Dietary Protein, Kidney Function and Mortality: Review of the Evidence from Epidemiological Studies

High-Protein Processed Foods: Impact on Diet, Nutritional Status, and Possible Effects on Health

Proteins are macronutrients with multiple health benefits, but excessive consumption can negatively affect health. This study aimed to evaluate the characteristics of a sample of high-protein processed foods (HPPFs), describe how their consumption affects dietary balance, and acquire knowledge of the consumption patterns of these products in a Spanish population. A sample of HPPFs available in supermarkets and on websites was collected. The contribution to recommended protein intakes was calculated using national and international references and considering the single consumption of the HPPFs and the product plus 150 g of meat. Furthermore, an online survey was conducted among a convenience sample. A total of 36 enriched protein products were evaluated. The percentage of proteins in these products ranges from 10 to 88%. The contribution of the protein recommended intake was within a range of 87.4-306.6% and 66.4-232.8% (women and men, respectively), only considering the additional proteins from 150 g of meat. One hundred thirty-nine participants completed the survey; 67.6% affirmed that they had consumed HPPFs, and half consumed them without following any consumption control. Since these products are accessible to everyone in supermarkets and protein intake is generally higher than the recommended limits, regulating the mass sale of HPPFs is essential to ensure they do not lead to protein overconsumption.

Diet and Physical Activity in Fabry Disease: A Narrative Review

Fabry disease (FD) is caused by mutations in the galactosidase alpha (GLA) gene which lead to the accumulation of globotriaosylceramide (Gb-3). Enzyme replacement therapy (ERT) and oral chaperone therapy are the current pharmacological treatments for this condition. However, in the literature, there is a growing emphasis on exploring non-pharmacological therapeutic strategies to improve the quality of life of patients with FD. In particular, the nutritional approach to FD has been marginally addressed in the scientific literature, although specific dietary interventions may be useful for the management of nephropathy and gastrointestinal complications, which are often present in patients with FD. Especially in cases of confirmed diagnosis of irritable bowel syndrome (IBS), a low-FODMAP diet can represent an effective approach to improving intestinal manifestations. Furthermore, it is known that some food components, such as polyphenols, may be able to modulate some pathogenetic mechanisms underlying the disease, such as inflammation and oxidative stress. Therefore, the use of healthy dietary patterns should be encouraged in this patient group. Sports practice can be useful for patients with multi-organ involvement, particularly in cardiovascular, renal, and neurological aspects. Therefore, the aim of this review is to summarize current knowledge on the role of nutrition and physical activity in FD patients.

Long-Term Renal Function in Adult Patients with Phenylketonuria

INTRODUCTION

In phenylketonuria (PKU), toxic phenylalanine (Phe) can harm other organs beyond the brain. Furthermore, the lifelong therapy of PKU consists of consumption of increased amounts of amino-acid mixture that provoke hyperfiltration in the glomeruli. Therefore, the adherence to therapy in PKU might influence the long-term kidney function in PKU patients.

METHODS

Data from 41 adult, early treated PKU patients were analyzed in this 10-year, retrospective, monocentric study. Two subgroups were created according to their therapy adherence: one with long-term blood Phe levels in the therapeutic range (<600 µmol/L), and one with suboptimal blood Phe levels. Renal function and metabolic parameters were collected over 10 years. Kidney function parameters were compared between the two groups and associations between blood Phe levels and kidney function were tested.

RESULTS

After 10 years, serum creatinine levels (p = 0.369) and estimated glomerular filtration rate (eGFR) (p = 0.723) did not change significantly from baseline in the good therapeutic group. The suboptimal therapeutic group's eGFR decreased in the same period (from 110.4 ± 14 mL/min/1.73 m2 to 94.2 ± 16 mL/min/1.73 m2, p = 0.017). At 10 years, the suboptimal therapeutic group had an increased serum creatinine level (81 ± 14.4 μmol/L vs. 71.5 ± 13 μmol/L, p = 0.038), and a decreased eGFR (94.2 ± 16 mL/min/1.73 m2 vs. 103.3 ± 13 mL/min/1.73 m2p = 0.031) compared to the good adhering group. Significant negative correlation between Phe levels and eGFR (r = -0.41, p = 0.008) was observed.

