Preexercise meal composition alters plasma large neutral amino acid responses during exercise and recovery

Preexercise meal composition amino acid responses during Gregory

L Paul,

ABSTRACT of ingesting exercise

and

and

food

intake

insulin

was

of tryptophan for

ratio

increased but

and

also

measured.

for

all

from

exercise

subjects,

but

recovery

period

preexercise

(LNAAs) the for

food

not different

but these

cognitive

values

in

fasting

acids,

Central exercise,

fatigue,

We conclude

that

cognitive

function,

neutral

INTRODUCTION Interrelations among (LNAA) concentrations, 25

demonstrated y ago.

tion,

by

In response

plasma

diet, plasma and brain Fernstrom

and

to either

carbohydrate

tryptophan

respectively,

large neutral amino serotonin synthesis

compared

with

(1,

Wurtman

concentrations

acid were 2) nearly

or protein

increase

concentrations

inges-

or decrease, of

the

other

LNAAs leucine, isoleucine, valine, methionine, phenylalanine, and tyrosine (1-6). LNAAs competitively bind to the L-carrier system at the blood-brain barrier (7, 8). Because LNAA transport kinetics and physiologic concentrations are similar (7, 8), an elevated plasma tryptophan concentration relative to the other LNAAs will

favor

brain

tryptophan

droxylase,

the rate-limiting

has

capacity

a high

iologic

phan 778

tryptophan

uptake,

and

uptake.

step does

concentrations

an event

regulated

not

Moreover,

for brain

tryptophan

serotonin

amount

approach (7,

9).

by the ratio

saturation Thus,

at phys-

tryptophan tivity

after

of

feeding

the and

should ratio

Factors

consumed

bound

such

(13)

to albumin increase

to LNAA,

to fatigue to

via

and

decreases

(16)

which

is thought

elevations

in brain

fatigue

and

by

as the the

sol-

is

suggested

to

ratios,

physical

as plasma

plasma

BCAA

oxidation the ratio

to heighten (20).

negatively

and

of

affect

Hyperexercise

(20). meal

mental

rates free

the sensi-

serotonin

performance and is termed “central fatigue” The effects of consuming a preexercise

on

plasma

performance,

and mood are poorly understood. To date, attempts to abate tryptophan-LNAA ratios during exercise have focused on maintaining plasma LNAA concentrations through supplementation with BCAAs (21-23). However, only one study was performed in a controlled environment, and measurements of cognitive

function

Furthermore,

LNAA pose

to

ratio

and our

study

preexercise

meals

mood

states

knowledge,

changes

of this

during was

no

recovery

to investigate

with

various

were

not

data

exist

from the

reported on

exercise. effect

macronutrient

(21).

tryptophan-

The

pur-

of consuming and

fiber

profiles

on plasma responses of tryptophan and the other LNAAs. We theorized that meal composition would alter postprandial plasma insulin responses. A lower plasma insulin response I

ology, 2

From

the

Division

University

Supported

of Nutritional

of Illinois, by The Quaker

3 Address reprint requests Goodwin, Urbana, IL 61801.

trypto-

Received

September

trypto-

Accepted

for

Nutr

uptake isoleucine,

tryptophan-LNAA

concentrations.

concentrations

brain

J C/in

in the

of carbohydrate

of tryptophan acid

of plasma Am

muscle leucine,

concentrations fall as skeletal muscle BCAA increase (1 7-1 9). These responses increase

hy-

synthesis,

the rate-

tryptophan-LNAA

hyperinsulinemia BCAA

tryptophan-LNAA

appetite

skeletal (BCAAs)

changes

plasma

and

fatty

large

is considered The

uble fiber, fat, and protein contents of the meal (14, 15) all reduce insulin responses after feeding. In addition to diet, prolonged exercise also perturbs the tryptophan-LNAA ratio. During endurance exercise the amount

tryptophan,

LNAAs, synthesis.

Minimizing attenuate

sensitivity

WORDS

first

type

of the

were not sufficient to Am J C/in Nutr

performance.

(2).

maintaining

fasted

before,

serotonin

insulin-stimulated amino acids

therefore

end

in

tryptophan:LNAA

changes

wheat

recovery,

at the

groups.

affected

and

During

greater

measured

among

was

of the other

in

through

valine

ratio

for corn

the fasting

were

intake

the

K Layman

ratio is clinically relevant because elevated ratios are associated with increased sleepiness ( 10), depressed hunger and altered food selection ( 1 1 ), and behavior (12). Carbohydrate ingestion increases the tryptophan-LNAA rabranched-chain

tryptophan-LNAA

unaffected.

ratings

consumption and

whereas

step

tio

plasma

Donald

to the sum

obtained

self-selected

or corn

postexercise

fatigue

and after exercise,

amino

values from

and

when

trial

and

limiting

function,

were

ingestion,

acids

was

consisting

A fasting

meal

exercise,

preexercise

was

alter physical l996;64:778-86.

