Understand What Supplements Can—and Cannot—Do

How Creatine Has Been Studied

Research has studied different ways of taking creatine: some raise the creatine stored in muscle quickly, others more gradually, and the two are not simply identical. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

Carbohydrate and Protein Co-Ingestion

Research reports that taking creatine together with carbohydrate, with or without protein, can increase how much creatine the muscles take up and retain. That does not mean carbohydrate or protein is required, and it does not establish a specific amount, timing or separate performance benefit.

Body Mass

Creatine use can increase body mass through factors including water retained within muscle and increases in muscle tissue. In the research summarized here, people supplementing with creatine for approximately 1–3 months gained about 1–2 kg more body mass than control groups. This is a study result relative to controls—not a guaranteed amount that every creatine user will gain.

Not Everyone Responds the Same Way

The evidence notes that some people are considered non-responders and may not experience the same benefits from creatine supplementation, possibly because their muscle creatine stores are already naturally higher.

Safety Context

The evidence describes a favorable safety profile for creatine monohydrate in healthy populations across both shorter- and longer-term use. Evidence in healthy populations should not be rewritten as proof that creatine is automatically appropriate for every individual regardless of health status.

Different Kinds of Exercise Were Studied Separately

Research has studied caffeine separately for resistance and short high-effort exercise and for endurance exercise, with different amounts and timing in each, and those findings should not be merged into one universal caffeine strategy. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

More Is Not Better

More caffeine does not bring more benefit. Higher amounts are likely to increase the risk of side effects and, for athletes in tested sport, may lead to a positive doping test. Very large amounts of caffeine can be fatal. Teenagers are advised to keep their caffeine intake well below that of adults. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

Possible Adverse Effects

The evidence discusses adverse effects including irritability, nausea, insomnia and restlessness.

Important Safety Context

The evidence identifies caffeine as contraindicated in people with heart disease, hypertension, thyroid disease or anxiety. It also states that caffeine is not recommended during pregnancy and lactation. People taking medications should discuss caffeine use with their physician because medication-related considerations may apply. The evidence further states that combining other sources of caffeine—including energy drinks; coffee; and herbal ingredients such as ma huang (ephedra), citrus aurantium (bitter orange) or other stimulants—can exacerbate side effects and is not recommended.

These caffeine-specific safety points apply in addition to the general safety guidance further down this page.

Research Context

Much of the resistance-exercise research on caffeine was conducted in males and commonly used caffeine anhydrous. That limitation applies to this research and should not be generalized to all caffeine research.

What the Research Looked At

Research on beta-alanine has used several different approaches in different contexts, and they should not be combined into one universal formula. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

In the research, the benefit appears mainly in demanding exercise lasting roughly 30 seconds to 10 minutes, and particularly around 1 to 4 minutes.

Paresthesia

Beta-alanine can cause paresthesia—a temporary tingling sensation of the skin. The evidence reports two side effects, skin tingling and rashes, and describes both as appearing to be harmless. How to limit them is part of the conversation with your GP, pharmacist or dietitian.

Where the Evidence Applies

The evidence applies particularly to short or intermittent strenuous exercise, and performance benefits become less apparent as exercise lasts beyond approximately 10 minutes. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

A separate practical discussion describes high-intensity efforts lasting approximately 60 seconds to 10 minutes.

GI Limitations

Gastrointestinal discomfort and taste are important practical limitations, and tolerance varies from person to person.

Daily Protein Intake

Research describes higher protein intakes for people who exercise and want to build or maintain muscle than for the general population, with somewhat higher figures discussed when the goal is maximising muscle gain. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

Spreading Protein Across the Day

In the muscle-focused research, protein is spread across several meals through the day rather than eaten in one or two large servings.

Does Protein Have to Be Taken Immediately After Training?

The evidence does not establish that protein must be consumed immediately after training to increase muscle growth when total daily protein intake is already adequate. Post-workout protein may still be useful for recovery and supporting subsequent training or performance. A protein-rich shake may also be practical after demanding training or competition when appetite is reduced and consuming a normal meal is less feasible.

The priority remains adequate total daily protein intake and appropriate distribution across the day.

Food First

Complete protein foods provide the essential amino acids needed for muscle protein synthesis. Protein supplements can make adequate intake more convenient. In a meta-analysis of healthy adults who were doing resistance training and not restricting calories, raising protein intake beyond a certain level did not further increase gains in fat-free mass.

