Daily meat consumption and variation with aging in communitydwellers: results from longevity check-up 7 + project| JOURNAL OF GERONTOLOGY AND GERIATRICS

Abstract

Background & aims. Behavioral factors, including protein intake, influence the quantity and quality of skeletal
muscle. The aim of this study was to provide a better insight into the comprehension of aging-related changes
of daily meat consumption throughout an individual’s life span (from 18 to 98 years).
Methods. For the present study, the database Longevity Check-up 7 + (Look-up 7 +) is used. A brief questionnaire exploring lifestyle habits, dietary preferences and the consumption of selected foods was administered.
A frequency questionnaire was administered to collect information on how often in a week participants consumed a standardized portion size of meat (beef, pork, chicken or turkey).
Results. The mean age of the 8,144 participants was 55.4 ± 15.1 years (range: 18-98 years), with 4624 (56.8%)
women. As compared with participants in the first tertile of daily meat intake, those in the third tertile were
younger and showed slightly higher BMI. Systolic and diastolic blood pressure, as well as blood cholesterol
level, was similar across different tertiles. Daily meat protein intake (as measured by the daily portion of meat)
declined significantly during the young and adult age, both in men and women. Overall, among old subjects
the meat-derived protein intake was less than 3.5 grams per day.
Conclusions. The results of the Look-up 7 + survey suggest a significant decline in daily meat-derived protein
intake with advancing age. Our findings also indicate that the higher meat consumption does not correlate with
higher prevalence of cardiovascular risk factors, such as blood pressure and cholesterol and glucose levels.

INTRODUCTION

The World Health Organization identified the healthy ageing of the global population as an important public health challenge in the 21st century ¹. In addition to providing medical management, healthcare professionals can advise patients about how to maintain wellness and quality of life. This can be achieved by encouraging patients to preserve physical activities, and by providing dietary recommendations and nutrition services to ensure they eat well and their nutrient needs are met ².

An adequate intake of dietary protein is vital to muscle health as it ensures the provision of essential amino acids (EAAs), which in turn stimulate muscle anabolism ³. The recommended protein intake, referred to as recommended dietary allowance (RDA) for protein, is based on the results of nitrogen balance studies as meta-analyzed by Rand et al. ⁴. Accordingly, a daily intake of ~ 0.8 g of good-quality proteins per kg of body weight is currently promoted by the World Health Organization as the amount that is sufficient to satisfy the metabolic demand and to achieve nitrogen equilibrium in 97.5% of the adult population ⁵.

Besides quantity, protein quality has a relevant influence on the health status. Protein quality is mainly determined by the amino acid profile (in particular, EAA content), digestibility, and absorption kinetics ⁶. In this context, it is important to highlight that the consumption of a moderate amount of lean meat-based high-quality protein maximally stimulated muscle protein synthesis both in young and old people ⁷. Notably, animal-derived protein was reported to stimulate protein synthesis to a greater extent than vegetable protein in older subjects both at rest and post-exercise ⁸. Furthermore, greater protein consumption, especially of animal origin, has recently been associated with higher levels of physical performance in community-dwelling older adults ⁹. These findings emphasize the relevance of ingesting adequate amounts of high-quality protein to promote muscle health and physical function across different age groups.

The present study was, therefore, undertaken to provide a better insight into the comprehension of aging-related changes of daily meat consumption throughout an individual’s life span (from 18 to 98 years), using an unselected sample of subjects assessed during the Longevity Check-up 7 + project.

MATERIALS AND METHODS

For the present study, the database Longevity Check-up 7 + (Look-up 7 +) is used. The Look-up 7 + study protocol has been previously described in detail elsewhere ^{10 11}. Briefly, this project is an ongoing initiative developed by the Geriatric Medicine Department of Catholic University of Rome planned with the aim to improve healthy lifestyles in the general population ¹¹. Subjects entering public environments (i.e., exhibitions, shopping centers, sport events) or subjects participating in prevention campaigns have been screened using a specific questionnaire on lifestyle and had a brief check-up, specifically assembled on the basis of the ideal cardiovascular health metrics indicated by the American Heart Association ¹². Participants are selected as eligible if they are at least 18 years of age and provide written informed consent. The exclusion criteria are: self-reported pregnancy, incapacity to perform the physical performance tests, denial of blood capillary check, and the refusal to give written informed consent. The Catholic University of Sacred Heart Ethical Committee ratified the study protocol ¹³.