KEY

amino

During

self-selected meal

wheat

to central

cognitive

recovery

After

performance

hunger

meals

measurements

for

neutral

with

cycling. and

during

than

increased

Also,

during,

oat

others.

tryptophan:LNAA trials.

samples

during

perturbations

A Boileau,

phan

effect

the

associated isoenergetic

sleepiness

to large

than

trials,

Blood

Richard

metabolism

metabolic

90 mm before

feeding

lower

less

to relate

consumed

and

was

to determine

on energy

measurements

control.

after

designed

L Dykstra,

1996;64:778-86.

Printed

publication

in USA.

12,

Sciences

and

Urbana. Oats Company, to

GL

E-mail:

Paul,

Department

Barrington, 438

Bevier

of KinesiIL.

Hall,

905

South

[email protected].

1995. June

© 1996

28,

1996.

American

Society

for Clinical

Nutrition

Downloaded from www.ajcn.org by guest on July 13, 2011

before

and

subjects

hunger,

Gregory

meals

or corn cereals

the

perceived

was

objective

Twelve

of oat, wheat, as

study

preexercise

recovery

and

served

T Rokusek,

This

three

subjective fatigue.

Joan

alters plasma large neutral exercise and recovery13

MEAL

would ing

minimize

perturbations

exercise,

and

thus

affected

mental

in tryptophan-LNAA

improve

ing sensitivity to fatigue. whether tryptophan-LNAA acuity,

FEEDINGS

physical

satiety,

or both

PLASMA

dur-

2.1%

fat,

third

of

ratios

performance

A second objective ratio responses

ALTER

by reduc-

or after

and

account

exercise.

breakfast.

AND

METHODS

characteristics are subject participation disorders

subjects capacity

provided were

including

(six men and six women) with served as subjects. Subject in Table 1. Exclusion criteria for

as

follows:

diabetes,

a history

hyperlipidemia,

of

was

metabolic

or thyroid

of the subjects

and

approved

University provided

Preliminary

by the

Institutional

dys-

9

exercise

test

themselves

to

minimum

the

demands

of three

separate

subjective

questionnaires

returned

ments

in test

road

the

performance

occasions

subjects

and were

bikes

affixed

ride.

On

until

a

all

cognitive/psychomotor

the tests

to

Chicago) and Subjects comstate workloads and to orientate completed

tests.

no further

improve-

observed.

protocol is provided in Figure into four time periods: a 90-mm

period, 90 a 6.4-km

mm of steady timed performance

state

exercise ride, and

1. The preex-

at 60% a 60-mm

of re-

covery period. At 1900 on the evening preceding each experiment, subjects consumed a standardized meal that was prepared for them from commercially available food that contained a mean (± SD) of 56 ± 3.1% carbohydrate, 27 ±

TABLE Subject

1 characteristics’ Males

6)

(n Age

(y)

Body weight (kg) Height (cm) Body surface area (m2) VO2,,, (Umin) (nit ‘

:

± SD.

kg’ /O2p,ak

.

min) peak

24.0

±

75.7 182.2 1.97 4.50

±

58.3 oxygen

Females

±

2.0 25.8 ± 4.4 8.7 58.9 ± 5.5 4.5 167.5 ± 7.9 0.1 1 1.65 ± 0.10

24.9 ± 3.4 67.3 ± I 1.2 174.9 ± 9.8 1.81

± 0.19

± 0.26

2.97

± 0.29

3.74

± 0.85

± 5.1

50.6

±

4.3

54.4

±

±

uptake.

6.0

h before

one-

which

expenditure 24) by

was

(accord1 .1 and 2 to

exercise, respecthen fasted until

testing,

into

a forearm

vein.

Catheters

periodically

with

I mL

10 000

of the experimental provided 645 and

respectively.

1540

subjects

avoided

were U

kept

patent

by

heparin/L

(USP)

±

71

and

The

total

1 176

±

In addition,

meal

582

mean 63

a fasting

kJ

was kJ/m2

(± for

based

in

SD) males

trial

served

on body

for males and energy intake and

females,

as the

control.

speed.

Financial

incentives

were

tied

to the

time

complete the performance ride, and subjects were results until all trials were completed. A 60-mm period followed the performance ride. Subjects seated

throughout

vided

at 15 and

35 mm.

Data

collection

and

Blood 12)

(n

36

provided

Treatments were administered at l-wk intervals in a singleblind, Latin-square design, and subjects served as their own controls. A sham trial using an oat-based ready-to-eat cereal was unknowingly completed by each subject as their first trial to minimize learning effects and to allow for final adjustments of meal energy and exercise workloads. A 90-mm preexercise period followed meal ingestion. Subjects were permitted to move freely about the test center for the initial 45 mm, but remained seated thereafter. After calibrating the Velodyne Trainers (for 3-5 mm), subjects cycled for 90 determined to elicit 60% of VO2ak. To mm at a workload minimize heat stress and dehydration effects on exercise performance, all trials were conducted at ambient temperature (23 #{176}C), and subjects consumed 3.5 mL water/kg after 24, 45, and 66 mm and 1.75 mL water/kg after 87 mm of exercise. Immediately after they finished the 90-mm ride, subjects completed a 6.4-km performance ride. During this test, subjects were aware only of the distance traveled. Subjects were free to change gears at will, and power output varied with cycling

Combined

6)

(n

energy equation;

effects of food and the meal by 1930,

the

component area, and

females, was

procedures

The experimental protocol was divided VO2pak,

of

to practice

scores

Experimental

ercise

all

experimental treatment, were determined dur-

on standard

energy

requirement,

salinelL.

g

cereal surface

testing

a progressive

inserted

respectively.

