Thumb through a muscle magazine, and you’re likely to see advertisements for amino acid supplements that offer the promise of bigger, stronger muscles. As it turns out, these claims are more than somewhat exaggerated. The key to a better bod can’t be found in any pill. But that doesn’t mean that you should forget about amino acids. They play critical roles in our day-to-day lives.
Amino acids are the building blocks of protein. Twenty of them combine to form the 50,000 to 100,000 different proteins in the body. Nine amino acids are classified as essential because your body is unable to produce them and you must get them by eating foods that supply them. They are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Meat, poultry, fish, eggs, milk, cheese, yogurt, and soy are considered complete proteins because they provide us with all nine aminos.
The other 11 amino acids that scientists have studied are considered nonessential. That doesn’t mean that they are unnecessary, only that we don’t need to get them from foods because most people’s bodies can produce them as needed. Our bodies use the essential amino acids to make the nonessential ones—alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
Just as your right hand is the mirror image of your left, amino acids occur as mirror image forms. The left-hand forms are known as "l" and the right-hand forms are known as "d." You get l-amino acids from food, since they’re part of proteins, and they are the ones that are packaged as supplements. If you look at the label of an amino acid supplement and it doesn’t indicate "l" or "d," you can’t assume it’s the "l" form, however. Choose only supplements that are labeled as the "l" form, says Joanne Larsen, R.D., of Nutritional Data Services in Minneapolis, author of Edmund’s Food Ratings for Doctors.
Amino Activities
Amino acids play several vital roles in keeping us healthy, says James Heffley, Ph.D., director of clinical nutrition for the Nutrition Counseling Service in Austin, Texas. Their main function is to build the protein that gives structure to such body components as skin, membranes, muscles, organs, and bones.
Some amino acids also act as neurotransmitters, the chemicals that ferry information from one nerve cell to another, says Dr. Heffley. Others are precursors of neurotransmitters, which means that they’re involved in creating the compounds that do the transmitting. Tryptophan, for example, is a precursor of the neurotransmitter serotonin, which in turn is a precursor of melatonin, a hormone that’s important in sleep and sensory perception. So, if you don’t get enough of the tryptophan that helps produce serotonin, you may end up with a shortage of that neurotransmitter. You may also have some sleep problems because you’re short on melatonin.
SUPPLEMENT SNAPSHOT
| Amino Acids May help: Heart disease, high blood pressure, low immunity, indigestion, heartburn, diarrhea, diverticulitis, prostate problems, intermittent claudication, infertility, and wound healing. Good food sources: Meat, poultry, fish, eggs, milk, cheese, yogurt, and soy supply all nine essential amino acids; other good sources are beans, peas, seeds, and nuts. Cautions and possible side effects: Don’t take amino acids without a doctor’s guidance. The use of individual amino acids in large doses is considered experimental, and the long-term effects on health are unknown. High doses of arginine may cause nausea and diarrhea. People who have genital herpes should not take arginine because it may increase herpes outbreaks. Also, don’t take arginine and lysine at the same time, as they can interfere with each other. Cysteine in high doses can cause kidney stones in people who have cystinuria, and it can inactivate insulin, so use caution if you have diabetes. Taking cysteine may deplete zinc and copper, so if you plan to use cysteine or n-acetylcysteine for more than a few weeks, take it with a multi-vitamin/mineral supplement that supplies the Daily Value of these minerals. Tyrosine and phenylalanine supplements can raise blood pressure to dangerous levels, especially in people taking MAO inhibitors as antidepressants. Do not take phenylalanine if you have phenylketonuria. |
Amino acids are also the foundation for certain hormones such as insulin, and they help vitamins and minerals do their jobs. Taurine, for example, is used to transport magnesium and potassium from the bloodstream into the cells.
Protein and amino acids are so abundant in the foods we eat that very few people in the United States are deficient. If anything, we consume too much protein, says Larsen.
The only people who might be low in a particular amino acid are those with genetic defects that prevent them from making or using certain amino acids, she says. People with a hereditary condition called phenylketonuria, for example, can’t metabolize phenylalanine properly. If they get this amino acid in their food, their bodies can’t process it, and if the condition is left untreated, mental retardation and poor muscle coordination can result.
Zooming In on Specifics
Amino acid supplements come in many forms. Some are combinations of many different kinds of amino acids, but you can also get individual supplements.
