14. Milk in human nutrition

Question 1

1) World milk consumption and production

Answer 1

• important in human diet
• supplies energy
• can provide very good protein and fat
• provides vitamins, especially for the growing
• as well as minerals especially calcium
• some countries have dietary guidelines: higher consumption in these countries
• important in economic point of view — important in agricultural sector
• can also have social aspects: production of milk can provide wide range of working opportunities
  e. g. processors, shop keepers, people involved in dairy production, transportation

Question 2

Factors influencing growth of milk production

Answer 2

• growth of world population
• growth of “middle class”: big difference in lifestyle e.g. consumption and dietary patterns
• urbanisation: affects lifestyle and consumption patterns
• changes in dietary composition mainly in the developing world: significant increase in
  consumption of food of animal origin in developing countries

Question 3

Dairy animals

Answer 3

• most common: cattle
• buffaloes, goats, sheep and camels
• others but less common: yaks, horses, reindeers and donkeys
• depends on environmental factors:
• e.g. Africa mostly uses small ruminants vs Europe that mainly uses cattle
• 81,8% of milk production from cattle
• buffaloes come in second with 14,2 % - 2,3% of goat milk
• 1,3% of sheep milk
• 0,4% of camel milk
• the others take 0,1% of milk production
• highest production of cow milk in Europe
• highest production of sheep, goat and buffalo milk in Asia

Question 4

Consumption of milk and dairy products

Answer 4

• big differences in certain part of the world
• highest consumption >150kg/capita/year in Europe, North Amoerica, Argentina, Australia, Israel,
  Pakistan
• medium consumption 30-150kg/capita/year in India, Iran, Mexico, Mongolia, North and Southern
  Africa, most of Near East
• low <30kg/capita/year in China, central Africa, East and Southeast Asia

Question 5

Role of milk in human nutrition

Answer 5

• important part of diet, especially in Europe and North America:
• represent 20-30% protein diet
• 15% lipids
• 80% of food calcium
• dietary source of orotic acid: good for low LDL cholesterol
• milk in human nutrition:
• one of the best balanced foods
• excellent source of calcium
• detoxification effect in poisoning
• well digested food
• good substrate for cultural microorganisms
• individual milk components can also be used separately

Question 6

Lactose

Answer 6

• only synthesised in the mammary gland
• not as sweet as the separate monosaccharides
• important for newborns
• increased availability of Ca and P
• less cariogenic than other carbohydrates
• maillard reaction:
• = non-enzymatic browning
• lactose is a reducing carbohydrate and easily enters reaction
• resulting in melanoidins —> affect colour, smell and taste of dairy products

Question 7

Lactulose

Answer 7

• found in heat treated milk — allowed to be up to 1%
• small change from lactose to form lactulose
• serves as an indicator of heat treatment
• important growth factor for bifidobacteria (important probiotics)
• laxative
• treatment for systematic encephalopathy

Question 8

Milk fat

Answer 8

• important for newborn energy requirements
• source of essential fatty acids, lipophilic vitamins (A) + cholesterol
• saturated: butyric, capronic, caprylic, capric — 4 carbons (absent in other fats)
• high saturation of milk fat is good for newborns but not adults (risk of LDL cholesterol)
• lower pH, short chain FA and vit D can protect against colonic cancer
• cholesterol in milk: 0,3%
• main component of milk fat = TAG — 99% of all milk fat
• form for most of fat = fat globules:

Question 9

Conjugated linoleic acid (CLA)

Answer 9

• produced by rumen fermentation
• 2-37 mg/g of fat
• protective functions:
• anti-carcinogenic - anti-mutagenic
• anti-diabetogenic - anti-allergenic
• immune modulating

Question 10

Vitamins

Answer 10

• fat soluble:
• =A,D,E,K
• vit D is low in milk (fortified in the USA)
• water soluble:
• =B,C,H(B7,biotin)
• B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (panthothenic acid), B6 (pyridoxine), B7 (biotin),
  B9 (folate), B12 (cobalamine)

Question 11

Calcium

Answer 11

• osteoporosis:
• most common bone disease in the world
• most at risk: menopausal women, higher prevalence in white population
• growth of bone is associated with the first 3 decades of life —> calcium = best support
• high milk availability: 30%
• other sources usually 10% (spinach, etc)
• supported by vitamin D (high availability due to lactose)
• high protein diets —> increased loss of Ca via urine —> higher risk of osteoporosis — most common in countries that consume high amounts of dairy and protein

Question 12

Dietary disorders of milk Milk allergy

Answer 12

= reaction of immune system against one or more of the proteins found in milk

• often confused with lactose intolerance
• casein:
• accounts for 80% of milk protein
• most allergenic protein = αS1 (casein)
• also the main allergen in cheese
• goat milk has very low αS1 concentration
• whey proteins:
• accounts for the other 20% of milk
• two main allergens: α-lactalbumin, ß-lactaglobulin - whey is removed during process of making cheese
• more common in children: usually grow out of it by 4 years old in 80% of the cases
• adults can gradually develop milk allergy and CS develop overtime
• symptoms: skin, GIT, respiratory
• soy and goat milk can be highly allergenic depending on the protein the person is allergic to

Question 13

Nutritional importance of milk products

Answer 13

• proteins:
• milk is an important source
• increased biological value of proteins:
• in incubation, maturation, and storage
• during processing —> add starter culture —> formation of new aa
• fermented dairy products:
• bacteria containing nitrogen —> increased availability of aa in GIT
• precipitated casein in these products are more digestible than those in milk —> better for
  young and elderly
• lactose:
• fermentation of lactose —> lactic acid and decrease lactose by 25% (better for lactose intolerant)
• products with lactobacilli can adapt GIT and produce lactase
• in mature cheese: lactose is completely cleaved
• milk fat:
• no significant difference
• high concentration of FFA
• minerals: Ca and P availability is increased due to lactic acid (and bioactive peptides) high ability
  to be absorbed in GIT
• vitamins: increased B12 and folic acid by bacteria
• probiotics e.g. L. acidophillus can inhibit proliferation of pathogenic bacteria
• protein and calcium:
• high protein intake —> acidification of internal environment —> MAC: - => liberate alkalines from bones —> Ca wasted in urine
• => stimulate osteoclastic activity