Fortification of L-valine in infant formula milk powder

L-valine, one of the essential branched-chain amino acids (BCAAs) for humans, plays a crucial role in the growth and development of infants. It is involved in protein synthesis, energy metabolism, and immune function regulation, making it an indispensable nutritional fortifier in infant formula. The following analysis focuses on its fortification strategies and safety assessment:

I. Fortification Strategies in Infant Formula

The fortification of L-valine in infant formula should be based on breast milk as the gold standard, combined with the nutritional needs of infants at different stages. It aims to achieve precise supplementation through scientific proportioning while considering synergistic effects with other nutrients.

Dosage design based on breast milk composition

The content of L-valine in breast milk changes dynamically with lactation stages, typically ranging from 200-300 mg/100 g protein in mature milk. The fortification of formula should refer to this range and be adjusted according to the infant’s age:

In formulas for infants aged 0-6 months, the L-valine content is generally controlled at 5%-7% of total protein to match the amino acid pattern of breast milk, meeting the needs of the rapid growth stage.

In formulas for older infants over 6 months, the content can be appropriately adjusted based on complementary food intake, usually slightly lower than that in infant formulas, to avoid excessive intake due to superimposed with dietary amino acids.

Synergistic proportioning with other branched-chain amino acids

L-valine, along with L-leucine and L-isoleucine, constitutes the branched-chain amino acids (BCAAs). Their metabolism in infants is synergistically regulated, and their ratio should be close to that in breast milk, approximately 1:2:1 (valine:leucine:isoleucine). An imbalance in this ratio may affect protein synthesis efficiency or increase metabolic burden. For example, excessive leucine may inhibit valine absorption. Therefore, precise proportioning is required during fortification to ensure a coordinated ratio in the formula, which collectively promotes infant muscle development and energy supply.

Optimization of stability and bioavailability

L-valine is susceptible to high temperatures, oxidation, and other factors during milk powder processing and storage, which may cause partial decomposition or Maillard reactions with other components (such as reducing sugars), reducing its biological activity. Therefore, attention should be paid to the following in the fortification process:

Adopting low-temperature spray drying technology to reduce structural damage to amino acids caused by high temperatures.

Controlling the water activity of the formula (Aw < 0.3) to avoid oxidation or degradation during storage.

Combining with carriers such as whey protein and casein, and using microencapsulation technology to improve its stability while promoting intestinal absorption and utilization of valine in infants.

II. Safety Assessment in Infant Formula

As an essential amino acid, the safety of L-valine needs to be comprehensively evaluated from aspects such as toxicological data, infant tolerance, and long-term intake effects to ensure no health risks at the fortified dose.

Toxicology and safe dosage range

Animal experiments and population studies have shown that L-valine has extremely low acute toxicity (LD50 > 5 g/kg body weight) and no genotoxicity or teratogenicity. The Codex Alimentarius Commission (CAC) and the European Food Safety Authority (EFSA) stipulate that the safe upper limit of daily L-valine intake for infants is 60 mg/kg body weight (converted based on body surface area). The valine fortified in formula should be combined with the daily milk intake of infants (usually 800-1000 mL/d for 0-6 months) to ensure that the actual intake does not exceed the safe upper limit. For example, if the valine content in 100 mL of formula does not exceed 30 mg, it can meet the safety requirements.

Infant tolerance assessment

The digestive and metabolic systems of infants are immature, and their tolerance to amino acids varies individually. Clinical studies have shown that infants have good tolerance to L-valine within the safe dosage range, with no adverse reactions such as vomiting, diarrhea, or allergies observed. However, attention should be paid to the following:

Premature infants or low-birth-weight infants have weaker metabolic capacity, so the fortification of valine in their formulas should be more conservative, and reference should be made to the standards for premature infant formula (usually slightly lower than that for full-term infant formulas).

Infants with congenital branched-chain amino acid metabolism disorders (such as maple syrup urine disease) need to strictly limit valine intake, and such special formulas should be designed separately.

Potential effects of long-term intake

Long-term intake of appropriate amounts of L-valine has no adverse effects on infant growth and development; instead, it can promote brain development by participating in protein synthesis and neurotransmitter metabolism (e.g., as a precursor of γ-aminobutyric acid). However, excessive intake may lead to:

Competition with other amino acids for absorption carriers, affecting the utilization of essential amino acids such as lysine and tryptophan.

Increasing the metabolic burden on the kidneys, which may pose potential pressure on infants with immature renal function. Therefore, the fortification of valine in formulas must strictly follow the principle of "supplementation on demand" to avoid blind excessive addition.

The fortification of L-valine in infant formula should be based on breast milk, achieving a balance between safety and efficacy through precise proportioning and process optimization. It should also comply with relevant international and national standards (such as GB 10765-2021 Infant Formula Foods) and verify its long-term applicability through continuous safety monitoring.