Nutrition for the Primary Care Provider

D. M. Bier, J. Mann, D. H. Alpers, H. H. E. Vorster, M. J. Gibney

• Éditeur: S. Karger
• Année: 2014
• ISBN:
  9783318026672
• Sujet: Medicina
• Sous-sujet: Salud pública, administración y atención

Nutrition is an integral part of the prevention and management of the most prevalent conditions faced by today's primary care providers. This book is aimed at physicians around the world who treat patients from all walks of life. The first section is devoted to the basic principles of nutrition, covering the fundamentals of body composition, energy balance, and appetite, as well as the importance of the different macro- and micronutrients. The following section builds on the principles of the first by focusing on the special needs for specific circumstances, including pregnancy, exercise, food allergies and religion. The third part provides an overview of our latest understanding of various disease states and how they are influenced by nutrition. The final part on Food Policy takes a bird's eye view, offering perspectives on global sustainability, the rapidly changing face of malnutrition and the role played by the food industry in consumer health. This book is a practical reference source that will guide physicians on how to use nutrition as a tool to prevent and cure disease.

Nutrition for Disease States

Bier D, et al. (eds): Nutrition for the Primary Care Provider. World Rev Nutr Diet. Basel, Karger, 2015, vol 111, pp 87-93
DOI: 10.1159/000362304

______________________

Approach to the Patient and Differential Diagnosis

L. John Hoffer^a Bruce R. Bistrian^b

^aLady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal, Que., Canada; ^bBeth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass., USA

____________

Key Words

Protein-energy malnutrition · Micronutrient deficiency · Intestinal malabsorption · Inflammation · Weight loss · Cachexia · Starvation · Vitamins · Minerals

____________

Key Messages

• Protein-energy malnutrition (PEM) ordinarily develops after a period of prolonged inadequate protein and energy consumption. The hallmarks of PEM are generalized muscle atrophy and subcutaneous adipose tissue depletion.

• Except for cachexia associated with chronic inflammatory, end-organ, and malignant diseases, the most common cause of weight loss in adults is depression. Chronic diseases, especially of the gastrointestinal tract, can negatively affect diet and nutrient absorption.

• Assessment of the severity of PEM and of the extent of systemic inflammation is important to determine when to begin invasive feeding (either by feeding tube or intravenously).

• The appearance of a vitamin or mineral deficiency in a normal adult eating a conventional diet suggests the possibility of a drug-nutrient interaction or an undiagnosed disease of the gastrointestinal system.

• It is important to identify the cause(s) of a diagnosed micronutrient deficiency in order to administer the appropriate treatment and to address the Underlying disease.

© 2015 S. Karger AG, Basel

Introduction

Primary care physicians encounter two general kinds of malnutrition, protein-energy malnutrition (PEM) and micronutrient (vitamin and mineral) deficiency.

PEM is the disease that results from chronic starvation or severe intestinal malabsorption. The clinical course of PEM is strongly influenced by systemic inflammation and coexisting muscle atrophy due to physical inactivity, a primary neuromuscular disease, or old age (sarcopenia). By definition, starving people do not consume (or absorb) enough food, so they are also at risk of micronutrient deficiencies.

With two important exceptions (vitamin D and iron), overt micronutrient deficiencies are rare in healthy adults whose body weight is maintained on a conventional diet. The development of a vitamin or mineral deficiency in such people strongly suggests the possibility of a drug-nutrient interaction or an as yet undiagnosed disease of the gastrointestinal system. Conversely, several chronic diseases affect diet and can impair nutrient absorption. People with these diseases are at risk of micronutrient deficiencies, even when their overall food intake is adequate and their body weight is normal.

Table 1. Characteristics of successfully adapted PEM

Metabolic and endocrine

Hypothermia

Secondary amenorrhea

Serum free thyroxin and TSH normal

Neurocardiovascular

Sinus bradycardia

Reduced cardiac output

Hypotension

Reduced sympathetic tone

Muscular and functional

Generalized muscle atrophy and weakness

Reduced myocardial mass

Ineffective cough

Reduced ventilatory response to hypoxia

Drug disposition

May be altered [9]

Immune function

Weakened body barriers due to skin thinning and

ineffective cough

Reduced febrile response to infection

Normal humoral and cellular immunity in the

absence of micronutrient deficiencies

Psychological abnormalities

Apathy

Anorexia

There are differences of opinion amongst experts as to the implications of subclinical deficiencies of vitamin D, omega-3 fatty acids, folic acid and cobalamin (vitamin B₁₂) with regard to cancer and cardiovascular disease risk, and age-related cognitive decline.

