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Fri Jan 25, 2008 1:40 pm

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The following review was part of my upcoming Nutrition Research column in Muscular Development magazine.

Vitamin C Prevents Adaptation to Endurance Exercise
Many endurance athletes take high doses of vitamin C to help them fight free radicals and boost immunity. Free radicals are highly reactive chemicals produced naturally during metabolism that are linked to membrane destruction, DNA damage, aging, and immune system depression. Antioxidants, such as vitamins C and E and beta-carotene bind with free radicals and buffer their negative effects. Free radicals also have positive effects. During endurance exercise, free radicals act as signaling chemicals to increase production of energy cell structures called mitochondria— sometimes called the powerhouses of the cells. The amount of mitochondria in muscle is the best predictor of its endurance. Spanish researchers found that vitamin C supplements (1 gram per day) interfered with the capacity to increase endurance through training because it prevented increases in cell mitochondria and oxygen-related enzymes that produce ATP— the cells’ major energy source. Endurance training triggers cell processes that help them cope with damaging free radicals. Vitamin C supplements interfered with cellular adaptations that occur with endurance training. The take-home message of this very important paper is that endurance athletes should not take high doses of vitamin C because they interfere with training gains.
(American Journal Clinical Nutrition 87: 142–149, 2008)

I discussed this paper with George Brooks from UC Berkeley. George studies exercise biochemistry. He confirmed that free radicals generated during exercise stimulate increases in mitochondrial mass, which are critical for increasing endurance.

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Thomas Fahey
Dept Kinesiology
California State University, Chico
Chico, CA 95929-0330
discusdoc@aol.com



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Sat Jan 26, 2008 9:59 am

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Here's more evidence showing the importance of free radicals (reactive oxygen species, ROS) for increasing mitochondrial mass. Mitochondrial mass is the best predictor of endurance capacity.


ABSTRACT We hypothesized that in addition to serving
as a fuel source and gluconeogenic precursor,
lactate anion (La) is a signaling molecule. Therefore,
we screened genome-wide responses of L6 cells to
elevated (10 and 20 mM) sodium-La! added to buffered,
high-glucose media. Lactate increased reactive
oxygen species (ROS) production and up-regulated 673
genes, many known to be responsive to ROS and
Ca2". The induction of genes encoding for components
of the mitochondrial lactate oxidation complex
was confirmed by independent methods (PCR and
EMSA). Specifically, lactate increased monocarboxylate
transporter-1 (MCT1) mRNA and protein expression
within 1 h and cytochrome c oxidase (COX)
mRNA and protein expression in 6 h. Increases in
COX coincided with increases in peroxisome proliferator
activated-receptor coactivator-1 (PGC1)
expression and the DNA binding activity of nuclear
respiratory factor (NRF)-2. We conclude that the
lactate signaling cascade involves ROS production
and converges on transcription factors affecting mitochondrial biogenesis.
Hashimoto, T., Hussien, R., Oommen, S., Gohil, K., Brooks, G. A. Lactate sensitive transcription factor network in L6 cells: activation of MCT1 and mitochondrial biogenesis.
FASEB J. 21, 2602–2612 (2007)

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Thomas Fahey
Dept Kinesiology
California State University, Chico
Chico, CA 95929-0330
discusdoc@aol.com


Last edited by Discusdoc on Sun Jan 27, 2008 5:07 pm, edited 3 times in total.


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Sun Jan 27, 2008 9:56 am

 
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Evidence-based training! Hooray!! A focus on evidence-based medicine has been ongoing for the past ten years or so and it's nice to see it in other fields. Let's not train in such and such manner simply because that's the way it's always been done! Thanks for sharing the data.

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Thu Jan 31, 2008 8:11 am

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Joined: Wed Jan 30, 2008 11:29 am
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What I have found is that most people don't tolerate high doses of C. Typically it leads to gastrointestinal stress in large doses. This keeps most of us away from megadosing!



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