While you need the essentials in your diet since your body can't manufacture them naturally, you don't have to worry about the non essentials since your body makes plenty of them. Yet some amino acids fall into the grey area of conditionally essential - sometimes you need them, sometimes you don't.

Even if you get plenty of protein, under specific conditions you may need these amino acids in greater amounts. These conditions include periods after surgery, during illness, and in my opinion, during times of heavy and intense exercise training. I'll go even further to state that for optimal muscle protein accretion, you may want to supplement with these special amino acids. Let's take a look at some of them.

Arginine

Arginine's unique functions include cellular regeneration, immune function, hormone regulation and protein metabolism. Although this amino is considered non essential in adults, in some instances (for example, catabolic conditions such as illness) it may be needed for its potential muscle sparing effects.

Arginine, in combination with other compounds, has been shown to have substantive effects on the immune system. For instance, the addition of arginine, glutamine and omega 3 fatty acids to the diets of severely ill patients reduced the incidence of major infection. With other substances in the mix, of course, we can't be sure how much of the effect could be attributed to the arginine. L-arginine given to rats prevented age related reduction in kidney function. Arginine showed that it can speed up the recovery process of the intestines after radiation induced injury.

Although these immune system benefits haven't been tested directly on athletes, we could conclude that arginine might have similar effects in exercising individuals. Many athletes, particularly bodybuilders, train at a very high intensity which may result in an impaired immune system and thus increase the risk for getting sick. Athletes should supplement with various amino acids like arginine and glutamine that have a positive effect on the immune system.

The aspect of arginine metabolism that's perhaps most relevant to bodybuilders is the role it plays in modulating hormone response. Several older studies indicate that arginine and ornithine can stimulate the secretion of growth hormone and insulin, two very anabolic hormones. Yet some newer work showed no changes of arginine alone on growth hormone.

Arginine has a multitude of effects that may apply to bodybuilders. The existing evidence suggests that oral arginine supplementation may cause hormonal changes beneficial for muscle growth and expedite the recovery process. Also, its potential role as an immune system modulator may benefit all athletes.

Cysteine

Cysteine is normally considered non essential, but keep in mind that this amino acid is made from 2 other aminos - methionine (essential) and serin (non essential) Thus, if one of the precursor molecules (such as methionine) is in low supply, then cysteine production may be impaired. For instance, the provision of L-cysteine in methionine deficient animals helps bring growth levels back to normal. Also, beagle pups supplemented with cysteine were found to have higher levels of liver glutathione, a potent antioxidant.

S-methyl-L-cysteine sulfoxide, a component of cabbage, has a cholesterol lowering effect in rats. N-actetylcysteine (NAC) has potent antioxidant effects and thus may prove beneficial in combating the effects of exercise generated free radicals. This form of cysteine shows the most promise as an ergogenic aid. Since free radicals generated by exercise can potentially damage our cell membranes, taking NAC may help offset this damage.

Glutamine

Glutamine is hands down the most impressive of the conditionally essential amino acids. It has been unequivocally demonstrated that both oral and intravenous administration of glutamine helps enhance the immune system. Glutamine is also quite important for skeletal muscle. Most of the glutamine found in your body is made in skeletal muscle and possibly adipose tissue. Glutamine has a plethora of good things to offer to bodybuilders.

If intra-muscular levels of glutamine decrease, muscle catabolism increases. A drop in plasma glutamine levels is also associated with excessive fatigue. Thus, the maintenance of optimal levels of plasma and intra-muscular glutamine is essential for an optimal anabolic state.

Giving glutamine to patients after major surgery can spare much of the muscle protein loss associated with disuse during the recovery process. Furthermore, glutamine can be used to form glucose (blood sugar) as well as provide fuel for immune system cells. In times of illness and stress, in fact, glutamine metabolism is sped up to promote antibody production and protein synthesis.

Glutamine is a favorite source of your immune system. Its role in providing fuel for immune cells may be the key to preventing muscle protein loss. If you don't consume enough glutamine (or protein), your immune cells may need to borrow glutamine from your muscle cells and you'll see an exodus of glutamine faster than a Japanese bullet train. It's robbing Peter to pay Paul.