This is a finding from that specific evidence set—not a universal protein ceiling for every person, goal, or dietary context.

Calorie Restriction Is a Separate Context

The evidence also discusses higher protein intakes in highly trained athletes during calorie restriction, to help preserve lean tissue while reducing body fat. This is not the routine target for most exercisers, and in that comparison the higher intake did not produce greater lean-mass gains.

Different EAA Contexts Appear in the Evidence

The evidence includes several separate EAA applications, in contexts such as supporting muscle protein synthesis, reducing soreness, calorie restriction, preserving muscle, or lower total protein intake. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

A Separate Study Used EAAs Between Meals

Another study in the evidence gave EAAs with carbohydrate between normal meals and reported a greater anabolic response than a similar amount of EAAs from whole food. That is a study result, not a general instruction.

What About Leucine?

Leucine acts as an important signal in muscle protein synthesis, but leucine alone does not replace the other amino acids needed to actually build protein. The evidence makes the broader principle clear: all of the required amino acids are still needed.

Who May Have More Reason to Consider EAAs?

The evidence discusses contexts including calorie restriction, preserving muscle and lower total protein intake. That is different from saying that EAAs are necessary for everyone who exercises.

What the Guidance Says

The evidence makes a specific distinction: when essential amino acids are already being consumed in amounts sufficient to maximize muscle protein synthesis, supplemental BCAAs are likely unnecessary. Separately, the evidence discusses a possible BCAA benefit when total protein intake is low.

A Lower-Protein Context Is Different

A separate research context discusses a possible BCAA benefit when total protein intake is low. The amounts used in that research belong to it and are not a general recommendation.

The Key Distinction

BCAAs should not be described as: “essential supplements for muscle growth.” But they also should not be described as biologically meaningless. The evidence specifically states that when enough EAAs are consumed to maximize muscle protein synthesis, additional BCAAs are likely unnecessary.

It separately discusses a possible benefit when total protein intake is low.

Evidence in Less-Trained Populations

The evidence discusses modest improvements in strength or muscle-related outcomes from calcium HMB, particularly in untrained individuals.

Evidence in Trained Populations Is Less Consistent

Separate studies in trained and highly trained populations have reported positive findings in specific situations. However, the evidence also cites a meta-analysis of trained and competitive athletes that found no meaningful impact. Other reviews are more favorable.

Because these findings do not all point in the same direction, it would be misleading to present HMB as either clearly proven or clearly ineffective.

Recovery and Muscle-Damage Outcomes Are Separate

Another body of evidence discussed in the guidance looks at markers of muscle damage and recovery rather than muscle gain or performance. Some of these findings appear only with longer-term use. That outcome should not be treated as proof of improved strength, hypertrophy, or competition performance.

Bottom Line on HMB

The evidence is mixed, depends on the population and the outcome studied, and is affected by replication concerns. HMB therefore deserves a nuanced explanation rather than a simple “works” or “doesn’t work” label.

Dietary Intake and Supplement Dosing Are Different

The evidence discusses reference values for omega-3 intake from the diet. These refer to dietary omega-3 intake; they are not fish-oil, EPA or DHA supplement doses.

General Omega-3 Supplement Evidence

In its general discussion of supplementation, the evidence describes the research as inconclusive: whether omega-3 supplements bring broad benefits is not yet settled. That means the evidence does not support a blanket statement that everyone benefits from routine supplementation.

Food Sources Remain Important

The guidance discusses foods such as salmon, herring, mackerel, flax, chia and walnuts. Fatty fish directly provides EPA and DHA. The evidence also notes that foods rich in EPA and DHA, particularly fish, may provide more significant health benefits than supplementation, while acknowledging that additional research is needed.

Plant-Based Omega-3 Is Not Converted Very Efficiently

The evidence states that conversion of ALA to EPA and DHA is low: less than 5%. This is relevant when relying heavily on plant sources.

A Separate No-Fish / Vegan Context

In a separate vegan-diet discussion, the evidence says that when fatty fish is not eaten, EPA and DHA supplementation may be advisable; for vegans, EPA and DHA can come from microalgae-derived supplements. This is a different context from the general statement that broad omega-3 supplement evidence remains uncertain.