Protein-Energy Malnutrition

Also known also as ‘hunger disease’, PEM typically develops after a period of prolonged inadequate protein and energy consumption. The cardinal signs of PEM are generalized muscle atrophy and subcutaneous adipose tissue depletion. The pathologic features of PEM emerge when the body's protein reserve, skeletal muscle, has become depleted seriously enough to impair specific physiological functions (table 1). Metabolic adaptation strongly influences the clinical course and prognosis of PEM. Survival is common even in prolonged uncomplicated semi-starvation, thanks to an adaptive reduction in resting and total energy expenditure, which, together with the reduction in the body's metabolically active tissue mass, lowers energy expenditure enough to match the low rate of energy provision. Metabolic adaptation also increases the efficiency of dietary protein assimilation, and modifies endogenous protein turnover to reestablish whole body protein homeostasis despite the subnormal level of protein consumption. Successfully adapted PEM is sometimes referred to as adult ‘marasmus,’ a term borrowed from pediatric medicine, and more recently, as ‘starvation-related malnutrition’. The metabolic response to systemic inflammatory disease, severe injury or severe infection amplifies body protein catabolism and prevents the adaptation to PEM, creating a potentially lethal condition. The terms ‘adult kwashiorkor’ and ‘acute disease or injury-related malnutrition’ are used to describe PEM that is induced or complicated by intense systemic inflammation. The terms ‘cachexia’ or ‘chronic disease-related malnutrition’ refer to partially adapted PEM in the context of chronic mild systemic inflammation, as occurs in inflammatory polyarthritis, advanced renal, liver, heart or pulmonary disease, and some cancers. PEM has a worse prognosis in the elderly, largely because their primary medical or surgical diseases tend to be more serious, and because sarco-penia has already reduced their body protein reserve [1-5].

PEM and sarcopenia are not uncommon in obese people. The diagnosis will be missed in these patients unless the physician specifically inquires about changes in food intake and body weight, and physically examines their muscles. At especially high risk are previously seriously obese people who have undergone gastric restriction surgery, or who have developed a serious chronic medical or surgical disease that induces the cachexia syndrome. In such cases, the loss of muscle outstrips that of fat, and can reach a critical degree even in the presence of ample residual adipose tissue.

Table 2. Adapted and maladapted PEM

Feature	Adapted PEM	Maladapted PEM
BMI	reduced	normal or reduced
Muscle mass	reduced	reduced
Edema	usually absent	often present
Body weight	reduced but stable	tissue loss often masked by extracellular fluid accumulation
Drug disposition	may be altered	may be altered
Immune function	normal	impaired
Serum albumin	normal	reduced
C-reactive protein	normal	increased
Transthyretin	reduced	reduced

Diagnosis and Assessment of Protein-Energy Malnutrition

Several screening tools are available for identifying people who have PEM or are at high risk of developing it [4]. The simple and well-studied Malnutrition Universal Screening Tool (MUST) categorizes a patient's risk of ‘malnutrition’ (and directs the management response) as low, medium, or high, based on a MUST score of 0, 1 or 2. The MUST score is calculated as the sum of points awarded by considering body mass index (BMI, weight/height²): >20, 18.5-20, or <18 (0, 1, or 2 points, respectively), history of involuntary weight loss: <5%, 5-10%, or >10% (0, 1, or 2 points, respectively), and acute illness or no food intake for >5 days (2 points; http://www.scottishintensive-care.org.uk/nutrition/docs/must.pdf).

Tools such as the MUST are valuable in high-patient flow situations for they are easy for paramedical staff to use and draw attention to high-risk situations and overt cases of severe PEM. However, they cannot replace specific diagnosis and medical evaluation in the large grey zone that lies between adequate nutritional status and clinically important PEM.

The most useful way to diagnose PEM is in the classical medical-narrative tradition, which recognizes PEM as a pathophysiological entity with well-defined signs and symptoms, all of which are strongly modi...