How does human milk compare with animal milks? Enumerate three key differences between them. Which micro-nutrients is natural milk deficient in?

Comparison of Human Milk and Animal Milks

Human milk is specifically designed to meet the unique nutritional and immunological needs of a human infant. Animal milks, on the other hand, are formulated to support the rapid growth and development of their respective species. Consequently, significant differences exist in their macronutrient composition, micronutrient profiles, and bioactive components.

Three Key Differences Between Human Milk and Animal Milks

1. Protein Content and Composition

Human milk has a relatively low protein content (around 0.8-1.0 g/100 mL) compared to cow’s milk (around 3.2-3.5 g/100 mL). More importantly, the *type* of protein differs. Human milk contains a higher proportion of whey proteins, particularly α-lactalbumin, which is easily digestible for infants. Cow’s milk contains a higher proportion of casein, which forms a larger, harder curd in the infant’s stomach, potentially leading to digestive discomfort and reduced nutrient absorption. This difference is crucial as infant kidneys have limited capacity to handle the high solute load from casein digestion.

2. Carbohydrate Composition

The primary carbohydrate in human milk is lactose (around 7% of energy), which promotes the growth of beneficial gut bacteria (Bifidobacteria) and enhances calcium absorption. While cow’s milk also contains lactose, the concentration is higher. However, the key difference lies in the presence of human milk oligosaccharides (HMOs) in human milk. HMOs are complex sugars that are not digested by the infant but act as prebiotics, selectively promoting the growth of beneficial gut bacteria, and also have anti-adhesive properties preventing pathogen binding to the intestinal wall. Animal milks lack HMOs.

3. Fat Composition and Digestibility

Human milk fat is richer in long-chain polyunsaturated fatty acids (LCPUFAs), particularly docosahexaenoic acid (DHA) and arachidonic acid (ARA), which are essential for brain and retinal development. These fatty acids are present in smaller amounts in animal milks. Furthermore, human milk fat is more easily digested due to the presence of bile salt-stimulated lipase (BSL), an enzyme that facilitates fat breakdown. Animal milk fat globules are larger and require pancreatic lipase for digestion, which infants may not produce in sufficient quantities initially.

Micronutrient Deficiencies in Natural Milk

While animal milks are generally rich in several micronutrients, they are naturally deficient in certain essential nutrients for human infants:

• Vitamin C: Animal milks contain very little or no Vitamin C, which is crucial for collagen synthesis, immune function, and iron absorption.
• Vitamin E: The concentration of Vitamin E is lower in animal milks compared to human milk, impacting antioxidant defense.
• Iron: Although animal milk contains iron, its bioavailability is low. Human milk iron is highly bioavailable due to the presence of lactoferrin, an iron-binding protein.
• Essential Fatty Acids (DHA & ARA): As mentioned earlier, animal milks generally have lower levels of DHA and ARA, vital for neurological development.

Therefore, unmodified animal milk is not nutritionally adequate for infants and requires fortification or modification to meet their specific needs. Infant formulas are designed to address these deficiencies by adding appropriate levels of these micronutrients.