Ammonia may be a central player in fatigue and exhaustion. Exercise releases of ammonia into the blood stream. Once in the blood stream it travels to the brain where it can accumulate if the pace of entry is faster than the body’s ability to metabolize it. Athletes in studies who had the hardest time completing an intense exercise task also had the highest ammonia levels.(Nybo 2005).
The brain gets rid of extra ammonia by combining it with glutamate to produce glutamine. If the brain is using glutamate to get rid of ammonia it is possible that glutamate levels decrease. Decreased brain glutamate can impair function and may contribute to some of the wonky feelings of exhaustion. Glutamate is an important neurotransmitter. It is an excitatory neurotransmitter. Glutamate makes it easier for nerves to fire and transmit information. Without glutamate brain function may slow. This is a very simplified picture. However, it may help explain a bit of what is going on with fatigue. Brain uptake of ammonia has been demonstrated in a number of studies. One thing that has been noted is that there may be a lot of variation in the amount of ammonia produced. This was found in a study of highly trained endurance athletes. Athletes were:
- young men
- very similar weight
- similar height
- similar VO2max
- living in Denmark (Nybo 2005).
Is it possible that variability in ammonia levels helps some people go longer or harder than others? Is it less ammonia production or better brain clearance? What causes it: genetics, diet, differences in training?
Reducing Ammonia: Is it possible? Would it help for competition or training? Would it hurt?
There have been several studies that have looked at reducing blood ammonia levels. Much of this comes from research on people with liver disease. People with liver disease tend to produce a lot of ammonia. They may also suffer a lot of muscle loss and brain dysfunction. Their situation though is quite different from that of an athlete.
Is there any research on reducing ammonia levels during exercise?
Yes. Apparently glucose does. Subjects (Nybo 2005) who were given glucose supplement had only about a third of the ammonia level as did subjects who did not. A 2008 paper found that giving professional football players 100 mg per kg of glutamine prior to training reduced ammonia in blood. Lastly, walnuts. A study of walnut extracts showed less ammonia in blood of mice after they were subjected to a forced swim test. Mice receiving walnut extract were able to swim quite a bit longer than those who did not (see reference for details.) One of the things that was particularly interesting is that mice were subjected to several tests over several weeks. Performance improved in the Walnut-Extract Mice from week 1 to week 2 to week 3 and then tapered off. They never dropped to the level of No-Walnut mice. Here is a link to the graph: Link. The researchers suggested that Walnuts may reduce ammonia and fatigue through their anti-oxidant properties.
Should I eat walnuts, glucose and glutamine during training?
There is no evidence that walnuts, glucose or gluamine will improve your performance over the long term. In fact, trying to lessen your ammonia production during training may hurt. In the Nybo study the athletes with the highest levels of ammonia in plasma and brain were the athletes who did not get glucose AND had the lowest VO2 max. VO2 max is a marker of aerobic conditioning. It is possible that the body gets more efficient in dealing with ammonia produced during exercise. If that is the case, minimizing ammonia production might also minimize your ability to deal with it. Its too early to know.
What about walnuts, glucose and/or glutamine for competition?
Hard to say too. But . . . an ability to reduce ammonia might reduce fatigue and let you go longer or faster. It might give a competitive edge. Keep in mind some people may simply be better at metabolizing ammonia. It might be genetic. Or it might be from hard training. For an overview of amino acid metabolism:
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Nybo L, Dalsgaard MK, Steensberg A, Møller K, & Secher NH (2005). Cerebral ammonia uptake and accumulation during prolonged exercise in humans. The Journal of physiology, 563 (Pt 1), 285-90 PMID: 15611036
Snow RJ, Carey MF, Stathis CG, Febbraio MA, & Hargreaves M (2000). Effect of carbohydrate ingestion on ammonia metabolism during exercise in humans. Journal of applied physiology (Bethesda, Md. : 1985), 88 (5), 1576-80 PMID: 10797115
Bassini-Cameron, A., Monteiro, A., Gomes, A., Werneck-de-Castro, J., & Cameron, L. (2008). Glutamine protects against increases in blood ammonia in football players in an exercise intensity-dependent way British Journal of Sports Medicine, 42 (4), 260-266 DOI: 10.1136/bjsm.2007.040378