Nutrition and Food Processing: Biochemical Assessment

Biochemical Assessment

• Biochemical assessment is used to detect subclinical deficiency states and to supplement other assessment methods.
• Subclinical deficiency can be identified by two methods: biochemical tests and functional tests.

Advantages of Biochemical Assessment

• The most objective and precise method among all other assessment methods.
• Detects marginal subclinical deficiency before they result in overt signs.
• The only method that can detect nutrient deficiency and supplement other methods of evaluation.
• Measures the extent of functional consequences of a specific nutrient deficiency.
• Useful to validate data obtained from dietary methods.
• Precise, accurate, and reproducible.

Disadvantages of Biochemical Assessment

• Affected by technical and biological factors other than depleted body stores of the nutrient.
• Limitations can be avoided by standardizing the sampling and collection procedure.
• May be altered due to organ function, disease states, hydration status, medications, and fasting or non-fasting.

Specimen Types

• Blood (whole, serum, or plasma) tends to reflect recent dietary intake (acute-term index).
• Erythrocytes (red blood cells) reflect only chronic status and are unlikely to be a valid index for some nutrients.
• Leukocytes (white blood cells) are more sensitive than erythrocytes but have technical difficulties.
• Storage tissues (liver, bone marrow, adipose tissue, and bones) can be used as specimens.

Clinical Chemistry Panels

• Basic Metabolic Panel (BMP) or Chem 7 includes sodium, potassium, chloride, CO2, glucose, blood urea nitrogen, and creatinine.
• Comprehensive Metabolic Panel (CMP) or Chem 20 includes BMP tests plus calcium, albumin, total protein, and liver function tests.
• Complete Blood Count (CBC) includes red blood cells, hemoglobin, hematocrit, mean corpuscular volume, white blood cell count, and differential.

Protein-Energy Malnutrition (PEM)

• Kwashiorkor: visceral proteins are depleted due to inadequate intake of protein and/or hypermetabolic state.
• Signs and symptoms: edema (moon face), muscle wasting, psychomotor changes, anemia, and growth retardation.
• Marasmus: represents the end result of starvation where both proteins and calories are deficient.
• Signs and symptoms: severe wasting of muscle and fats, growth retardation, looks older than age, no edema or hair changes, diarrhea, and dehydration.

Acute-Phase Proteins

• Change by 25% during an acute-phase response.
• Positive or negative.
• Important to consider half-life (t1/2) of protein when evaluating.

Somatic and Visceral Proteins

• Somatic proteins: skeletal muscle.
• Visceral proteins: hepatic protein, organs, structural protein, and protein found in blood.

Assessment of PEM

• Biochemical tests provide the most objective and quantitative assessment for PEM.
• Assessment includes hormonal and cell-mediated response to stress, negative and positive acute-phase respondents, nitrogen balance, hepatic transport proteins, and immunocompetence.