Goat milk in human nutrition

1. Introduction

The The importance of goats importance of goats as providers as providers around the world of essential food in meat around the world of essential food in meat

and dairy products has been and dairy products has been discussed and discussed and documented documented in many recent proceedings of in many recent proceedings of

national and international conferences.national and international conferences.

This importance is also reflected in the This importance is also reflected in the largest animal largest animal number increasenumber increase for goats for goats

during the last 20 years.during the last 20 years.

the the largestlargest increase in goat milk increase in goat milk productionproduction tonnage compared to other tonnage compared to other mammalian mammalian

farm animals.farm animals.

Milk production of goats is likely to be Milk production of goats is likely to be much much greater than greater than in these official in these official

statisticsstatistics, because of the large amounts of , because of the large amounts of unreported unreported home consumptionhome consumption, especially , especially

in developing countries.in developing countries.

More than any other mammalian farm More than any other mammalian farm animal, the animal, the goatgoat is a main supplier of is a main supplier of dairy dairy and meat products for ruraland meat products for rural people, which people, which is one of the three aspects of demand for is one of the three aspects of demand for

goat milk: goat milk: home consumption.home consumption.

This demand is This demand is increasing increasing because of the because of the growing populations growing populations of people, and here of people, and here

the old saying of the the old saying of the “goat being the cow “goat being the cow of the poor people”of the poor people” is quite fitting. is quite fitting.

The The secondsecond aspect of demand for goat milk is aspect of demand for goat milk is the connoisseur the connoisseur interestinterest in goat milk products in goat milk products

especially especially cheeses and yoghurt cheeses and yoghurt in many in many developed countries. developed countries.

The The thirdthird aspect of demand for goat milk derives aspect of demand for goat milk derives from the from the afflictionaffliction of people with cow milk of people with cow milk

allergiesallergies and other and other gastro-intestinal ailmentsgastro-intestinal ailments.. This demand also is growing because of a wider This demand also is growing because of a wider

awareness of problems with awareness of problems with traditional medical traditional medical treatments to such afflictions, especially in treatments to such afflictions, especially in

developed countries.developed countries.

2. Nutritional studies with goat milk

Many anecdotal Many anecdotal experiences about the experiences about the nutritional and medical benefits nutritional and medical benefits of goat of goat milk have been reported in the popular milk have been reported in the popular

press, press,

but but few technical studies few technical studies have been have been conducted and published in refereed conducted and published in refereed

journalsjournals or technical or technical books.books.

The The nutritional and health benefits nutritional and health benefits of goat milk of goat milk are related to a number of are related to a number of medical problems medical problems of of people, foremost being food people, foremost being food allergiesallergies with cow with cow

milk proteins the dominant food cause.milk proteins the dominant food cause.

The The prevalenceprevalence of cow milk of cow milk allergyallergy varies with varies with countries and age countries and age of people, but exact data are of people, but exact data are

lackinglacking partly because differential diagnostic partly because differential diagnostic methods are difficult to perform in the apparent methods are difficult to perform in the apparent

absence of standardized antigensabsence of standardized antigens..

because cow milk contains because cow milk contains 18 different 18 different proteins proteins against which antibodies in animal against which antibodies in animal

experiments have been demonstrated .experiments have been demonstrated .

B -Lactoglobulin is not present in human milk B -Lactoglobulin is not present in human milk and has therefore been assumed to be the and has therefore been assumed to be the

most offending most offending protein in cow milk,protein in cow milk,

however comparative studies showed however comparative studies showed no no difference difference between the between the allergenicity of B-allergenicity of B-

lactoglobulin and caseinslactoglobulin and caseins..

In actual clinical In actual clinical skin prick-tests skin prick-tests on 21 adult on 21 adult and 13 infant patients with suspected cow milk and 13 infant patients with suspected cow milk

allergies, allergies, a-lactalbumina-lactalbumin caused the most caused the most positive skin reactions.positive skin reactions.

Ten of the 13 infants Ten of the 13 infants showed positive showed positive reactions, while only reactions, while only 5 of the 21 adults 5 of the 21 adults reacted.reacted.

The The highesthighest titer of 1:3200 was found titer of 1:3200 was found against against a-s-casein and B-casein a-s-casein and B-casein in an infant 2.5 years in an infant 2.5 years

old.old. Generally, IgG-titers were Generally, IgG-titers were higher against higher against

caseins than against whey proteins.caseins than against whey proteins.

Cow milk allergy is considered a common Cow milk allergy is considered a common disease with disease with a prevalence of 2.5% a prevalence of 2.5% in children in children

during the first during the first 3 years of life 3 years of life , occurring in , occurring in 12–12–30%30% of infants less than of infants less than 3 months 3 months old , with an old , with an

overall frequency in overall frequency in Scandinavia of 7–8% Scandinavia of 7–8% , even , even as high as as high as 20%20% in some areas , and reported in in some areas , and reported in

Italy in 3%Italy in 3% of children under of children under 2 years 2 years of age . of age .