STUDY SAMPLE

Between June 1^st, 2015 and October 30^th, 2017, we enrolled 8242 subjects. Recruitment took place in several Italian cities adhering to the Look-up 7 + project: Milan EXPO 2015 (Milan, June-October 2015), Mese del Cuore (Rome, September-October 2016), La Romanina (Rome, December 2017), Mese del Cuore (Milan, March-April 2017), Ministry of Health Women’s Day (Rome, April 2017), CamBio Vita (Catania, May 2017), COOP shopping centers (Bologna, Modena, Genoa, Rimini, Grosseto, May-June 2017), Mese del Cuore (Rome, September-October 2017), Tennis&Friends (Rome, October 2017), CONAD shopping centers (Terni, Perugia, Viterbo, Anzio, Caserta, November 2017) and Longevity Run (Rome, April 2018). For the present study, 98 subjects were excluded for missing values in the variables of interest; as a consequence, a sample of 8144 subjects was considered.

DATA COLLECTION

Seven parameters indicated as the most important cardiovascular risk factors ^{13 14}, were assessed through closed questions and direct measurements. Smoking habit was categorized as current or never/former smoker. Sedentariness was considered as the lack of involvement in any kind of physical activity. Body weight was assessed by an analogue medical scale, while a standard stadiometer was used to measure body height. The body mass index (BMI) was then calculated as the weight (kg) divided by the square of height (m). Healthy diet was considered as the consumption of at least three portions of fruit and/or vegetables per day. Cholesterol was measured from capillary blood samples using disposable electrode strips based on a reflectometric system with a portable device (MultiCare-In, Biomedical Systems International srl, Florence Italy) ¹⁵. Blood glucose was measured from capillary blood samples using disposable electrode strips based on an amperometric system with a MultiCare-In portable device ¹⁵. Blood pressure was measured – in the sample Milan EXPO 2015 – with a clinically validated Omron M6 electronic sphygmomanometer (Omron, Kyoto, Japan), and in all other samples with a manual sphygmomanometer according to recommendations from international guidelines ¹⁶.

DIETARY ASSESSMENT

A frequency questionnaire was administered to collect information on how often in a week participants consumed a standardized portion size of meat (beef, pork, chicken or turkey). For the present study, the mean daily intake of meat-derived protein was calculated by multiplying the consumption frequency of meat by the mean protein content of its standard portion, then dividing by seven (the days of a week). The daily meat-derived protein intake was calculated considering the average amount of 25.0 grams of protein for each portion of any meat.

STATISTICAL ANALYSES

Data are expressed as proportions (%) or mean ± standard deviation (SD). For analytical purposes, three groups of daily meat-derived protein intake were created based on the tertiles of this variable: first tertile (5.85.2 g/day; n = 2183), second tertile (> 5.85 and < 8.78 g/day; n = 2617), and third tertile (8.78 g/day; n = 3344).

The characteristics of the study sample are presented according to the tertiles of meat-derived protein intake. Differences in proportions or means of covariates among tertiles were assessed using Fisher’s Exact Test and ANCOVA, respectively.

All analyses were performed using the SPSS software package (version 11.0, SPSS Inc., Chicago, IL).

RESULTS

The mean age of the 8,144 participants was 55.4 15.1 years (range: 18-98 years), with 4624 (56.8%) women. The main characteristics of the study sample according to the tertiles of meat protein consumption are presented in Table I. As compared with participants in the first tertile, those in the third tertile were younger, had a higher prevalence of smoking habit, and showed slightly higher BMI. Conversely, participants in the third tertile were characterized by a marginally lower prevalence of healthy diet compared with the other participants. Systolic and diastolic blood pressure, as well as blood cholesterol level, were similar across different tertiles. Finally, serum glucose level was significantly lower among participants in higher tertile group of meat consumption compared with subjects with lower daily meat intake.

Figure 1 shows the mean and standard deviation of daily meat-derived protein intake across age groups. Meat protein intake (as measured by the daily portion of meat) declined significantly during the young and adult age, both in men and women. In particular, among men, daily meat protein intake decreased significantly from 18 years (11.1 grams) to 50-54 years (7.4 grams); after 55 years of age a further slightly decline is observed with a loss of 4.4 grams per day in the group of oldest subjects (11.1 grams vs 6.7 grams, respectively; p < 0.001). Similarly to men, a linear meat protein intake decline was detected in women, with about a 2.4 grams difference between the youngest group and the oldest group (8.9 grams vs 6.5 grams, respectively; p < 0.001).

