Most nitric oxide supplements do not contain nitric oxide itself. Instead, they contain amino acids, nitrate sources or combinations of ingredients used in pathways involved in the body’s production of nitric oxide.
Common ingredients include L-citrulline, citrulline malate, different forms of L-arginine and beetroot. However, these ingredients are not interchangeable, and the evidence for exercise performance varies according to the ingredient, formulation, quantity and activity being studied.
The most important label checks are the exact ingredient form, the amount in the complete serving and whether a blend discloses the quantity of every active ingredient. A large blend total or long ingredient list does not automatically make a product more suitable.
This guide explains how to compare products commonly found in energy and performance supplement ranges without assuming that every nitric oxide formula produces the same outcome.
What is nitric oxide?
Nitric oxide is a signalling molecule naturally produced by the body. It is involved in several biological processes, including the regulation of blood-vessel tone.
The body can produce nitric oxide through more than one pathway. One involves the amino acid L-arginine. Another involves dietary nitrate, which can be converted into nitrite and then nitric oxide.
This explains why products marketed as nitric oxide supplements may contain quite different ingredients. It does not mean that consuming any ingredient associated with these pathways will automatically produce a noticeable or clinically meaningful effect.
What do nitric oxide supplements contain?
| Ingredient or format | What to check |
|---|---|
| L-citrulline | Check the amount of pure L-citrulline in the complete daily or pre-exercise serving. |
| Citrulline malate | Check the citrulline-to-malate ratio and how much actual citrulline the serving supplies. |
| L-arginine | Identify the exact form, such as L-arginine base, hydrochloride or alpha-ketoglutarate, and the individual amount. |
| Beetroot or nitrate | Check whether the label declares dietary nitrate rather than only giving the weight of beetroot powder or extract. |
| Multi-ingredient blend | Check whether each ingredient has a separate quantity or whether only the total blend weight is disclosed. |
L-citrulline and citrulline malate
L-citrulline is an amino acid that the body can convert into L-arginine. The L-arginine can then be used in a pathway involved in nitric oxide production.
Citrulline malate combines citrulline with malate, a form of malic acid. The two names should not be treated as interchangeable because a given weight of citrulline malate does not necessarily provide the same quantity of citrulline.
Some products state a ratio such as 2:1, while others only provide a total amount of citrulline malate. If the ratio and actual citrulline content are not supplied, it can be difficult to compare that product with research involving pure L-citrulline.
The US National Institutes of Health exercise-supplement fact sheet describes the evidence for citrulline and exercise performance as limited and inconsistent. Some studies have reported an effect, while others have found no improvement or even poorer performance.
How does L-arginine differ?
L-arginine is an amino acid found naturally in protein-containing foods. It can be converted directly into nitric oxide by enzymes in the body.
L-arginine supplements may be labelled as:
- L-arginine base
- L-arginine hydrochloride or L-arginine HCl
- L-arginine alpha-ketoglutarate or AAKG
- A combination of several forms
The total weight of an arginine compound may not always be equivalent to the amount of L-arginine itself. Look for a label that makes the ingredient form and quantity clear.
Research has found that oral L-citrulline can increase circulating L-arginine more efficiently than an equivalent amount of oral L-arginine. However, this biochemical finding does not prove that every citrulline product will improve strength, endurance or training results.
The NIH review concludes that there is little scientific evidence supporting L-arginine supplements for improving strength, exercise performance or post-exercise recovery.
What about beetroot supplements?
Beetroot naturally contains nitrate, although the quantity can vary according to the plant, growing conditions and processing method.
A label stating “1,000 mg beetroot” does not necessarily tell you how much nitrate the serving contains. A concentrated extract ratio also describes the relationship between the starting material and extract; it does not automatically establish the nitrate quantity.
When comparing beetroot products, check:
- The amount of beetroot powder or extract
- Whether an extract ratio is provided
- Whether the dietary nitrate content is separately declared
- Whether the amount applies per capsule, scoop or complete serving
- Whether other ingredients are included
The NIH reports that many, but not all, studies of beetroot juice have found improvements in certain aerobic activities. It also notes that it is not known whether supplements containing beetroot powder produce the same effects as beetroot juice.
Do nitric oxide supplements improve exercise performance?
The evidence cannot be summarised as a simple yes or no. Results vary according to the ingredient, amount, study duration, participant’s training status and type of exercise.
Research involving one particular quantity of pure L-citrulline cannot automatically substantiate a multi-ingredient capsule containing an undisclosed amount of citrulline. Similarly, findings involving nitrate-standardised beetroot juice should not automatically be transferred to a beetroot capsule that does not declare its nitrate content.
The National Center for Complementary and Integrative Health states that there is no clear evidence that supplements marketed using nitric oxide or L-arginine improve athletic performance.
A supplement should not be viewed as a replacement for an appropriate training programme, sufficient food, hydration, sleep or recovery.
Seven label checks before buying
1. Read the complete serving size
Check whether the displayed amount applies to one capsule, two capsules, a scoop or the complete recommended serving. Also calculate how many full servings the container provides.
2. Look for individual ingredient quantities
A label may display a large number for the complete blend while including several amino acids, botanicals and minerals within that amount.