It should not be simplified into either “Everyone should take fish oil.” or “Fish oil never helps.”

Fish Oil Is Not the Only EPA/DHA Option

The evidence discusses omega-3 intake and EPA/DHA supplementation in different contexts. General omega-3 supplementation evidence is described as inconclusive, while diets without fatty fish—including vegan diets—are discussed separately as situations in which EPA+DHA supplementation may be more relevant.

Performance Evidence

In the supplement-evidence framework, MCTs are classified as having weak evidence for performance. This means their dietary or metabolic context should not be used as proof of an ergogenic benefit.

No Established Performance Protocol

The evidence does not establish a general performance-enhancing MCT dose, timing, frequency, or duration, and none is given here.

When Sports Drinks Become More Relevant

Sports beverages have a more meaningful role during intense and prolonged training. Fluid replacement, electrolyte considerations and carbohydrate intake are addressed in separate exercise and hydration contexts. A rule from one of those contexts should not automatically be applied to the others.

The “Over 60 Minutes” Rule Needs Precision

A common oversimplification is: “After 60 minutes, you need electrolytes.” That is not what the evidence establishes. The 60-minute threshold in the endurance research relates to carbohydrate intake during continuous endurance exercise, not to electrolytes.

It is not a universal threshold for electrolyte supplementation.

Fluid Intake Depends on Sweat Losses

How much to drink during exercise depends on individual sweat rate. Other exercise and environmental conditions are discussed separately and can also influence hydration needs.

Sports Drink Carbohydrate Concentration

In endurance contexts, the guidance discusses sports beverages by their carbohydrate content. That is a sports-drink formulation question, not an electrolyte “dose.”

Rehydration After Exercise

Rehydration after exercise is based on how much body mass was lost through sweat during the session. It is not a fixed amount everyone needs after every workout.

Why Individual Sweat Rate Matters

Sweat loss can vary substantially between people. A more individualized approach uses body-mass changes and sweat-rate assessment rather than assuming everyone needs the same fluid or electrolyte intake.

More Water Is Not Always Safer

The evidence also discusses exercise-associated hyponatremia, defined around a blood sodium concentration below 135 mmol/L. The evidence warns that excessive fluid intake during prolonged exercise can contribute to exercise-associated hyponatremia when fluid intake greatly exceeds sweat losses.

This is not a minor risk. The evidence describes exercise-associated hyponatremia as a potentially deadly medical condition: as the sodium in the blood is diluted, water moves into cells, including in the brain, which can lead to coma or death. It is uncommon, and the practical protection is to listen to your own body's cues and not to drink well beyond your natural thirst.

Signs, Symptoms and Scope

A coach does not diagnose exercise-associated hyponatremia but should know its signs. Severe symptoms include seizures and coma; someone with severe symptoms will likely be unable to continue drinking and needs medical attention straight away. Less-severe symptoms include weakness, cramping, vomiting, disorientation and confusion. These can also occur with severe dehydration, but they should still be treated medically; this is a medical matter, not a coaching one.

If someone shows signs of under- or over-hydration, their recent fluid intake matters: severe thirst or a lack of thirst can help indicate whether they are dehydrated or have exercise-associated hyponatremia. If hyponatremia is suspected, get the person to a hospital as quickly as possible, where sodium levels can be checked.

A Multivitamin Does Not Guarantee Complete Coverage

Even when someone uses a multivitamin, certain nutrients may still remain inadequate. The evidence specifically notes that nutrients such as Vitamin D, calcium and magnesium may still require attention. Taking a multivitamin does not automatically mean all micronutrient needs are being met.

More Is Not Automatically Better

Some products provide well over 100% of the reference intake (RI) for certain nutrients. That does not automatically make the product better. The evidence explains that higher amounts may or may not be appropriate depending on the nutrient and the person.

It also warns that high doses can sometimes be unnecessary, inappropriate, or potentially harmful depending on the context.

What % of the Reference Intake (RI) Does—and Does Not—Mean

% of the reference intake (RI) helps show how much of a recommended daily value is provided in one serving. It is not the same as an effective performance dose, a research dose, a treatment dose or a safety upper limit, and 100% of the reference intake (RI) is not the same thing as the Tolerable Upper Intake Level.

