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Protein In Diet From Plant Or Animal: Cardiovascular Outcomes In Men

Protein In Diet From Plant Or Animal: Cardiovascular Outcomes In Men


In this cross-sectional study involving 357 elderly men, the research aimed to explore the relationship between dietary protein intake—both total and categorized as plant or animal protein—and cardiovascular outcomes and inflammatory factors. Utilizing a reliable food frequency questionnaire (FFQ) to assess dietary intake, the study measured various biochemical factors, including triglycerides (TG), fasting blood sugar (FBS), high-sensitivity C-reactive protein (hs-CRP), interleukin 6 (IL6), and tumor necrosis factor-α (TNF-α). Additional assessments included waist circumference (WC) and blood pressure (BP).


The findings revealed a notable inverse association between animal protein intake and systolic blood pressure (SBP), suggesting that higher animal protein consumption was linked to lower SBP (OR: 0.62; 95% CI: 0.42, 0.91; ptrend = .014). Similarly, significant inverse associations were identified between plant protein intake and WC (OR: 0.34; 95% CI: 0.17, 0.68; ptrend < .001), FBS (OR: 0.51; 95% CI: 0.29, 0.89; ptrend = .018), and Hs-CRP (OR: 0.39; 95% CI: 0.21, 0.70; ptrend = .002).


Moreover, total protein intake exhibited significant inverse associations with SBP (OR: 0.54; 95% CI: 0.33, 0.86; ptrend = .010) and Hs-CRP (OR: 0.50; 95% CI: 0.28, 0.88; ptrend = .015). These results indicated that higher total protein intake, both from plant and animal sources, was associated with reduced odds of elevated SBP and lower Hs-CRP levels.


The study emphasized that in elderly men, a diet rich in plant protein was linked to lower odds of high WC, FBS, and Hs-CRP. Conversely, a higher intake of animal protein, particularly from dairy products, was associated with an increased likelihood of elevated SBP. These findings contribute valuable insights into the nuanced relationship between protein intake and cardiovascular and inflammatory parameters in the elderly male population.


The demographic shift towards an aging population in Iran, with individuals aged 60 and above surpassing 10% of the total population, poses significant challenges for healthcare, economic growth, and the overall well-being of the elderly. Cardiovascular diseases (CVDs) emerge as a major global concern, particularly affecting the elderly, constituting a substantial proportion of global disease burden and mortality. CVD prevalence in Iran, as reported in 2015, stands at 39.9% among the elderly.


The surge in CVDs is attributed to factors such as socioeconomic changes, cultural shifts, dietary habits, physical inactivity, and increased metabolic risk factors. As nutrition plays a pivotal role in CVD prevention and management, the study aims to explore the influence of protein source and quantity on cardiovascular risk factors in elderly men. Research indicates that nutritional factors contribute significantly to CVD cases, with protein intake being a key focus. Plant-based proteins, including unprocessed animal proteins, are suggested to reduce CVD risk compared to typical Western diets.


Divergent findings exist regarding the impact of specific protein sources on CVD risk. While some studies propose that poultry and dairy products may effectively control CVD risk factors, others associate processed and red meat with increased CVD risk. Limited research has focused on the elderly population, warranting a thorough examination of the association between protein intake and cardiovascular outcomes and inflammatory factors in this demographic.


This cross-sectional study involving 357 elderly men aims to fill this research gap. With cardiovascular disease predominantly affecting men, the study aims to provide insights into the cross-sectional association between the quantity and sources of protein intake and cardiovascular risk factors in elderly men. By addressing these gaps in understanding, the study contributes to the broader discourse on effective dietary strategies for preventing and managing cardiovascular diseases in the aging population.


This cross-sectional study conducted in southern Tehran, Iran, from March to August 2017, aimed to investigate the association between dietary protein intake and cardiovascular outcomes in elderly men. The study included 365 men from health centers, with ethical approval obtained from Tehran University of Medical Sciences. Inclusion criteria comprised Iranian males over 60 years, without self-reported malignant diseases or changes in diet due to illness or dietitian recommendation.


Hypertension guided the sample size estimation, resulting in 357 participants for analysis after excluding those with extremely low or high calorie intake. A semiquantitative food frequency questionnaire (FFQ) facilitated nutritional data collection, categorizing protein sources into animal protein (AP), plant protein (PP), and total protein (TP). The NUTRITIONIST IV software adapted for Iranian foods computed nutrient intake.


Biochemical assessments involved fasting blood samples to evaluate glucose, triglycerides, and high-sensitive C-reactive protein (hs-CRP). Inflammatory biomarkers were determined through enzyme-linked immunosorbent assay (ELISA). Anthropometric measures, including weight, height, and waist circumference, were obtained by a trained assistant, and BMI was calculated. A questionnaire assessed socioeconomic status, demographics, chronic diseases, and medication use.


Blood pressure was measured twice, and participants’ activity levels were recorded as metabolic equivalent of task hours per week. The study aimed to explore the intricate relationship between dietary protein intake and cardiovascular outcomes, incorporating a comprehensive assessment of participants’ nutritional, biochemical, anthropometric, and socioeconomic profiles.

