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GLUTAMINE (L-GLUTAMINE) - Supplement Superstar!
by Jim Wright, PhD
posted on 02-21-2007
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Glutamine is one of the new whiz kids on the block when it comes to bodybuilding supplements. Although it's been around for a while - articles in Muscle & Fitness were touting it in the early 90's, and medical journals were raving about it years before that - it's finally caught on big time with serious athletes in virtually every sport.
Although less familiar to the average athlete than creatine monohydrate (CM), many experts feel that glutamine actually has more long-term potential for promoting growth, strength and health than CM. CM works - no doubt - but glutamine also works, and it does a lot more things than creatine. To put it another way, if you look at creatine as if it's the winner of the Olympic 100 meter dash - the fastest person in the world, the absolute best at what it does - you could consider glutamine to be the winner of the decathlon, the jack of all trades, the master of many, and the world's best over all athlete.
Glutamine is an amino acid, one of the building blocks of protein. But it's much more than just a building block for proteins. It has so many critical roles in so many physiological processes - and especially those related to maintaining and growing muscle mass - that even scientists consider it a legitimate nutritional superstar. And athletes, from bodybuilders to marathon runners, are increasingly accepting it as "standard issue", an indispensable part of their supplement array.
Glutamine is the most abundant
amino acid in the body. It's especially concentrated in muscle where it makes up more than 60% of the "free" amino acids,
which are readily available for various uses by the muscle or by other parts of the body.1 Although glutamine was once
considered a non-essential amino acid, meaning that the body did not need to take it in but could synthesize it from others,
it's recently been elevated to the status of a conditionally essential amino acid, meaning that while the body can indeed
make glutamine, there are circumstances in which the need/use outstrips the rate at which it can be made.1,2 This is true
even though muscle can synthesize glutamine faster than it can any other amino acid. 3
Exactly why is glutamine so revered
as a nutrient, especially for a bodybuilder? One reason is because it serves as a direct regulator of protein synthesis and
breakdown in muscle. Muscle tissue is the major site of synthesis and storage of glutamine.4 As doctors and scientists have
been discovering over the past two decades, any type of stress - trauma, surgery, burns, infections, fasting, malnutrition,
and hard or prolonged exercise - causes glutamine to be released from muscle. 5,6,7,8 The losses are proportional to the
stress, and during the more extreme states of stress/catabolism, glutamine stores can be very rapidly and substantially
depleted.9
This occurs because glutamine is needed more critically by other tissues of the body which cannot synthesize it,
including cells of the immune system and the intestines. Although this might sound strange, the building of muscle tissue
takes a back seat to functions which are much more essential to actual survival, regardless of how mild or extreme the
situation might be. And, after all, the immune system does play a critical role in the repair of tissue "damaged" by
intense exercise.
Once depleted, glutamine is virtually the last nutrient to be restored to pre-stress levels. What's so important about this is that many experts feel that the amount of glutamine in muscle is the single most important factor influencing the rates of protein building and breakdown.10-12
When glutamine leaves muscle, not only is there no glutamine
available for incorporation to any muscle proteins that could've or would've been built, but branched-chain amino acids
(BCAAs) are also less available for protein synthesis because they are then used by the muscle to make up more glutamine
(which may or may not be released from the muscle).
