Proteins are composed of various combinations of amino acids, and all dietary proteins are eventually converted into amino acids. The amino acids, which number about
22, are classified as either essential or nonessential. Essential amino acids are so-named because your body can't synthesize them and so it's essential that you get
them in your diet.
The balance of essential amino acids in any particular protein determines its biological value. Since animal protein sources are higher in essential amino acids and
more closely duplicate the amino acid pattern found in the human body, they're considered superior to plant-derived proteins, which often have either low or no amounts
of essential aminos.
Recent research proves that from the perspective of muscle protein synthesis, essential aminos are extremely important. In fact, some studies show that getting as
little as six grams a day of an essential amino acid mixture promotes muscle protein synthesis following resistance exercise, such as weight training. But watch out:
Information on the importance of essential amino acids may lead you to conclude that the so-called nonessential amino acids are not very important.
That would be incorrect. Some nonessential amino acids have been reclassified as "conditionally" essential because under certain circumstances, such as high-stress conditions,
the body cannot sufficiently synthesize them and their status changes from unessential to essential.
Examples of conditionally essential amino acids include glutamine and arginine. Normally, the body can synthesize them if you've taken in a sufficient supply of essential
aminos. Sometimes, however, that synthesis can't take place rapidly enough glutamine and arginine are among the most popular amino acid supplements with athletes and bodybuilders
today. Research on glutamine was originally derived from hospitalized patients, especially burn patients, who lose vast amounts of protein as a result of their injuries.
Giving them glutamine reversed or halted the cascading catabolic effects on muscle that can result in death.
Thanks to the anticatabolic effect, glutamine earned a place in the supplement regimen of intensely training athletes. Later studies showed that it also appeared to prevent
the immune-suppression effects of extended exercise-endurance events, for instance.
Arginine was initially promoted as a growth hormone releaser because doctors gave it intravenously to patients to treat growth hormone deficiency. Forms of arginine used
for other purposes have also turned up in various food supplements, notably those that increase nitric oxide. Many of the food supplements that contain glutamine and/or arginine
also contain another amino acid, taurine-particularly creatine supplements. That's because creatine is thought to encourage the cellular hydration that signals increased muscle
protein synthesis. Glutarnine and taurine also appear to promote cellular hydration, which makes them synergistic with creatine.
If taurine did nothing more than promote cellular hydration, it would likely still be considered a useful supplement. But taurine-conditionally essential like glutamine and
arginine-is far more essential to those engaged in exercise.
What Is Taurine?
Taurine was discovered in 1827 as a component of ox bile, which explains its name; Taurus is Latin for bull. Taurine is not incorporated into muscle and other tissues of the
body like other amino acids but instead is found as a free, or unbound, amino acid or as part of short chains of aminos known as peptides. The significance of taurine wasn't
recognized until studies in the 1970s found that it was an essential nutrient for cats. Without it, cats develop retinal degeneration leading to blindness and serious heart
problems, which explains why cat food labels prominently display the taurine content.
Research on cats led some scientists to investigate whether taurine had any use for human nutrition. Initial studies found that babies fed on formula instead of mother's milk
often developed taurine deficiency, since their bodies lacked the enzyrnes needed to synthesize it. Normally, taurine is synthesized from two other amino acids-the essential
methionine and the nonessential cysteine-both of which contain sulfur.
In fact, some scientists suggest that taurine isn't a true amino acid, since it contains a sulfonic acid group; other aminos contain a carboxylic acid group. Taurine is found
abundantly in the body, in brain, skeletal and heart muscle tissue. In muscle, it's the second most abundant free amino acid, behind glutamine. Taurine's presence in muscle
suggests that it must be there for a reason.
The body can synthesize taurine from methionine and cysteine but not without the presence of the activated form of vitamin B6, or pyridoxine. So a lack of B6 in the diet can
impair taurine synthesis. Controversy exists about just how well the body is able to make taurine. The main enzyme involved not that active in either humans cats. That's why
some theories suggest that many people can benefit from taking supplemental taurine.
