Journal Articles

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    Achieving High Protein Quality Is a Challenge in Vegan Diets: A Narrative Review.
    (Oxford University Press, 2024-12-11) Soh BXP; Smith NW; von Hurst PR; McNabb WC
    The transition toward plant-based (PB) diets has gained attention as a plausible step toward achieving sustainable and healthy dietary goals. However, the complete elimination of all animal-sourced foods from the diet (ie, a vegan diet) may have nutritional ramifications that warrant close examination. Two such concerns are the adequacy and bioavailability of amino acids (AAs) from plant-sourced foods and the consequences for older vegan populations who have elevated AA requirements. This narrative review describes the challenges of achieving high protein quality from vegan diets. Data were synthesized from peer-reviewed research articles and reviews. Plant-sourced proteins provide poorer distribution of indispensable AAs (IAAs) and have poorer digestibility, partly due to their inherent structural components within the food matrix. The review addresses complexities of combinations of varied plant protein sources and why the inclusion of novel PB alternatives adds uncertainty to the achievement of adequate protein adequacy. Meal distribution patterns of protein and the ensuing physiological impacts deserve further research and are outlined in this review. Particular attention is given to describing the challenges of achieving sufficient protein and IAA intakes by aging populations who choose to follow a vegan diet. This review contributes to the emerging discussions of nutritional risks associated with vegan diets and adds perspective to the current dietary shifts toward PB diets.
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    Protein Intake at Twice the RDA in Older Men Increases Circulatory Concentrations of the Microbiome Metabolite Trimethylamine-N-Oxide (TMAO)
    (MDPI (Basel, Switzerland), 2019-09-12) Mitchell SM; Milan AM; Mitchell CJ; Gillies NA; D'Souza RF; Zeng N; Ramzan F; Sharma P; Knowles SO; Roy NC; Sjödin A; Wagner K-H; Zeisel SH; Cameron-Smith D
    Higher dietary protein intake is increasingly recommended for the elderly; however, high protein diets have also been linked to increased cardiovascular disease (CVD) risk. Trimethylamine-N-oxide (TMAO) is a bacterial metabolite derived from choline and carnitine abundant from animal protein-rich foods. TMAO may be a novel biomarker for heightened CVD risk. The purpose of this study was to assess the impact of a high protein diet on TMAO. Healthy men (74.2 ± 3.6 years, n = 29) were randomised to consume the recommended dietary allowance of protein (RDA: 0.8 g protein/kg bodyweight/day) or twice the RDA (2RDA) as part of a supplied diet for 10 weeks. Fasting blood samples were collected pre- and post-intervention for measurement of TMAO, blood lipids, glucose tolerance, insulin sensitivity, and inflammatory biomarkers. An oral glucose tolerance test was also performed. In comparison with RDA, the 2RDA diet increased circulatory TMAO (p = 0.002) but unexpectedly decreased renal excretion of TMAO (p = 0.003). LDL cholesterol was increased in 2RDA compared to RDA (p = 0.049), but no differences in other biomarkers of CVD risk and insulin sensitivity were evident between groups. In conclusion, circulatory TMAO is responsive to changes in dietary protein intake in older healthy males.
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    Ageing Is Associated with Decreases in Appetite and Energy Intake--A Meta-Analysis in Healthy Adults.
    (7/01/2016) Giezenaar C; Chapman I; Luscombe-Marsh N; Feinle-Bisset C; Horowitz M; Soenen S
    It is not well recognized that in the elderly weight loss is more common than weight gain. The aim of this analysis was to determine the effect of ageing on appetite (hunger/fullness) and energy intake, after overnight fasting and in a postprandial state, by meta-analyses of trials that included at least two age groups (>18 years). We hypothesized that appetite and energy intake would be less in healthy older compared with younger adults. Following a PubMed-database systematic search up to 30 June 2015, 59 studies were included in the random-effects-model meta-analyses. Energy intake was 16%-20% lower in older (n = 3574/~70 years/~71 kg/~25 kg/m²) than younger (n = 4111/~26 years/~69 kg/~23 kg/m²) adults (standardized mean difference: -0.77 (95% confidence interval -0.90 to -0.64)). Hunger was 25% (after overnight fasting; weighted mean difference (WMD): -17 (-22 to -13) mm) to 39% (in a postprandial state; WMD: -14 (-19 to -9) mm) lower, and fullness 37% (after overnight fasting; WMD: 6 mm (95% CI: 1 to 11 mm)) greater in older than younger adults. In conclusion, appetite and energy intake are less in healthy older than younger adults, suggesting that ageing per se affects food intake.