The Practical Point

A multivitamin may help fill gaps. It should not be used as proof that the diet is adequate, as a substitute for food quality, or as justification for automatically choosing the product with the highest percentages.

Who May Be More Likely to Have Low Vitamin D Status?

The evidence discusses risk contexts including limited sun exposure, spending substantial time indoors, living at higher latitudes, reduced effective sun exposure and low dietary intake. Low Vitamin D status is also reported in some athletic populations. These are reasons to pay attention to status—not proof that every person in one of these groups is deficient.

Deficiency Correction Is Different From Routine Supplementation

When Vitamin D deficiency is present, correcting it may be associated with improvements in areas such as strength, aerobic performance and recovery. But this is a deficiency-correction context. It should not be rewritten as: “Vitamin D supplements improve performance.”

A person who already has adequate Vitamin D status is not the same scientific situation as someone with a confirmed deficiency.

Assessment Matters

The evidence connects Vitamin D status with appropriate assessment and, where needed, healthcare involvement and laboratory testing. That can include asking your doctor to include Vitamin D status in laboratory testing and then following their advice when a deficiency or other concern is identified. Treating a deficiency belongs in that professional context. Vitamin D is a fat-soluble vitamin, which means it is stored in the body's tissues rather than cleared quickly, and high doses of fat-soluble vitamins taken over long periods can lead to toxicity. This page states no upper limit for Vitamin D, which is a further reason why any higher amount belongs with your doctor or a dietitian who can monitor your status, rather than being self-selected.

No Universal TRUE FORM Dose

The evidence used for this page does not establish one general Vitamin D supplement dose, frequency, timing, or duration for every client. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

B12 Is Not a Universal Energy or Performance Supplement

The evidence does not establish that B12 supplementation improves athletic performance in people simply because they exercise. Research discussed in the source includes a trial in which B12 supplementation did not improve strength or aerobic performance. The dose used in that study is evidence from a research protocol—not a recommended TRUE FORM dose.

Vegetarian and Vegan Diets Are a Different Context

B12 deficiency is more common in people following vegetarian or vegan diets. The evidence therefore gives B12 supplementation greater relevance in these populations, and vegan-diet guidance specifically treats supplementation as advisable. This is a population-specific nutritional issue.

It does not turn B12 into a general performance supplement.

Pregnancy Is Another Context

The evidence also identifies B12 status as something that deserves attention during pregnancy. That is separate from sports-performance use.

Dose Information

The evidence does not establish one general B12 dose, form, timing, frequency, or duration for every vegan, athlete, or fitness client. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

The Key Distinction

B12 can be critically important when intake or status is inadequate. That is different from saying: more B12 automatically creates more energy or better performance.

The Evidence Is Strongly Tied to Deficiency

The evidence discusses women who were iron deficient but not anemic, and found that correcting iron deficiency improved adaptation to aerobic exercise. The evidence also makes the boundary clear: correcting iron deficiency can improve performance, but taking additional iron when someone is not deficient does not automatically improve performance. This distinction must remain explicit.

Iron Status in Athletes

The evidence specifically states that athletes, especially female endurance athletes, should be tested for iron status. This is an assessment recommendation, not a recommendation that all female endurance athletes take iron. The evidence distinguishes correcting iron deficiency from supplementing someone who is not deficient.

Vegetarian and Vegan Diets

Plant-based diets rely more heavily on non-heme iron, which has lower bioavailability than heme iron. This means iron intake and status may deserve closer attention in some plant-based diets. Again: plant-based diet ≠ confirmed iron deficiency.

No Routine Iron Dose

The evidence does not establish a universal iron-supplement dose, timing, frequency, or duration for ordinary fitness clients. A treatment dose or a dose appearing in a study should not be converted into general advice.

Supplement Use Is Context-Dependent

The evidence discusses calcium supplementation in selected populations and health contexts rather than as a universal recommendation. Examples in the source include some older or institutionalized populations, selected bone-health contexts, and certain nutritional concerns associated with conditions such as celiac disease. These examples do not establish that every adult, athlete, older person, or woman should routinely take calcium supplements.

Vegan Diets

For vegan diets, the evidence emphasizes paying attention to adequate calcium intake from the diet. That is not the same as recommending a calcium supplement to every vegan.

