Recommended Dietary Allowance (RDA) of Lysine for Children
The recommended dietary allowance (RDA) of lysine for children is 58 mg/kg/day for school-aged children, while infants require 130 mg/kg/day. 1, 2
Age-Specific Lysine Requirements
Lysine is an essential amino acid that cannot be synthesized by the human body and must be obtained through diet. The requirements vary by age:
- Infants (term neonates): 130 mg/kg/day 2
- School-aged children: 58 mg/kg/day (population-safe upper 95% CI) 1
- Children in developing countries: Similar requirements (46.6 mg/kg/day upper 95% CI) with no evidence of adaptation despite different dietary patterns 3
Scientific Basis for Recommendations
The lysine requirements have been determined using the indicator amino acid oxidation method, which is considered the gold standard for determining amino acid requirements. This method measures the oxidation of labeled phenylalanine in response to graded intakes of lysine.
The mean requirement for school-aged children was determined to be 35 mg/kg/day, but to ensure adequate growth, an additional 6 mg/kg/day is added, bringing the mean requirement to 41 mg/kg/day. For population safety, the upper 95% CI value of 58 mg/kg/day is recommended 1.
Clinical Significance and Growth Impact
Lysine plays a critical role in:
- Protein synthesis
- Growth and development
- Nitrogen retention
- Hormonal function
Studies have shown that lysine supplementation can enhance:
- Anthropometric measurements (height, weight, BMI)
- Developmental quotient
- Various biochemical parameters 4
Practical Considerations
Dietary Sources
- Animal proteins (meat, poultry, fish)
- Legumes
- Dairy products
Monitoring Parameters
- Growth velocity
- Weight gain
- Nitrogen balance
- Plasma amino acid levels in specific clinical scenarios
Special Populations
Preterm Infants
For preterm infants receiving parenteral nutrition, lysine requirements are higher:
- Recommended parenteral lysine intake: 105 mg/kg/day 5
Children on Parenteral Nutrition
Total amino acid recommendations for children on parenteral nutrition:
- Preterm infants: 2.5-3.5 g/kg/day 5
- Term infants: 1.5-3.0 g/kg/day 5
- Children 1 month to 3 years: Minimum 1.0 g/kg/day 5
- Children 3-12 years: 1.0-2.0 g/kg/day 5
- Adolescents: 1.0-2.0 g/kg/day 5
Safety Considerations
- Upper limit for lysine intake is estimated at 300-400 mg/kg/day 6
- Excessive intake may lead to amino acid imbalances
- Side effects are generally limited to gastrointestinal symptoms 4
Clinical Application
When assessing lysine adequacy in a child's diet:
- Calculate weight-based requirement (58 mg/kg/day for school-aged children)
- Evaluate dietary sources and potential deficiencies
- Consider supplementation only if dietary intake is inadequate
- Monitor growth parameters regularly
The lysine requirement is particularly important in populations consuming predominantly cereal-based diets, which are typically lower in lysine content compared to animal protein-based diets.