Carnitine concentrations in the milk of different species and infant formulas.

The study explores the differing amounts of a nutrient called carnitine in the milk of various animals, human milk, and different types of infant formulas. It warns that a deficiency of carnitine in certain infant formulas might lead to nutritional issues for infants who consume them.

Research Methodology and Findings

• The researchers measured carnitine concentrations in the milk of several animal species, including sheep, cows, goats, and horses. They also studied the milk of human mothers, both those who delivered at term and those who had premature infants.
• The findings indicated significant differences in carnitine concentrations among the different species’ milk.
• Further, the concentration of a specific form of carnitine, acylcarnitine, ranged from 13 to 47% of the total carnitine content. This range is believed to be connected to variations in the metabolism of the mother and/or mammary gland.
• In all the species examined, the concentration of long-chain acylcarnitine (another form of carnitine) in milk was discovered to be less than 1%.
• When considering changes over time, researchers found that the acylcarnitine concentration in cow’s milk lessened during the first two months of lactation whereas human milk showed no variation in carnitine concentrations during the first month after birth.
• However, the plasma (blood) levels of carnitine in human mothers increased postpartum, and plasma levels of acylcarnitine were always found to be lower than those in milk sampled at the same time.

Implications for Infant Formulas

• The study revealed that European formulas based on cow’s milk contained slightly more carnitine than human milk.
• However, soy-based or protein hydrolysate formulas had extremely low carnitine concentrations.
• This result is concerning because it implies infants fed these types of formulas without carnitine supplementation could develop a nutritional carnitine deficiency.
• Milk carnitine concentrations in mothers of premature infants were not different from those in mothers of term infants, meaning that all infants, regardless of whether they are premature or not, need an optimum level of carnitine in their diets.