when tolerance to caffeine develops, which at this dose can last a week or so. Due to this, caffeine seems to be more of a competition supplement than a basic training supplement.

The time where caffeine still has benefit to persons who are tolerant to it is for the antisleep properties, which are not lost with tolerance. For people who are sleep deprived and need to hit the gym, caffeine supplementation can still prevent the lack of sleep from destroying your workout.

Notables: Caffeine tolerance is known to be insurmountable. In other words, once tolerance develops you cannot just simply take more caffeine to try and overcome tolerance.

> Helps keep you awake, and in non-habitual users has a definitive increase in power output, but only at higher doses. Cannot be used regularly or the increase in power output is lost.

Mass-gainer supplements

Claim: Mass-gainer supplements are marketed to hardgainers (a term used to refer to people who cannot gain mass, usually due to undereating) that carry the claim that they are able to increase mass even in people who have difficulty in doing so. Although “˜mass’ is usually said, the primary focus for these supplements is muscle gain.

Reality: Mass gainer supplements are essentially protein powder with extra calories thrown in. Usually the calories are from nutrient-poor sources to boot (such as straight maltodextrin) and these extra ingredients somehow warrant an incredible price increase. Although it appears to be a deal due to the large size of most mass gainer supplements (many coming in bags), the price per serving frequently exceeds $2-3.

Mass-gain supplements have little to no benefit over simply buying a protein powder supplement without the added calories, and then just making a shake at home with other additives. Adding peanut butter or cream to your protein powder is significantly cheaper, and you can control the added nutrients easier with protein powder and perhaps even add in some healthy stuff (like blueberries).

Assuming a protein powder is used, there is absolutely no need for mass-gaining supplements, and there is no benefit associated with mass gainers that cannot be mimicked by just adding calories to protein powder.

Notables: There are no significant notables about mass-gain supplements aside from unscrupulous marketing.

> A very expensive way of just getting extra calories into your diet. A smarter solution would be to add food products into a shake made with basic protein powder.

About the Authors

This dissection was written by Kurtis Frank and Sol Orwell, co-founders of They recently released The Supplement-Goals Reference, a quick and easy way to see which supplements work, and which don’t.