CONCLUSION

Long-term suboptimal therapy adherence in PKU patients with high blood Phe levels may lead to deterioration in kidney function.

Efficacy and Safety of 6-Month High Dietary Protein Intake in Hospitalized Adults Aged 75 or Older at Nutritional Risk: An Exploratory, Randomized, Controlled Study

The aim of this study was to investigate the effects of increased dietary protein in daily-life settings in Japan for 6 months on the activities of daily living (ADL) in adults aged 75 or older at nutritional risk. The study was an open-label, exploratory, randomized controlled trial conducted at seven hospitals in Japan. The study participants were adults aged 75 or older who were hospitalized for treatable cancer, pneumonia, fractures, and/or urinary-tract infection at nutritional risk. The primary outcome was change in grip strength, skeletal muscle, and ADL indices (Barthel index, Lawton score). One hundred sixty-nine patients were randomly assigned to the intensive care (IC) or standard care (SC) group; the protein intake goals (g/kgw/day) were 1.5 for IC and 1.0 for SC. There was a significant improvement in grip strength only in the IC group (1.1 kg: 95% CI 0.1 to 2.1) (p = 0.02). While the skeletal muscle index and ADL indices were not significantly improved in either group, the improvement ratio tended to be greater in the IC group. There was no decrease in renal function in either group. Thus, intervention of increased dietary protein in daily-life settings for 6 months in adults aged 75 or older with treatable cancer, pneumonia, fractures, and/or urinary-tract infection and at nutritional risk may be effective in ameliorating loss of muscle strength.

Protein Supplementation for Strength and Functionality in Older Adults: Is There Still Any Doubt? A Brief Update Review

It is widely known that the aging process induces relevant impairments on both muscle morphology and function. In this sense, resistance training alongside proper protein intake are important strategies to mitigate the sarcopenia process in older individuals. However, adding protein supplementation (PS) to resistance training interventions for enhancing muscle strength and functional performance has shown mixed results in this population. Therefore, the present study aimed to review the most recent evidence regarding PS and its effects on muscle strength and functional parameters of older adults. In addition, the effect size of each individual study (post-pre intervention) was also calculated to provide further clinical relevance on the topic. The results of the studies included do not seem to support PS for healthy older adults with proper protein intake. However, further studies with other sample characteristics (very old, frail, obese, and inadequate protein consumption) must be carried out to better understand the effects of PS in an older population.

The water footprint and nutritional implications of diet change in Mexico: a principal component analysis

PURPOSE

Nutrition transition (NT) has modified the way that the Mexican population eats, while their body composition has also been modified. These changes have been linked with environmental impacts; however, little is known regarding water footprint (WF). The objective of this paper was to analyze the NT process in Mexico and evaluate its impact on WF using principal component analysis (PCA).

METHODS

A validated Food Consumption Frequency Questionnaire (FCFQ) was modified and applied to 400 adults from the Metropolitan Zone of Guadalajara, Mexico. The WF was calculated according to the WF Assessment Method. PCA and tertiles analysis was carried out to define dietary patterns WFs (DPWF). Questions covering sociodemographic and socioeconomic factors, as well as body composition data and physical activity levels were measured.

RESULTS

The average DPWF was 6619.58 ± 3182.62 L per person per day (L p^-1d^-1). We found three DPWF by PCA: Medium NT (55% from the total sample), Healthy plant-based (28%), and High in animal protein (17%). The highest energy consumption, western and Mexican foods intake, and dietary WF were found in Medium NT DPWF, as well as obesity prevalence. Fruits and vegetable consumption was higher in Healthy plant-based DPWF. Muscle mass percentage was higher in the High in animal protein DPWF.

CONCLUSIONS

Although most of the population is currently on Medium NT, new dietary patterns have emerged, where there was found a trend to plant-based diets but also diets high in animal food sources that can influence nutritional status.

Protein intake and renal function in older patients

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is highly prevalent in elderly patients. There is growing recognition of the importance of attention to dietary protein intake (DPI) in this population given their predisposition to age-related changes in kidney function and coexisting comorbidities (i.e., hypertension). We reviewed the impact of DPI on kidney health and survival and the role of dietary protein management in older CKD patients.

