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03.05.2014


Animal study: endurance athletes perform best on diet where 20 percent energy comes from protein

Usually you can't just extrapolate the results of animal studies and apply them to humans, and the same goes for research done by Masanori Mitsuishi on the effect of protein on nutrition and endurance performance. Nevertheless we think it's an interesting study for endurance athletes. According to Mitsuishi, a diet with too much protein leads to a long-term decline in performance in endurance athletes.
Usually you can't just extrapolate the results of animal studies and apply them to humans, and the same goes for research done by Masanori Mitsuishi on the effect of dietary protein on endurance performance. Nevertheless we think it's an interesting study for endurance athletes. According to Mitsuishi, a diet with too much protein leads to a long-term decline in performance in endurance athletes.

High-protein diets remain popular in the sports world. Logical: muscles are paramount in sport, and a high-protein diet helps muscle recovery.


Usually you can't just extrapolate the results of animal studies and apply them to humans, and the same goes for research done by Masanori Mitsuishi on the effect of protein on nutrition and endurance performance. Nevertheless we think it's an interesting study for endurance athletes. According to Mitsuishi, a diet with too much protein leads to a long-term decline in performance in endurance athletes.


Mitsuishi gave 8-week-old mice feed that consisted for 10, 20, 30 or 50 energy percent out of protein.


Usually you can't just extrapolate the results of animal studies and apply them to humans, and the same goes for research done by Masanori Mitsuishi on the effect of protein on nutrition and endurance performance. Nevertheless we think it's an interesting study for endurance athletes. According to Mitsuishi, a diet with too much protein leads to a long-term decline in performance in endurance athletes.


When the mice were 20 weeks [equivalent to 18-year-old humans] and 50 weeks [40-year-olds in human terms] Mitsuishi got them to run to the point of exhaustion. He also measured their muscle strength [Grip Power].

Figure A below shows that the mice had more Grip Power the more protein there was in their diet. A protein-rich diet protects muscle strength during the aging process. But a diet consisting of 30 or 50 energy percent protein resulted in a decrease in the number of metres 50-week-old mice were able to run. This is shown in Figure B. In the long term an extremely high-protein diet reduces endurance capacity.


Usually you can't just extrapolate the results of animal studies and apply them to humans, and the same goes for research done by Masanori Mitsuishi on the effect of protein on nutrition and endurance performance. Nevertheless we think it's an interesting study for endurance athletes. According to Mitsuishi, a diet with too much protein leads to a long-term decline in performance in endurance athletes.


Mice perform best on a diet where 20 percent of the energy is derived from protein. 20 percent protein is more than the average endurance athletes consumes. Most athletes don't get further than deriving 12 percent of their energy from protein.

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The figure below shows how a diet consisting of 50 energy percent protein [HP] reduces endurance capacity in comparison with a diet consisting of 20 energy percent protein. It reduces the number of mitochondria, the cell's power stations. A high-protein diet also reduces the activity of the mitochondrial enzymes, which convert nutrients into energy.


Usually you can't just extrapolate the results of animal studies and apply them to humans, and the same goes for research done by Masanori Mitsuishi on the effect of protein on nutrition and endurance performance. Nevertheless we think it's an interesting study for endurance athletes. According to Mitsuishi, a diet with too much protein leads to a long-term decline in performance in endurance athletes.


A protein-rich diet activates the anabolic signal protein S6K1, but deactivates AMPK. As a result the high-protein diet also decreases the activity of the PCG1a gene. PGC1a induces the mitochondria to make more cells.

The key anabolic molecule in muscle cells is called mTOR. When Mitsuishi gave his mice a substance that deactivates this molecule, the negative effect of the high-protein diet on endurance capacity disappeared to a large extent.

It seems that if you increase muscle bulk and strength by following an extremely high-protein diet, you reduce your endurance capacity at the same time. But it's not 100 percent certain that this is the case. Mitsuishi's mice didn't train. It could be that the negative effects of an extreme high-protein diet are mitigated by frequent training sessions.

Source:
Am J Physiol Endocrinol Metab. 2013 Oct 1;305(7):E776-84.

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