Milk CompositionMinerals & Vitamins

Leo TimmsIowa State University

Composition of Milk

• Water, CHO (lactose), fat, protein,• MINERALS

– Milk contains most minerals found and needed in the body!

• VITAMINS– Milk contains all vitamins found and needed in

the body!• It really is the most perfect food!

Minerals• Role in the body:

– Metabolism– Bone formation and growth– Oxygen transport– Water balance and maintenance– Immune system– Antioxidants

• Mineral interactions• Toxicity vs. Deficiency

Minerals

• Functions in the mammary gland:– Maintain

• pH• Ionic strength• Osmotic pressure

– Contribute to buffering capacity

MINERALS• 20 MINERALS ESSENTIAL TO HUMANS?

• MACRO

• MICRO

Constituent mg/100ml milk

Calcium (Ca) 123

Phosphorous (P) 95

Magnesium (Mg) 12

Potassium (K) 141

Sodium (Na) 58

Chlorine (Cl) 119

Sulfur (S) 30

Citric acid 160

Cow(Paul & Southgate 1978)

Human (DHSS, 1977)

Sow (Elliot et al. 1971: Bowland, 1966)

Sodium 50 45 50

Potassium 150 55 80

Calcium 120 33 210

Magnesium 12 3 30

Chloride 95 43 100

Phosphorus 95 45 150

Calcium/Phosphorus

1.26 2.20 1.40

Milk MACROminerals

Sodium Potassium Chloride

Calcium Magnesium Phosphorus• Independent of dietary intake!!!• Colostrum: higher in everything but K• 3 days in milk: normal but K high• Little variation across lactation

Sodium, Potassium, Chloride

• Normal milk: – higher in [K] – lower in [Na]

• compared to blood plasma • Membrane Na-K pump eliminates Na and concentrates K

– Na, K, Cl follow the concentration gradient into the vacuole or alveolar lumen

– Cl is actively pumped by a membrane pump into the cell against a gradient

– Na: primary regulator of extracellular fluids• Na / K / Cl: free ions in milk- totally absorbed

– concern for human neonate – renal

Calcium and Phosphorus

• Required in large quantities for the growing neonate

• Calcium is found as:– Free calcium– Casein-bound calcium (majority; up to 90%)– Calcium--inorganic anions

• Ca / P / Mg : 40-90% assoc. w/ casein micelle– highly absorbed due to casein / lactose inter.

Calcium transport

• Little movement from milk to blood– Cannot pass through tight junctions

• Golgi– Bulk of uptake

• Calcium pumps – Up and down regulated depending on stage of

lactation

• Can you change Ca content of milk through diet? (Extra credit #3!!!!!)

Milk MICROminerals

• Trace minerals enter the milk by– Diet– Contamination

• Metal containers• Environment

• Many are co-factors for enzymes

Iron

• Low in milk• Bound to:

– Lactoferrin (humans – better absorption)• Protein• Anti-microbial

– Some caseins

*** no correlation with intake!!!!!!!!!

Copper

• Bound to:– Caseins– β-lactoglobulin– Lactoferrin– Milk fat membrane proteins

Zinc• Bound to:

– Casein – Lactoferrin– Formation and maintenance of keratin in teat

canal

Sulfur

• Transported into cell as part of AA• Met, Cys

• Milk protein

Molybdenum

• Bound to:– Xanthine oxidase

• Cell membrane• Inner surface of milk fat globule membrane

Manganese– 67% casein bound– Milk fat membrane proteins

Cobalt– Vitamin B-12– Incorporated into protein in RER– High in colostrum– Propionate Glucose

Iodine• Organic Iodine

– Chelated– EDDI

• Iodine dips/foot rot treatment• Mammary tissue sequesters iodine

– Iodine totally available• Legal limits

– Toxicity• Decreases immune function• Cause of acne??

Vitamins

• Vita – Latin word for “life”• Amine – compound containing nitrogen• Roles in the body include:

– Metabolism– Oxygen transport– Antioxidants– Immune system– Help the body use

• CHOs• Protein• Fat

• Milk contains all vitamins required by mammals

Mastitis• Infection of mammary gland• Clinical mastitis: visible signs• Subclinical mastitis: elevated SCC

What do vitamins have to do with it?

53,000 IU/d vitamin A; 173,000 IU/d, 53,000 IU/d + 300 mg beta-carotene• Less new mammary gland infections

(clinical mastitis)

Fat-soluble Vitamins

• Includes Vitamins:–A–D–E–K

• Associated with the milk fat globule

Vitamin A

• Yellow color of milk fat is from ß-carotene• Lower efficiency of conversion• Some countries fortify with vitamin A• Species differences

– Cows, humans, and mares contain both Vit. A. & b-carotene

– Goat, ewe, buffalo, and sows milk contains Vit. A only

Vitamin D

• Antirachitic activity • Levels related to ergosterol in

feed/sunlight– Feeds drop in ½ during winter – Summer milk higher

• Higher in Guernseys, Jerseys, colostrum• Ca absorption from the intestine• Milk is often vitamin D fortified in US

Vitamin E and Vitamin K

• Vitamin E : tocopherol– Antioxidant, protects lipids in milk fat– Related to diet (summer pasture > winter feed)– Highest in colostrum– Low levels in milk– Associated with selenium

• Vitamin K : – Very low levels in milk

HOW MANY B VITAMINS

ARE THERE?

Water-soluble Vitamins- found in the aqueous phase

• B-Vitamins – Thiamin, riboflavin, folate, B12, etc.

• All are found in milk • Influenced by diet & breed and species

– Change to pasture – Guernsey/Jersey higher than Holstein– Colostrum higher than normal milk

• Synthesized by rumen microflora and large intestine

• Many are enzymatic co-factors

• Extremely important in nutrient metabolism!

Vitamin C

• Synthesized by ruminants

• Two forms – Ascorbic acid – Dehydroascorbic acid

• Colostrum higher than normal milk • Much is destroyed during milk processing

Other normal constituents in milk:

• Hormones – Levels follow trends of blood levels – Changes with estrous cycle, pregnancy, etc. – Usually lower than blood

• Oligosaccharides – Breakdown products of glycosylated proteins

• Cell Metabolites – Gases, alcohols, aldehydes, ketones, carboxylic

acids, nonprotein nitrogen, sulfur-containing compounds, phosphate esters, nucleotides and nucleic acids

• Epithelial cells – Sloughed off from duct linings

Abnormal constituents in milk:

• Toxins – Plants, metals (lead, arsenic, etc.)

• Viruses • Pesticides and Herbicides • Radionuclides • Bacterial Organisms

– Johnnes, Mycoplasma, Salmonella• Drugs

– Antibiotics • Off-flavors

– Weeds, poor barn ventilation, ketosis, etc.• Oxidized flavors

– Exposure to Cu and Fe • Exposure to light

– Causes lipid oxidation, rancid flavors