The Associations of Habitual Intake of Sulfur Amino Acids, Proteins and Diet Quality with Plasma Sulfur Amino Acid Concentrations: The Maastricht Study.

BACKGROUND: Plasma sulfur amino acids (SAAs), i.e., methionine, total cysteine (tCys), total homocysteine (tHcy), cystathionine, total glutathione (tGSH), and taurine, are potential risk factors for obesity and cardiometabolic disorders. However, except for plasma tHcy, little is known about how dietary intake modifies plasma SAA concentrations. OBJECTIVE: To investigate whether the intake of SAAs and proteins or diet quality is associated with plasma SAAs. METHODS: Data from a cross-sectional subset of The Maastricht Study (n = 1145, 50.5% men, 61 interquartile range: [55, 66] y, 22.5% with prediabetes and 34.3% with type 2 diabetes) were investigated. Dietary intake was assessed using a validated food frequency questionnaire. The intake of SAAs (total, methionine, and cysteine) and proteins (total, animal, and plant) was estimated from the Dutch and Danish food composition tables. Diet quality was assessed using the Dutch Healthy Diet Index, the Mediterranean Diet Score, and the Dietary Approaches to Stop Hypertension score. Fasting plasma SAAs were measured by liquid chromatography (LC) tandem mass spectrometry (MS) (LC/MS-MS). Associations were investigated with multiple linear regressions with tertiles of dietary intake measures (main exposures) and z-standardized plasma SAAs (outcomes). RESULTS: Intake of total SAAs and total proteins was positively associated with plasma tCys and cystathionine. Associations were stronger in women and in those with normal body weight. Higher intake of cysteine and plant proteins was associated with lower plasma tHcy and higher cystathionine. Higher methionine intake was associated with lower plasma tGSH, whereas cysteine intake was positively associated with tGSH. Higher intake of methionine and animal proteins was associated with higher plasma taurine. Better diet quality was consistently related to lower plasma tHcy concentrations, but it was not associated with the other SAAs. CONCLUSION: Targeted dietary modifications might be effective in modifying plasma concentrations of tCys, tHcy, and cystathionine, which have been associated with obesity and cardiometabolic disorders.

Protein intake and bone mineral density: Cross-sectional relationship and longitudinal effects in older adults.

BACKGROUND: There are several mechanisms via which increased protein intake might maintain or improve bone mineral density (BMD), but current evidence for an association or effect is inconclusive. The objectives of this study were to investigate the association between dietary protein intake (total, plant and animal) with BMD (spine and total body) and the effects of protein supplementation on BMD. METHODS: Individual data from four trials that included either (pre-)frail, undernourished or healthy older adults (aged ≥65 years) were combined. Dietary intake was assessed with food records (2, 3 or 7 days) and BMD with dual-energy X-ray absorptiometry (DXA). Associations and effects were assessed by adjusted linear mixed models. RESULTS: A total of 1570 participants [57% women, median (inter-quartile range): age 71 (68-75) years] for which at least total protein intake and total body BMD were known were included in cross-sectional analyses. In fully adjusted models, total protein intake was associated with higher total body and spine BMD [beta (95% confidence interval): 0.0011 (0.0006-0.0015) and 0.0015 (0.0007-0.0023) g/cm2 , respectively]. Animal protein intake was associated with higher total body and spine BMD as well [0.0011 (0.0007-0.0016) and 0.0017 (0.0010-0.0024) g/cm2 , respectively]. Plant protein intake was associated with a lower total body and spine BMD [-0.0010 (-0.0020 to -0.0001) and -0.0019 (-0.0034 to -0.0004) g/cm2 , respectively]. Associations were similar between sexes. Participants with a high ratio of animal to plant protein intake had higher BMD. In participants with an adequate calcium intake and sufficient serum 25(OH)D concentrations, the association between total protein intake with total body and spine BMD became stronger. Likewise, the association between animal protein intake with total body BMD was stronger. In the longitudinal analyses, 340 participants [58% women, median (inter-quartile range): age 75 (70-81) years] were included. Interventions of 12 or 24 weeks with protein supplementation or protein supplementation combined with resistance exercise did not lead to significant improvements in BMD. CONCLUSIONS: An association between total and animal protein intake with higher BMD was found. In contrast, plant protein intake was associated with lower BMD. Research is warranted to further investigate the added value of dietary protein alongside calcium and vitamin D for BMD improvement, especially in osteopenic or osteoporotic individuals. Moreover, more research on the impact of a plant-based diet on bone health is needed.

A 4-week exercise and protein program improves muscle mass and physical functioning in older adults - A pilot study.

BACKGROUND: Prehabilitation might attenuate common surgery-induced losses in muscle mass and physical performance. Beneficial effects of physical exercise with protein supplementation have been reported in older adults, but typically after an intervention of at least 12 weeks. The time-window for pre-surgery training is often limited to around 30 days, and it is not known if it is possible to achieve comparable results in such a short time window. OBJECTIVES: The aim of this study was to pilot-test the effectiveness of a controlled four-week combined exercise and protein supplementation program on skeletal muscle-related outcomes in a Dutch older adult population. DESIGN: This study was a one-armed pilot trial. PARTICIPANTS: Seventeen older men and women, aged 55-75y, not scheduled for surgery. INTERVENTION: A 4-week intervention program consisting of a twice-weekly supervised resistance and high-intensity aerobic exercise training of 75 min, combined with daily protein supplementation (2 doses of 15.5 g/day at breakfast and lunch). MEASUREMENT: After two and four weeks, isometric quadriceps maximal voluntary contraction (MVC) was assessed via Biodex and quadriceps cross-sectional area (CSA) via magnetic resonance imaging. Other outcome measures were handgrip strength, chair rise time and maximal aerobic capacity (VO2-max), as assessed from a submaximal exercise test. RESULTS: Compliance to the supervised training sessions (99.3%) and the protein supplementation (97%) was very high. The 4-week exercise and protein program led to an increase in quadriceps CSA of 2.3 ± 0.7 cm2 (P = 0.008) in the dominant leg and 3.2 ± 0.7 cm2 (P < 0.001) in the non-dominant leg. Isometric quadriceps MVC increased in the dominant leg (Δ14 ± 4 Nm, P = 0.001) and in the non-dominant leg (Δ17 ± 5 Nm, P = 0.003). Chair rise test time improved with -3.8 ± 0.5 s (P < 0.0001), and VO2-max improved with 3.3 ± 1.1 ml/min/kg (P = 0.014). We observed no changes in body weight and handgrip strength. CONCLUSION: A 4-week exercise and protein intervention led to improvements in muscle-related outcomes in older adults with low levels of physical activity.