Keywords

1 Introduction

In this volume of the bookseries “Healthy Ageing and Longevity”, we have succeeded in bringing together a diversified group of researchers and academicians reviewing the published literature and presenting their personal views about nutritional components, foods, dietary patterns, and nutrition- and diet-based interventions for health and longevity.

It is worth repeating from our preface to this volume that nutrition, food and diet are the terms often used casually and uncritically as overlapping ones. However, while “nutrition” generally refers to the macro- and micro-nutrients essential for health and survival, nutrition is normally obtained from animal- or plant-based foods. We do not eat nutrition, we eat food, without always being aware or conscious of the nutritious value of the food. Moreover, these nutritional values may or may not match our bodily requirements which depend upon various factors, such as age, general health status, physiological demands and accessibility. Even more importantly, there are crucial socio-cultural dimensions which give shape to our taste, preferences and taboos towards food (Samaddar et al. 2020). Furthermore, the three commonly identified meals of the day – breakfast, lunch and dinner – are as varied globally as different populations, societies and cultures. And above all of this lurks in the background the evolutionary history of Homo sapiens from being hunter-gatherers to becoming agriculturists (Finch 2010), and to the present state of becoming the consumers of highly processed food products with overeating behaviors wherever food is available in abundance.

In this concluding chapter, we try to recapitulate the main messages which can be derived from various chapters in this book (Table 30.1), and how that information can be useful for making recommendations and suggestions for practical use and for future research. Perhaps the central carry home message is obvious that optimizing our nutrition by making the “right” choice of food and aligning our eating behaviors with our bio-social rhythms are the most effective general strategies to maintain, recover and even enhance individual- and public-health.

Table 30.1 Chapter sequence, titles, authors and page numbers
Full size table

2 Nutrition

Proteins, carbohydrates and lipids are the three essential nutritional components which provide us the basic material for building our biological structures and for producing the energy required for all physiological and biochemical processes. Additionally, minerals and micronutrients, including vitamins, facilitate the optimal utilisation of the primary nutritional components by catalyzing numerous biochemical processes, by increasing their bioavailability and absorption, and by balancing the microbiome crucial for maintaining health (see Chapters 1 to 5). Another category of nutrients, termed nutritional hormetins, are various compounds in the food, which by virtue of their toxic nature, induce and stimulate body’s intrinsic repair and maintenance systems. This apparently paradoxic effects of toxic compounds in the food as health-beneficial nutritional hormetins is in line with the basic understanding of the biological mechanisms of health and survival through adaptive responses and hormesis (Rattan and Kyriazis 2019) (see chapter 6). Furthermore, it is in this context that we need to understand and appreciate the evolutionary basis of human nutritional requirements (see chapter 7). This is also the basis of understanding human nutrigenomics (how nutritional components affect gene expression) and nutrigenetics (how our genetic heterogeneity affects our response to various nutrients) (Mutch et al. 2005; Wittwer et al. 2011).

3 Food

Almost all the food we eat is of the animal and plant origin, although continuing advancements in nutrition research and innovation of food industry may open up new vistas including man-made synthetic foods. Besides the inherent nutritional composition of plant- and animal-based foods, farming and agricultural practices, methods of food preparation and preservation, and the amounts consumed are equally important factors for their eventual health benefits (see chapter 8 and 9). Moreover, prevalent climatic conditions and the local production of raw materials have always challenged human-beings across civilizations and cultures to explore and develop different processes of preservation and modification, such as fermentation. The claimed health benefits of fermented foods are attributed to a combination of bioactive components released as by-products of the fermentation process and the presence of probiotics in these foods, which support the gut microbiota (see chapter 9).

Various foods consumed traditionally in different cultures, and some of the claims made for their potential modes of action, have been scientifically validated to some extent. Such foods are often touted as complete foods, anti-inflammatory foods, food for brain, food for physical endurance, functional foods and so on (see chapter 11–13). Traditional foods enriched with a variety of phytoconstituents and other minerals, vitamins and natural or synthetic hormetins are generally promoted under the banner of “functional foods”. A similar trend can be seen for milk and dairy products with novel and innovative formulationswith a focus on functionality, health, and easy availability (see chapter 10).

