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Performance While On A Low-Protein Vegetarian Diet

A study published yesterday looked at the effects of a low-protein, vegetarian diet on blood pH and cycling performance. Led by Dr. Hietavala, researchers from University of Jyväskylä in Finland hypothesized the following.

"a diet low in protein and rich in alkali-producing vegetables and fruits may have the potential to alter the blood acid-base status and, thus, enable higher aerobic capacity and influence fuel selection during exercise."

On the first count, researchers didn’t see any change to blood pH after having subjects follow a low-protein vegetarian diet (LPVD). However, they only had the subjects follow this diet for four days, so perhaps this wasn’t long enough to see an effect. 

Even though no pH changes were seen, researchers observed something unexpected. 

"…energy expenditure was greater and cycling economy poorer after LPVD."

In other words, after following the vegetarian diet the subjects had to expend more energy to perform a set amount of work during cycle ergometer testing. Dr. Hietavala’s team concluded the following.

"According to these results, a low-protein vegetarian diet cannot be recommended as a means to improve submaximal or maximal aerobic performance via acid–base balance as opposed to what was hypothesized."

So, the question now is, what caused this performance decrease? Is it possible that the vegetarian diet given to the subjects was too extreme? Was it too low in protein and/or calories? Was the limited grain or dairy intake a factor? Did subjects not have enough time to adapt to it?

As often happens, this study yielded more questions than answers. I’m excited to see where this leads.

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