Statistical Analysis

The study employed statistical tests and analyses to explore the associations between protein intake and cardiovascular outcomes in elderly men. The normal distribution of covariates was assessed using the Kolmogorov–Smirnov test and histogram curves. Participants were categorized based on their dietary intake of animal protein (AP), plant protein (PP), and total protein (TP) into tertiles. Descriptive statistics were employed to illustrate the general characteristics of the three protein categories.


Statistical tests, including the chi-squared test and one-way analysis of variance (ANOVA), were used to assess the distribution of continuous and categorical variables among tertiles of protein intake. One-way analysis of covariance (ANCOVA), with energy intake adjustment, compared nutrient and food group intakes across protein tertiles. Additionally, ANCOVA was utilized to compare cardiovascular and inflammatory parameters across protein tertiles in both crude and adjusted models.


Binary logistic regression was conducted to assess cardiovascular risk factors, categorizing participants based on established cutoffs. Adjusted models included confounders such as age, marital status, physical activity, socioeconomic status, smoking status, diseases and drugs, BMI, and specific dietary components. Plant protein was included as a cofounder in models with animal protein, and vice versa. The statistical analysis was performed using SPSS software version 26.0, with a significance level set at p < .05. The study’s robust statistical methodology adds credibility to its findings on the association between protein intake and cardio-metabolic risk factors in elderly men.


The study analyzed the general characteristics, dietary intakes, and cardiovascular risk factors of participants across tertiles of animal protein (AP), plant protein (PP), and total protein (TP) intake. Participants in the highest AP tertile were older, had higher waist circumference (WC) and body mass index (BMI), and were more likely to be nonsmokers. Those in the highest PP tertile were younger, had lower WC and weight, and were less likely to use certain medications. High TP tertile participants were more likely nonsmokers and less likely to use specific medications.


Dietary intakes varied across protein tertiles, with the highest AP tertile associated with increased intake of energy, minerals, and dairy products but decreased intake of carbohydrates, fiber, and n-3 fatty acids. The highest PP tertile showed increased intake of energy, carbohydrates, fiber, minerals, fruits, and vegetables but decreased intake of phosphorus, calcium, and dairy products. The highest TP tertile was associated with increased intake of energy, fiber, minerals, fruits, vegetables, and dairy products, and decreased intake of fat.


Regarding cardiovascular risk factors, participants in the highest AP tertile had higher WC but lower systolic blood pressure (SBP), fasting blood sugar (FBS), and LDL/HDL ratio. The highest PP tertile was associated with lower WC, FBS, LDL/HDL ratio, and high-sensitivity C-reactive protein (Hs-CRP). The highest TP tertile had higher WC but lower SBP, FBS, LDL/HDL ratio, and Hs-CRP.


Binary logistic regression, adjusted for various confounders, revealed a significant inverse association between AP and SBP. Similarly, PP was inversely associated with WC, FBS, and Hs-CRP, while TP showed inverse associations with SBP and Hs-CRP.


Further analysis indicated that the consumption of dairy products had a significant inverse association with SBP, emphasizing the potential role of specific dietary components in cardiovascular health. Additionally, an inverse association was found between egg consumption and diastolic blood pressure (DBP).


In conclusion, the study highlighted associations between protein intake, dietary patterns, and cardiovascular risk factors in elderly men, emphasizing the potential protective effects of certain protein sources.


The study underscores the significant impact of both the total amount and sources of protein on cardiovascular outcomes and inflammatory factors, with higher protein intake exhibiting a notable inverse association with systolic blood pressure (SBP) and high-sensitivity C-reactive protein (Hs-CRP). Specifically, elevated plant protein (PP) intake demonstrated favorable associations, including lower waist circumference (WC), fasting blood sugar (FBS), and Hs-CRP. Meanwhile, animal protein (AP) intake was linked to lower SBP, with dairy product consumption playing a pivotal role in this association.


Prior research on protein intake and cardiovascular outcomes has primarily focused on adults, lacking specificity for the elderly population due to distinct body fat distribution and quantity variations. The study identified a positive association between higher dairy intake and SBP, aligning with previous meta-analyses highlighting the blood pressure-lowering effects of milk proteins. The potential mechanisms involve the inhibition of angiotensin-converting enzyme activity, lactokinins, casokinins, and amino acids like glutamic acid and tyrosine found in dairy products.


Regarding plant protein, the study uncovered a significant inverse association with WC, FBS, and Hs-CRP. This aligns with findings from various studies emphasizing the benefits of plant protein intake, such as improved insulin sensitivity, glycemic control, and reduced risk of type 2 diabetes. The anti-inflammatory effects of plant-based proteins are attributed to bioactive peptides regulating pathways like the MAPK pathway and NF-Κb.


In conclusion, the study emphasizes the potential benefits of higher plant protein intake, specifically noting its positive associations with cardiovascular and inflammatory outcomes in the elderly. This contrasts with the lower blood pressure association observed with animal protein intake, particularly influenced by dairy consumption. These findings contribute valuable insights into dietary considerations for promoting cardiovascular health in the elderly population.

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