**1. Introduction**

In recent years, the world has been experiencing a steady increase in the aging population. It is expected that by 2050, one in six people will be over the age of 65, including one in four in Europe and northern America [1]. This increased life expectancy is associated with a higher risk of morbidities. In fact, nearly a quarter (23%) of the overall global burden of death and illness is in people aged over 60, and much of this burden is attributable to longterm illnesses [2]. Advancing age is indeed accompanied by common geriatric syndromes, such as frailty [3]. Frailty is characterized by a depletion in the functional reserves of physiological systems, which limits the possibility to adapt to changes in the environment over time, leading to falls, hospitalization, disability, and death [4]. Nevertheless, frailty can be prevented, and diet appears to be a major determinant of its development [5,6]. Several studies have reported that particular macronutrients [7,8], food groups [9–11] and dietary patterns are associated with frailty [12–17]. Particularly, our group has previously reported the relevance of protein intake (>1 g/d being associated with a lower prevalence of frailty) [18], of fruit and vegetable intake (>5 servings/d being associated with a lower risk of frailty) [9], and of the Mediterranean diet (a higher adherence being associated with a lower frailty risk) [17]. In line with our findings, several other longitudinal studies have showed that a higher protein intake is protective against frailty [19–21].

**Citation:** Rahi, B.; Pellay, H.; Chuy, V.; Helmer, C.; Samieri, C.; Féart, C. Dairy Product Intake and Long-Term Risk for Frailty among French Elderly Community Dwellers. *Nutrients* **2021**, *13*, 2151. https://doi.org/10.3390/ nu13072151

Academic Editor: Emmanuel Biver

Received: 5 May 2021 Accepted: 21 June 2021 Published: 23 June 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

<sup>1</sup> Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Byblos 36, Lebanon; berna.rahi@gmail.com

Dietary sources of protein include dairy products (DP), which are also important sources of calcium and vitamin D. Interestingly, recent studies have showed that higher DP consumption was associated with better age-related health outcomes, and particularly lower risks of type 2 diabetes [22,23], cardiovascular diseases and mortality [24,25]. The type of DP (i.e., milk, fresh DP and cheese) appears to be key component of such associations. In fact, a meta-analysis on 938,415 participants and 93,518 mortality cases reported an absence of association between total dairy (high- or low-fat) and milk with the risk of death, while total fermented dairy (including sour milk products, yogur<sup>t</sup> or cheese; +20 g/day) were associated with a significant 2% reduced risk of all-cause mortality and cardiovascular diseases [26]. While two systematic reviews also observed that higher DP intakes were associated with higher appendicular muscle mass, improved balance-test scores, and an attenuation of the loss of muscle strength [27,28], the direct potential benefit of DP on frailty as a whole has scarcely been studied. To the best of our knowledge, a single prospective study implemented in the Spanish Seniors-ENRICA cohort [29] reported that consuming seven or more servings per week of low-fat milk was associated with a significantly lower risk of frailty compared with consuming less than one serving per week. The external validity of such results remains uncertain. Indeed, the SHARE database demonstrated significant heterogeneity in DP consumption across Europe, with higher levels in central and northern countries and in Spain, and the lowest prevalence of dairy intake in eastern European countries [30]. Of note, high cheese consumption is a hallmark of French dietary habits, and France is also characterized by low milk consumption. Finally, several sociodemographic, nutritional characteristics and lifestyle factors have been associated with the French DP consumption, with specificities according to each DP sub-type [31]. Altogether, it is conceivable that the featured consumption of DP sub-types among French older adults could be differentially associated with frailty.

Therefore, our objective was to assess the cross-sectional and prospective associations between total DP and DP sub-types (milk, fresh DP and cheese) consumption and the 10-year frailty risk among older adults of the Three-City (3C) Bordeaux cohort.
