title: Acute effects of fructose and glucose ingestion with and without caffeine in young and old humans.
abstract: Aging is associated with a decline in energy expenditure (EE), glucose intolerance, and a reduction in body nitrogen content. In addition, a reduction in the thermic response to glucose but not to fructose or protein has been reported in the elderly. The present study was conducted to further examine nutrient-induced thermogenesis and the effects of specific sugars on amino acid metabolism in relation to age. After 3 days on a weight-maintaining, 250-g carbohydrate diet, 16 healthy non-obese men and women in two age groups (18 to 29 and 66 to 80 years) consumed on 4 different days 500 mL of either a 75-g fructose or 75-g glucose solution, with or without 300 mg caffeine or vitamin C as a placebo. Blood substrate and hormone levels and EE, using indirect calorimetry, were measured at timed intervals for 3 hours after consumption of the drinks. There was no difference in the carbohydrate-induced increase in EE in either young or old even after adjustments for body weight and fat-free mass (FFM). An approximately 20-fold increase in serum caffeine levels increased EE in both groups (P < .003), but had minimal effects on substrate and hormone responses. In contrast to glucose, fructose induced a marked elevation in plasma alanine from combined basal levels of 301 +/- 24 to approximately 500 +/- 18 mumol/L (mean +/- SEM) in both groups (P < .001). However, both fructose and glucose ingestion resulted in a similar decline in branched-chain and aromatic amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Clinical Research Center, Massachusetts Institute of Technology, Cambridge, USA.
authors.forename: N K
authors.initials: NK
authors.lastname: Fukagawa
authors.forename: H
authors.initials: H
authors.lastname: Veirs
authors.forename: G
authors.initials: G
authors.lastname: Langeloh
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D000409:Alanine / Q000097:blood; D000704:Analysis of Variance; D001786:Blood Glucose / Q000378:metabolism; D001833:Body Temperature Regulation / Q000187:drug effects* / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology*; D004347:Drug Interactions; D004734:Energy Metabolism / Q000187:drug effects*; D005260:Female; D005632:Fructose / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005632:Fructose; D002110:Caffeine; D005947:Glucose; D000409:Alanine