Discussion on protein recommendations for supporting muscle and bone health in older adults: a mini review.

Muscle and bone tissues are interconnected, and both rely on an adequate protein intake. Recommendations for protein intake for older adults specifically vary across countries. The purpose of this narrative review is to discuss the existing evidence for protein recommendations for supporting muscle and bone health in older adults and to evaluate if a protein intake above the current population reference intake (PRI) for older adults would be scientifically justified. First, this review summarizes the protein recommendations from bodies setting dietary reference values, expert groups, and national health organizations. Next, relevant studies investigating the impact of protein on muscle and bone health in older adults are discussed. In addition, the importance of protein quality for muscle and bone health is addressed. Lastly, a number of research gaps are identified to further explore the added value of a protein intake above the PRI for older adults.

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.

The Nutritional Benefit of UV-Exposed Mushrooms for the Dutch Population: Modeling the Addition of UV-Exposed Mushrooms to the Diet.

Background: Mushrooms are rich in fiber and vitamins B and vitamin D when exposed to UV light and are sometimes used as a meat substitute. A modeling study showed that adding a mushroom portion (84 g/d) to the diet of an American population caused a significant improvement in the intake of several nutrients. Objective: To study the association between habitual intake of mushrooms and nutrient intake and to assess the change in micronutrient intake with the modeled addition of 60 or 84 grams of UV-exposed mushrooms to the diet of the Dutch population, with a subanalysis on subjects with a low animal: plant protein ratio. Methods: A modeling study was conducted in 3121 Dutch persons aged 9-80 y, using cross-sectional data from the Dutch National Food Consumption Survey 2012-2016. Linear regression was used to explore the association between habitual intake of mushrooms and nutrients. Habitual intake and nutritional adequacy were calculated before and after the modeled addition of mushrooms. Results: A small association was observed between the habitual intake of mushrooms and the intake of copper, niacin, and vitamin B2 (beta ranging from 0.002 to 0.039). The modeled addition of UV-exposed mushrooms increased the intakes of plant protein (by 5-7%), fiber (4-6%), niacin (10-20%), vitamin D (176-388%), folate (11-17%), potassium (6-10%), and copper (29-48%). Nutritional adequacy also improved significantly. For subjects with a low animal:plant protein ratio, the added mushrooms increased the intakes of niacin (11-22%), potassium (6-11%), and vitamin D (190-445%). Conclusions: Consumption of mushrooms contributes to higher intakes of copper, niacin, and vitamin B2. Addition of UV-exposed mushrooms to the diet of the Dutch further improves nutrient intakes and, most notably, vitamin D, especially for people with low animal food consumption.

The Association between Malnutrition and Physical Performance in Older Adults: A Systematic Review and Meta-Analysis of Observational Studies.

In recent years the focus of healthcare and nutritional science in older adults has shifted from mortality towards physical performance and quality of life. The aim of this review was to summarize observational studies on physical performance in malnourished (MN) or at risk of malnutrition (RMN) older adults compared with well-nourished (WN) older adults. Eligible studies had to report on nutritional status and objectively measured physical performance in older adults (≥60 y). MN or RMN groups had to be compared with a WN group, measured with a validated nutrition screener. Ovid Medline and Web of Science were searched until 13 November, 2020. Study quality was scored using a modified Newcastle-Ottawa Scale (NOS). Results were analyzed by meta-analysis when possible, or narratively reviewed otherwise. Forty-five studies (16,911 participants in total) were included from studies in outpatient clinics (n = 6), nursing homes (n = 3), community-dwelling older adults (n = 20), hospitalized patients (n = 15), or a combination (n = 1). Studies used 11 different screeners of malnutrition, and 8 types of physical performance measures. Meta-analysis showed that compared with MN, WN groups had better hand grip strength (mean difference [MD] = 4.92 kg; 95% CI: 3.43, 6.41; P < 0.001; n = 23), faster gait speed (MD = 0.16 m/s; 95% CI: 0.05, 0.27; P = 0.0033; n = 7), performed faster on timed-up-and-go (MD = -5.94 s; 95% CI: -8.98, -2.89; P < 0.001; n = 8), and scored 1.2 more short physical performance battery points (95% CI: 1.32, 2.73; P < 0.001; n = 6). Results were less pronounced when compared with RMN. Narratively, all studies showed an association for knee extension strength, 6-min walking test, and multicomponent tests, except for the chair stand test. Study limitations include no studies scoring "good" on NOS, lack of confounder adjustment, and high heterogeneity. Overall, evidence from cross-sectional studies indicate an association between malnutrition and worse physical performance in older adults. This study is registered in PROSPERO as CRD42020192893.

Impact of magnesium on bone health in older adults: A systematic review and meta-analysis.

BACKGROUND: Magnesium plays a key role in bone health and may, therefore, represent an interesting nutrient for the prevention of bone loss and osteoporosis. The aim of this systematic review and meta-analysis was to investigate the impact of magnesium intake from any source on bone mineral density (BMD), bone mineral content (BMC), bone turnover markers, and fracture risk in older adults. METHODS: A systematic search was conducted using Embase, Medline Ovid and Cochrane Central from database inception to October 2020. All studies that related magnesium intake with bone health outcomes among adults aged ≥60 years were included. Two investigators independently conducted abstract and full-text screenings, data extractions, and risk of bias assessments. Authors were contacted for missing data. RESULTS: Once 787 records were screened, six cohort studies, one case-control study and five cross-sectional studies were included. Qualitative evaluation demonstrated a positive trend between higher magnesium intake and higher hip and femoral neck BMD. Meta-analysis of four studies showed a significant positive association between magnesium intake and hip BMD (pooled beta: 0.03, 95% CI: 0.01-0.06, p < 0.05). CONCLUSIONS: This systematic review indicates that a higher magnesium intake may support an increase in hip and femoral neck BMD. Due to limited research no associations with BMD at other sites or fractures were found. There is a need for properly designed cohort studies to determine the association between magnesium intake and bone health in older adults. Next, large and long-term randomized controlled trials in older adults are needed to determine whether an increase in magnesium (supplementation) intake can improve bone health. The combination of several bone nutrients (calcium, vitamin D, protein, magnesium and potentially more) may be needed for the most optimal effect on bone health and to delay or prevent the development of osteoporosis.

