80nutritionalassessm ent2008

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Nutritional assessment HE 3511 2008 Dr Alex Mavroeidi School of Medical Sciences

Outline: 

Outline Definition Methods Dietary Assessment Clinical Assessment Anthropometric Assessment Biochemical Assessment Advantages and limitations

Nutritional Assessment: 

Nutritional Assessment Definition Nutritional assessment is the interpretation of information obtained from a variety of methods to identify populations or individuals at risk of poor nutritional status. Evaluation of nutritional status: 1. Dietary Assessment – covered in different lecture 2. Clinical Assessment 3. Anthropometric Assessment 4. Biochemical Assessment

Clinical Indicators of Deficiency: 

Clinical Indicators of Deficiency Includes information from medical history and physical examination by health professional to identify signs and symptoms of deficiency Examination of hair, skin, eyes, muscles, teeth, gums, nails, skeletal structure etc. Limitations Signs & symptoms often non specific They only become apparent when diet has been lacking for some time

Clinical Indicators - Example: 

Clinical Indicators - Example Hair - an epidermal structure which sometimes reflects a state of nutritional deficiency Clinical signs - dispigmentation, easy pluckability, thin, sparse Possible Deficiency - Kwashiorkor

Anthropometry: 

Anthropometry Anthropometry is the measurement of the human body Greek ‘anthropos’ = man, ‘metro’= measurement “measurements of the variations of the physical dimensions and the gross composition of the human body at different age levels and degrees of nutrition” Jelliffe 1966 General uses To identify people whose growth is outside normal values suggesting under or over nutrition Screening tool to identify individuals at high risk of malnutrition To monitor effects of nutrition intervention for treatment of disease, surgery or malnutrition In sport Monitor training programmes Monitor dietary interventions As part of talent identification

What can we measure?: 

What can we measure? Indices & ratios to describe body size Generalised equations to predict body fat & FFM Skinfolds, girths, lengths & breadths

Advantages & limitations of anthropometry: 

Advantages & limitations of anthropometry Advantages cheap easy to do (mostly) Limitations does not detect changes over a short period of time does not distinguish between specific nutrient deficiencies

Anthropometric Measurements: 

Anthropometric Measurements Length - < 2yrs Height Demispan Weight Arm circumference Head circumference Waist circumference / hip circumference Skinfold thickness

Body Mass Index (BMI) or Quetelet’s Index: 

Body Mass Index (BMI) or Quetelet’s Index BMI = weight (kg) height (m2) This ratio was first suggested as a measure of fatness by Quetelet in 1869 E.g. If I weigh 58 kg and subject is 165 cm tall, what is his BMI? BMI = 58 = 58 = 21.3 kg/m2 1.652 2.7225

Classification of overweight in adults according to BMI (WHO, 1998): 

Classification of overweight in adults according to BMI (WHO, 1998) BMI (kg/m2) Underweight < 18.5 Normal range 18.5 - 24.9 Overweight >25 Obese class I: 30.0 - 34.9 Obese class II: 35.0 - 39.9 Obese class III: > 40.0 Chart from www.food.gov.uk

An example…: 

An example… Subject: Male Age: 48 y Height: 1.96 m Weight: 125 kg BMI: 33 kg/m2 Classification: Obesity level I Sir Steve Redgrave: quintuple Olympic gold medallist rower

Anthropometric indices of growth - 1: 

Anthropometric indices of growth - 1 Head circumference for age Index of chronic protein energy nutritional status during first 2y of life Weight for age Index of acute malnutrition widely used to assess protein energy malnutrition & over-nutrition in children from 6mo to 7y . Limitations include 1. age often unknown 2. composition of the weight unknown (lean, fat, oedema, tumour etc..)

