Journal Articles

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Start date: 2024Subject: search.filters.subject.dietary protein

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    Editorial: Dietary protein for human health.
    (Frontiers Media S.A., 2025-01-15) Moughan PJ; Hendriks WH; Hodgkinson SM; Chungchunlam SMS; Lim WXJ; Mensink M; Stroebinger N; van der Wielen N; Pivovarova-Ramich O
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    Consideration of the role of protein quality in determining dietary protein recommendations
    (Frontiers Media S.A., 2024-11-13) Wolfe RR; Church DD; Ferrando AA; Moughan PJ; Grootswagers P
    The quality of a dietary protein refers to its ability to provide the EAAs necessary to meet dietary requirements. There are 9 dietary amino acids that cannot be metabolically produced in the body and therefore must be consumed as part of the diet to avoid adverse metabolic consequences. These essential amino acids (EAAs) serve a variety of roles in the body. The amount and profile of the dietary EAAs relative to the individual EAA requirements and the digestibility of the dietary protein are the key factors that determine its quality. Currently the Digestible Indispensable Amino Acid Score (DIAAS) is the best available approach to quantifying protein quality. The most prominent metabolic role of dietary EAAs is to stimulate protein synthesis by serving as signals to activate molecular mechanisms responsible for the initiation of protein synthesis and, most importantly, to provide the necessary precursors for the synthesis of complete proteins. Current dietary recommendations generally do not consider protein quality. Accounting for protein quality in dietary patterns can be accomplished while staying within established ranges for dietary protein consumption. Poor protein quality can be compensated for to some extent by eating more low-quality protein, but to be effective (“complementary”) the limiting EAA must differ between the low-quality protein and the base diet to which it is being supplemented. Adding a high-quality protein to a dietary pattern based on low-quality protein is more effective in meeting EAA goals than increasing the amount of low-quality protein, even if the low-quality proteins are complementary. Further, reliance entirely on low-quality protein food sources, particularly in circumstances that may benefit from a level of dietary EAAs greater than minimal requirements, is likely to include excessive caloric consumption. While protein consumption in high-income nations is generally perceived to be adequate or even excessive, assessment of dietary patterns indicates that a significant percentage of individuals may fall short of meeting optimal levels of EAA consumption, especially in circumstances such as aging in which the optimal EAA consumption is greater than basal values for healthy young individuals. The case is made that protein quality is an important consideration in meeting EAA requirements.
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    Effects of Different Protein Sources on Amino Acid Absorption and Plasma Appearance of Tryptophan, Large Neutral Amino Acids, and Tryptophan Metabolites in Pigs
    (Elsevier Inc on behalf of American Society for Nutrition, 2024-07-15) Giezenaar C; Montoya CA; Kreutz K; Hodgkinson S; Roy NC; Mace LJ; Fraser K; Fernstrom JD; McNabb WC; Moughan PJ
    BACKGROUND: Absorption of tryptophan (TRP) across the gut epithelium is potentially modulated by competing large neutral amino acids (LNAAs), which could affect the appearance of TRP and its metabolites in the bloodstream. OBJECTIVES: This study aimed to determine, in a growing pig model of an adult human, the absorption of TRP and other LNAAs from the gastrointestinal tract, and plasma appearance of TRP, LNAAs, and TRP metabolites, in response to dietary proteins varying in TRP content. METHODS: Pigs were adapted for 7 d to each of 4 diets that differed in their protein source and TRP content: 1) alpha-lactalbumin (AL; 9.95 mg TRP/g diet DM), 2) whey protein (6.59 mg TRP/g), 3) casein (3.73 mg TRP/g), or 4) zein (0.14 mg TRP/g). On day 8, pigs were euthanised after a 12-h fast (baseline), or 1, 2, 3, 4, or 6 h after they received a test meal consisting of 45 g protein, or a protein-free meal (n = 6 pigs at each time in each meal group). Tryptophan and LNAA absorption from the small intestine, and appearance of TRP, LNAAs, and TRP metabolites (melatonin, serotonin, kynurenine pathway metabolites), in the portal vein and systemic circulation, were determined. RESULTS: AL intake resulted in sustained elevated plasma TRP concentrations after an overnight fast. The amount of TRP absorbed was dose-dependently related to protein TRP content (P = 0.028), with fastest rates for pigs fed AL (371 mg/h). Portal and systemic plasma TRP, TRP/LNAA, and the TRP metabolites were highest (P ≤ 0.05) after AL intake, and remained above baseline levels for ∼4 h postprandially. Absorption rates of TRP correlated with postprandial plasma TRP and TRP metabolites (P ≤ 0.05). CONCLUSIONS: In adult humans, postprandial plasma TRP and TRP metabolite concentrations can likely be modulated by the TRP content of the meal.