L-arginine: What You Need to Know

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What systems in your body rely on L-arginine?
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Wow, that guy looks good with his rippling abs, immense pecs, biceps the size of melons -- and it looks like he doesn't have even one ounce of body fat. He points confidently to the camera and announces it's all due to daily supplements of an incredible little amino acid, L-arginine. It's a miracle treatment, a naturally occurring chemical with all the benefits of human growth hormone.

Can you trust him?


He's right about one thing: L-arginine (also called just plain arginine) is indeed an amino acid. Can it improve your health? Yes, in some cases. Is it going to turn you into a strapping, muscle-bound colossus? No, and taking as much as that guy recommends may actually damage your health.

L-arginine helps the body get rid of waste and synthesize proteins. Certain conditions such as severe burns, sepsis, jaundice, protein deficiencies and malnutrition can affect your ability to produce L-arginine [source: Drugs.com]. So can dialysis. People who don't have enough L-arginine may have symptoms such as constipation, alopecia (hair loss) and skin problems. Their wounds may heal slowly, and fat may have built up in their livers [source: Mayo Clinic].

This article will tell you a bit more about L-arginine: what it does and doesn't do, what we know and what we don't, the benefits and risks of taking it, and its role in human growth.


L-Arginine at Work in Your Body

L-arginine is defined as a semi-essential amino acid. That sounds a bit odd -- something is either essential (shelter) or it isn't (cable TV), right?

Sort of. "Essential" has a slightly different meaning in nutrition. An essential nutrient is one that you must obtain somehow, either through diet or through supplements, because your body can't manufacture it on its own [source: Baggott]. L-arginine is described as semi-essential because usually the body produces enough L-arginine on its own [source: MedlinePlus]. But in some cases, such as trauma or liver disease, people can develop deficiencies, and then an L-arginine supplement is called for [source: Drugs.com].


Your body needs L-arginine to make urea, the waste product that you get rid of when you urinate [source: Mayo Clinic]. Urea is a byproduct created when your body breaks down proteins. Your body needs some nitrogen, but the breakdown of protein creates more than you need. Making urea is a very efficient way for your body to get rid of excess nitrogen [source: WebMD]. L-arginine helps your body regulate its waste and certain chemical balances.

L-arginine helps your body manufacture creatine, a protein that contributes to muscle mass and power. L-arginine also helps the body get rid of creatinine, the waste product associated with this process [source: Mayo Clinic]. For these reasons, the bodybuilding industry loves to tout creatine and L-arginine supplements.

Some effects of L-arginine depend on the method in which the body is exposed to the chemical. L-arginine can be administered as a nutritional supplement, inhaled or injected [source: Mayo Clinic]. And, of course, you get some of it through the foods you eat.

When it's administered as a medicine, L-arginine is a vasodilator -- that is, it dilates the blood vessels, allowing more blood to pass through at once. That has the effect of lowering blood pressure and, in some cases, helping the body negotiate the arterial blockages that can come with conditions such as atherosclerosis [source: Mayo Clinic].

To learn about some of the health benefits of L-arginine, read on.


L-Arginine Benefits

How can L-arginine help? Let us count the ways.

First, it may treat disorders of urea production and waste removal. Some chemical imbalances cause the body to accumulate waste products. Depending on the chemicals involved, L-arginine can restore the balance [source: MedlinePlus].


L-arginine may also reduce symptoms of angina (chest pain) and coronary disease. Both the National Institutes of Health and the Mayo Clinic caution that more research is necessary, but L-arginine may be a good treatment for some heart patients. The supplement may also improve blood flow. For certain patients, L-arginine can help reduce blood pressure. People with blood clots, especially in the legs, may find some relief from supplemental L-arginine [source: MedlinePlus].

If you find yourself with an open wound, L-arginine may be a good alternative. People with severe burns, malnutrition and certain wasting diseases may heal more slowly, raising the risk of infection and other complications. L-arginine is promising as a treatment in these cases [sources: Medline, Drugs.com].

Some people also believe L-arginine regulates growth. Erratic or excessive growth may be a symptom of an L-arginine deficiency [source: MedlinePlus]. It may also reduce migraine pain. More research is needed, but L-arginine may work well in combination with other pain drugs such as ibuprofen [source: MedlinePlus].

As discussed in the body builder scenario on the first page, many people purport L-arginine can build muscle mass. However, L-arginine is not the miracle muscle builder some snake-oil salesmen make it out to be, but what chemical could possibly live up to all those claims? The amino acid may at least help you maintain muscle mass. Maybe.

Lastly, it may improve sexual function [source: Drugs.com]. There's some evidence that L-arginine can help with the function of body parts that rely on dilated blood vessels. That includes the sexual organs. Some think L-arginine can boost endurance -- but the jury's still out on that one, too. Before you get too excited, remember that L-arginine can't treat cases of erectile dysfunction that aren't related to blood flow. And it may not be as effective as a prescription drug -- or, for that matter, therapy.