Anthropometric indices of growth - 2: 

Weight for height Sensitive index of current nutritional status which is relatively independent of age between one and 10y. Can be used in conjunction with weight for age. (See also BMI for adults) Height for age Within populations heights of children at a given age reflect their nutritional status Anthropometric indices of growth - 2

Demispan: 

A measurement of skeletal size Used as an alternative to height measurement when difficult to obtain an upright posture in a subject Demispan is the distance between the sternal notch and the roots of the middle and third fingers with the arm stretched out at shoulder height to the side of the body Demispan

Waist circumference: 

Waist circumference Ref: Han et al, BMJ 1995 311:1401-5 Girth in centimetres Cardiovascular Risk A useful indicator of obesity, especially of central obesity Measurement are taken at the narrowest part of the upper body (above your “belly button”) at the end of a normal breath Anatomic location of umbilicus changes with respect to skeleton in the obese and is posturally dependent Breathing artefact for waist girth

Waist circumference / hip circumference: 

Waist circumference / hip circumference An indicator of body fat distribution High health risk at 0.82 for women & 0.94 for men indicating a tendency for central fat deposition & possible  health risk Hip circumference with clothing introduces error

Skinfold thickness: 

Skinfold thickness Most of the fat stored in the body lies immediately under the skin The thickness of a fold of skin picked at strategic sites indicates the amount of subcutaneous fat Based on the idea that a measure of the largest deposit of body fat may provide a reasonable estimate of TOTAL body fat Total body fat: fat within subcutaneous adipose, bone marrow, visceral and intermuscular fat

Skinfold thickness at 4 sites: 

Barasi, 1997, p15 Skinfold thickness at 4 sites Barasi, 1997: p15

Skinfold thickness: 

Skinfold thickness 3 measurements made at each site the median of the 3 readings are calculated and summed The sum of the 4 skinfolds is then entered into a table (Durnin & Womersley, 1974), taking the age and sex of the subject into account. Examples In a 24y old male with SFT = 40mm, % body fat = 16.4% In a 24y old female with SFT = 40mm, % body fat = 23.4%

Anthropometric assessment of body composition: 

Anthropometric assessment of body composition Underwater weighing measures body fat Archimedes’ principle: an object’s loss of weight in water = the weight of the volume of water it displaces, because the object in the water is buoyed up by a counterforce which = the mass of water it displaces. Duel Energy X-ray Absorptiometry (DEXA) measures bone mass, lean tissue (and fat by difference). Bioelectrical Impedence Analysis (BIA) Principle: tissues such as blood or muscle are highly conductive whereas fat and bone are highly resistive The volume of these tissues can be estimated from the measurement of the resistance to an applied electric current flowing through the body.

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Underwater weighing Bod pod

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Biochemical indicators of nutritional status : 

Biochemical indicators of nutritional status Biochemical indicators can include assessment of blood & urine samples for levels of a variety of nutrients &/or their by-products or for levels of nutrient-linked enzyme activities. Analysis may also be performed on samples of hair or urine

Blood samples: 

Blood samples Blood can provide a great deal of information. Analysis can be used to determine: Actual levels of a nutrient in relation to expected values Plasma vit C, red cell folate The activity of a nutrient-dependent enzyme Transketolase for thiamin The activity of a nutrient-related enzyme Alkaline phosphatase for vit D The rate of a nutrient-dependent reaction Clotting time for vit K The presence of a nutrient carrier or its saturation level Retinol-binding protein Transferrin (iron) Levels of nutrient-related products Lipoprotein levels

Urine & hair: 

Urine & hair Urine For some nutrients such as sodium, iodine, phosphorus urinary excretion is the best way to establish status….. But complete urine collections are difficult to obtain. Hair Levels of some trace elements Scientific accuracy not proven

Data Interpretation: 

Data Interpretation Caution… for many nutrients there is inadequate info to establish guidelines Guidelines for interpretation must take into account age, sex, pregnancy, lactation, inflammation, infection,trauma etc.. Cut-offs - often derived from healthy individuals

Past exam questions: 

Past exam questions BMI is used to classify obesity. How is it calculated and what are its limitations? (short answer Q) Give 1 example of each of the following used to assess nutritional status and for each give advantages and disadvantages Clinical indicator Anthropometric indicator Biochemical indicator (short answer Q)