BMA Board of ScienceWhat is good nutrition?Good nutrition implies that the body’s needs for energy <strong>and</strong> nutrients, from the macronutrientsprotein, carbohydrate <strong>and</strong> fats to the micronutrients such as vitamins <strong>and</strong> trace elements, arebeing met by the diet. The body’s needs for nutrients arise from a wide range of processes. Themost immediately obvious are linked to basal metabolism – such as the need for dietary fat <strong>and</strong>carbohydrate to produce energy, <strong>and</strong> thiamine (vitamin B1) in its active pyrophosphate form as acofactor in oxidative decarboxylation of pyruvic acid <strong>and</strong> -ketoglutaric acid. Although physicalactivity <strong>and</strong> work require energy, the greater part of our need for dietary energy is to support basalmetabolism. Nutrient intake needs to be sufficient to maintain body reserves <strong>and</strong> to replace theturnover of components such as muscle proteins that are broken down during normal function.An adequate nutrient intake is essential for immunity; nutritional status <strong>and</strong> the intake of nutrientssuch as n-3 polyunsaturated fatty acids, antioxidant nutrients <strong>and</strong> zinc affect immune function –<strong>and</strong> the activities of the immune system may themselves have negative effects on nutritionalstatus. Finally, nutrient requirements are increased during pregnancy, <strong>and</strong> during postnatal growth<strong>and</strong> development. The many functions of nutrients means that adequate nutrition is central tometabolic integrity, <strong>and</strong> of key importance to growth, reproductive function <strong>and</strong> the maintenanceof good health.Key messageThe many functions of nutrients mean that adequate nutrition is central to metabolic integrity,<strong>and</strong> of key importance to growth, reproductive function <strong>and</strong> the maintenance of good health.Malnutrition implies that the body’s needs for nutrients are not being met; it also describes animbalance of these constituents that can be associated with either inadequate or excessive foodintake. During short periods of insufficient energy supply the body can use reserves, such as fat<strong>and</strong> glycogen in liver <strong>and</strong> muscle, <strong>and</strong> degrade some tissues to preserve its function. In the longerterm, an insufficient supply of nutrients will become limiting to function. In early life an insufficientsupply of nutrients will result in reduced growth <strong>and</strong> impaired development. It is noteworthy thatduring development these effects may be due to deficiencies in dietary constituents that are notusually essential in adult life. For example, because the fetal requirements for the non-essentialamino acid glycine are large, it becomes conditionally essential in late gestation <strong>and</strong> poor nutritioncan produce effects of glycine insufficiency. 6The developmental consequences of inappropriate nutritionThe focus of this report is on the long-term consequences for health arising from impaired growth<strong>and</strong> development in early life – both in prenatal life <strong>and</strong> in early childhood. Every individual has a‘blue-print’ that is genetically determined, <strong>and</strong> that sets their growth potential; but realisation ofthis potential is only possible if the nutrient supply during growth is adequate. 7 Among babiesborn to chronically malnourished women, low birth weight is relatively common, <strong>and</strong> stunting ininfancy is prevalent in communities where food supplies are insufficient. Beyond these extremeexamples though, our underst<strong>and</strong>ing of the importance of variations in diet <strong>and</strong> nutritional status,such as those seen in the UK population, <strong>and</strong> how these impact on early development, is limited.Babies continue to be born <strong>and</strong> to survive in populations that are chronically malnourished, <strong>and</strong>nutrient supplementation studies carried out in these communities often result in small changes inbirth size. 8, 9 In the past it might have been concluded that prenatal growth is largely protectedfrom variations in maternal diet <strong>and</strong> nutritional status. We now know that variations in birth size,that we describe as being within the normal range, are predictive of disease incidence much later<strong>Early</strong> life nutrition <strong>and</strong> lifelong health 7
BMA Board of Sciencein life – <strong>and</strong> that this is evident even in developed communities such as the UK. Within this range,lower birth weight <strong>and</strong> impaired early growth are linked to an increased occurrence of chronicconditions such as cardiovascular disease <strong>and</strong> type 2 diabetes in adult life. 10The importance of development for later healthThe discovery that adult chronic disease is linked to low birth weight <strong>and</strong> poor weight gain in infancyled Hales <strong>and</strong> Barker, in 1992, to put forward the ‘thrifty phenotype’ hypothesis 11 (see Figure 2). Thecentral element of the hypothesis is that fetal <strong>and</strong> infant malnutrition are important drivers of theprocesses leading to disease in later life. Fetal malnutrition could arise through maternalmalnutrition or failure of the ‘fetal supply line’ such as placental insufficiency. It was proposed thatmalnutrition during these periods of rapid development forced the fetus or infant to become‘thrifty’ <strong>and</strong> to prioritise limited resources to some tissues at the expense of others. Thus, braingrowth would be supported, but truncal growth, the growth of skeletal muscle, the developmentof abdominal organs (liver, pancreas, kidneys) <strong>and</strong> some parts of the vascular tree would bedeprived. It was also proposed that this altered growth led to permanent changes in the structure<strong>and</strong> physiology of many tissues, leading to reduced functional capacity in later life. This reducedcapacity may not be important to individuals who continued to be poorly nourished, but diseasewould be triggered more readily by ‘stressors’, such as obesity, in later life. Hence if fetal <strong>and</strong>/orinfant undernutrition resulted in a reduced pancreatic beta cell mass, this would be more likely toresult in type 2 diabetes <strong>and</strong> the metabolic syndrome if the individual became obese in childhoodor adult life.Key messageIt has been known for many years that unbalanced nutrition during development can causelong-term consequences leading to permanent changes in the structure <strong>and</strong> physiology ofmany tissues, leading to reduced functional capacity in later life. The consequences of this forhuman chronic disease are now increasingly appreciated.8<strong>Early</strong> life nutrition <strong>and</strong> lifelong health
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