Velodyne Trainers (Schwinn Bicycle Company, standard open-circuit spirometric techniques. pleted a second test ride to ensure that steady calculated to elicit 60% of VO2p,ak were correct

Subjects

and

Meal

energy

Subjects then received one of three experimental meals (Table 2) containing either wheat or corn as ready-to-eat cereals or oats as oatmeal, skim milk (I 25 mL for males, 95 mL for females), 4 g sucrose, and water (equivalent to the amount required to cook the oatmeal). The energy provided by the

Board

of Illinois at Urbana/Champaign, informed consent.

Beginning 2 wk before the first subjects’ peak oxygen uptakes (VO2,) ing

Review

protein.

daily

85

mm

recovery,

samples after

water

(3.5

mLlkg)

to

blinded to recovery remained was

pro-

analyses

(10 mL)

breakfast,

and

required

were after

collected 42

and

on catheter 84

mm

of

insertion, steady

state

exercise, immediately after completion of a 6.4-km performance ride, and at 30 and 60 mm of recovery (Figure 1). All blood samples were collected 15 mm after subjects assumed a seated position. Hematocrit changes were used to calculate percentage changes in plasma volume during exercise and recovery (28). Aliquots of plasma, collected from tubes contaming EDTA and centrifuged at 1800 X g and 4 #{176}C for 15

Downloaded from www.ajcn.org by guest on July 13, 2011

reviewed

During

flushing

function; a history of psychiatric illness including any eating disorders; a history of serious premenstrual distress; pregnancy; current prescription or nonprescription drug use; weight < 90% or > 120% of ideal body weight; typical consumption of > 200 mg caffeine/d; a history of lactose intolerance; and habitual abstention from breakfast. The experimental protocol was

1 .7%

alcohol, caffeine, and exercise. At 0700, subjects reported to the testing center and completed an initial questionnaire to chronicle their physical activity, sleep, and dietary habits for the preceding 36 h. Afterward, with subjects in a seated position, a 22-gauge flexible catheter

Subjects Twelve healthy adult above average aerobic

±

subject’s

for the thermic Subjects finished

tively.

SUBJECTS

17

the

779

ACIDS

calculated by multiplying resting ing to the revised Harris-Benedict

was to determine to meal ingestion

before

AMINO

780

PAUL

Cognitive

$

Tests

Body

El

AL

4!

I

4!

wt+

t t

Water? FIGURE ratings

1. Experimental

of perceived

mm,

were

acids

frozen

(NEFA

protocol.

Arrows

correspond

to the time

that

events

at -70

C kit;

#{176}C for subsequent

Wako

Pure

analysis

Chemical

of fatty

Industries,

containing

5

g sodium

dodecyl

standard).

After

(internal

were

precipitated

This

mixture

resulting

by adding was

300

was

and

mm

0.4 mmol

plasma

proteins

pL 50 g trichloroacetic mm, and 50 pL with phenylisothiocyanate

microcentrifuged

supernate

sulfatefL 15

for

derivatized

5

acidlL. of the

(29) and analyzed by HPLC (Waters, Marlborough, MA). This measurement technique produced intra- and interassay CVs of 1. 1 ± 1.2% and 2.3 ± 2.6%, respectively, for the LNAAs. Ratings of perceived exertion (30) were recorded at the end of the preexercise period, every 10 mm during steady state exercise,

and

at

1.6

and

4.8

km

of

the

performance

Serving

on a separate

TABLE

2

Selected

nutrient

profiles

sheet

of the

to reduce

the

preexercise

chance

portions

determined

ride.

Between the initial blood draw and the experimental meal, 65 mm after meal ingestion, and 45 mm after exercise, subjects completed a series of subjective state questionnaires and cognitive/psychomotor tests. Hunger and satiety ratings were determined from visual analog scales (3 1 ). Each question was presented

line

occurred.

pea’( oxygen

VO2ak,

consumption;

aware

were

before

calculated

and

that the meal

Statistical

was

after

from

the

being

individual

meal,

and

food

subjects

(ANOVA)

(SAS

version

6.0;

SAS

and energy analysis Institute,

(g) fiber (g) Insoluble (g)

Dietary

Cary,

Tryptophan Tyrosine

,

The preexercise

the corn

and

wheat

meal also included cereals

were also used for nutrient

(1),

1 1.5 0 0

15.0 0 0 0

3.3

1 .4

0

3.8

1.4

0.5

0.5

10.0

7.2

8.1

10.5

184

408

322

484

637

754

494

785

1031

265 508

I 15

184

100

200

243

527

346

387 112

148

200

339

172

387

508

243

551

418

537

706

138

4 g sucrose.

the oat cereal

profiles.