Food Intake First

The first issue is whether calcium needs are being met. If food intake is adequate, the existence of calcium supplements does not itself create a need to use one.

No Universal Supplement Protocol

The evidence does not provide one calcium supplement dose, frequency, timing, or duration for all general fitness clients. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

Food Sources

The evidence discusses magnesium-rich foods including whole grains, nuts, spinach and cocoa. Food intake remains part of the first-line approach to adequacy.

When Supplementation May Be More Relevant

The evidence says magnesium supplementation may be considered in people with very low magnesium levels. That is a status-specific context. It is not equivalent to “everyone who trains needs magnesium.”

Performance Evidence

In the athletic-performance research, magnesium supplementation has no demonstrated general performance benefit. The broader micronutrient guidance similarly finds little evidence that supplementing micronutrients improves athletic performance outside correcting a deficiency or inadequacy.

Keep Both Truths Together

It would be misleading to say: “Magnesium is useless.” Magnesium is essential. It would also be misleading to say: “Magnesium improves performance because it is involved in energy metabolism.”

The scientific distinction is: physiological importance does not automatically establish an additional benefit from supplementation when magnesium status is already adequate.

Pregnancy Is a Specific Context

The evidence discusses folate supplementation during pregnancy and describes potential benefits related to areas such as hemoglobin status and reducing certain birth-related complications. The best-established of those is specific enough to name directly: since folate fortification of grains was introduced in some countries in the late 1990s and early 2000s, rates of neural tube defects have fallen dramatically, and it is considered one of the most successful public health measures in history. This is a pregnancy-specific nutritional context. It should not be presented as evidence for folate supplementation in all fitness clients.

Assessment in Selected Populations

The evidence specifically discusses routine measurement of blood folate in selected populations, including pregnancy and certain anemia or depressive-disorder contexts. This is a population-specific assessment recommendation, not a recommendation that every fitness client undergo folate testing.

Low Intake or Low Status

Supplementation may also become relevant when folate levels are low or when dietary intake is inadequate. Vegetarian and vegan dietary patterns may deserve attention depending on actual intake and status. But once again: diet pattern alone does not prove deficiency.

Athletic Performance

The evidence does not establish a meaningful general athletic-performance benefit from folate supplementation, and research in this area is limited.

No General Dose Established

The evidence does not provide one general folate supplementation dose, timing, frequency, or duration for ordinary fitness clients. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

Possible Exercise-Related Effects

Some of the evidence suggests Vitamin C supplementation may reduce exercise-related muscle damage and muscle soreness. But that is only part of the picture.

Antioxidants and Training Adaptation

The evidence raises the possibility that antioxidant supplementation can interfere with some exercise adaptations. For that reason, an improvement in a soreness or oxidative-stress outcome should not automatically be interpreted as evidence of improved long-term training adaptation.

Is Vitamin C an Ergogenic Supplement?

For most people consuming a balanced diet, the evidence does not support routine Vitamin C supplementation as an ergogenic aid.

High Single Doses

Large single servings can produce gastrointestinal effects such as GI distress and diarrhea.

The Correct Conclusion

The evidence includes some reductions in muscle damage or soreness, but the overall exercise evidence is mixed and also includes concerns about interference with training adaptation.

Performance Evidence

The evidence does not establish a robust athletic-performance benefit from routine Vitamin E supplementation. For most people, a well-designed diet can also provide Vitamin E without requiring supplementation solely for adequacy. Vitamin E is fat-soluble, which means it is stored in the body's tissues, and high doses of fat-soluble vitamins taken over long periods can lead to toxicity. No upper intake limit for Vitamin E is published in the evidence used for this page, so no ceiling is stated here.

The Key Distinction

Improved antioxidant biomarkers ≠ proven improvement in exercise performance.

Athletic Performance

The evidence does not show that Vitamin A supplementation improves athletic performance. A historical study discussed in the source used high-dose Vitamin A in a specific research setting and did not improve incline-treadmill performance. That dose belongs to the study, and it should not be copied for a second reason: Vitamin A is fat-soluble, so it is stored in the body's tissues, and high doses of fat-soluble vitamins taken over long periods can lead to toxicity. The evidence used for this page publishes no upper intake limit for Vitamin A, so there is no safe ceiling for a high dose that could be quoted here.

It is not a supplementation recommendation.

