hGH and Arginine Confusion

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Who are we to believe??

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J Gerontol A Biol Sci Med Sci 1999 Aug;54(8):M395-9

Oral arginine does not stimulate basal or augment exercise-induced

GH secretion in either young or old adults.

Marcell TJ, Taaffe DR, Hawkins SA, Tarpenning KM, Pyka G, Kohlmeier

L, Wiswell RA, Marcus R.

Dept of Exercise Science, University of Southern California, LA, USA.

BACKGROUND: Growth hormone (GH) helps maintain body composition and

metabolism in adults. However, basal and peak GH decline with age.

Exercise produces a physiologic GH response that is subnormal in

elderly people. Arginine (Arg) infusion can augment GH secretion,

but the efficacy of oral Arg to improve GH response to exercise has

not been explored. We investigated whether oral Arg increases GH

secretion in young and old people at rest and during exercise.

METHODS: Twenty young (Y: 22.1 ± 0.9 y; SEM) and 8 old (O: 68.5 ±

2.1 y) male and female subjects underwent three different trials

following determination of their one-repetition maximum strength (1-

RM); exercise only (EO; 3 sets, 8-10 reps at 85% of 1-RM; on 12

separate resistive lifts), Arg only (5.0 g), or Arg + exercise.

Blood samples were collected between successive lifts, and GH (ng x

ml(-1)) was determined via RIA.

RESULTS: In Y vs O: Basal GH secreted (area under the curve) was

543.6 ± 84.0 vs 211.5 ± 63.0. During EO, values were

986.6 ± 156.6 and 517.8 ± 85.5. Both were significantly lower

in the older individuals. Oral Arg alone did not result in any increase

in GH secretion at rest (310.8 ± 73.2 vs 262.9 ± 141.2). When Arg

was co-administered during exercise, GH release was not affected in

either the young or old and appeared to be blunted in the young

compared with the exercise only trial in the young.

CONCLUSION: Based upon these findings, we concluded that oral Arginine

does not stimulate GH secretion and may impair GH release during

resistive exercise.

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Int J Sport Nutr 1997 Mar;7(1):48-60

Acute effect of amino acid ingestion and resistance exercise on

plasma growth hormone concentration in young men.

Suminski RR, on RJ, Goss FL, Arslanian S, Kang J, DaSilva S,

Utter AC, Metz KF.

Human Performance Laboratory, University of Houston, TX 77204, USA.

Sixteen men completed four trials at random as follows: (Trial A)

performance of a single bout of resistance exercise preceded by

placebo ingestion (vitamin C); (Trial ingestion of 1,500 mg L-

arginine and 1,500 mg L-lysine, immediately followed by exercise as

in Trial A; (Trial C) ingestion of amino acids as in Trial B and no

exercise; (Trial D) placebo ingestion and no exercise. Growth

hormone (GH) concentrations were higher at 30, 60, and 90 min during

the exercise trials (A and compared with the resting trials (C

and D) (p < .05). No differences were noted in [GH] between the

exercise trials. [GH] was significantly elevated during resting

conditions 60 min after amino acid ingestion compared with the

placebo trial.

It was concluded that ingestion of 1,500 mg arginine and 1,500 mg

lysine immediately before resistance exercise does not alter

exercise-induced changes in [GH] in young men. However, when

the same amino acid mixture is ingested under basal conditions, the

acute secretion of GH is increased.

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Parks

Phoenix, AZ