RECENT FINDINGS

While kidney function parameters including glomerular filtration rate (GFR) and renal plasma flow are slightly lower in elderly patients irrespective of CKD status, the kidneys' ability to compensate for increased DPI by augmentation of GFR is preserved until 80 years of age or less. However, long-term consumption of high DPI in individuals of older age and/or with CKD may contribute to kidney function deterioration over time. Prescription of a plant-dominant low-protein diet of 0.6-0.8 g/kg/day with more than 50% from plant sources or very low protein diets less than 0.45 g/kg/day supplemented with essential amino acids or their keto-analogues may be effective in preserving kidney function in older patients and their younger counterparts, while also monitoring for development of protein-energy wasting (PEW).

SUMMARY

Using tailored precision nutrition approaches in prescribing plant-dominant low DPI that also maintains adequate energy and nitrogen balance may ameliorate kidney function decline while also preventing development of PEW in elderly patients with CKD.

Prevalence of protein intake below recommended in community-dwelling older adults: a meta-analysis across cohorts from the PROMISS consortium

BACKGROUND

Lower protein intake in older adults is associated with loss of muscle mass and strength. The present study aimed to provide a pooled estimate of the overall prevalence of protein intake below recommended (according to different cut-off values) among community-dwelling older adults, both within the general older population and within specific subgroups.

METHODS

As part of the PRevention Of Malnutrition In Senior Subjects in the EU (PROMISS) project, a meta-analysis was performed using data from four cohorts (from the Netherlands, UK, Canada, and USA) and four national surveys [from the Netherlands, Finland (two), and Italy]. Within those studies, data on protein and energy intake of community-dwelling men and women aged ≥55 years were obtained by either a food frequency questionnaire, 24 h recalls administered on 2 or 3 days, or food diaries administered on 3 days. Protein intake below recommended was based on the recommended dietary allowance of 0.8 g/kg body weight (BW)/d, by using adjusted BW (aBW) instead of actual BW. Cut-off values of 1.0 and 1.2 were applied in additional analyses. Prevalences were also examined for subgroups according to sex, age, body mass index (BMI), education level, appetite, living status, and recent weight loss.

RESULTS

The study sample comprised 8107 older persons. Mean ± standard deviation protein intake ranged from 64.3 ± 22.3 (UK) to 80.6 ± 23.7 g/d [the Netherlands (cohort)] or from 0.94 ± 0.38 (USA) to 1.17z ± 0.30 g/kg aBW/d (Italy) when related to BW. The overall pooled prevalence of protein intake below recommended was 21.5% (95% confidence interval: 14.0-30.1), 46.7% (38.3-55.3), and 70.8% (65.1-76.3) using the 0.8, 1.0, and 1.2 cut-off value, respectively. A higher prevalence was observed among women, individuals with higher BMI, and individuals with poor appetite. The prevalence differed only marginally by age, education level, living status, and recent weight loss.

CONCLUSIONS

In community-dwelling older adults, the prevalence of protein intake below the current recommendation of 0.8 g/kg aBW/d is substantial (14-30%) and increases to 65-76% according to a cut-off value of 1.2 g/kg aBW/d. To what extent the protein intakes are below the requirements of these older people warrants further investigation.

Effect of low-protein intake on all-cause mortality in subjects with an estimated glomerular filtration rate higher than 60 mL/min/1.73 m2 with or without albuminuria

BACKGROUND

We aimed to investigate the effect of a low-protein intake on all-cause mortality in subjects with an estimated glomerular filtration rate (eGFR) ≧60 mL/min/1.73 m² with or without albuminuria using data from the National Health and Nutrition Examination Survey (NHANES).

METHODS

We analysed participants in the NHANES from 2003 to 2010. We excluded participants with an eGFR less than 60 mL/min/1.73 m² from the analyses. Low-protein intake was defined as a protein intake of less than 0.8 g/kg/day. The Healthy Eating Index 2010 was used to assess diet quality. The vital status of all participants in the NHANES was determined by linking to the National Death Index through the end of 2011. The hazard ratios (HRs) for the association of low-protein intake and mortality were determined using weighted Cox proportional hazards regression models.

RESULTS

A total of 7730 participants were included in the analyses. After a median follow up of 4.7 years, 462 participants died. A low-protein intake was associated with a higher risk of mortality (HRs 1.394, 95% CI 1.121-1.734, P = .004) with adjustment for diet quality and relevant risk factors. The higher risk of mortality associated with a low-protein intake was consistent in subjects with or without albuminuria (P interaction .280).