125 mL

0

29

(mg)

95 mL

711

(mg) (mg)

milk

Wheat

0.2 4.5

Methionine (mg) Phenylalanine (mg)

Valine

Oat

53.9 7.2 5.7

(g) (mg)

All

41.5 5.7 2.4

(g)

(mg)

NC).

54.7 0.7 0.5

Fat(g)

Leucine

intake were of variance

meals’

Carbohydrate

Isoleucine

un-

analyses

Skim

Protein

weights

were

measured.

Main effects for performance times determined by one-way repeated-measures

of answers

Corn

Soluble

RPE,

(2),

and

Corn,

oat, and wheat

the skim

milk

62

values

(Nutritionist

given

per MI (239 kcal)

III, N-Squared

Computing,

of cereal. Salem,

Macronutrients OR);

fiber

data

and amino (3).

References

acids

for

25-27

Downloaded from www.ajcn.org by guest on July 13, 2011

and insulin (Coat-A-Count radioimmunoassay; DiagProducts Corp, Los Angeles). For amino acid analysis, a lOO-pL aliquot of plasma was mixed 1:1 with a 0.1-mol HC1IL

solution

on the same

from one question influencing the rest. Self-rated indexes of sleepiness (Stanford Sleepiness Scale; 32) and mood state [Profile of Mood States (POMS); 33] were obtained next. The Digit Symbol Substitution lest (DSST; 34), Multiple Choice Reaction Time Task (35), and Divided Attention Task (35) were then completed to assess cognitive/psychomotor function. All tests were completed together within 15 mm in a room isolated from the exercise area, and testing order was preserved for each trial. After the recovery period, subjects selected freely from a wide variety of foods and beverages. Energy intake was calculated from the manufacturer’s information provided on the label or by a computerized nutrient analysis program (NUTRJTIONIST III, release 6.0; N-Squared Computing, Salem, OR).

Rich-

mond) nostic

norleucine/L

listed

exertion.

MEAL

FEEDINGS

ALTER

PLASMA

AMINO

781

ACIDS

1.2

other main effects were determined by two-way repeatedmeasures ANOVA. When a significant treatment or treatment X time interaction was observed, Fisher’ s least-significant-difference test was used to assess mean differences. Relations among dependent variables were assessed by using Pearson’s product-moment correlation. The level of signifias mean ± cance was set at P < 0.05, and all data are presented SEM unless otherwise noted.

-0--1.0

.-J 0

E

Corn

.

Wheat Oat

-0---

0.8

E

Fast

-A

U)

#{149}0 C)

0.6

>.

0.4

(U

RESULTS

E

Plasma

insulin

Plasma

fatty

0.2-

0

Plasma insulin concentrations were elevated in fed trials at the end of the preexercise period (Table 3) compared with the fasted trials; however, concentrations associated with oat ingestion were less than those for corn and wheat. No treatment differences were observed for plasma insulin concentrations during exercise or recovery (data not shown).

I

0.0 0 FIGURE cereal from

acids

2. Plasma

ingestion all

with

decline

responses

was

centrations

below

was

related

-0.41;

=

continued

both

mm. The

inversely

(r

P

to

preexercise

decline

tryptophan-LNAA

lower

than

ratio

all others

during

premeal

and

recovery

associated

at the

and

concentrations

end

with

of the

corn

(Figure creased

3). During exercise, the tryptophan-LNAA during the corn and wheat trials, but ratios

TABLE

3

Insulinemic

responses

to meal

time value,

and

values;

all

at

P

corn

ingestion

after corn,

recovery. 0.05

post

remained

lower

hoc

from

corre-

repeated-measures test).

ofNutrizion

than

or oat different

different

(two-way

Journal

wheat,

asignificantly

bsignificantly <

5

n 12. M, meal. (l996;l26:l378).

all others.

Although

and cognitive exertion

performance

and

ratings

of

Despite significant differences in tryptophan-LNAA ratios at the end of the preexercise period and during exercise and recovery, no treatment differences were found for performance ride times (637.7 ± 14.3, 631.7 ± 12.7, 632.2 ± 14.2, and 642.6 ± 15.7 5 for the fast, and corn, oat, and wheat meals, respectively), DSST scores, Divided Attention Task scores, Multiple Reaction Time Task scores (data not shown), or Ratings of Perceived Exertion (data not shown).

60

states

Mood

ingestion

preexercise

exercise

and a least-significant-difference with permission from the

Physical

were

after

fasting

perceived

to preexercise plasma insulin 0.003). Plasma LNAA con-

=

fatty acid concentrations

during

4

mean tryptophan-LNAA ratios ranged from 0.091 to 0.100 after steady state exercise, all values declined significantly to 0.084 or 0.085 in response to the performance ride. Plasma tryptophan-LNAA ratios increased during recovery, particularly in fasted subjects, in whom the final value exceeded all those observed before and during exercise.