DISCUSSION

In the present study, we explored the association between habitual consumption of meat-derived protein and age in a large sample of unselected community-dwelling adults. Our findings show that the mean daily meat-derived protein intake significantly decreased with advancing age. In particular, people over 50 years old showed a meat intake of about half of that they eat at a young age. Furthermore, it is important to underline that the greater consumption of meat was higher in men, but overall it was not associated with the higher levels of blood pressure or serum cholesterol levels. On the contrary, subjects who consumed more portions of meat per week showed lower blood glucose levels.

Recent evidence suggests that an adequate protein intake is required for the preservation of lean body mass and muscle function across different life stages ^{17 18}. This is particularly relevant considering that, for muscle strength (as measured by hand grip test) and physical performance (as measured by chair stand test), there is stability in the first decades of adulthood, and decrements in the middle years (45 +) and late adulthood. In particular, individuals of more than 75 years lose about 60% of their muscle strength and 30% of their physical function. We previously observed a linear pattern of age-decline that was surprisingly similar in men and women, and in different race, across the entire course of life ^{19 20}. Loss of muscle mass and function has a multifactorial origin; however, lifestyle factors, including poor nutrition and sedentary behavior, seem to play a major role ²¹. Indeed, the combination of nutritional interventions and physical activity is to date the most effective strategy to counteract muscle aging ²².

Meat contains a large quantity of essential amino acids and nutritional factors of high quality and availability, including minerals like iron and zinc, and a variety of vitamins, especially B group vitamins, and even a modest intake can improve muscle protein synthesis in older subjects. Nevertheless, several studies indicate that the consumption of different meats, with high intake of processed meats, may enhance the risk of negative health-related events, including cardiovascular disease, metabolic syndrome, type-2 diabetes, cancer, and death ²³. However, risks for fresh white and red meat are significantly less, and moderate consumption is encouraged as part of a healthy diet plan for older population to guarantee an adequate protein intake. Other nutritional strategies of importance for lean body mass loss include fortifying the nutrient value of meats. Some studies on muscle cells and animal models recognized the potential effects of the amino acid, for example glycine, to downgrade inflammation, reduce muscle mass loss, and improve muscle cells anabolic stimuli. Notably, greater consumptions of animal-derived proteins have recently been associated with lower insulin resistance, inflammation, arterial stiffness, blood pressure, and adiposity-related metabolites in adult twins, independent of genetics ^{2 24 25}.

Although reporting potentially relevant findings, our study presents limitations that need to be discussed. First, due to the particular setting in which the investigation was conducted, we could not administer a comprehensive dietary questionnaire. Second, the study setting may have influenced the assessment of some health metrics. Indeed, random cholesterol and glucose determinations could overestimate both parameters. Furthermore, cholesterol and glucose levels were determined in capillary blood samples. Even though this procedure was previously validated ¹⁰, the standard error of portable devices is higher than the standard equipment. Third, although anthropometric measures are frequently adopted for estimating lean body mass, they do not represent the gold standard for the quantification of muscle mass. Finally, although blood pressure was measured according to international guidelines, it is likely that the particular settings where the study sample has been enrolled may have influenced the measurement outcome.

In conclusion, the results of the Look-up 7 + survey suggest a significant decline in daily meat-derived protein intake with advancing age. Our findings also indicate that the higher meat consumption does not correlate with higher prevalence of cardiovascular risk factors, such as blood pressure, cholesterol and glucose levels. These results form the basis for future investigations aimed at establishing the possible strategies to increase protein intake among old subjects. Some studies addressed the potential diet for preventing sarcopenia that proposes eating meat 3-5 times a week (including white meat twice per week, lean red meat less than twice per week, and processed meat less than once per week) ²⁶. In the context of sarcopenia, where reduced protein intake has significant health implications for older people, particular attention should be focused on increasing protein through meats, fish and vegetable sources, and through supplements and fortified foods ^{6 27 28}.

Figures and tables

Figure 1.Meat protein intake (mean and SD) according to age group and gender (triangle for men, circle for women).

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