title: Acute effects of breakfasts containing alpha-lactalbumin, or gelatin with or without added tryptophan, on hunger, 'satiety' hormones and amino acid profiles.
abstract: Proteins are the most satiating macronutrients. Tryptophan (TRP) may contribute to the satiating effect, as it serves as a precursor for the anorexigenic neurotransmitter serotonin. To address the role of TRP in the satiating properties of dietary protein, we compared three different breakfasts, containing either alpha-lactalbumin (high in TRP), gelatin (low in TRP) or gelatin with added TRP (gelatin+TRP, high in TRP), on appetite. Twenty-four subjects (22-29 kg/m2; aged 19-37 years) received a subject-specific breakfast at t = 0 with 10, 55 and 35 % energy from protein, carbohydrate and fat respectively in a randomised, single-blind design. Hunger, glucagon-like peptide (GLP)-1, ghrelin, amino acid concentrations and energy intake during a subsequent lunch were determined. Suppression of hunger was stronger 240 min after the breakfast with alpha-lactalbumin compared with gelatin and gelatin+TRP. Total plasma amino acid concentrations were lower with alpha-lactalbumin compared with gelatin with or without TRP (from t = 180-240 min). TRP concentrations were higher after alpha-lactalbumin than after gelatin with or without TRP from t = 0-100 min, whereas from t = 100-240 min, TRP concentrations were lower after gelatin than after alpha-lactalbumin and gelatin+TRP. The plasma ratio of TRP to other large neutral amino acids (LNAA) was, only at t = 100 min, lower after gelatin+TRP than after the other breakfasts. Plasma amino acid responses, TRP concentrations and TRP:LNAA ratios were not correlated with hunger. GLP-1 and ghrelin concentrations were similar for all diets. Energy intake during a subsequent lunch was similar for all diets. Summarised, an alpha-lactalbumin breakfast suppresses hunger more than a gelatin or gelatin+TRP breakfast. This cannot be explained by (possible) differences found in TRP concentrations and TRP:LNAA ratios in the breakfasts and in plasma, as well as in circulating total amino acids, GLP-1 and ghrelin.
authors.affiliation: Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht, Maastricht University, PO Box 616, Maastricht 6200 MD, The Netherlands. a.nieuwenhuizen@hb.unimaas.nl
authors.forename: Arie G
authors.initials: AG
authors.lastname: Nieuwenhuizen
authors.forename: Ananda
authors.initials: A
authors.lastname: Hochstenbach-Waelen
authors.forename: Margriet A B
authors.initials: MA
authors.lastname: Veldhorst
authors.forename: Klaas R
authors.initials: KR
authors.lastname: Westerterp
authors.forename: Mariëlle P K J
authors.initials: MP
authors.lastname: Engelen
authors.forename: Robert-Jan M
authors.initials: RJ
authors.lastname: Brummer
authors.forename: Nicolaas E P
authors.initials: NE
authors.lastname: Deutz
authors.forename: Margriet S
authors.initials: MS
authors.lastname: Westerterp-Plantenga
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000097:blood; D019540:Area Under Curve; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D005780:Gelatin / Q000008:administration & dosage*; D052216:Glucagon-Like Peptide 1 / Q000097:blood; D006801:Humans; D006815:Hunger / Q000502:physiology*; D007768:Lactalbumin / Q000008:administration & dosage*; D008297:Male; D012044:Regression Analysis; D012528:Satiety Response; D016037:Single-Blind Method; D014364:Tryptophan / Q000008:administration & dosage* / Q000097:blood; D055815:Young Adult
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D052216:Glucagon-Like Peptide 1; D014364:Tryptophan; D005780:Gelatin; D007768:Lactalbumin