Since most of us don’t have an amino acid deficiency, you may wonder why you would take any supplements at all. In Dr. Heffley’s view, it really doesn’t make much sense to take a supplement that includes a mixture of amino acids, but it might be a good idea to take a single kind of amino acid, as long as you take it for a limited time with some guidance from a doctor.
Here’s why Dr. Heffley makes that distinction. If we get all the protein—and therefore, amino acids—we need from food, there’s no reason to take a combination supplement. Our bodies break down these supplements into protein and use them in the same way as they would use protein from soybeans or eggs, he says. "It makes more economic sense to increase the amount of protein in your diet than to buy a mixture of amino acids in a supplement."
It’s a different matter, however, when you supplement with individual amino acids that might play very specific roles in the body. Sometimes, people can benefit from these, says Dr. Heffley. "If you take a single amino acid by itself, there’s a tendency for it to do its nonprotein functions. You increase the level of that amino acid without competition from other amino acids."
You shouldn’t take individual amino acids for more than two to three months at a time, but in his practice, Dr. Heffley has observed that the benefits of taking a single amino acid can persist long after supplementation has ended.
His explanation for the extended benefits of supplementation is based on his own theory that "once you open up pathways by using rather large amounts of amino acids, those pathways will stay open, and the end product will be made even without the extra amino acid—assuming it was what the body needed."
Keep in mind that the long-term effects and safe doses of most amino acids are unknown. Although you’ll find supplements on the shelves of drugstores and health food stores, that doesn’t mean that it’s all right to take large doses for as long as you want.
Individual amino acid supplements should be used only for a specific reason and only under the supervision of a medical professional who’s familiar with amino acids, says J. Alexander Bralley, Ph.D., director and CEO of Metametrix Clinical Laboratory in Atlanta.
As for the kinds of supplements to take, Dr. Bralley advises doctors and their patients to stick with amino acids labeled "free-form." These types of amino acids are easily abosrbed into the bloodstream and don’t have to be digested, according to Dr. Bralley.
Here is what some of the specific amino acid supplements might be able to do for you, if taken with a doctor’s guidance.
Alanine, glutamic acid, and glycine. Some studies have shown that these three amino acids may help relieve the symptoms of one kind of prostate problem in men. Called benign prostatic hyperplasia (BPH) , the problem occurs when the prostate gland swells and presses against one part of the urinary tract, the urethra. BPH is especially prevalent among older men and is characterized by an increased frequency of urination, waking at night to empty the bladder, and a reduced flow of urine. Many amino acids are present in the prostate, but alanine, glutamic acid, and glycine seem to be the ones that can help control BPH symptoms.
Arginine. This supplement is commonly used by body builders who want to put on weight by increasing body mass—but they just might be wasting their time. Although arginine may release a growth hormone, there’s little evidence that this action actually improves muscle growth or strength, says Michael Janson, M.D., president of the American College for Advancement in Medicine, based in Laguna Hills, California, and author of The Vitamin Revolution in Health Care.
This nonessential amino acid is involved in nitric oxide production, and it may be this action that makes it helpful to our bodies. Nitric oxide relaxes the muscles of the arterial walls and helps to open up the arteries, says Dr. Janson. Studies suggest that arginine supplements may help with high blood pressure and coronary heart disease. It is also thought to help boost immunity and speed wound healing.
Branched-chain amino acids (BCAAs). This is a group that includes three essential amino acids—leucine, isoleucine, and valine—branched-chain amino acids are a favorite with body builders and other athletes. Dr. Bralley says they may improve performance and help prevent the muscle breakdown that occurs during endurance training.
BCAAs are found mostly in muscle, and they break down and are used up for energy during prolonged exercise. If there isn’t a readily available pool of amino acids to draw upon, the protein synthesis doesn’t remake muscle as quickly and efficiently. BCAAs help to boost the muscle-building process. "From what we’ve seen, branched-chain amino acids do tend to conserve muscle mass," says Dr. Bralley.
Carnitine. Carnitine is an amino acid made in the liver from two other amino acid building blocks. It’s not one of the 20 amino acids that are used in protein synthesis, says Dr. Bralley, but it helps transport fat into the mitochondria within cells, where fat is burned for energy.