Deficiency Is a Separate Issue

If Vitamin A status is inadequate, correcting the nutritional problem is a different question from using Vitamin A as a performance supplement. Those two contexts should not be confused.

Supplementation Can Still Have a Legitimate Nutritional Role

In deficiency or selected nutritional contexts, restoring Vitamin K status may be appropriate. The guidance discusses dietary sources such as leafy green vegetables and, in appropriate contexts, consideration of supplementation. Any vitamin or mineral supplement is best considered on the advice of a dietitian or your doctor, who can look at your test results and your diet as a whole; a coach can then support that advice. Vitamin K is also fat-soluble, so it is stored in the body's tissues, and high doses of fat-soluble vitamins taken over long periods can lead to toxicity; this page states no upper limit for Vitamin K. And none of that is evidence that taking extra Vitamin K improves exercise performance.

The Important Distinction

No proven ergogenic benefit does not mean there is no legitimate nutritional or deficiency-related role for supplementation.

The Evidence Is Framed Differently in Different Sources

One evidence passage states that additional thiamine does not improve performance outside preventing or correcting deficiency. Another source puts the same question less definitely, describing research on Vitamin B1 supplementation and performance in humans as equivocal, with effects that do not appear to be robust. Both descriptions should stay visible, and neither should be reported as the stronger of the two: neither supports extra thiamine for performance in someone whose intake is already adequate.

Supplementation and Performance

The evidence does not establish a general athletic-performance benefit from additional B2 supplementation. The evidence indicates that supplementation is generally unnecessary when intake from a balanced diet is adequate. Suspected deficiency belongs in an appropriate assessment context.

The Key Distinction

Used in energy metabolism ≠ an energy-enhancing supplement.

Performance Research

The evidence describes performance research as limited. One study in trained runners did not improve 10-mile running performance. That single result should not be expanded into a universal statement that niacin can never affect any outcome in any population.

Overall Evidence

The evidence does not establish routine niacin supplementation as an effective athletic-performance strategy for people with adequate nutritional status.

Performance Evidence

The evidence does not establish a robust athletic-performance benefit from additional B5 supplementation, and it does not provide an evidence-supported performance protocol.

Performance Evidence

The evidence states that there is no robust athletic-performance benefit and specifically does not recommend zinc supplementation for athletic performance.

An Important Safety Issue

High supplemental zinc intake can contribute to copper deficiency. That safety relationship matters when discussing unnecessary high-dose supplementation.

Research Results Are Not Recommendations

One study in the evidence reported an improvement in peak isometric torque at one specific angle with high-dose zinc over a short period. Another repletion study did not demonstrate an aerobic-performance benefit. A research protocol is not a recommendation. The right amount, if any, is something to discuss with your GP, pharmacist or dietitian.

Potassium and Exercise Cramps

A common claim is that taking potassium prevents exercise-related muscle cramps. The evidence does not support that specific claim. This is an outcome-specific conclusion.

It does not mean potassium has no nutritional or medical importance.

Low Dietary Intake Is a Different Issue

The evidence also discusses potassium underconsumption at the population level. But a population consuming too little potassium does not automatically mean everyone should take potassium supplements. Dietary intake, actual status, health context, and the reason for supplementation remain separate questions.

Performance and Muscle-Building Evidence

In the supplement-evidence framework, arginine is classified as having weak evidence for performance, and also appears under weak or lacking evidence for muscle gain and recovery. This means the evidence is not strong enough to support arginine as an established performance or muscle-building supplement. It does not mean arginine has no biological function.

No General Performance Protocol

The evidence does not establish a general evidence-supported arginine dose, timing, frequency, or duration for improving exercise performance.

What the Performance Evidence Shows

The evidence places glutamine under weak evidence for performance, and weak or lacking evidence for muscle gain and recovery. The key distinction is that glutamine can be physiologically important without being an established performance supplement.

No General Training Dose Established

The evidence does not establish a general glutamine dose, timing, frequency, or duration for improving exercise performance in ordinary fitness clients.

Performance Evidence

In the performance framework, carnitine is classified as having weak evidence. That means the evidence does not place it among the better-supported performance supplements.