CONCLUSION

A protein intake of less than 0.8 g/kg/day was associated with a higher risk of mortality in subjects with an eGFR ≧60 mL/min/1.73 m² , irrespective of whether they had albuminuria.

Optimizing Adult Protein Intake During Catabolic Health Conditions

The DRIs define a range of acceptable dietary intakes for each nutrient. The range is defined from the minimum intake to avoid risk of inadequacy (i.e., the RDA) up to an upper limit (UL) based on a detectable risk of adverse effects. For most nutrients, the minimum RDA is based on alleviating a clear deficiency condition, whereas higher intakes are often recommended to optimize specific health outcomes. Evidence is accumulating that similar logic should be applied to dietary recommendations for protein. Although the RDA for protein of 0.8 g/kg body weight is adequate to avoid obvious inadequacies, multiple studies provide evidence that many adults may benefit from protein quantity, quality, and distribution beyond guidelines currently defined by the RDA. Further, the dietary requirement for protein is a surrogate for the constituent amino acids and, in particular, the 9 considered to be indispensable. Leucine provides an important example of an essential amino acid where the RDA of 42 mg/kg body weight is significantly less than the 100-110 mg/kg required to optimize metabolic regulation and skeletal muscle protein synthesis. This review will highlight the benefits of higher protein diets to optimize health during aging, inactivity, bed rest, or metabolic dysfunction such as type 2 diabetes.

Effects of Self-Weighing During Weight Loss Treatment: A 6-Month Randomized Controlled Trial

Objective

To examine the effectiveness of self-weighing for weight loss in men for 6 months.

Methods

In the present study, 54 men, mean age of 40.1 ± 11.1 years, with overweight or obesity, were recruited and randomly assigned into two groups: control group (CG), without weight self-monitoring and intervention group (IG), with weight self-monitoring. Both groups received the same nutritional and educational advice and the establishment of a weight target to reach in the weight loss program. Subjects of IG also had individualized motivating content to improve self-management for 24 weeks. Anthropometric indices were measured at baseline and weekly for 24 weeks.

Results

When the group assigned after randomization was introduced in the analysis, its influence was significant in weight loss (F1.52 = 19.465, ± 2 = 0.272, p < 0.001) and in the decrease in body fat percentage (F1.52 = 8,306, ± 2 = 0.132, p < 0.01).

Conclusion

Study results indicate that self-weighing can help patients to lose additional weight. Our findings have implications in the emerging area of the behavioral approach of patients undergoing weight-loss treatment, as well as clinical care processes.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier NCT04032249.

Effects of dietary protein intake on renal outcome and mortality in patients with advanced diabetic nephropathy

BACKGROUND

The difficulty of adhering to a low-protein diet is a serious limitation of randomized controlled trials aimed at validating the efficacy of this therapy. In this observational study of patients with diabetic nephropathy, we examined the association of dietary protein intake (DPI) with renal outcome and mortality, taking into account the nutritional status.

METHODS

We conducted a single-center historical cohort study of 449 adult Japanese patients with type 2 diabetes and the urinary albumin-to-creatinine ratio of ≥ 300 mg/g or estimated glomerular filtration rate of < 30 mL/min/1.73 m². DPI was estimated with a formula using nitrogen levels in spot urine and body mass index. Malnutrition was defined as the Geriatric Nutritional Risk Index of ≤ 98. The primary and secondary endpoints were renal replacement therapy (RRT) initiation and mortality before RRT initiation, respectively. The Fine and Gray subdistribution hazard model was used to determine the relative effects of DPI on the respective endpoint.

RESULTS

Decreased DPI was associated with lower incidence of RRT with an adjusted hazard ratio of 0.81 (95% confidence interval: 0.72-0.92, p < 0.001). The interaction between DPI and nutritional status with respect to mortality was significant (p interaction = 0.047). Decreased DPI was a risk factor for mortality in patients with malnutrition (p = 0.009) but not in those without malnutrition (p = 0.559).

CONCLUSIONS

In patients with type 2 diabetic nephropathy, lower DPI was associated with lower incidence of RRT initiation, suggesting beneficial effects of a low-protein diet on kidneys. Conversely, lower DPI might lead to increased mortality in patients with malnutrition.