Carnitine has been found to lower serum cholesterol and triglycerides, build muscle tissue, and increase stamina. A deficiency may cause muscle weakness, confusion, or angina. A deficiency can also lead to an increase of fats in your bloodstream, especially a harmful type called triglycerides. Your doctor can spot a deficiency of carnitine with a blood or urine test.
Studies have shown that l-carnitine increases exercise capacity in people with some kinds of artery disease, and improves muscle function and exercise capacity in people with kidney disease. Acetyl-l-carnitine, a closely related amino acid, has been found to slow memory loss. A third form, d-carnitine, is synthetic and does not have any beneficial effect in the body. There is no reason to take d-carnitine or dl-carnitine.
Cysteine. Cysteine is needed to make another amino acid, taurine, which is a good anti-inflammatory, says Dr. Bralley. According to studies, cysteine can remove heavy metal toxins from the body, including mercury, cadmium, lead, and Arsenic.
In the form of n-acetylcysteine, cysteine has been used to stimulate the synthesis of another amino acid, glutathione. Glutathione has antioxidant properties, so it helps to block free radicals, the free-roaming unstable molecules that harm cells.
N-acetylcysteine may also help combat the side effects of chemotherapy and radiation therapy as well as help to clear mucus out of the lungs of smokers.
Glutamine. Under normal circumstances, glutamine is not considered an essential amino acid, but some people do need supplements in certain situations, says Dr. Heffley. Cancer cells like an acidic environment, and glutamine helps to shift the body chemistry in the other direction—that is, creating a less acidic, more alkaline environment. This happens even when cancer is present.
Glutamine has also been used for its calming effects. Once in the body, it’s made into gamma-aminobutyric acid (GABA), a neurotransmitter in the central nervous system. But the calming effect is not universal. In fact, Dr. Heffley says that in 1 person in 10, glutamine can act as a stimulant. That’s because it can also be made into glutamic acid, which sends signals that excite the nerves rather than calming them. There’s no real danger, however, even if you happen to experience stimulating effects from glutamine, he adds. The worst that can happen is a restless night’s sleep.
Glutamine is also used for wound healing, to boost depressed immunity, and to break addictions to caffeine and other stimulants. It may also help treat diarrhea that’s caused by gluten intolerance, Crohn’s disease, AIDS, and other conditions, adds Larsen. If you take it for this purpose, you’ll know within three days if it’s working.
Lysine. This essential amino acid can decrease outbreaks of the herpes simplex virus, which is responsible for cold sores and genital herpes. With either kind of outbreak, a lysine supplement can help the infection heal more quickly.
If you’re low in lysine, you might end up with a deficiency of carnitine. A lysine deficiency may also lead to calcium loss, which could increase your risk of developing osteoporosis. Lysine deficiencies occur more often in people who do not consume any animal products than in those who do, says Dr. Heffley. The best way to tell if you are lysine deficient is to have your doctor perform a urine or blood test.
Lysine competes with arginine for absorption and use by the body, so if you’re taking lysine, you’ll get less-than-optimal results from arginine, and vice versa.
Phenylalanine and tyrosine. Phenylalanine is an essential amino acid that is used to make another amino acid, tyrosine. Tyrosine in turn is transformed into three kinds of neurotransmitters, the nerve-related chemicals that help messages travel through your body. Since phenylalanine and tyrosine have an energizing effect, studies suggest that they are useful in treating depression and lethargy.
There’s a synthetic form of phenylalanine called d-phenylalanine. It’s not used by the body in the same way that the naturally occurring l-form is, but it may be beneficial as a treatment for chronic pain, especially lower back pain and dental pain.
A combined form, called dl-phenylalanine, however, does have some separate benefits. Some studies suggest that it may be useful in treating the chronic pain of osteoarthritis and rheumatoid arthritis, lower back pain, menstrual cramps, and migraine, among other conditions. It’s thought that it blocks certain enzymes in the central nervous system that are responsible for breaking down the brain’s own painkillers. If it interferes with those enzymes, the theory is that the natural painkillers in your brain will be free to do their work of suppressing pain.
Taurine. This amino acid is important for the normal functioning of the heart, brain, gallbladder, eyes, and vascular system. It’s the most abundant free amino acid found in the heart. In Japan, it’s widely used to treat heart disease.
In the brain, taurine acts as a neurotransmitter that, among other things, inhibits anxiety. Preliminary trials suggest that it may be useful in treating some forms of epilepsy.
