Lecture 18 Protein Intake Requirements Elango

Fundamentals of Nutrition: Protein Requirements Lecture Notes

Understanding Protein Requirements
- Describe methods for determining protein needs.
- Identify factors affecting protein requirement estimates.
- List protein requirements for healthy adults and infants.
- Discuss adverse effects of excess protein intake.
- Recognize symptoms of protein malnutrition and differentiate between Kwashiorkor and Marasmus.
Reading Reference: Textbook: Chapter 6

Essential Amino Acids: Proteins are essential due to their constituent 20 amino acids (AA).
Dietary Protein Functions:
- Supplies nitrogen for dispensable AA synthesis.
- Provides essential AAs.

Key Processes:
- Breakdown of body proteins into amino acids (AA).
- Catabolism of amino acids involves separating amino groups from carbon skeletons.

Nitrogen Source:
- Proteins are the primary source of nitrogen in food and excreta, with ~16% of proteins being nitrogen by weight.
Calculation:
- Protein (g) = Nitrogen (g) x 100 / 16 = Nitrogen (g) x 6.25.

FDA/WHO Definition:
- Minimum dietary protein necessary to balance nitrogen losses, maintaining body protein mass during energy balance and modest physical activity.
- Special considerations for children and pregnant/lactating women due to tissue deposition needs.

Infant Requirements:
- AI for infants (0-6 months) = 1.52 g/kg/d (based on average human breast milk).
Age-Based Requirements:
- 7-12 mo: EAR 1.0, RDA 1.2 g/kg/d
- 1-3 years: EAR 0.87, RDA 1.05 g/kg/d
- 4-8 years: EAR 0.76, RDA 0.95 g/kg/d
- 9-13 years: EAR 0.76, RDA 0.95 g/kg/d
- 14-18 years (boys): EAR 0.73, RDA 0.85 g/kg/d
- 14-18 years (girls): EAR 0.71, RDA 0.85 g/kg/d
- Adults (19+ years): EAR 0.66, RDA 0.8 g/kg/d
- Pregnancy: EAR 0.88, RDA 1.1 g/kg/d
- Lactation: EAR 1.05, RDA 1.3 g/kg/d

Nitrogen Balance Method:
- Determines intake vs. losses to estimate protein requirements.
Factorial Method:
- Combines maintenance needs with tissue deposition needs, particularly for children and pregnant women.

Definitions:
- Nitrogen Balance = Nitrogen Intake – Total Nitrogen Losses.
Calculations:
- Nitrogen Intake from ingested protein:
  - Nitrogen Ingested (g) = Protein Ingested (g) x 0.16 or Protein Ingested (g) / 6.25.
Losses:
- Urine, feces, and skin contribute to nitrogen losses.

Zero Nitrogen Balance:
- Intake equals losses; reflects adequate protein intake.
Positive Nitrogen Balance:
- Intake exceeds losses; indicates growth or recovery.
Negative Nitrogen Balance:
- Losses exceed intake; seen in undernutrition or stress conditions.

Applications:
- Assessing protein adequacy in hospitalized patients or those with conditions like cancer.
Limitations:
- Measuring accurate intake/losses can be challenging, and confounding factors (e.g., diarrhea) may skew results.

Indicator Amino Acid Oxidation (IAAO):
- Focuses on amino acid carbon skeleton utilization; rapid and ethical for vulnerable populations.
New Recommendations suggest higher protein needs than previously estimated based on IAAO data.

Pregnant Women:
- Special demands for protein intake based on gestation stage.
Elderly:
- Higher intake estimates, particularly for women aged over 80.

Dehydration and Renal Function:
- Increased workload on kidneys.
Kidney Stones:
- Correlation with high protein diets and calcium/oxalate intake.
Cancer and Cardiovascular Risks:
- Associations with high intake of unhealthy fats and processed meats.

Kwashiorkor:
- Typically due to inadequate protein during weaning; characterized by edema and poor visceral protein status.
Marasmus:
- Chronic energy and protein deficiency leading to severe weight loss and muscle wasting.

Protein Requirements Assessment:
- Current recommendations may be underestimates; recent methods (IAAO) proposed for refined estimates.
Nutritional Implications:
- Higher protein intakes from high-quality food sources recommended for overall health.