OK, so those are the possible benefits. But can L-arginine hurt you? Yes, it can. To find out how, read on.


L-Arginine Side Effects

Any drug or supplement can cause side effects. L-arginine is no exception.

L-arginine affects the way your body handles waste, so it can have adverse effects on the organs involved in waste disposal. Some liver and kidney problems can be exacerbated by L-arginine. Using L-arginine can also lead to problems of potassium balance and dehydration, as well as stomach cramps, nausea and other digestive discomfort [source: MedlinePlus].


There can also be some circulatory side effects associated with L-arginine. People recovering from heart attacks shouldn't take it [source: Drugs.com]. There's a possibility that, because it dilates blood vessels, it increases the risk of excessive bleeding. Hemophiliacs and people on blood thinners should probably steer clear. So should people who are taking gingko biloba, another herbal supplement that can heighten the risk of bleeding [source: MedlinePlus]. Sometimes L-arginine can make problems of low blood pressure more severe. And people with sickle cell disease may find that their symptoms get worse [source: Mayo Clinic].

You'd think that, because L-arginine production can be hindered by dialysis, it'd be a natural choice to recommend L-arginine supplements to diabetics. However, there's some evidence that the amino acid actually raises blood sugar [source: Mayo Clinic]. Once again, the workings of chemicals in the body are incredibly complicated.

One of the most severe potential side effects of L-arginine is anaphylaxis [source: Mayo Clinic]. That's a very severe allergic reaction that can result in shock and potentially even death. In an anaphylactic reaction, you may experience sudden chills, sweating, tremors, hives, vomiting, and diarrhea, shortness of breath and light-headedness or fainting -- all at once. It's not pleasant. If you have any allergies, don't take L-arginine before being tested for an allergy to it.

One final note: Beware of herbal supplements promising L-arginine. Herbal supplements are not subject to the same FDA regulations as prescription pharmaceuticals are. Among other things, this means that in two identical-looking pills from the same bottle, the dosage may vary. You may not always be able to predict the effects of the supplement -- even from day to day.

On the next page, we'll take a look at the ways L-arginine might be able to aid in human growth.


L-Arginine and Human Growth

If L-arginine stimulates protein production, especially creatine, shouldn't it be a natural choice to aid in human growth? Yes and no. We don't yet know -- or understand -- all the effects that L-arginine has on the body.

Arginine has been approved by the U.S. Food and Drug Administration to test for certain human growth disorders. In these tests, arginine is injected into the body. Its presence helps doctors detect the levels of growth hormones [source: Mayo Clinic].


L-arginine may boost the activity of certain hormones, including human growth hormone. But that's a big maybe. The ways in which L-arginine interacts with hormones are numerous and complicated. Estrogen may boost its activity; progesterone may suppress it [source: MedlinePlus].

There's a possibility that L-arginine can actually assist with human growth before birth. There haven't yet been enough studies to determine it conclusively, but it's possible that one day pregnant women will take supplements of L-arginine to aid in fetal growth, especially in cases of preeclampsia (a potentially dangerous condition in which the mother suffers high blood pressure during pregnancy) [source: Mayo Clinic]. Low birth weight is a major risk factor for infant mortality and numerous other health problems.

One interesting use of L-arginine is not so much to foster growth as to prevent wasting. In people with chronic wasting diseases such as HIV/AIDS, L-arginine seems to have the ability to help the body hang on to its muscle mass [source: Mayo Clinic]. Plummeting body weight can be a risk for numerous other conditions, and muscle loss can also mean a loss of independence. So L-arginine may help such patients' quality of life.

Ironically, even though it's touted as a bodybuilder's dream supplement, L-arginine gets a "D" rating as an exercise enhancer from the Mayo Clinic [source: Mayo Clinic]. So don't quit the gym just yet. In the quest for chiseled biceps and sculpted abs, there do not seem to be any shortcuts.

To learn more, visit the links on the next page.


Lots More Information

Related HowStuffWorks Articles

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  • Creatine Information Center. January 6, 2009. (Accessed 3/9/09) http://www.creatinemonohydrate.net/index.php
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  • MedlinePlus. "Arginine (L-arginine)." MedlinePlus Herbs and Supplements. February 1, 2008. (Accessed 3/9/09)http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-arginine.html
  • PDR Health. "Arginine." (Accessed 3/9/09)http://www.pdrhealth.com/drugs/altmed/altmed-mono.aspx?contentFileName=ame0335.xml&contentName=Arginine&contentId=491
  • Smart Publications. "L-Arginine, the Prosexual Nutrient with Numerous Health Benefits." (Accessed 3/9/09)http://www.smart-publications.com/sexual_health/l-arginine.php
  • WebMD. "Blood Urea Nitrogen." (Accessed 3/9/09) http://www.webmd.com/a-to-z-guides/blood-urea-nitrogen