At the end of the preexercise period, plasma tryptophan and other LNAA concentrations were greater after oat and wheat ingestion than after either corn or the fasting trial (Figure 3). This difference was most likely due to the amino acid content of the meals (Table 2). The different LNAA responses for the oat and corn trials were maintained throughout exercise and recovery. Preexercise feeding was associated with a decline in plasma LNAAs during the final 45 mm of exercise (Figure 3). concentrations

and

corresponding

ANOVA Reprinted

recovery.

This

3 (h)

POMS

period

ratio inassociated

confusion,

time

(POMS

scores and

effect

test)

for anxiety,

depression,

friendliness

only

for

revealed

fatigue

anger,

vigor,

a significant

(Table

4).

fatigue,

treatment

Subsequent

X

analysis

ingestion’

Treatment Time

Fast

Corn

Oat

Wheat

pmoL/L

7.2

Premeal

205.2

± 13.6

208.8

±

Preexercise

195.9

±

378.1

± 30.9

‘i±SEM;n= 2

and

Significantly

3

Significantly

7.2

200.2

±

299.2

± 10.8’

195.9

± 7.9

358.0

±

15.8

12. different

from

a least-significant-difference

ANOVA

932

different

all other post

from

hoc

corresponding

and a least-significant-difference

corresponding

time

values,

P < 0.05

(treatment

X

time interaction

from a two-way

repeated-measures

ANOVA

test). time

values

post hoc test).

of corn

and

wheat,

P < 0.05

(treatment

X

time

interaction

from

a two-way

repeated-measures

Downloaded from www.ajcn.org by guest on July 13, 2011

Meal consumption was associated with a significant decline in plasma fatty acid concentrations (Figure 2). Plasma fatty acid concentrations changed similarly among all treatments during steady state exercise in response to the performance ride and during recovery; however, fasting concentrations were greater than fed concentrations during exercise, but not during

LNAA

2

Time

sponding

Plasma

1

I.!!!?.!.!!!J

Exercise

782

PAUL

El

AL

ingestion

and

during

recovery,

fasted

perceived hunger and desire fullness than did fed subjects.

subjects

to eat

and

scored

lower

higher

for

for

stomach

-J 0

E

Energy meal

C CU

intake

and

macronutrient

profile

of self-selected

.C

Despite differences hunger, total energy

0

0. CU

E U)

CU

protein

intakes

differ

significantly

in subjective consumption,

at the

ratings associated with and carbohydrate, fat, and

self-selected

among

meal

after

recovery

treatments

(Table

effect

of consuming

did

not

7).

0

DISCUSSION This

study

0

E

:

z

-J

the

isoenergetic

E

CU

ingestion compared this would improve

with the physical

performance by helping to attenuate ratio responses. In humans, elevated

3-

have

been

0.105

23,

gestion z

0.100

-J C CU

and

0.090#{149} CU

0.085.

CU

0

0.080

0

1

2

3 Time

FIGURE

3.

(LNAA),

ingestion

and

Responses and

esignificantly

exercise time

different

from different

ed-measures

of plasma

most

likely

content.

plasma tryptophan-LNAA tryptophan-LNAA ratios

physical

and

mental

function

of fatigue ( I 2) and sleepiness and satiety ( 1 1 , 38). ratios observed after corn in-

related

to the meal

Martin-Du

Pan

of a protein-free

tryptophan

et al (4)

glucose

solution

content

reported

ANOVA

and

values, oat

other

large

ratio

corn,

wheat,

from and

after

recovery.

aSignificantly

bsignificantly

meal,

meal,

5

amino

fast,

from

all at P < 0.05

(two-way post

hoc

from

increased

slightly

(6%),

decreased

(3%),

respectively)

repeat-

n

=

direct has

affected

similarly

by

simple

or complex

is

effect a greater

ingested

with

of the tryptophan effect

on

a high-carbohydrate

and LNAA

changes

in plasma

content

that the recovery feeling of fatigue

score for the fasted trials indicated than did for all other test scores (P

a <

questionnaires

No

These

authors

differences

of hunger

existed

and

among

satiety

(C,, simple

Subjective ratings of sleepiness are shown in Table 5. No mean differences existed; however, the recovery score for the fasted trials tended to be greater than all others (P = 0.08 for treatment X time main effect). scores

finding.

fed

subjects

fed

(Table

trials

for

subjective

6). However,

rating

after

meal

and

complex

carbohydrate

meals,

the

tryptophan-LNAA

than does the indirect effect of insulin on lowering LNAA by stimulating skeletal muscle uptake (4). The results of Christensen and Redig (40) further this

carbo-

meal,

isoenergetic

protein, simple-carbohydrate, or complex-carbohydrate The protein content of the carbohydrate meals (16 and state

and

of the protein

ratio

Subjective

tryp-

meals (39), the data of Martin-Du Pan et al (4) and the study indicate that when a small amount of protein (an of 9, 1 5, and 12 g for corn, oat, and wheat meals,

average

meal,

test).