4 Diet and Culture

The next stage after having access to food is the manner in which that food is consumed, and that is what gives it the status of becoming diet or a meal. This is also where the socio-cultural aspects of dietary habits and traditions become more important than the biochemistry and molecular biology of the nutritional components of food (Samaddar et al. 2020). The so-called Mediterranean diet, paleo diet, ketogenic diet, Chinese diet, Ayurvedic diet, vegetarian diet, and more recently, vegan diet, are some of the varied expressions of such social and cultural practices (see chapter 15-18). The health outcomes of these variety of dietary and mealing patterns prevalent in different cultures have been helpful in cross-cultural adaptation to both healthy eating patterns on one hand and bringing awareness about the health-risk associations of certain food habits on the other. It is in this context that the subject of chrononutrition, that is how our daily rhythms affect and regulate our nutritional needs, has become an important aspect of healthy eating (see chapters 17, 18). Similarly, the so-called “nutrient timing” involves eating foods at strategic times in order to achieve certain outcomes, such as muscle growth, sports performance and fat loss (Kessler and Pivovarova-Ramich 2019). Looking back into the cultural history of longevity foods, one realizes that it is not just the right combination of nutrients which is important, but the elaborate social practices, rituals and normative behaviors for obtaining, preparing and consuming food are equally, if not more, important aspects of health-promoting eating (see chapter 20).

Thus, dietary patterns and meal-timing seem to be more predictive of health-related quality of life than foods or nutrients on their own (Fontana and Partridge 2015; Kessler and Pivovarova-Ramich 2019). Encouraging a shift to healthy dietary patterns, however, critically depends not only on the food availability, accessibility and affordability, but also on the behavioral, intentional and socio-cultural conditions of consumers for making their food choices. An old saying that “we are what we eat” may be corrected to that “we eat what we are”!

5 Nutritional and Dietary Interventions

Food is often considered as one of the three pillars of human health and survival – the other two being physical activity, and social and mental engagement. Therefore, manipulating and modifying food components and food habits have always been attractive targets for intervention. This is exemplified by extensive research done on the effects of individual nutrients, short peptides, and plant extracts in stimulating, inhibiting or regulating various molecular pathways in relation to ageing, and age-related diseases, including cancer, in experimental animal model systems and cells in culture (see chapters 21, 23, 28). More recently, single-nutrient-based or multiple-nutrients-based selective killing of senescent cells, and calorie restriction mimetics as anti-ageing therapies are being tested and developed (see chapters 22, 25). These therapeutic strategies follow the same “one target, one missile” pharmaceutical rationale, and consider ageing as a treatable disease. However, often the promises made, based on the results obtained from such experimental studies, are either naïve extrapolations from experimental model systems or overhyped claims for human applications, which deliver very little in reality (Rattan 2020) (see chapter 29).

Some other innovative, holistic and relatively easy to implement food- and diet-based interventions strategies are caloric/dietary restriction and time restricted eating (TRE) regimens. For example, intermittent fasting (IF), based on feeding/fasting timing manipulation, is emerging as a promising intervention to promote health and longevity. Meta-analyses of several pilot studies in human subjects show that TRE, with eating restricted to a few hours in the day time, has beneficial effects on several health parameters (Mattson et al. 2014) (see chapter 24). Similarly, several other practical recommendations are made for the optimal nutrition in old age (see chapter 26), and for the regulation of metabolic syndromes, especially metabesity (see chapter, 27).

6 Conclusions and Suggestions

Food is more than just being one of the three pillars of health. Food is both the foundation and the scaffolding for the building and survival of an organism on a daily basis. Scientific research on the macro- and micro-nutrient components of food has developed deep understanding of their molecular, biochemical and physiological roles. Various recommendations are repeatedly made and modified for some optimal daily requirements of nutrients for maintaining and enhancing health, and for the prevention and treatment of diseases. Can one envisage developing a “nutrition pill” for perfect health, which could be used globally, across cultures, and at all ages? We don’t think so.

So far, most of our knowledge about nutrients comes from the experimental studies made with individual active components, or, at best, with the combination of one or two compounds. However, in reality, we obtain these nutrients from the food where they exist together with hundreds of other interacting compounds, and become modified through the process of cooking and preservation. Scientifically, there is very little known about the health-related effects of innumerable combinations of food sources, cooking methods, dietary combinations and other factors. However, there is a lot of folk knowledge available in all cultures about the dos and don’ts of food, for which we need scientific verification and validation. For this purpose, we must rethink and modify our presently established scientific protocols of double blinded randomized control trials which are practically impossible to apply on food and dietary research at the population level.

Finally, nutrition, food and diet are the basis of life, health and longevity. We have gathered a huge amount of information with respect to what nutrition is required for health and survival, which foods can provide what nutrition and to what extent, and which dietary and eating practices seem to be more or less health beneficial. Whereas in some parts of the world, abundant availability and accessibility of food has led to its overuse, abuse and consequent life-style diseases, in other parts of the world economic disparity and food scarcity keep perpetuating starvation, malnutrition, poor health and shortened lifespan. It is usually not the lack of knowledge about the optimal nutrition, food and diet that forces us to make bad choices; rather it is either our inability to access such foods, or our gullibility to fall prey to the exaggerated claims in the commercial interests of the food companies, which determine what and how much we consume. Science will and must continue to gather more information about the biochemical, physiological and other aspects of food, which we should apply wisely and globally for the health and longevity of all.