Hip Fracture Patients in Geriatric Rehabilitation Show Poor Nutritional Status, Dietary Intake and Muscle Health.

The aim of this study was to gain insight into the nutritional status, dietary intake and muscle health of older Dutch hip fracture patients to prevent recurrent fractures and to underpin rehabilitation programs. This cross-sectional study enrolled 40 hip fracture patients (mean ± SD age 82 ± 8.0 years) from geriatric rehabilitation wards of two nursing homes in the Netherlands. Assessments included nutritional status (Mini Nutritional Assessment), dietary intake on three non-consecutive days which were compared with Dietary Reference Intake values, and handgrip strength. Muscle mass was measured using Bioelectrical Impedance Analysis and ultrasound scans of the rectus femoris. Malnutrition or risk of malnutrition was present in 73% of participants. Mean energy, protein, fibre and polyunsaturated fat intakes were significantly below the recommendations, while saturated fat was significantly above the UL. Protein intake was <0.8 in 46% and <1.2 g/(kg·day) in 92%. Regarding micronutrients, mean intakes of calcium, vitamin D, potassium, magnesium and selenium were significantly below the recommendations. The prevalence of low muscle mass, low handgrip strength and sarcopenia were 35%, 27% and 10%, respectively. In conclusion, a poor nutritional status, dietary intake and muscle health are common in older hip fracture patients in geriatric rehabilitation wards.

A Combined Nutrition and Exercise Intervention Influences Serum Vitamin B-12 and 25-Hydroxyvitamin D and Bone Turnover of Healthy Chinese Middle-Aged and Older Adults.

BACKGROUND: Hong Kong faces several public health problems including malnutrition and osteoporosis. Considering the typical Chinese diet and overall low physical activity levels of Chinese adults, timely interventions to improve nutritional status and bone health are needed. OBJECTIVES: We examined the effects of a nutrition plus exercise intervention on serum vitamin B-12 and 25-hydroxyvitamin D [25(OH)D], bone turnover markers, and parathyroid hormone (PTH) concentrations in apparently healthy Chinese middle-aged and older adults. METHODS: In this 24-wk randomized controlled trial, 180 Chinese adults (85 women, mean ± SD age: 61 ± 6 y) were randomly assigned to receive a fortified milk supplement (2 × 30 g/d) and an exercise program (2 × 1 h/wk including resistance, balance, and aerobic training) or no intervention. The primary outcome was physical performance. In this article we analyzed the secondary outcomes serum vitamin B-12 and 25(OH)D concentrations, assessed at baseline, 12 wk, and 24 wk. Also, bone turnover markers and PTH concentrations were studied. Linear mixed models evaluated group differences over time. RESULTS: A significant time × group interaction (P < 0.001) was found for serum vitamin B-12 and 25(OH)D concentrations and the bone turnover markers, but not for serum PTH concentrations (P = 0.09). The intervention increased mean ± SD vitamin B-12 concentrations from baseline (345 ± 119 pmol/L) to 24 wk (484 ± 136 pmol/L), whereas concentrations remained stable within the control. For 25(OH)D concentrations, the intervention group had a greater increase from baseline (54.7 ± 14.2 nmol/L) to 24 wk (80.1 ± 19.2 nmol/L) than the control (60.6 ± 15.2 compared with 65.6 ± 14.6 nmol/L). The ratio of the net effect of bone formation and resorption was greater in the intervention group, suggesting less bone remodeling, irrespective of sex. CONCLUSIONS: A fortified milk supplement and exercise intervention successfully improved vitamin B-12 and 25(OH)D concentrations as well as the balance of bone turnover markers of Chinese middle-aged and older adults.This trial was registered at trialregister.nl as NTR6214.

High Versus low Dietary Protein Intake and Bone Health in Older Adults: a Systematic Review and Meta-Analysis.

Protein may play a beneficial role in the prevention of bone loss and in slowing down osteoporosis. The effect of dietary protein may be different in older adults compared to younger adults, since this population has a greater need for protein. The aim of this systematic review and meta-analysis was to investigate the impact of a dietary protein intake above the Recommended Dietary Allowance (RDA) of 0.8 g/kg body weight/day from any source on Bone Mineral Density (BMD)/Bone Mineral Content (BMC), bone turnover markers, and fracture risk in older adults compared to a lower dietary protein intake. A systematic search was conducted through October 2018 in 3 databases: CENTRAL, MEDLINE, and EMBASE. We included all prospective cohort studies and Randomized Controlled Trials (RCTs) among adults aged ≥65 years that examined the relation between protein intake on bone health outcomes. Two investigators independently conducted abstract and full-text screenings, data extractions, and risk of bias assessments. Authors were contacted for missing data. After screening of 523 records, twelve cohort studies and one RCT were included. Qualitative evaluation showed a positive trend between higher protein intakes and higher femoral neck and total hip BMD. Meta-analysis of four cohort studies showed that higher protein intakes resulted in a significant decrease in hip fractures (pooled hazard ratio: 0.89; 95% confidence interval: 0.84, 0.94). This systematic review supports that a protein intake above the current RDA may reduce hip fracture risk and may play a beneficial role in BMD maintenance and loss in older adults.