are

hydrate present

csignifi

corn

ratios

responses

or oat cereal

from

different

a least-significant-difference

neutral different

different

dsigificantly

wheat

4

12. M, meal.

showed greater 0.05)

that

increased

remained unchanged after wheat, corn, and oat ingestion, respectively. In addition, plasma tryptophan and LNAA concentrations increased after wheat and oat consumption, but did not change when corn was ingested. Because tryptophan-LNAA

(h)

tryptophan,

tryptophan-LNAA

during

corresponding

cantly

were

LNAA

LNAA Exercise

acids

impaired

or wheat cognitive

tophan-LNAA ratios 20% because of insulin-stimulated LNAA uptake by skeletal muscle. In the present study, the wheat and corn meals contained similar amounts of carbohydrate, and elicited postprandial insulinemic responses similar to those reported by Martin-Du Pan et al (4). However, tryptophan-

0

E Cl)

with

36),

consumption

0.095#{149}

.C 0.

reported

elevated perceptions ( 10), altered mood states (37), The lower tryptophan-LNAA (22,

corn and

respectively)

plasma support high-

meals. 10 g for was

nearly identical to the protein content of the meals ingested in the present study. Although carbohydrate content was doubled 130 g), postprandial plasma tryptophan-LNAA ratios were quite similar to ours. Unfortunately, these authors did not report plasma insulin values. However, if the meal carbohydrate content were related to changes in the tryptophan-LNAA

Downloaded from www.ajcn.org by guest on July 13, 2011

tions after meal cereals. In turn,

CU

Cl)

all

examined

cereal-based meals before exercise on plasma tryptophan and LNAA responses. It was postulated that soluble fiber and macronutrients in the oat cereal would attenuate the insulinemic response and subsequent fall in plasma BCAA concentra-

MEAL

TABLE

FEEDINGS

ALTER

PLASMA

AMINO

783

ACIDS

4

Subject

perceptions

of fatigue’ Treatment

Time

Fast

Corn

Oat

Wheat

Premeal

0.50

± 0.17

0.57

±

0.15

0.75

±

Preexercise

0.49

± 0.17

0.39

± 0.12

0.62

± 0.21

0.43

Postrecovery

1.42 ± 0.30

1.06

± 0. 19

1 . 12 ± 0.22

I 2

the Profile of Mood State questionnaire; from all others, P < 0.05 (treatment

Scores derived from Significantly different

difference

post

hoc

0.99

± 0.20

± SEM; n = X time interaction

and

tryptophan-LNAA

ratios

in

the

corn

trials

from

ues

site

(43).

tryptophan

Thus,

is bound

as fatty

acid

run

(16).

country

may

heighten

the

fatigue via elevations in brain serotonin (20). Plasma free tryptophan was not measured However,

Davis

increasing

et al (21)

reported

Addition-

concentrations

mmolIL)

and

plasma

of free

in the

a strong

plasma tryptophan

a BCAA

ratio

marathon

placebo into

and BCAA

faster

h). The

times

runners

rationale

until

3.05

h) and

selecting

these

not provided. Moreover, consumption of the idensolution by subjects competing in a 30-km crossfailed

to improve

run

times

(22).

Hence,

it appears

not influence tryptophan-

an

plausible among

inadequate

reasons why exercise perforgroups in the present study, in-

difference

among

plasma

tryptophan-

ratios and the nature of the performance ride itself. data indicate that brain serotonin concentrations do not

Animal

to

not

groups

(< for

(val-

were

ratios.

LNAA

increase

until

plasma

tryptophan-LNAA

ratios

have

doubled (2). Additionally, Ashley et al (5) cite unpublished data that indicate that a 50% rise in plasma tryptophan-LNAA

present

correlation

fatty

subdivided

There are several mance did not differ

sensitivity

ingested

tryptophan-LNAA

between

(3.05-3.30

race

LNAA

ratio

acids

significantly

increases

brain

5-hydroxyindoleacetic

acid

(a serotonin metabolite formed by the monoamine oxidase pathway), and that a 30% reduction in the ratio reduces brain serotonin concentrations. More recently, Fernstrom (44) suggested that a ratio change of 0.07 is required before physiologic effects are realized. The 4-7% increase in plasma tryptophanLNAA ratios during exercise in the present study (0.007 over

(‘=0.5-12

during exercise. In the present study, plasma fatty acid concentrations increased similarly to those reported by Davis et al (21); thus, plasma free tryptophan concentrations presumably also increased. Additionally, the decline in plasma LNAA concentrations during exercise likely increased plasma free tryptophan-LNAA ratios as well. Although tryptophan-LNAA ratios were different at the start of the exercise performance task, 6.4-km cycling times did not differ among treatments. This contradicts the only published

Subjective

a least-significant-

that BCAA supplementation during exercise does physical performance although it may influence

reliably

that

were

runners

plasma However,

different

cutoffs was tical BCAA

tryptophan-LNAA

ratio

reported).

times

slower

concentrations

to albumin

favorable

not

significantly

cluding

TABLE

and

subjects

when

a more were

ally, plasma LNAA concentrations can decrease during exercise as BCAAs are oxidized by skeletal muscle (18). Combined, these peripheral effects produce an elevated plasma

(“0.25-1.25 mol/L)

ANOVA

preexercise

values)

the differences Thus, although nificantly

brain

at the

serotonin

did

not

in ratios plasma time

come

close

to these

between treatments tryptophan-LNAA of

the

performance

concentrations

was

likely

values

nor

did

(10-15%, or 0.01). ratios differed sigride,

the

effect

on

minimal.