When only a combined blend total is declared, you cannot determine the amount of each individual ingredient from the label. This makes comparisons with separately studied ingredients more difficult.
3. Identify the exact ingredient form
L-citrulline, citrulline malate, L-arginine HCl and AAKG are different label descriptions. Avoid comparing them solely according to the largest front-of-pack number.
4. Check beetroot nitrate information
The total weight of beetroot is not the same as its nitrate content. Look for a separately declared nitrate quantity if that information is important to your comparison.
5. Check for stimulants and additional ingredients
Some pre-exercise supplements combine amino acids with caffeine or other stimulants. Combining several products could unintentionally duplicate ingredients.
If you are also comparing hydration products, our guide to what to look for in an electrolyte powder explains how to compare sodium, potassium, sugar and serving information.
6. Compare the cost per complete serving
A lower bottle price does not always mean a lower cost per serving. Divide the price by the number of complete servings rather than the number of capsules.
7. Check quality and traceability
Look for clear manufacturer or responsible-business details, a batch number, best-before date, storage directions, ingredient information and appropriate warnings.
Competitive athletes should take additional care because supplements can sometimes contain undeclared substances. Consider whether a product has been tested through a recognised sports batch-testing programme.
How the current Vitarosa formula is labelled
The current label for Vitarosa Nitric Oxide Booster 90 Capsules states that a two-capsule serving provides:
- 10 mg niacin
- 1.5 g combined Nitric Oxide Complex
- 45 servings per bottle
The 1.5 g complex lists L-citrulline, L-arginine alpha-ketoglutarate, L-arginine HCl, L-arginine base, L-taurine, L-norvaline, vanadyl sulphate, tribulus fruit extract, muira puama bark extract and Asian ginseng root.
The label gives one total for the full complex rather than declaring the amount of each ingredient. It is therefore not possible to determine from the label how much L-citrulline, L-arginine or each botanical is provided in the serving.
The verified 10 mg of niacin is equivalent to 63% of the adult nutrient reference value. Niacin contributes to normal energy-yielding metabolism and the reduction of tiredness and fatigue. These are authorised claims for qualifying amounts of niacin under the Great Britain Nutrition and Health Claims Register.
These niacin functions should not be interpreted as evidence that the complete amino acid and botanical blend increases nitric oxide or improves exercise performance.
For more context on how nutrients differ from stimulants and calories, read our guide to supplements associated with energy and tiredness.
Safety and suitability
Nitric oxide formulas can contain several amino acids, botanical extracts, vitamins and minerals. Safety therefore needs to be assessed using the complete ingredient list rather than only the product’s main name.
The NIH reports that higher intakes of L-arginine can cause digestive discomfort and may slightly lower blood pressure. It also notes that available safety information for citrulline is limited and that some users have reported stomach discomfort.
Products containing Asian ginseng require additional care. The NCCIH Asian ginseng guidance identifies insomnia as a possible side effect and advises that ginseng can interact with certain medicines.
Speak to a GP, pharmacist or appropriately qualified healthcare professional before using a multi-ingredient formula if you:
- Take prescription medicines or other supplements
- Take medicine affecting blood pressure, circulation or blood clotting
- Have low or high blood pressure
- Have a heart, kidney, liver or blood-sugar condition
- Are pregnant or breastfeeding
- Are under 18
- Are awaiting surgery or medical treatment
Follow the product directions and do not exceed the recommended daily intake. Food supplements should not be used as a substitute for a varied, balanced diet and healthy lifestyle.
Frequently asked questions
Do nitric oxide supplements contain nitric oxide?
Usually not. They generally contain amino acids such as L-citrulline or L-arginine, dietary nitrate sources such as beetroot, or combinations of ingredients associated with nitric oxide-production pathways.
Is L-citrulline better than L-arginine?
L-citrulline has been shown to increase circulating L-arginine efficiently, but this does not establish that it is better for every person or exercise goal. Evidence for consistent performance improvements remains limited.
Is citrulline malate the same as L-citrulline?
No. Citrulline malate combines citrulline and malate. Check the stated ratio and actual citrulline quantity before comparing it with pure L-citrulline.
Is beetroot powder the same as beetroot juice?
No. Products may contain different quantities of beetroot and nitrate. Findings from studies using a specified beetroot juice should not automatically be applied to a powder or capsule with different or undeclared nitrate content.
Does a higher blend quantity mean a better product?
No. A larger number may describe the total of several ingredients. Individual quantities, ingredient forms, serving size and product suitability are more informative than the blend total alone.
Can I combine a nitric oxide supplement with a pre-workout?
Check both labels for duplicated amino acids, caffeine, botanical ingredients, vitamins and minerals. Ask a healthcare professional before combining products if you take medicines or have a medical condition.
The bottom line
When comparing nitric oxide supplements, start with the exact ingredient form and amount per complete serving. Check whether the formula contains L-citrulline, citrulline malate, L-arginine or beetroot, and whether individual quantities or nitrate content are clearly declared.
Evidence relating to one isolated ingredient should not automatically be applied to a different multi-ingredient product. A transparent label, clear directions, appropriate warnings and realistic claims are more useful than an oversized front-label number.
You can compare other products in the capsule supplement collection or browse products grouped within the Heart & Circulation collection. Always check the complete label and suitability information before ordering.