Weight-Loss Claims Are a Separate Evidence Context

The evidence also discusses carnitine within a broader group of ingredients used in weight-loss products. For that group, the evidence describes the research as either lacking strong well-designed evidence or showing little effect on body weight. However, that passage discusses multiple ingredients together.

It does not allow us to assign one specific conclusion from that group statement exclusively to carnitine. So it would be too strong to write: “Carnitine has been proven not to help fat loss.” The source does not establish that exact individual conclusion.

What That Does Not Mean

This classification does not prove that ribose has no biological role or that no study has ever reported an effect. It means the body of evidence does not support presenting ribose as an established performance supplement.

No General Protocol

The evidence does not provide an evidence-supported general ribose supplementation protocol for ordinary performance use.

Why Monohydrate Remains the Evidence-Based Reference

Creatine monohydrate has an exceptionally large evidence base, with the evidence citing more than 1,000 studies. The evidence says data on alternative forms is much more limited.

Do Not Overstate the Comparison

The evidence supports saying that creatine monohydrate has the established evidence base and that alternative forms have not demonstrated superiority. It does not establish that every alternative form is ineffective or inferior, that all forms are exactly equivalent, or that alternative forms are unsafe.

The Research Context Matters

The evidence discusses liquid meal replacements used within structured reduced-calorie eating plans, particularly in adults with overweight or obesity, over longer periods. Reported benefits included weight loss, adherence, body composition and weight maintenance.

Why They May Help

In the evidence, meal replacements are discussed alongside factors including portion control, reduced-calorie intake, dietary structure and convenience, and protein-related satiety. These factors appear in the structured weight-management evidence and should remain attached to that context. This is different from saying that meal replacements directly “burn fat” or “boost metabolism.”

Not a Universal Meal-Replacement Rule

The evidence does not justify telling every client to replace meals every day. The support comes from a structured weight-management context, and that context must stay attached to the recommendation.

The Formulation Matters

The evidence discusses green tea extracts containing compounds such as EGCG together with caffeine in research showing effects such as increased metabolism, increased fat oxidation, modest additional weight loss and reductions in waist circumference. But the evidence separately notes that green tea extract alone does not appear to have the same impact. That distinction matters.

It would therefore be misleading to write: “Green tea extract burns fat.” The evidence depends on the formulation and context being discussed.

Possible Adverse Effects

The evidence discusses adverse effects including nausea, stomach upset and increased blood pressure.

These are described as side effects of stimulants associated with green tea extracts.

The same passage states that combining other sources of caffeine—including energy drinks; coffee; and herbal ingredients such as ma huang (ephedra), citrus aurantium (bitter orange) or other stimulants—can exacerbate side effects and is not recommended.

The formulation described above is green tea extract together with caffeine, so this warning applies to it directly.

No General Dose Established Here

The evidence used for this page does not establish one general green tea extract dose for ordinary clients. Because the formulation the evidence describes as having effects contains caffeine, the caffeine safety context applies here as well: higher caffeine intakes, and combining caffeine with other stimulants, may result in adverse side effects. Caffeine is contraindicated in people with heart disease, hypertension, thyroid disease and anxiety, and is not recommended during pregnancy and lactation. People taking medications should consult their physician about possible interactions. The hypertension contraindication is directly relevant here, because increased blood pressure is one of the adverse effects noted above.

1. Is There Good Evidence for the Ingredient?

Before considering the product itself, ask whether there is a well-established body of evidence supporting the ingredient for the specific outcome you want. The evidence does not consider the following sufficient by themselves for recommending a supplement: animal research without appropriate human follow-up, a single study, case studies, testimonials, commercials, or anecdotal claims. A supplement can therefore truthfully be described as “studied” without having strong enough evidence to support the claim being made.

2. Look at the Weight of the Evidence

One positive study does not settle a scientific question. The evidence emphasizes looking at where the overall body of research points. Replication also matters: when an impressive result cannot be reproduced by other researchers, confidence in that result is reduced.

This is one reason supplements such as HMB require more nuanced explanations than a single positive study might suggest.

3. Was the Research Done in Humans?

Animal research can be valuable for scientific investigation, but it does not automatically demonstrate that the same supplement will produce the same outcome in humans. The evidence specifically warns against marketing a product to people based on findings that have not been established in humans.

4. Who Was Actually Studied?

Even human research needs context. Ask whether the participants were similar to the people for whom the product is being promoted. Evidence in one group should not automatically be generalized to another age group, training status, health status, population or goal.