When glutamine leaves muscle, the muscle begins to dehydrate. And it's now well known by bodybuilders, as well as scientists, that dehydration leads to protein degradation. Conversely, as you might expect, increasing the amount of water inside muscle fibers - which glutamine, like creatine, does although not quite as dramatically - leads to an increase in protein synthesis. 13
Studies with animals and many different groups of patients have demonstrated that adding glutamine to their nutrient intake can reverse protein catabolism and loss of muscle mass. Even though these studies have not been conducted on healthy human athletes, the basic physiological changes/responses to the situation are very similar to those of hard training; and it's strongly suggestive that in these studies glutamine prevented the loss of what are called myosin, heavy chain proteins, because these are the ones that determine a muscles contractile properties and capabilities.14
Over training in athletes - all too common in serious bodybuilders - can lead to glutamine depletion and a weakened immune system, in addition to impaired energy and performance. Experts have, in fact, suggested that plasma glutamine concentrations - reduced from severe/over training - can be used as a measure of both the relative state of over training/overreaching and the recovery from this condition. 15,16 Again, animal studies indicate that supplemental glutamine can mitigate or neutralize the loss of muscle glutamine following exercise. 17
In addition to
its anticatabolic and anabolic effects, glutamine also affects carbohydrate metabolism.18 A recent study in humans found
that infusions of glutamine lead to increases in blood glucose without any changes in either insulin or glucagon, the two
primary hormones that regulate glucose levels. 19 This could have a major impact when dieting down, cutting carbs, and
trying to minimize and stabilize insulin levels (to inhibit fat deposition) and glucagon (to minimize cell dehydration
and related effects), especially since cutting carbohydrates and calories can result in muscle protein catabolism. With
glutamine converting to glucose and fueling the brain and nervous system, precious muscle mass is spared.
In another study, glutamine infusion, prior to exercise, resulted in an increased muscle glycogen concentration two hours
after exercise causing the researchers to speculate that glutamine might serve as a direct precursor for muscle glycogen
replenishment after exercise.20 Glutamine has also been shown to affect the metabolism of free fatty acids and fat deposition, all in ways that reinforce its potential benefits for over weight individuals, as well as bodybuilders and other athletes.
Bottom line:
To maximize recovery and growth, you have to keep glutamine stores in muscle topped off. Every day. This is not a supplement that you need to or should cycle. To reiterate: As long as glutamine content remains high in the cell, cell hydration and anabolic processes remain elevated. When glutamine leaves muscle, the cells lose water and catabolic processes begin.24,25
It's not enough to take just a protein powder, not if you're really serious, even if it's a really good one. Glutamine is not just another amino acid building block of protein. You need glutamine just as much, if not more, than you need creatine. In fact, the actions of glutamine and creatine on cell hydration and increasing the energy stores of muscle are mutually supportive and complement one another.
You can get glutamine from food as it makes up roughly 4-8% of most
food protein with the highest concentrations occurring in milk, meat, and some nuts. You may get as much as 10 grams a
day from your diet, but that's very likely still not optimal for serious training. And since the cells of the intestines
are such voracious consumers of glutamine, not much makes it through to your muscles, except in very high protein diets.
26
To keep your muscles really flush, you probably need around 20-25 grams a day in your diet and maybe more during the
more extreme periods of training and/or dieting. That means supplementing. And not just with glutamine-enriched protein
supplements. They may help, but they won't usually give you that much unless you use very large amounts every day.
Taking
glutamine will actually enhance the biological value of the rest of the protein in your diet, whether food or supplement.
It does this by reducing the use of the aminos in those proteins to make glutamine. They are therefore available for use
in synthetic - anabolic - processes in the muscles and elsewhere.
 The simple, easy way is to use a supplement consisting of pure glutamine powder. Simply take a slightly rounded teaspoon three or four or even five times a day: when you get up, before bed, before and after your workout, and maybe one other time. You can put it on your tongue and then take a drink. You can mix it in a little water. It has very little taste, and certainly not an unpleasant one.
The key is to include glutamine in your supplement program and to take it consistently. Even 10 grams a day will make a difference in your recovery. And better recovery is the foundation for more overload, which is the foundation of bigger, stronger muscles. And glutamine is not just for use when training hard, it's made to order for whenever you're stressed, whether fighting off a cold, flu, sore throat, dieting, sleep deprived, emotionally out of whack, or more severely impacted by wasting diseases.
I have been strongly recommending glutamine supplementation in my fitness and nutrition seminars for many years, and I have never had anyone who used glutamine faithfully - at 20-25 grams a day along with a good basic bodybuilding diet for one month - fail to tell me that it made a very significant and noticeable difference.
Scientific References
1. Lacey JM et al. Is glutamine a conditionally essential amino acid? Nutrition Reviews 1990; 48(8):297-309.
2. Smith RJ. Glutamine metabolism and its physiologic importance. Journal of Parenteral and Enteral Nutrition 1990; 14(4 Supplement):40S-44S.
