NUTRITION THROUGH THE LIFE CYCLE

1.1 Approaches to the Study of Human Nutrition

Most texts on the subject of nutrition approach it from the viewpoint of the various nutrients present in food in our daily diet; provide information on the chemical structure of the nutrient, its important biological actions and their physiological role in the body; highlight the important sources of these nutrients in the foods that compose our daily diet; explain how the nutrients are made available to the body from the food ingested; and provide descriptions of the various pathological conditions that are associated with their deficiency or excess.

Another approach would be to characterise the stages of life through the cycle of life from conception to death, with the reproduction of the species, through this cycle (see Fig. 1.1). This approach provides a detailed account of the nutritional needs throughout the life cycle and highlights the special nutritional features of each of these stages. It also provides an opportunity to highlight the nutritional problems (related to both deficiency and excess) that characterise that particular phase in the life cycle and gives an opportunity to suggest ways and means to intervene during these phases taking into consideration the special problems that one needs to be aware of during this period in the individual's life. It also enables one to look at the promotion of good nutrition, taking care of identified vulnerabilities during each of these periods and thus helping to ensure the nutritional well-being and good health of the population as a whole.

The expectation is that the latter approach to the study of nutrition is more holistic and puts the individual at the various life stages of growth, development and the continuing ageing process at the centre rather than the nutrients in our daily diet. A subtle but important distinction that needs to be made when one approaches the study of human nutrition through the life cycle is to recognise that health and nutritional problems that manifest at the various life stages are not wholly dependent on inadequate or poor nutrition during that phase, although several nutrients may affect the individual during these critical periods in growth and development. The appreciation that what has happened in the past may continue to affect the individual and will interact with events and nutritional stresses later in life provides a life course perspective to nutritional problems that manifest at the various life stages throughout the life cycle. The life cycle approach to nutrition enables one to discuss these important interactions in a more meaningful manner than a didactic and reductionist approach to the science of human nutrition.

It would not be out of place to state that, just as one may consider the various life stages through one's life cycle, one has to acknowledge that the food industry that caters to us as consumers recognises us as several life style groups, which are specifically researched and targeted, such as for instance teenagers, young free and single, traditional families and retirees. On the other hand, organisations involved with promoting good nutrition and health may specifically target identified stages in the life cycle, such as pregnant mothers, babies, toddlers, school children, adolescents, adults (early, middle and late), elderly, etc.

1.2 Nutrition through the Life Cycle

The life cycle approach to nutrition provides an opportunity to look at the individual as she or he passes through the various life stages (the main stages of the life cycle are outlined in Fig. 1.1), as well as enabling the student to look at the entire population distributed at any given time throughout the various stages in the life cycle.

This approach has several advantages (1). It helps recognise age-specific vulnerability throughout the life cycle. Bartley et al. (2) summarise the various critical transitions and life events in human development, which occur side by side with the biological growth and development of the individual and may characterise periods of vulnerability of an individual in society (Fig. 1.2).

The life cycle approach helps us to understand that maximum benefits in one age group at a particular stage in the life cycle can best be derived from interventions made in an earlier stage or age group of individuals. For instance, it helps us to recognise that better nutrition and health during pregnancy will improve intra-uterine growth, improve birth outcomes and result in fewer complications related to pregnancy outcome; or that improved physical growth and development in infancy translates into improved cognitive function and intellectual development during childhood and leads to better economic prospects both for the individual in adulthood and in turn for society; or that improved birth weights mean less risk of chronic disease and premature death in adulthood.

This approach also reinforces the view that interventions at several points across the life cycle are needed to sustain improvements in health and nutritional outcomes. For instance, one will find it easy to consider that, for good health outcomes, the importance of good nutrition begins in the diet and nutrition during pregnancy, and continues in exclusive breast feeding at birth and the timely and adequate provision of complementary feeds, and good nutrition and diets during childhood, adolescence and adulthood to ensure healthy ageing and a good quality of life in the last stage of one's life.

The life cycle approach also enables us to consider risks and benefits through the entire life cycle and across generations and thus provides an opportunity to understand the importance of the increasingly popular life course approach to health and nutritional well-being.

Thus, a life cycle approach can help us to assess risks at various life stages, recognise important environmental influences that may be inimical to good nutrition and health, and identify key interventions at the various stages in the life cycle to prevent or deal with these external factors. An understanding of the importance of the life cycle approach implies that we recognise that ensuring good nutrition and healthy lifestyles is a life-long function. An elderly individual is unlikely to benefit much from a change in diet and life style late in life; nor does the pursuit of good nutrition and healthy lifestyles come easy to someone who has not followed this course in the earlier phases of life.

1.3 Nutrition over the Last Century in the United Kingdom

Childhood malnutrition and nutritional deficiencies are now things of the past in the developed industrialised west – in the United Kingdom and the rest of Western Europe and in the USA. However, it may not be out of place to remind ourselves that at the end of the 19th and around the beginning of the 20th century, malnutrition was a...