The studied population matters.

5. What Outcome Was Actually Measured?

A study may show a change in one outcome without proving another. For example, a biological marker changing does not automatically mean athletic performance improved. Similarly, reduced soreness ≠ greater muscle growth; correcting a deficiency ≠ benefit in someone without a deficiency; and product purity ≠ product efficacy. Evidence that a supplement changes fat oxidation or metabolism should be interpreted according to the outcome actually measured; it should not automatically be treated as evidence of body-weight loss.

The claim should match the outcome that was actually studied.

A Note About Proprietary Blends

The evidence used for this guidance does not provide a specific evidence-based rule telling consumers to automatically avoid all proprietary blends. For that reason, this guide does not create one. When evaluating a product, consider each of these separately: the ingredient, its form and amount, the supporting human research, the population studied and the outcome measured.

What Certification Does Not Prove

This distinction is critical: Third-party testing does not prove that a supplement is effective. The evidence explicitly separates independent product testing from efficacy. Independent certification addresses product-testing questions according to the certification program.

Separately, the evidence requires evaluation of whether the ingredient amount matches the research and whether the studied population is relevant to the intended user. These are independent checks. Certification itself should not be used as evidence that the product contains an effective research-matched dose or that research in one population applies to another.

Certification can provide useful information about product quality and what is in the product. It does not replace the scientific evidence for whether the ingredient works.

“Natural” Means Nutritionally Superior

Marketing idea: A product described as “natural” must be nutritionally superior. Evidence: In the food-label terminology discussed here, “natural” is described as having “no true definition.” That food-label context does not establish nutritional superiority.

Supplement safety and efficacy should be evaluated separately through the evidence relevant to the product.

“Third-Party Tested Means Effective”

Marketing idea: If an independent organization tested the product, it must work. Evidence: No. Third-party testing may verify areas such as identity, stated amounts, purity, contaminants or banned substances.

The evidence explicitly states that these programs do not evaluate product efficacy or establish the truth of every marketing claim.

“BCAAs Are Essential for Muscle Growth”

Marketing idea: You need a BCAA supplement to build muscle. Evidence: Muscle protein synthesis requires all essential amino acids. When EAAs are already being consumed adequately to maximize muscle protein synthesis, the evidence says supplemental BCAAs are likely unnecessary.

That does not mean BCAAs are biologically unimportant. It means: physiological importance ≠ universal need for a BCAA supplement.

“Any Creatine Form Is as Good”

Marketing idea: All forms of creatine have equivalent scientific support. Evidence: The evidence does not establish that. Creatine monohydrate has an exceptionally large evidence base, while data for alternative forms is more limited.

Alternative forms have not demonstrated superiority over monohydrate. That does not prove that every alternative form is inferior.

“Everyone Should Take Fish Oil”

Marketing idea: Omega-3 is important, therefore everyone should take fish oil. Evidence: The general evidence for omega-3 supplementation is described as inconclusive. Separate nutritional contexts—such as diets without fatty fish—may make EPA+DHA supplementation more relevant.

For vegans, microalgae-derived EPA/DHA is also discussed. So: nutrient importance ≠ universal fish-oil recommendation.

“Everyone Who Trains Needs Magnesium”

Marketing idea: Because magnesium participates in energy metabolism and muscle-related processes, everyone who exercises should supplement it. Evidence: The evidence does not establish that. Magnesium supplementation may be considered when magnesium status is very low.

Its physiological importance does not demonstrate that extra magnesium improves performance when status is already adequate.

“Iron Gives Athletes More Energy”

Marketing idea: Athletes can take iron to increase energy or performance. Evidence: The benefit discussed in the evidence is tied to iron deficiency. Correcting inadequate iron status can improve relevant performance outcomes.

That does not mean additional iron improves performance in someone who is not deficient. Deficiency correction ≠ universal performance supplementation.

Product Contamination Is Not Only an Athlete Issue

Contamination is a general safety consideration, not only a banned-substance problem for competitors. Inspections of supplement manufacturers have found widespread compliance problems, which can mean poor product quality, ineffective formulas and contamination with hidden ingredients, and contaminated supplements have been linked to health problems in the general population as well as to positive drug tests among athletes.