Glutamine, a Better Glucose Source Than Glucose? Can You (Ab-)Use It As an Intra-/Post Workout Supplement? Human Study Suggest: Yes You Can! 8g Will Do the Trick

Could it be better to use glutamine as the main energy source in an intra-workout beverage? Or is the latter superior to glucose, only when it's already to late, meaning only, when you already are hypoglycemic?
I see the irritation on your face. How on earth should glutamine be a better glucose source than glucose: Adel obviously has lost his mind under the pressure of putting out interesting stuff on a daily basis... well, while the latter may be true (how would a sane person do what I do?), I am actually just reformulating the main message of a recently conducted study from the State University of Maringá in Brazil. In the corresponding paper, which was published online in the International Journal of Endocrinology (Nunes Santiago. 2013).

So yes, glutamine is in fact the better glucose...or maybe I should clarify it is a superior source of glucose to promote glycemia recovery after insulin-induced hypoglycemia. In other words, it will help you to lose the dizziness, the tiredness, the shaking and the sweating that are only a handful of the symptoms of low blood sugar (=hypoglycemia) more readily than glucose.

How do the scientists know?

Actually Nunes Santiogo et al. tested not just glucose and glutamine, they also provided their rodents which had been injected with a non-lethal but profoundly hypoglycemic dose of 1U/kg insulin at the beginning of their experiment with either of these substances:
  • alanine
  • glutamine, or
  • saline (control group)
  • glucose
  • glycerol
  • lactate
The dosage was identical (100mg/kg) for all of them, so that we had a "level playing field". Now, if I had not given away all the information right in the headline, you would probably have expected glucose to rule, right?
Figure 1: Glucose (mg/dl) levels after administration of 100mg/kg of saline, glucose (Glu), glycerol (Gly), lactat (Lac), Glutamine (Gln) or alanine (Ala) to hypoglycemic mice (Nunes Santiago. 2013)
What? Your money was on Lactate? Well that's actually a smart choice, as well and shows me that you have been attentive over the past months.

A note on lactate: In view of the results of a recent study that showed that lactate may not be able to completely replace glucose, but can modulate metabolic and neuronal activity in a way that the glucose contribution to brain metabolism under hypoglycemic conditions is restored to levels otherwise only observed at euglycemia (Herzog. 2013), it is likely that it could sooth the symptoms of hypoglycemia without even replenishing blood glucose to normal. Well, as long as it is buffered (NaHCO3 ;-) and is not converted to lactic acid, at least.
Yeah, lactate is an emergency fuel, so it does not seem totally unlikely that it works, but if you take a look at the study outcome in figure 1 you will realize that glutamine was not just a notch, but rather significantly more effective in getting the ~70% reduced glucose levels back up in the normal zone. It's also better than the #1 source of gluconeogenesis alanine, which in turn was still superior to "the real deal", i.e. glucose.

The glucose, diabetics, for example are so desperate to find ("Where's my Snickers?"), when they realize that they are about to go hypo after an insulin injection or workout, on the other hand, brought the levels back up to only 63% and was thus only slightly better than lactate of which I already hinted at in the box to the right that the actual blood sugar levels may not adequately reflect the symptoms, due to it's ability to modulate the energy flux to the brain.

How could that be? Why is glutamine more effective than glucose?

It still sounds odd, I know, so let's see what the scientists have to say about their own results:
"In contrast with rats, oral glutamine showed better glycemia recovery compared with alanine (Figure 1). This difference could be attributed to the possibility that in mice the catabolism of glutamine in the enterocytes is lower than in rats" (Nunes Santiago. 2013)

Now this is a problem, because it makes the usual question of whether or not these results apply to human beings, or not even more difficult to answer. Are we more like rats or rather like mice? And what would be the perfect "blood sugar restoration agent" for us - Glucose or glutamine. I honestly cannot answer this question, but I can still give you a decent bottom line, I guess.

Suggested read: "Post-Workout Glycogen Repletion - The Role of Protein, Leucine, Phenylalanine and Insulin. Plus: Protein & Carbs How Much do You Actually Need After a Workout?" | read more
Bottom line: Irrespective of whether it is "optimal" it is certainly a viable way to keep your glucose up and even replenish your glycogen levels after a workout by supplementing with l-glutamine. In 2005, for example, Iwashita et al. were able to show that 8g of glutamine promote storage of muscle glycogen to an extent similar to 330ml of 8.5% (wt/vol) glucose polymer solution (Bowtell. 1999); and this would not work if the glutamine was not turned into glucose by the liver and transported to the muscle in the blood stream so that it will - at least for as long as it disappeared in the skeletal muscle glycogen stores - also be available for the brain, the heart and all the other organs.

Whether things look different in insulin induced hyperglycemia is questionable, but I tend to think that 99% of you are interested in it's use as a workout / post-workout fuel in exchange for carbs and not so much as a means to save your life, when you you've been overdoing your slin shots.

If that's what you want to do, the optimal strategy would be to combine both. According to Bowtell et al. this will increase the non-oxidative glucose disposal by another +25%. This would also have the advantage that you are not overtaxing the glyconeogenic pathway in the liver. A potential overload of the latter is by the way also the reason why I strongly advise against trying to live off glutamine let alone other not as readily metabolized amino acids as your sole source of glucose (or energy in general).

Additional reads:
  • "30g of oral glutamine have similar effects on GLP-1 as 75g of glucose" | read more
  • "7 Rarely Thought of Side Effects of High Dose Glutamine" | read more
  • "Chronic High Dose BCAA Supplementation Reduces Endurance Performance by 43% Plus: How Ammonia, Glutamine, Arginine & Low Carb Could be Involved" | read more
  • "New Role for Glutamine in Protein Synthesis? Study Suggests Direct Effects on Mammalian Target of Rapamycin (mTOR) - EAAs Alone Won't Produce Optimal Results" | read more
  • "Use Glutamine to Heal the Gut and Hinder Your Gut Bacteria from Eating Away Your BCAA, Arginine and Other Aminos" | read more

  • Bowtell JL, Gelly K, Jackman ML, Patel A, Simeoni M, Rennie MJ. Effect of oral glutamine on whole body carbohydrate storage during recovery from exhaustive exercise. J Appl Physiol. 1999 Jun;86(6):1770-7.
  • Herzog RI, Jiang L, Herman P, Zhao C, Sanganahalli BG, Mason GF, Hyder F, Rothman DL, Sherwin RS, Behar KL. Lactate preserves neuronal metabolism and function following antecedent recurrent hypoglycemia. J Clin Invest. 2013 May 1;123(5):1988-98. 
  • Nunes Santiago A, Ferreira de Godoi-Gazola VA, Milani MF, et al. Oral Glutamine Is Superior Than Oral Glucose to Promote Glycemia Recovery in Mice Submitted to Insulin-Induced Hypoglycemia. International Journal of Endocrinology, vol. 2013, Article ID 841514, 7 pages, 2013.
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