Citrulline Malate

The verdict

Is Citrulline Malate worth taking?

Citrulline raises nitric oxide more effectively than supplemental arginine, which absorbs poorly and breaks down before reaching the bloodstream. Use 6 to 8 g citrulline malate or 3 to 4 g pure L-citrulline, taken 45 to 60 minutes before training. Most pre-workout products include 2 to 3 g which is below the effective threshold. Check your label. Stacks genuinely and additively with beetroot nitrates.

What it does

What Citrulline Malate does in the body

Nitric oxide production, blood flow, muscular endurance, reduced fatigue, and enhanced muscle pump. Citrulline is an amino acid that converts to arginine in the kidneys, which then drives nitric oxide synthesis. Nitric oxide relaxes and dilates blood vessels, increasing blood flow to working muscle tissue. The malate component contributes independently to energy metabolism by supporting the Krebs cycle and reducing the ammonia accumulation that contributes to fatigue. This makes citrulline malate a genuinely dual-action compound.

The evidence

What the research actually shows

Multiple trials confirm citrulline malate’s ability to improve endurance, reduce muscle soreness, increase repetition volume, and enhance blood flow markers. It has largely superseded arginine as the preferred nitric oxide supplement because oral citrulline raises plasma arginine levels far more effectively than supplemental arginine itself.

The dose confusion

Citrulline malate and L-citrulline are not the same number

This is the most common error in the category, and it is in almost every product description.

Citrulline malate is L-citrulline bound to malic acid. It is sold in two ratios. A 2:1 product is roughly two parts citrulline to one part malate, so eight grams of citrulline malate delivers somewhere near five and a half grams of actual citrulline. A 1:1 product delivers about four grams from the same eight. Some products do not state the ratio at all.

That matters because the ergogenic literature does not use one number. The studies that used citrulline malate generally used six to eight grams of the combined compound. The studies that used plain L-citrulline generally used three to six grams of citrulline. Those are roughly comparable doses of citrulline, arrived at from different directions, and they are routinely quoted as if they were interchangeable.

The practical consequence is that someone taking six grams of a 1:1 citrulline malate, on the strength of a study that used six grams of L-citrulline, is taking about half the dose they think they are.

Malate is not inert filler. It is a Krebs cycle intermediate and some of the fatigue findings have been attributed to it rather than to citrulline. But the attribution is unresolved, and no one should pay a premium for malate on the assumption that it is doing the work.

Read the ratio. If the label does not give one, that is the answer.

The part you throw away

The rind is richer than the flesh

Watermelon is the food source for citrulline. The amino acid was first isolated from it, and the name comes from Citrullus, the botanical genus.

The part that carries the most is the part nobody eats. Analyses consistently find higher citrulline concentrations in the rind than in the flesh, and red-fleshed varieties carry more than pale or yellow ones. The white layer between the pink flesh and the green skin is the richest section of the fruit and the section that goes in the trash.

Exact figures vary a great deal between studies, cultivars, ripeness and analytical method, and a lot of the numbers circulating online come from freeze-dried extracts rather than fresh fruit, which inflates them by an order of magnitude or more. Treat any confident milligram-per-gram claim about fresh watermelon with suspicion, including this page's. What is not in dispute is the ordering: rind above flesh, red above pale.

It is also not in dispute that you cannot eat your way to a study dose. Fresh watermelon carries citrulline on the order of one to two grams per kilogram of fruit, which puts a six gram dose somewhere in the range of several kilograms of watermelon a day. Nobody is doing that.

The reason to care about the rind is not that it replaces a supplement. It is that pickled watermelon rind is a real preparation with a long history in the American South, in parts of China and across the Balkans, and it uses the most nutritionally interesting part of a fruit that is otherwise mostly water and sugar. That is a good argument for making it whether or not citrulline is the point.

Food first

Getting Citrulline from food

Watermelon is effectively the only meaningful dietary source. Citrulline is a non-protein amino acid, so it does not turn up in the places other amino acids do, and no common food comes close to watermelon. Cucumber, melon and squash, the other cucurbits, carry traces.

Three things decide how much a given watermelon delivers.

Variety. Red-fleshed cultivars carry more than yellow or orange ones. Seeded varieties tend to test higher than seedless, though the difference is smaller than the difference between red and pale.

Ripeness. Citrulline content rises as the fruit ripens. An underripe watermelon is a worse source as well as a worse eat.

Which part you use. The rind holds more than the flesh. In practice the whole white layer is usable: pickled, braised, stir-fried, or grated raw into a slaw where it behaves like a firm cucumber.

Storage matters less than people assume for a fruit this perishable, but whole melons hold their amino acid content better at room temperature than cut fruit in a refrigerator. Cut watermelon is a short-dated ingredient for several reasons.

What none of this does is reach a performance dose. Six grams of citrulline is several kilograms of watermelon, eaten in a day, repeatedly. Watermelon is not a pre-workout.

What watermelon is, is a very good source of a compound most diets contain almost none of, delivered with water, potassium and lycopene, in a fruit that is in season for about three months and worth using properly while it is. Using the rind is the part most cooks skip.

Check your own plate: USDA does not list citrulline, but the free Food vs. Capsule calculator tracks arginine, which your body makes from citrulline, and shows how much your usual foods already give you.

What the guide adds

The part that is not on this page

Everything above is the assessment. What the guide adds for Citrulline Malate is the protocol:

• Optimal Form
• Bioavailability
• Purity Red Flags
• Stack With / Avoid

147 entries across nine categories, every one graded against the clinical literature the same way.

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About the author

Who graded this

Daniel Edlund is a Le Cordon Bleu-trained private chef in Los Angeles, a certified personal trainer and strength coach, and an internationally licensed massage therapist. Thirty years of strength training and fifteen years cooking in private estate kitchens. He is the author of The Complete Supplement Guide, which grades 147 entries against the clinical literature, and of The EASY Way to Organic Cooking, first published in 2013.

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This page is information, not medical advice. Supplements interact with prescription medication and with each other, and the right answer depends on your own bloodwork and history. Talk to your doctor before starting anything, particularly if you are pregnant, nursing, managing a health condition, or already taking medication.

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