L-arginine and L-citrulline are two amino acids closely tied to nitric oxide (NO) metabolism, a signalling molecule that promotes vasodilation — the widening of blood vessels. Arginine is the direct precursor of NO via the NO-synthase enzyme, while citrulline is converted into arginine in the kidneys, sustaining and extending arginine’s availability in the body.

Now Foods has combined both actives in a single vegetable capsule, dosed at 500 mg L-arginine and 250 mg L-citrulline, for a balanced, convenient intake. This duo is highly sought after in sports nutrition as well as for circulation support.

Taken alone, arginine is partly broken down in the gut and liver before reaching circulation, limiting its bioavailability. Citrulline largely escapes this breakdown and is then converted into arginine. Combining the two produces a more sustained effect on plasma arginine levels, and therefore on nitric oxide production, compared with arginine alone — one of the reasons this duo has become a reference among athletes.

By supporting nitric oxide production, the arginine-citrulline duo supports blood flow to muscles during exertion. Many strength-training practitioners seek this effect for the sensation of muscle “pump” and better oxygen and nutrient delivery to working muscles. During recovery, improved circulation helps clear metabolic waste produced during training.

Beyond sport, nitric oxide contributes to maintaining vessel flexibility and normal blood circulation, as part of a healthy lifestyle. Arginine also participates in the urea cycle, which eliminates ammonia produced from protein metabolism.

The Now Foods recommended dose is 1 capsule twice a day, ideally between meals with a large glass of water. For a performance goal, athletes often favour taking it 30-45 minutes before training. The 120-capsule bottle covers about two months at 2 capsules a day.

Do not exceed the recommended daily dose. Not recommended for pregnant or breastfeeding women or people undergoing treatment (particularly cardiovascular) without medical advice. Keep out of reach of children. Store in a dry place away from light.

How much arginine and citrulline per capsule?

Each vegetable capsule provides 500 mg of L-arginine (free form) and 250 mg of L-citrulline, a 2:1 ratio.

How many capsules per day?

Now Foods recommends 1 capsule twice a day. The 120-capsule bottle therefore represents about two months of use.

Is this product suitable for vegans?

Yes. The capsules are plant-based (hypromellose) and the formula is vegan, gluten-free, soy-free and GMO-free. The amino acids are produced by fermentation.

Herba Barona is an independent specialist supplement shop in the heart of Paris — established in 2006. What you order is genuinely on our shelves: we ship from our own stock, with no dropshipping and no long waits.

Visit us at 10 rue Théophile Roussel, Paris 12 — or use Click & Collect and pick up your order in-store. We also deliver across France and Europe. Friendly, expert advice in English from our team.

Where is the shop?

Herba Barona is at 10 rue Théophile Roussel, 75012 Paris — a two-minute walk from Ledru-Rollin (line 8), close to Bastille. Open Tuesday to Saturday, 9:30 am–6:30 pm.

Can I order online or collect in store?

Yes. We ship across France and Europe under the same conditions as our French store, or choose Click & Collect to pick up your order for free at our Paris shop.