The most recognized function of taurine is its role in the production of bile salts. Bile, composed mainly of cholesterol, is a substance manufactured in the liver and stored
in the gallbladder. In fact, the primary way the body rids itself of excess cholesterol is by shunting it into bile production. Bile itself promotes the digestion of fat by
reducing its surface area, which makes it more digestible bylipases, or fat-digesting enzymes.
Even so, bile isn't soluble enough to work unless it's conjugated, or combined with other substances. When that happens, bile becomes bile salts, and the two main conjugating
agents are the amino acids glycine and taurine. So taurine helps create bile salts and lower blood cholesterol, keeping it from floating through the bloodstream as low-density
lipoprotein (the bad kind of cholesterol). High levels of LDL are a major risk factor for cardiovascular disease, especially oxidized LDL. The less LDL in the blood, the less
chance of cardiovascular disease.
Taurine accelerates bile salt synthesis by boosting the genes responsible for making an enzyme called 7-alpha hydroxylase. The increased use of cholesterol for bile synthesis
lowers blood levels of cholesterol, which in turn opens up LDL receptors on cells, also lowering cholesterol levels.
One study examined the effects of providing either three grams a day of taurine or a placebo to 30 overweight college students for seven weeks. Those in the taurine group had
lower triglyceride levels in the blood, along with a reduced atherogenic index, a measure of the ratio of HDL cholesterol (the good kind) to triglycerides in the blood. Taurine
increases HDL production by boosting the activity of the protein carrier of HDL, apolipoprotein.
A beneficial side effect also occurred in the students who took the taurine supplements: They all lost bodyfat. Studies done with diabetic rats show that taurine prevents buildup
of abdominal fat, which is considered the most dangerous to health, being linked to insulin resistance, heart disease and diabetes.
Taurine also functions as an antioxidant, which protects against such diseases as cardiovascular disease and cancer. 'When certain immune cells destroy invading organisms, they
release a stream of free radicals, which are unstable oxygen by-products that destroy the invading organism's cellular membrane, killing it. Free radicals can also damage normal
tissue. When the body has sufficient taurine, however, the taurine soaks up the excess free radicals, rendering them neutral.
Smoking damages artery linings and leads to cardiovascular disease. A 2003 study, however, found that in smokers who took taurine, the function of the lining, or endothelium,
rapidly improved to the point where it worked similarly to that of nonsmokers. That occurred after only five days on a 1.5-gram dose of taurine, about the same amount found in a
100-gram serving of fish.
Although omega-3 fats are considered the health-promoting component in fish, its high taurine content also offers protective benefits that are frequently overlooked. Some
studies show that the taurine content of fish helps lower blood pressure and reduce the negative effects of a high salt intake. Stress also increases blood pressure by increasing
the release of such hormones as epinephrine and norepinephrine, which constrict blood vessels. Taurine counteracts that effect, leading to lower blood pressure. Interestingly,
the populations with the lowest rates of cardiovascular disease in the world, those of Japan and the Mediterranean countries, also get the greatest amounts of taurine in their
Still another way that taurine protects the heart is by modulating electrolyte function. Excess calcium can rapidly lead to cellular death, but taurine prevents that. It also
favorably affects the balance of sodium and potassium in heart tissue, thus maintaining proper heart function.
As noted previously, highly refined sugars, such as in high-fructose corn syrup, are thought to be responsible for the rising epidemic of obesity, especially in younger people.
Eating excess fructose causes sugar to be deposited into protein tissues, an effect called glycation that's considered a major cause of aging and the major cause of the stiffness
and lack of mobility many people experience as they get older.
