1. INTRODUCTION AND OVERVIEW
Try these questions:
Q1. The Recommended Daily Allowance within a group of healthy people of a given age and gender is set at:
A. The minimum intake (5th %ile) of a nutrient of needed.
B. The average intake (50th %ile) of a nutrient of needed.
C. The maximum intake (95th %ile) of a nutrient of needed.
D. The intake in childhood needed to protect a group of healthy children when they reach adulthood.
Q2. True or false: A general rule for laboratory assessment is that nutrient stores fall before biochemical markers are affected. Functional signs of disease follow.
And these techniques
1. Take a well-known classic disease of childhood such as rickets or pellagra and imagine what levels of the missing essential nutrients would be needed to prevent active disease using a Gaussian distribution curve (maybe include a diagram of the curve). What level might be needed to prevent a disease later in life: more than RDA? Less than RDA? See sections 3 and 4 of these Nutrition Notes for more information.
2. Find a colleague, or if in a seminar, the person sitting next to you. Explore the consequence of having chronic negative nutrient balance - e.g., losing or using more than you take in.. See Part II Section 2 on Nutritional Assessment for more information.
Introduction
Much of the field of pediatrics derives from work on the diet and nutrition of children. The volume and scope of material available to medical students are overwhelming. These short statements, "Nutrition Notes," were written to provide information essential to begin a career in medicine during which the importance of nutrition to clinical care will be emphasized continually. Each Note, when appropriate, will provide an introductory overview, important terms and concepts, requirements expressed as the ratio of nutrient required to energy consumed (nutrient density), consequences of disordered nutrition, diagnosis, prevention, and treatment.
Important terms and concepts
Nutrient (micro-, macro-, deficiency, excess, imbalance, and density); Recommended Daily Allowance (RDA) and Daily Recommended Intake (DRI).
The dilemma with Recommended Daily Allowances
Recommended Daily Allowances (RDA) were established to recommend a level of nutrient intake sufficient to keep healthy children and adults healthy. Except for calorie intake (set at the mean), the RDA is set at two Standard Deviations above the mean for a healthy reference population. Although this may seem straight forward, critics point out that RDA makes policy based on current practice rather than nutritional science. An alternative position is that a Daily Recommended Intake (DRI) should recommend nutrient intake so as to protect vulnerable populations for what might happen in the future or for problems associated with intakes unlikely to cause any of the classic nutrient deficiency diseases. Examples include levels of folate needed to prevent neural tube defects in pregnancy and coronary heart disease among all adults, or calcium intake by girls in childhood and adolescence necessary to prevent osteoporosis later in life. Because DRI levels are often higher than those recommended under RDA, it is necessary to watch for potential toxicity levels (TL) for intake of all micronutrients (both water and fat soluble vitamins and minerals).
Nutrients
Nutrients are the substances consumed which either promote growth (the energy containing macronutrients: proteins, carbohydrates, and fats) or elements (minerals) or chemicals (vitamins) necessary for metabolism - those not generated by the body in sufficient amount. The vitamins and minerals, together, are referred to as micro-nutrients. In addition, one must consider the importance of water and fiber. Lack of fiber in the diet is a cause for constipation. Elevated intraluminal pressures increase the risk of appendicitis (in youth), varicose veins, and diverticulosis (among adults). In addition, a low fiber diet has been associated with an increased incidence of degenerative diseases in adulthood in industrial societies.
The consequences of malnutrition
The variety of consequences to be considered result from 1) deficient intake, 2) malabsorption, 3) problems of nutrient-nutrient or drug-nutrient interaction or affect of nutrition on pre-existing disease, and 4) heritable responses to nutrients as in hypercholesterolemia.
The nutrient density (ND) of food items consumed and the diet as a whole is the most important influence on the likelihood of malnutrition occurring.
% of RDA for specific nutrients
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% of RDA for calories
Five potato chips or one orange have 100 calories = 5% of RDA. Potato chips do not contain >5% of RDA for any nutrient while an orange contains >5% of RDA for several. Thus potato chips are considered a "junk food" while fruits and vegetables are not.
FIGURE
The four general categories of malnutrition, as defined by the World Health Organization, are:
In addition, it is important to consider the consequences of using nutrients as pharmacological agents, so-called macronutrient therapies.
Diagnosis
As with all areas of clinical medicine, the most important element in establishing a diagnosis is to take a good history. Almost all nutritional disorders can be predicted from the medical, social and dietary history. The physical examination is important as well, but clinical findings come late in the course of nutritional disorders.
A general rule for laboratory assessment is that nutrient stores fall before biochemical markers are affected. Functional signs of disease follow.
Prevention is a part of every treatment plan
The mainstays for preventing nutritional disorders are 1) affordable nutritious food, 2) nutrient fortification, 3) nutrient supplementation and, 4) dietary counseling. In developing societies, the scarcity of adequate energy and protein are complicated by an unsanitary water supply, poor hygiene and consequent recurrent infection. In industrial societies, adequate energy and even adequate protein are generally present. However, poor housing and poor parenting skills often associated with poverty and ignorance frequently lead to bad outcomes that could be prevented by assuring safe housing, reducing the likelihood of accidents, and preventing inappropriate dietary practices.
The Answers are in the text. Like all primers, however, there are some exceptions:
A1. The correct answer is C. The 95th %ile sets the standard for concurrent disease prevention. DRIs however are used to address potential future illness.
A2. This is True. Beneath the surface, however, there is a debate in the literature whether for some nutrients (iron and folate for example) consequences occur with diminished storage and metabolic alterations.