5

ratings

of sleepiness’ Treatment

Time

Fast

Corn

Oat

Wheat

Premeal

2.42 ± 0.21

2.58

± 0.31

2.83

± 0.32

2.67

± 0.26

Preexercise

2.00

± 0.40

1 .92

± 0.26

1 .92

± 0.26

1.92

±

Postrecovery

2.08

± 0.26

1.58

±

0.19

1.42

±

0.19

1.25

± 0.13

‘

Scores

significant

are

derived

differences

from among

the

Stanford

scores.

Sleepiness

Scale;

1 being

the

most

awake

and

7 being

the

most

sleepy.

i

± SEM;

n

=

I 2.

There

were

0.23 no

Downloaded from www.ajcn.org by guest on July 13, 2011

binding

between

repeated-measures

improvements

taming

ratio during performance (20). As exercise duration progresses, plasma fatty acid concentrations rise (41, 42). Fatty acids reduce the binding affinity of albumin for tryptophan by an allosteric modification of the

study.

a two-way

solution during a 42.2-km marathon competition. Compared with placebo ingestion, they found that the BCAA solution increased plasma BCAA concentrations by 140%, thus main-

An increase in plasma free tryptophan-LNAA exercise has been implicated as a factor limiting

less

12.

performance

were

concentrations.

increase,

± 0.14

report attempting to link changes in tryptophan and LNAA to exercise performance (22). Those authors reported physical

significantly lower than in all other trials. Throughout the entire experimental period for all treatments, fluctuations in plasma tryptophan concentrations had a far greater influence on tryptophan-LNAA ratios than did changes in plasma LNAA concentrations (Table 8). These data indicate that future attempts to control tryptophan-LNAA ratios should focus on regulating plasma tryptophan concentrations rather than LNAA

tryptophan

0.68 ± 0.15

test).

ratio, the tryptophan-LNAA ratios reported by Christensen and Redig (40) should have exceeded those reported here. During steady state exercise, plasma tryptophan concentrations

0.25

784

PAUL

TABLE

El

AL

6

Subjective

ratings

of hunger

and

satiety’

Treatment Question

How hungry Premeal

and

time

Fast

Corn

Oat

Wheat

do you feel right now?2

Preexercise

Postrecovery How full does Premeal

your

stomach

feel

right

± 0.71

5.26

5.13

±

0.72

4.77

± 0.56

6.43

± 0.63

1.32

± 0.23

1.52

± 0.30

1.73

± 0.36

7.16 ± 0.78

6.01

± 0.70

6.03

± 0.45

5.71

± 0.58

±

0.72

now?”

Preexercise

Postrecovery How strong is your desire

4.86

2.63

±

1.31

± 0.24

0.49

0.80

± 0343

1.76

2.74 6.52

± 0.54

0.62

2.41

± 0.61

2.85

±

6.19

± 0.62

6.64

± 0.38

± 0.26

2.44

±

0.42

2.19

±

± 0.34

0.43

to eat right now?5

Premeal

4.95

± 0.63

4.77

± 0.70

5.44

± 0.60

5.35

± 0.68

Preexercise

7.17

± 0.78

1.30

± 0.26

2.10

± 0.47

1.48

± 0.28

7.47

± 0.68’

5.94

± 0.66

5.82

± 0.46

5.61

± 0.65

5.48 ± 0.45 6.72 ± 0.50’ 7.34 ± 0.75

4.82

± 0.46

5.51

± 0.54

5.26

± 0.59

2.19

± 0.30

2.51

± 0.33

2.32

± 0.48

6.31

± 0.58

6.50

± 0.36

6.72

± 0.49

Postrecovery

How much do you think you could

eat right now?”