In a recent experiment rats were put on a 60 percent fructose diet but also got a 2 percent taurine solution for 30 days. That prevented the formation of glycation end products
while also enhancing the use of glucose. Taurine worked with insulin to affect glucose, although it worked independently of insulin in promoting glucose use. Some studies show that
taurine may help prevent some serious diabetic complications, including neuropathy (nerve degeneration) and retinopathy (blindness).
Can Taurine Help Your Workouts?
Slow-twitch muscles have higher levels of taurine than fast-twitch muscles. That's likely because slow- twitch fibers have a greater oxidative capacity, and taurine has antioxidative
properties. Studies show that the body loses the greatest amount of its taurine after intense anaerobic exercise, such as weight training.
Experiments done with rats demonstrate that taurine increases exercise capacity, especially in older anima1s. Another study found that taking taurine may help protect against
exercise-induced muscle injuries. The authors of that study observed that taurine supplementation reversed certain types of functional deficits in skeletal muscle. Our results
suggest that taurine supplementation may facilitate exercise performance and reduce some limited aspects of muscle injury caused by exercise."
A later study that used human subjects confirmed the protective effects of taurine during exercise. Because of the increased oxygen intake that occurs, exercise also ups the
production of dangerous free radicals, and rampant free-radical release can damage DNA in cells, leading to mutations that may cause cancer and other diseases. In this study,
however, giving men supplemental taurine before exercise significantly prevented DNA strand breakage, an effect attributed to taurine's antioxidative properties. In addition, the
subjects who took taurine also showed increased VO2- max, an indicator of increased endurance, increased time to exercise exhaustion and increased maximal workload. That effect could
come from taurine's role in increasing the pumping power of the heart and improving the electrical and contractile properties of skeletal muscle.
In muscle, taurine stabilizes cell membranes, including the sarcolemma, the membrane that surrounds muscle fibers. By controlling calcium entry into muscle, it promotes muscle contraction
as well. Taurine's effect on electrolyte functions in muscle may also explain why it helps prevent severe muscle cramps. One theory suggests that exercise-induced loss of sodium and calcium
may precipitate such cramps. By stabilizing those minerals during exercise, taurine may help prevent postworkout muscle cramps. The transport of taurine into muscle is promoted by sodium
and chloride and decreased bylactate and beta-alanine.
A recent study found that taurine content in fast-twitch muscle significantly decreased during extended exercise sessions and noted that it enhances the enzymes in muscle that regulate
energy production and fat oxidation. flurine also stimulates cyclic AM1I which leads to a greater release of catecholamines, such as epinephrine and norepinephrine. The latter two
substances activate the enzyme hormone-sensitive lipase in fat cells, which leads to the release of fat for use as energy during exercise.
Words of Caution
For those considering supplementing taurine, several caveats are in order. The precise optimal dose of taurine for increasing exercise performance has been calculated- in rats. It's
between 100 and 500 milligrams per kilogram (2.2 pounds) of bodyweight. The dose depends on body size and would be considerably lower in a human. Good food sources of taurine include
most animal protein foods, particularly fish. Oysters are a superior source.
Those who use the drug denbuterol should be aware that it causes a rapid and severe depletion of taurine from muscle and heart tissue. That could explain the heart damage and muscle
cramps that can occur with its use. Ephedrine and mahuang supplements also reduce taurine muscle content, the amino acid beta-alanine is now being added to various food supplements because
it's the precursor of L-carnosine synthesis in the body. Beta- alanine and taurine compete for the same uptake carrier into the body, and beta-alanine can block taurine uptake by 50 percent
or more. Best to use the two amino acids at different times.
Finally, be aware that taurine functions in the brain as an inhibitory neurotransmitter- meaning that it has a depressant action on brain function. So taking too much taurine in a single
dose can lead to feelings of fatigue and lack of energy. Smaller doses of tanrine, less than a gram, have a reverse effect: providing energy. That's ostensibly why taurine is a major
ingredient of a popular energy drink that includes the word bull in its name. But since the drink also contains caffeine, the taurine addition could indeed represent a lot of bull.