Interactions of gut microbiota with functional food components and nutraceuticals

Abstract

The human gut is populated by an array of bacterial species, which develop important metabolic and immune functions, with a marked effect on the nutritional and health status of the host. Dietary component also play beneficial roles beyond basic nutrition, leading to the development of the functional food concept and nutraceuticals. Prebiotics, polyunsaturated fatty acids (PUFAs) and phytochemicals are the most well characterized dietary bioactive compounds. The beneficial effects of prebiotics mainly relay on their influence on the gut microbiota composition and their ability to generate fermentation products (short-chain fatty acids) with diverse biological roles. PUFAs include the ω-3 and ω-6 fatty acids, whose balance may influence diverse aspects of immunity and metabolism. Moreover, interactions between PUFAs and components of the gut microbiota may also influence their biological roles. Phytochemicals are bioactive non-nutrient plant compounds, which have raised interest because of their potential effects as antioxidants, antiestrogenics, anti-inflammatory, immunomodulatory, and anticarcinogenics. However, the bioavailability and effects of polyphenols greatly depend on their transformation by components of the gut microbiota. Phytochemicals and their metabolic products may also inhibit pathogenic bacteria while stimulate the growth of beneficial bacteria, exerting prebiotic-like effects. Therefore, the intestinal microbiota is both a target for nutritional intervention and a factor influencing the biological activity of other food compounds acquired orally. This review focuses on the reciprocal interactions between the gut microbiota and functional food components, and the consequences of these interactions on human health.

Introduction

The intestinal tract harbours a complex bacterial community (microbiota), integrated by more than 800 different bacterial species, which have an enormous impact on the nutritional and health status of the host. The metabolic activity developed by the gut microbiota contributes to the digestion of dietary compounds, salvage of energy, supply of (micro)nutrients and transformation of xenobiotics. Overall, a balanced gut microbiota composition confers benefits to the host, while microbial imbalances are associated with metabolic and immune-mediated disorders [1], [2]. The composition of the gut microbiota is influenced by endogenous and environmental factors (diet, antibiotic intake, xenobiotics, etc.). Of these factors, the diet is considered a major driver for changes in gut bacterial diversity that may affect its functional relationships with the host [3]. In fact, the microbiome of the adult-type and infant-type microbiota has distinct gene contents to accommodate nutrient acquisition strategies to different diets [4].

The primary role of diet is providing sufficient nutrients to meet the basic nutritional requirements for maintenance and growth, while giving the consumer a feeling of satisfaction and well-being. In addition, some food components exert beneficial effects beyond basic nutrition, leading to the concept of functional foods and nutraceuticals [5]. Functional foods are those foods that provide benefits beyond basic nutrition when consumed as part of the regular diet. Nutraceuticals are extracts containing the biologically active food components supplied in other than a food form. Dietary components with biological effects are susceptible to be metabolized by intestinal bacteria during the gastrointestinal passage, prior being absorbed. The colon has the highest bacterial load and constitutes an active site of metabolism rather than a simple excretion route [6]. The metabolic activity of the gut microbiota on bioactive food components can modify the host exposure to these components and their potential healthy effects. Furthermore, some functional food components influence the growth and/or metabolic activity of the gut microbiota and, thereby, its composition and functions [7], [8]. Therefore, the intestinal microbiota is both a target for nutritional intervention to improving health and a factor influencing the biological activity of other food compounds acquired orally. This review focuses on the reciprocal interactions between the gut microbiota and functional food components, and the consequences of these interactions on human health (Fig. 1).