About Citrulline (from Jerry Brainum)
" While arginine offers heady health benefits, there are problems with supplementing it. In solution it's strongly alkaline, and it has to be compounded with hydrochloric acid to create a supplemental form. Supposedly that prevents acid-base problems when you take a concentrated dose, but taking more than nine grams a day often leads to nausea, gastrointestinal discomfort and diarrhea. The side effects may be due to 1) the rapid conversion of arginine to NO in the gut coupled with 2) impaired intestinal absorption of other amino acids, such as lysine and histidine.
Looking for more options about now? You could take L-citrulline, another amino acid that is a precursor of arginine. Because arginine is a basic amino acid, it competes with other aminos for uptake into the body. Citrulline is a neutral amino acid, which means that it doesn't compete with other aminos. Nor does it have to be made with hydrochloric acid, which reduces gut problems. In its conversion to arginine, citrulline also uses up ammonia, which is good since excess ammonia is related to fatigue.
So where do you get citrulline? It turns out that watermelon is a superior source.[SUP]1[/SUP] There are 0.7 to 3.6 milligrams of citrulline per gram of watermelon. Eating two pounds of watermelon daily would supply enough to provide 40 percent of the average daily arginine intake of 3.6 grams. In the new study, subjects who drank a lot of watermelon juice (0.52 kilograms with each of three meals) had higher plasma arginine levels than a control group. Fasting plasma arginine increased 12 percent after three weeks of lower-dose watermelon intake and 22 percent after high intake.
Those in the high-intake group also showed an 18 percent rise in plasma ornithine.None of the subjects who drank watermelon juice showed any interference with the uptake of other amino acids, so amino acid balance wasn't upset. Those who drank large amounts of the juice—amounting to six cups daily—produced two grams of citrulline. Studies show that 40 percent of dietary arginine is degraded by the intestinal tissues of adult humans during initial entry into the gut. In contrast, citrulline (which converts into arginine in the kidneys) undergoes little breakdown. The liver absorbs 10 to 15 percent of ingested arginine, which is then broken down by the enzyme arginase. Citrulline bypasses the liver and acts as a nutrient precursor of arginine synthesis in the kidneys. From 5 to 15 percent of arginine produced in the body is made that way. Another source is glutamine, which small-intestine cells also convert into citrulline that bypasses the liver and travels directly to the kidneys—where it's converted into arginine.[SUP]2[/SUP]So those who want to get the considerable nutritional benefits of arginine without the side effects should consider adding some watermelon to their diets. It tastes pretty good, too.
References
[SUP]1 [/SUP]Collins, J.K., et al. (2007). Watermelon consumption increases plasma arginine concentrations in adults. Nutrition. 23:261-66.
[SUP]2 [/SUP]Curis, E., et al. (2005). Almost all about citrulline in mammals. Amino Acids. 29:177-205. "