Premeal Preexercise Postrecovery

--;

±

n =

SEM;

Not

3

Significantly

12.

at all hungry

=

0,

different

least-significant-difference

and extremely from

all others

post

hoc

for that

=

Not at all full

0, and extremely

5

Not at all strong Nothing at all

=

question

full

=

at P < 0.05

(treatment

extremely strong = a large amount 10.

all

ratios

were

similar

maintained ever, the

TABLE

from

a two-way

repeated-measures

(0.084-0.085)

during the event by BCAA field nature of these tests,

statistical

groups, though

ANOVA

and

a

study,

comparison

between

supplementation. as well as the

placebo

and

Howlack of

experimental

casts doubt on the significance of these findings. Alcognitive performance was not affected in the present the

20%

increase

in tryptophan-LNAA

ratio

from

the

end of the performance ride to the end of recovery in fasted subjects was associated with a higher perception of fatigue (POMS score) and a lower rating of satiety compared with fed subjects. Lieberman et al (12) reported that 2 h after subjects ingested a large tryptophan dose (50 mg/kg body wt in pill form), POMS scores for fatigue were significantly higher than after a placebo trial, but cognitive performance was not impaired. The researchers did not provide tryptophan-LNAA ratios, but Ashley et al (5) reported that a similar tryptophan dose nearly doubled the plasma tryptophan-LNAA ratio, which can

immediately

after the ride. Therefore, brain tryptophan uptake and brain serotonin concentrations would theoretically have been similar among trials and performance time differences would not have been expected. Cognitive performance has been reported to increase after exercise (22, 23) when plasma tryptophan-LNAA ratios are

Total

interaction

10.

Physiologic responses to the 6.4-km performance task may have also precluded treatment effects. In response to the performance ride (Figure 3), plasma tryptophan concentrations decreased significantly across treatments despite a 15% average reduction in plasma volume. Plasma LNAA values increased only slightly, such that the net effect of the performance task was to significantly reduce plasma tryptophan-LNAA ratios. Note that despite the significant differences in preperformance ride plasma tryptophan-LNAA ratios,

X time

10.

0, and

0, and

10.

test).

4

6

hungry

7

energy

intake

and macronutrient

profiles

of the meal consumed

after the recovery

period’ Treatment

Energy intake (kJ) Carbohydrate (g) (% of energy) Fat (g)

(% ofenergy) Protein (g) (% of energy) ‘i±SEM;n

12.

Oat

Fast

Corn

6906 ± 636

701 1 ± 783

6655

Wheat

± 745

6764

242 ± 24 58.7 ± 1 .5

57.0

±

2.2

57.5

±

2. 1

57.9

57.5

± 6.0

60.0

± 6.9

57.9

±

7.3

31.4

± 1.5

33.2

± 2.3

33.2

± 2.2

41.4 ± 4.3 9.9 ± 0.8

42.4

± 5.6

36.6

± 4.5

± 0.4

9.3

241 ± 28

9.8

231 ± 27

±

0.6

± 557

237 ± 22 ±

2.1

56.0

±

5.1

31.8

± 2.3

41.4

± 4.5

10.2

±

0.7

Downloaded from www.ajcn.org by guest on July 13, 2011

2

MEAL

ALTER

PLASMA

AMINO

5. Ashley

TABLE

8

Changes

in plasma

correlate

with

amino

FEEDINGS

acids

tryptophan,

changes

but

in the

(LNAA)

ratio

not

plasma

large

of plasma

after a meal

neutral

amino

tryptophan-large

and during

exercise

DVM,

influences

acids,

Liardon

plasma

period

for the ratio change

and recovery’

90-mm

Exercise

Final

45

mm

LNAA

change

change

0.552

-0.28

period of the

Performance

90-mm

exercise

period

ride

Recovery Final

Tryptophan

to preexercise

Premeal

period

30 mm

of the recovery

period

0.672

-0.22

0.812

-0.02

0.942

-0.11

0.772

-0.1

0.842

-0.08

7. Bender

Pearson

tryptophan

LNAA plasma nine,

product-moment

2p

other

large

leucine,

neutral

valine,

amino

and

acids

1

change

(phenylala-

Rev

in new of

glucose

In:

dietary

DJA,

ceptionally

energy

intakes,

overriding

16.

in fasted

the

stronger

a fast;

however,

these

differences

did

not

other

acid

S.

New

dietary

availability

ed.

York:

influences

on

to the brain.

In:

on appetite

Amino

Alan

acids

R Liss,

Inc.

on

J. Postprandial complex

and food

in

health

and

1987:403-19.

Ri, Growden

precursors

different

19.

TMS,

blood

human

JH. The behavior.

plasma

insulin

carbohydrates.

Nutr

l98l;34:362-6.

Curzon

G, Friedel

Barker

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Diabetes

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PJ. The

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exercise performance. After 1 h of recovery, tryptophan-LNAA ratios normalized when a preexercise meal was consumed, but peaked if subjects fasted. This peak tryptophan-LNAA ratio was associated with increased feelings of fatigue and hunger, but cognitive function was not impaired. We conclude that the small amount of protein in the meals influenced plasma tryptophan and LNAA responses such that the changes in tryptophan-LNAA ratio were insufficient to effect physiologic or psychologic function. Finally, this study shows that preexercise meal composition can affect plasma tryptophan and LNAA concentrations during the early absorptive period. Because the concentration differences were maintained throughout exercise, it appears that dietary amino acid patterns could be manipulated to elicit desired physical responses once a physiologically efficacious pattern is identified. U

by type of

l988;47:433-9.

l986;38:82-6.

of tryptophan

Kaufman

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of

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