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[A1CR]

The title to the paper below appears to summarize the
salient findings.

Rankin JW, Shute M, Heffron SP, Saker KE.

Energy restriction but not protein source affects
antioxidant capacity in
athletes.

Free Radic Biol Med. 2006 Sep 15;41(6):1001-9. Epub 2006 Jul 4.
PMID: 16934684

Abstract:

The primary purpose of this study was to examine the effect
of energy restriction on antioxidant capacity in trained
athletes. Secondly, our study determined whether dietary
protein source influenced the antioxidant response,
performance, and immunity. Twenty male cyclists consumed
either whey or casein supplement (40 g/day) in addition to
their diet for 17 days. All subjects subsequently underwent
4 days of energy restriction using a formula diet (20
kcal/kg) while continuing protein supplementation. Energy
restriction caused 2.7 +/- 0.3 kg weight loss, increased
lymphocyte total glutathione (tGSH) 37%, red blood cell
glutathione peroxidase 48%, plasma cysteine 12%, and
decreased whole blood reduced to oxidized GSH (rGSH/GSSG)
ratio by 52%. The only immunity factor altered by energy
restriction was an increase in stimulated phagocytosis
(65%). Acute submaximal exercise reduced blood tGSH but
increased glutathione peroxidase. Performance of a high
intensity cycle test following 45 min of moderate exercise
tended to be reduced by energy restriction (P = 0.06) but
was unaffected by protein source. Energy restriction caused
a negative nitrogen balance with no difference from dietary
protein source. In conclusion, acute energy restriction
increased plasma cysteine and several markers of the
glutathione antioxidant system in trained athletes. A high
cysteine dietary protein source did not influence these
responses.

Excerpts:

... trained athletes. ... whether dietary protein
source influenced the
antioxidant response, performance, and immunity. Twenty male
cyclists
consumed either whey or casein supplement (40 g/day) in
addition to their
diet for 17 days. All subjects subsequently underwent 4 days
of energy
restriction using a formula diet (20 kcal/kg) while
continuing protein
supplementation. Energy restriction caused 2.7 +/- 0.3 kg
weight loss,
increased lymphocyte total glutathione (tGSH) 37%, red blood
cell
glutathione peroxidase 48%, plasma cysteine 12%, and
decreased whole blood
reduced to oxidized GSH (rGSH/GSSG) ratio by 52%. The only
immunity factor
altered by energy restriction was an increase in stimulated
phagocytosis
(65%). Acute submaximal exercise reduced blood tGSH but
increased
glutathione peroxidase. Performance of a high intensity
cycle test following
45 min of moderate exercise tended to be reduced by energy
restriction
(P=0.06) but was unaffected by protein source. Energy
restriction caused a
negative nitrogen balance with no difference from dietary
protein source. In
conclusion, acute energy restriction increased plasma
cysteine and several
markers of the glutathione antioxidant system in trained
athletes. A high
cysteine dietary protein source did not influence these
responses.

Abbreviations: CAS, casein-supplemented group; CD3+, T
cells; CD4+,
T-helper cells; CD8+, T cytotoxic cells; REST, EXER, EXH,
times of blood
withdrawal as part of exercise test, represents priorafter
45 min submaximal
exercise, and after the maximal performance test,
respectively; rGSH,
reduced glutathione; GSSG, oxidized glutathione; GPx,
glutathione
peroxidase; LPO, lipid peroxides; NAC, N-acetylcysteine;
tGSH, total
glutathione; RBC, red blood cell; ROS, reactive oxygen
species; EBAL, trial
1, during energy balance; NEG, trial 2, during negative
energy balance;
VO2peak, peak oxygen consumption; WHEY, whey-supplemented group.
... purposeful energy restriction and weight loss ...
boosted the
dietary intake of cysteine using whey protein ... increase
in GSH of ...
athletes [9]. ... boost GSH because ... performance is
impaired by ... ROS
... connection ... and ... fatigue ... Glutathione
concentration ...
implicated in immune function ...

... cycling for ... over 100 miles per week, between
the ages of 19 and
29 years ... randomized to either a nonhydrolyzed whey
protein isolate ...
(WHEY, n=10) or isoenergetic, isonitrogenous placebo
(nonhydrolyzed casein,
CAS, n=10) ... experimenters and subjects were blinded ...
40 g/day of
protein ... Days 18-21 ... energy-restricted ... for all
subjects. ... 20
kcal kg/day of Ensure ... 63.9% carbohydrate, 14.1% protein,
22% fat ...
continued their protein supplement ... represented
approximately 50% of
their energy needs. The protein supplement ... approximately
25% of total
protein intake during the weight maintenance period and 46%
during the
energy restriction phase. ... cysteine content of [Ensure]
... very low
(0.00032 g >>> 2.4-fold difference in daily cysteine
consumption by WHEY and
CAS.

[...]

... It is possible that a longer supplementation
period would have an
impact on tGSH as [the free full text
http://tinyurl.com/efp4h paper] used a
3-month supplementation period. ... Physical performance
tended to be
impaired by energy restriction. ... Product and partial
financial support
were provided by AmmunoMed Llc., Toledo, Ohio. Other funding
sources
included the Gatorade Sports Science Institute.