Effects of An Oral Mixture Containing Glycine, Glutamine and Niacin on Memory, GH and IGF-I Secretion in Middle-aged and Elderly Subjects

Authors: Arwert, L.I.; Deijen, J.B.; Drent, M.L.

Source: Nutritional Neuroscience, Volume 6, Number 5, October 2003 , pp. 269-275(7)

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Abstract:

Aging is associated with declining activity of the growth hormone-insulin-like growth factor-I (GH-IGF-I) axis and with a decrease in cognitive function. The stimulatory effect of an orally administered nutritional supplement, mainly containing glycine, glutamine and niacin on the GH-IGF-I axis and on mood and cognition was investigated. Forty-two healthy subjects (14 men and 28 women, aged 40-76 years) were enrolled in a randomised, double blind, placebo-controlled trial. They received 5 g of a nutritional supplement or placebo, twice daily orally for a period of 3 weeks. At baseline and after 3 weeks, blood was collected for measurement of serum GH and IGF-I levels and mood and cognitive function were tested. The nutritional supplement ingestion for 3 weeks was found to increase serum GH levels with 70% relatively to placebo, whereas circulating IGF-I levels did not change. Mean GH (�SD) increased in this group from 3.23 (�4.78) to 4.67 mU/l (�5.27) (p=0.03). GH increase was not associated with improvement in mood or memory. Correlation analyses, however, revealed that individual increases in IGF-I, but not GH, were associated with improved memory and vigour. It is concluded that an oral mixture of glycine, glutamine and niacin can enhance GH secretion in healthy middle-aged and elderly subjects.

Keywords: Growth hormone; Glutamine; Glycine; Insulin-like growth factor-I; Niacin; Cognition

Document Type: Research Article

DOI: http://dx.doi.org/10.1080/10284150310001612195

Publication date: 2003-10-01

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