Milk Vitamins

Milk contains both fat-soluble vitamins (A, D, E, K) and water-soluble vitamins (B-complex, C). Their concentrations are expressed per 100 mL of whole cow milk (typically 3.5-4% fat) unless otherwise noted.

Fat-Soluble Vitamins

These vitamins are associated with milk fat and are more abundant in whole milk than in skimmed varieties.

1. Vitamin A (Retinol and β-Carotene)

• Form: Present as retinol (preformed vitamin A) and β-carotene (provitamin A, converted to retinol in the body).

• Concentration: ~30-40 µg retinol equivalents (RE) per 100 mL; β-carotene varies with diet (~10-20 µg).

• Source: Derived from the cow’s diet (e.g., green forage rich in carotenoids) and stored in milk fat globules.

• Function: Supports vision, immune function, and skin health.

• Variability:

  • Higher in pasture-fed cows (more β-carotene) vs. grain-fed (more retinol).

  • Sheep and buffalo milk are richer (~50-60 µg/100 mL) due to higher fat.

• Stability: Sensitive to light and oxidation; lost in skim milk processing.

2. Vitamin D (Cholecalciferol, D3)

• Form: Naturally as vitamin D3; fortified milk may include D2 (ergocalciferol).

• Concentration: Naturally low, ~0.01-0.05 µg (0.4-2 IU) per 100 mL; fortified milk ~1-2.5 µg (40-100 IU).

• Source: Synthesized in the animal’s skin via UVB exposure or added during processing.

• Function: Enhances calcium absorption, supports bone health.

• Variability:

  • Higher in summer milk (more sunlight) or in species like camel (~0.1 µg/100 mL).

  • Fortification common in many countries (e.g., U.S., Canada) to meet dietary needs.

• Stability: Stable in milk but reduced in low-fat versions.

3. Vitamin E (Tocopherols)

• Form: Primarily α-tocopherol.

• Concentration: ~0.05-0.1 mg per 100 mL.

• Source: From dietary antioxidants (e.g., green forage, grains); concentrated in milk fat.

• Function: Antioxidant, protects cell membranes and milk fat from oxidation.

• Variability:

  • Higher in pasture-fed cows (~0.1-0.2 mg) vs. silage-fed (~0.03 mg).

  • Sheep and buffalo milk have more due to higher fat content.

• Stability: Sensitive to heat, light, and oxygen; pasteurization causes minor losses.

4. Vitamin K (Phylloquinone, K1; Menaquinones, K2)

• Form: Mostly K1 from diet; traces of K2 from microbial synthesis in the rumen.

• Concentration: Very low, ~0.5-1 µg per 100 mL.

• Source: Plant-derived K1 (e.g., forage); K2 from rumen bacteria.

• Function: Supports blood clotting and bone metabolism.

• Variability:

  • Slightly higher in ruminant milk (e.g., cow, sheep) due to rumen synthesis.

  • Negligible in horse or human milk.

• Stability: Stable during processing but tied to fat content.

Water-Soluble Vitamins

These are found in milk’s aqueous phase and are less affected by fat removal.

5. Vitamin B1 (Thiamine)

• Concentration: ~0.03-0.05 mg per 100 mL.

• Source: From the animal’s diet (e.g., grains); synthesized by rumen microbes in ruminants.

• Function: Energy metabolism (carbohydrate breakdown).

• Variability: Fairly consistent across species; slightly higher in goat milk (~0.06 mg).

• Stability: Heat-sensitive; ultra-high temperature (UHT) processing reduces levels by ~20-30%.

6. Vitamin B2 (Riboflavin)

• Concentration: ~0.15-0.18 mg per 100 mL.

• Source: Synthesized by rumen bacteria; diet contributes minimally.

• Function: Energy metabolism, antioxidant activity; gives milk a slight yellow tint when concentrated (e.g., whey).

• Variability: Higher in sheep milk (~0.2 mg); lower in horse milk (~0.1 mg).

• Stability: Light-sensitive (degrades in clear containers), but heat-stable.

7. Vitamin B3 (Niacin)

• Form: Niacin and nicotinamide.

• Concentration: ~0.08-0.1 mg per 100 mL.

• Source: Rumen synthesis and dietary tryptophan conversion.

• Function: Energy production, cellular repair.

• Variability: Similar across species; slightly higher in buffalo milk.

• Stability: Stable during processing.

8. Vitamin B5 (Pantothenic Acid)

• Concentration: ~0.3-0.4 mg per 100 mL.

• Source: Rumen synthesis and feed.

• Function: Coenzyme A synthesis, fat and carbohydrate metabolism.

• Variability: Consistent across ruminants; lower in horse milk (~0.2 mg).

• Stability: Heat-sensitive; some loss in UHT milk.

9. Vitamin B6 (Pyridoxine)

• Concentration: ~0.03-0.05 mg per 100 mL.

• Source: Diet and microbial synthesis.

• Function: Amino acid metabolism, neurotransmitter synthesis.

• Variability: Slightly higher in goat milk (~0.06 mg).

• Stability: Sensitive to heat and light; reduced in processed milk.

10. Vitamin B7 (Biotin)

• Concentration: ~2-5 µg per 100 mL.

• Source: Rumen synthesis.

• Function: Fatty acid synthesis, glucose metabolism.

• Variability: Higher in colostrum; stable across species.

• Stability: Heat-stable.

11. Vitamin B9 (Folate)

• Concentration: ~5-10 µg per 100 mL.

• Source: Diet and microbial synthesis.

• Function: DNA synthesis, cell division.

• Variability: Higher in goat milk (~15 µg); lower in processed milk.

• Stability: Heat- and light-sensitive; pasteurization reduces levels.

12. Vitamin B12 (Cobalamin)

• Concentration: ~0.4-0.5 µg per 100 mL.

• Source: Exclusively from rumen bacteria in ruminants.

• Function: Red blood cell formation, neurological health.

• Variability: Absent in plant-based milks; low in horse milk (~0.1 µg); high in sheep milk (~0.7 µg).

• Stability: Heat-sensitive; UHT reduces content by ~20%.

13. Vitamin C (Ascorbic Acid)

• Concentration: ~1-2 mg per 100 mL (fresh milk).

• Source: From blood plasma, not synthesized in mammary glands.

• Function: Antioxidant, collagen synthesis.

• Variability:

  • Higher in human milk (~5 mg) and horse milk (~3 mg).

  • Lower in ruminants due to rumen degradation of dietary vitamin C.

• Stability: Highly unstable; destroyed by heat (pasteurization reduces it to trace levels), light, and oxygen.

Factors Affecting Vitamin Content

1. Species: Human and horse milk are richer in vitamin C; ruminants excel in B12 and riboflavin due to rumen synthesis.

2. Diet: Pasture-fed animals have more A, E, and D; grain-fed increase B vitamins.

3. Processing: Pasteurization reduces B1, B6, B12, C, and folate; UHT causes greater losses; fortification boosts D.

4. Season: Summer milk has more D and E due to sunlight and fresh forage.

5. Fat Content: Skim milk loses A, D, E, and K; whole milk retains them.

Nutritional Significance

• Growth: Vitamins A, D, and B-complex support neonatal development (e.g., vision, bones, metabolism).

• Immunity: Vitamins C, E, and A enhance immune function.

• Bioavailability: Milk’s fat enhances absorption of A, D, E, and K; calcium boosts D utilization.