Читать книгу Recent Research in Nutrition and Growth - Группа авторов - Страница 7

This workshop addressed a series of challenges that limit the present understanding of the biology by which diet and nutrition influence the growing human body, identified areas of expanding knowledge, and highlighted focal areas in which increased attention may contribute to improving healthy early development. The speakers provided interdisciplinary viewpoints elucidating the importance of understanding growth and development as a process in nutritional studies. Examples from both physical growth and cognitive development emphasized the need for accuracy and sensitivity of assessment in the context of the developmental process in an effort to allow for the clarification of more meaningful and impactful outcomes.

A central challenge addressed is the need to clarify what is actually being measured in studies aiming to identify causal relationships between nutrition and development. A foundational step is the precision of measured variables. Speakers considered what it means to evaluate physical growth and behavioral development, and how these assessments are best carried out in the context of questions about nutritional modulation. We have traditionally been functioning with concepts that are far more general than the processes that we aim to capture, and this has resulted in a large gap between what we think we know and what is actually occurring biologically. For example, body weight tells us something about the energetic status but very little about the process of growth in terms of body composition that will ultimately influence health, and traditional behavioral and biobehavioral assessments, as well as global standardized tests, are unlikely to be sensitive to nutritional manipulations that seek to affect later cognition and language. Studies have long focused on broad concepts while effects occur at proximal levels. The granularity of what has traditionally been measured versus the nature of the actual processes and outcomes is a serious factor in need of more careful consideration. Advanced technology has expanded anatomical knowledge and brought more specific physiological insights to bear on the broad questions of nutrition and growth, revealing tissue specificity and documenting that the causal center of action for predictability in both neurocognitive and physical development is at the cellular level. The workshop emphasized that it is time to upgrade our approaches and move beyond associations with uncertain mechanisms to the detection of causal pathways, and in this way enhance the ability to intervene.

The importance of new more granular evidence cannot be underestimated. Attention to physiology and anatomy underlying phenotype and function documents the centrality of this deeper look. Understanding that core processes are often controlled through cascade effects in cellular systems brings the importance of timing in intervention strategies and outcome measurement to the fore. The realities are that not all interventions in a developmental process have observable phenotypic effects, some effects are delayed, and some are silent from the viewpoint of measurable phenomena until a confluence of events occurs. This is well illustrated by work documenting the importance of specific nutrients acting at the cellular level by way of myelination effects, for example. By targeting this most critical process to neurocognitive development, interventions can have efficacy key to coordinated activity across multiple brain areas. Likewise, a shift in targeted outcomes from lower-order cognitive components, such as attention and memory, to more nuanced behaviors, such as inhibition, goal-directed behavior, and other higher-order executive functions, has been important in shedding light on mechanisms by which specific nutritional elements, e.g., docosahexaenoic acid (DHA) and arachidonic acid (ARA), contribute to the emergence and refinement of these functions in late infancy and early childhood. Positive effects of supplementation include long-term benefits that emerge beyond the end of feeding, including modest improvements in behavioral control and reading. Similar approaches will be usefully employed in the realm of physical growth, wherein health outcomes associated with growth patterns in early life are likely to reflect long-term effects of muscle cell adequacy and fat cell abundance, not overall body size. Traditional interventions based on weight changes reveal nothing about nutritional effects on the physiology of growing tissue cells, the basis of lifetime health. Key directions for the future include identifying markers that can be applied in practice to measure physical growth and cognitive/behavioral development as the specific approaches used in research settings do not lend themselves to large-scale use at this time.

A further central challenge is clarifying the nature of the nutritional input under investigation and identifying salient elements that effect modulatory developmental effects. These questions range from large-scale issues of macronutrient mechanistic effects, such as the cell level differences distinguishing protein and fat content pathways, to broad multisystem questions of when is a nutritional effect actually nutritional? For example, considerations of what exactly is being investigated in breast- versus bottle feeding protocols beyond nutritional content have arisen. Temporal aspects of a feeding strategy may underlie physical growth modulation, and aspects of psychological attachment may relate to associations with brain and behavioral development in childhood.

Key directions for the future include a focus on the prenatal period and the effects of nutrients and nutritional status during pregnancy on the development of the central nervous system.

In summary, the workshop speakers articulated the importance of recognizing that development is a time-sensitive process across the body, involving all tissues albeit with different maturational programs. Identifying nutritional modulators of these processes is challenging and requires designing protocols to both capture time-sensitive interactions and document outcomes of developmental processes that by definition involve time lags and may include phenotypic changes compared to initial conditions. The discussions emphasized the needs for both a multidisciplinary approach in expanding knowledge about the nexus of nutrition, growth, and development and a long-range focus that encompasses the broader environment incorporating consideration of the fundamental importance of developmental time, including preconception conditions in studies of nutrition. Optimal development has long been a concept associated with both adequate nutrition and quality environmental conditions, as the latter are potentially powerful moderators of nutritional effects. Retaining developmental principles in these efforts and employing more proximal indicators of how nutritional modulations occur will be central in expanding our abilities to improve growth during the earliest ages to optimize health across the lifespan.

John Colombo

Berthold Koletzko

Michelle Lampl