Citrulline is highest in watermelon (where it derives its name, as watermelons are known as Citrullus vulgaris[1]), which contains an average of 2.1 milligrams of citrulline per gram of wet weight (although absolute numbers vary).[2] Consuming watermelon has been noted to acutely increase both plasma arginine and citrulline (3.3 kilograms of watermelon is equivalent to 10 grams of supplemental L-arginine)[3][4] and to increase fasting arginine and ornithine in the range of 12%–22% following consumption of 780–1560 grams daily.[5]
Other food sources of citrulline include muskmelons (cantelope), bitter melons, squashes, gourds, cucumbers, and pumpkins.[1]