But if you get plenty of glutamine, you'll in essence feed your immune cells and prevent the glutamine from leaving your muscle cells. Athletes who supplement with glutamine report a subjective feeling of better recovery between training sessions. Perhaps glutamine is best utilized or most needed under times of illness or stress. If you're sick, the fact that your immune cells are kicking into high gear to fight the illness practically begs for you to supplement with glutamine. Or if you're trying to lose weight, glutamine may help alleviate the loss of muscle that often accompanies weight loss.

Histidine

Evidence is accumulating that histidine has potent anti inflammatory and antioxidant properties, and athletes would be wise to consider using antioxidant and anti inflammatory supplements for their multiple benefits. For instance, these compounds may reduce minor joint aches and pains. Antioxidants play a vital role in the adaptive response to exercise stress as well as inhibit oxidative stress that can occur in muscle tissue after intense exercise, which can only expedite the recovery process.

You might think that oxidant stress (which generates free radicals) is problematic mainly for aerobic athletes, but intense anaerobic work requires much higher oxygen consumption than you use at rest, particularly during the rest or recovery intervals between sets. So don't ignore the benefits of antioxidants if you happen to be an anaerobe.

Although histidine is classified as an essential amino, you could argue that many people don't get enough, particularly vegetarians. Now recognized as one of the most effective antioxidant agents, histidine plays an important role in inhibiting peroxidation (damage to the fat component of the cell's membrane).

Sport scientists found that training induced fatigue was closely related to low blood levels of glutamine and histidine. Low intake of protein and therefore low plasma levels of certain amino acids such as glutamine and histidine are associated with persistent fatigue.

Taurine

Taurine, which isn't typically listed as either an essential or non essential amino acid can be made from the aminos methionine (essential) and cysteine (conditionally essential). What's interesting about taurine - the second most abundant amino acid in muscle (after glutamine) - is that it is not incorporated into proteins, but exerts various effects on metabolism and growth. Although we can normally make a certain amount of taurine, a deficiency could functionally impair certain tissues. Some researches have suggested that taurine may act as a growth modulator.

Taurine has been shown to mimic the action of insulin both in vivo (living organisms) and in vitro (test tube). Some studies report that more than 50 years ago, scientists discovered that taurine had an effect on carbohydrate metabolism similar to that of insulin and acted as a strong hypoglycemic agent (lowering blood sugar). In 1964, researches found that taurine could increase glucose utilization in the diaphragm muscles of rats. This amino also stimulated glucose uptake into cells in a manner similar to insulin and insulin and taurine had very similar effects on increasing the uptake of the amino acid proline into rat diaphragms.

These insulin mimetic properties made taurine an amino with exciting possibilities. We know insulin is an anabolic protein that helps bring amino acids and glucose into our cells, including muscle cells. Now if taurine acts like insulin, perhaps amino acid and glucose uptake could be augmented without changes in insulin levels.

We also know that maintaining a given cellular volume effects the anabolic machinery of a given tissue or cell, and that the regulation of cellular volume is intimately associated with protein synthesis (buildup) and degradation (breakdown). An increase in cellular volume or hydration status acts as an anabolic signal, while a decrease in cellular volume promotes catabolic processes. Taurine regulates cellular volume, as for instance in the brain, in cells in culture and in nervous tissue, but does it have similar effects on muscle fibers? Good question. The jury's still out on this one, but theoretically, it seems plausible.

Essential for athletes

Despite the classification of amino acids as essential and non essential, several aminos not designated essential are, in fact, essential under certain conditions. And the essential amino histidine could become more essential, meaning that even if you get plenty of protein , under certain conditions you need extra histidine for optimal recuperation and growth.

The stress of intense training coupled with dietary restriction (in some instances) may create the need to supplement with amino acids. Otherwise, you could run the risk of having a slight deficiency in a particular amino, which could lessen your ability to retain muscle protein and weaken immune function.