3. Golden MN et al. Glutamine production rate and its contribution to urinary ammonia in normal man. Clinical Science 1982; 62:299-305.
4. Newsholme EA et al. Properties of glutamine release from muscle and its importance for the immune system. Journal of Parenteral and Enteral Nutrition 1990; 14:635-675.
5. Newsholme EA et al. A role for muscle in the immune system and its importance in surgery, trauma, sepsis and burns. Nutrition 1988; 4:261-268
6. Wernerman J et al. The effect of trauma and surgery on inter-organ fluxes of amino acids in man. Clinical Science 1987; 73:129-133.
7. Rennie MJ. Muscle protein turnover and the wasting due to injury and disease. British Medical Bulletin 1985; 41(3):257-264.
8. Bulus N et al. Physiologic importance of glutamine. Metabolism Clinical and Experimental 1989; 38(8 Supplement 1):1-5.
9. Furst P et al. Evidence for a nutritional need for glutamine in catabolic patients. Kidney Int Supplement 1989; 27:S287-S292.
10. MacLennan PA et al. Inhibition of protein breakdown by glutamine in perfused rat skeletal muscle. FEBS Letters 1988; 237:133-136.
11. Jepson MM et al. Relationship between glutamine concentration and protein synthesis in rat skeletal muscle. American Journal of Physiology 1988; 255:E166-E172.
12. Rennie MJ et al. Characteristics of a glutamine carrier in skeletal muscle have important consequences for nitrogen loss in injury, infection, and chronic disease. Lancet 1986; 2:1008-1012.
13. Low SY et al. Responses of glutamine transport in cultured rat skeletal muscle to osmotically induced changes in cell volume. Journal of Physiology 1996; 492(part 3):877-885.
14. Hickson RC et al. Glutamine prevents the down-regulation of myosin heavy chain synthesis and muscle atrophy from glucocorticoids. American Journal of Physiology 1995; 268:E730-E734.
15. Keast D et al. Depression of plasma glutamine concentration after exercise stress and its possible influence on the immune system. Medical Journal of Australia 1995; 162(1):15-18.
16. Rowbottom DG et al. The emerging role of glutamine as an indicator of exercise stress and overtraining. Sports Medicine 1996; 21(2):80-91.
17. Moriguchi S et al. Glutamine supplementation prevents the decrease of mitogen response after a treadmill exercise in rats. Journal of Nutrition Science Vitamins 1995; 41(1):115-125.
18. Nurjhan N et al. Glutamine: a major gluconeogenic precursor and vehicle for interorgan carbon transport in man. Journal of Clinical Investigation 1995; 95(1):272-277.
19. Perriello G et al. Regulation of gluconeogenesis by glutamine in normal postabsorptive humans. American Journal of Physiology 1997; 272(3 Part 1):E437-E445.
20. Varnier M et al. Stimulatory effect of glutamine on glycogen accumulation in human skeletal muscle. American Journal of Physiology 1995; 269(2 Part 1):E309-E315.
21. Welbourne TC. Increased plasma bicarbonate and growth hormone after an oral glutamine load. American Journal of Clinical Nutrition 1995; 61:1058-1061.
22. Bourguignon JP et al. Endogenous glutamate involvement in pulsatile secretion of gonadotropin-releasing hormone: evidence from effect of glutamine and developmental changes. Endocrinology 1995; 136(3):911-916.
24. Haussinger D et al. Cell volume and hormone action. Trends in Pharmacological Science 1992; 13:371-373.
25. Hallbrucker C et al. Control of hepatic proteolysis by amino acids ? the role of cell volume. European Journal of Biochemistry 1991; 197:717-724.
26. Remesy C et al. Inter-organ relationship between glucose, lactate, and amino acids in rats fed on high-carbohydrate or high-protein diets. Biochemical Journal 1978; 170:321-329.
27. Carlson HE et al. Stimulation of pituitary hormone secretion by neurotransmitter amino acids in humans. Metabolism Clinical and Experimental 1989; 38(12):1179-1182.
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