Treatment with goat milk Treatment with goat milk resolvedresolved between between 30 30 and 40% and 40% of the problem cases, and in one of the problem cases, and in one particular particular study 49 of 55 study 49 of 55 treated children treated children benefited from benefited from treatment with goat milktreatment with goat milk..

The wide variety of The wide variety of genetic genetic polymorphisms polymorphisms of the different caseins of the different caseins

and whey proteins adds to the and whey proteins adds to the complexitycomplexity of the cow milk allergy of the cow milk allergy

situation and situation and difficultydifficulty to determine to determine which which protein is mainly responsible protein is mainly responsible for for

an allergic reaction.an allergic reaction.

Goat milk Goat milk as a as a substitutesubstitute for cow milk was for cow milk was studied in studied in 38 children 38 children during a 5 months during a 5 months

period . period .

The children on goat milk surpassed those The children on goat milk surpassed those on cow milk in on cow milk in weight gain, height, skeletal weight gain, height, skeletal

mineralization, and blood serum contents of mineralization, and blood serum contents of Vitamin A, calcium, thiamin, riboflavin, Vitamin A, calcium, thiamin, riboflavin,

niacin and hemoglobin. niacin and hemoglobin.

Similar findings Similar findings were obtained in studies were obtained in studies with with ratsrats..

In French clinical studies over In French clinical studies over 20 years 20 years with with cow milk allergy patients the conclusion was cow milk allergy patients the conclusion was that substitution with goat milk was followed that substitution with goat milk was followed

by “by “undeniable” improvements undeniable” improvements ..

In other French extensive clinical studies In other French extensive clinical studies with children allergic to cow milk, the with children allergic to cow milk, the

treatment with goat milktreatment with goat milk produced produced positivepositive results in results in 93%93% of the children and was of the children and was

recommendedrecommended as a valuable aid in child as a valuable aid in child nutrition because of nutrition because of less allergenicity less allergenicity and and

better digestibility better digestibility than cow milk.than cow milk.

In Spanish studies with rats, which had 50% In Spanish studies with rats, which had 50% of their of their distal small intestine removed distal small intestine removed by by

resection, simulating the pathological resection, simulating the pathological condition of condition of malabsorption syndromemalabsorption syndrome, the , the

feeding of goat milk instead of cow milk as feeding of goat milk instead of cow milk as part of the diet resulted in significantly part of the diet resulted in significantly

higher digestibility higher digestibility and and absorption of iron absorption of iron and copperand copper, thus preventing anemia ., thus preventing anemia .

Also in these studies, the Also in these studies, the utilization of fat utilization of fat and weight gain was improved and weight gain was improved with goat with goat

milk in the diet, compared to cow milk, and milk in the diet, compared to cow milk, and levels of levels of cholesterol were reducedcholesterol were reduced, while , while

triglyceride, HDL, GOT and GPT values triglyceride, HDL, GOT and GPT values remained normal.remained normal.

It was concluded that the consumption of It was concluded that the consumption of goat milk goat milk reduces total cholesterol reduces total cholesterol levels and levels and

the the LDLLDL fraction because of the fraction because of the higher higher presence of medium chain triglyceridespresence of medium chain triglycerides

(MCT) ((MCT) (36% 36% in goat milk versus in goat milk versus 21%21% in cow in cow milk), which decreases the synthesis of milk), which decreases the synthesis of

endogenous cholesterol.endogenous cholesterol.

In an Algerian study of In an Algerian study of 64 infants with 64 infants with malabsorption syndromesmalabsorption syndromes, the substitution of , the substitution of

cow milk with goat milk caused significantly cow milk with goat milk caused significantly higher rates of intestinal fat absorptionhigher rates of intestinal fat absorption..

Goat milk Goat milk besides other milks is a besides other milks is a significant food significant food and and nutrient source nutrient source for people in many countries, for people in many countries, up to up to 55% 55% of all milks produced in one country. of all milks produced in one country.

However, the apparent daily supplies of animal However, the apparent daily supplies of animal protein and calcium protein and calcium per person from domestic per person from domestic production, according to production, according to world statisticsworld statistics, , varyvary

widely between countries, and are mostly widely between countries, and are mostly deficientdeficient..

3. Comparative protein composition of goat milk

documenting many unique documenting many unique differences between differences between the two speciesthe two species, and showing a wide diversity , and showing a wide diversity

due to due to geneticsgenetics of different breeds within each of different breeds within each species, influences of species, influences of stage of lactationstage of lactation, ,

feedingfeeding, , climateclimate, and subclinical , and subclinical mastitismastitis..

It has been found that It has been found that goat milk goat milk has a has a significantly significantly higher dye-binding capacity per higher dye-binding capacity per unit protein unit protein (1% more than cow milk) and a (1% more than cow milk) and a

lower infra-red absorptionlower infra-red absorption (4% less than cow (4% less than cow milk).milk).

Goat milk Goat milk proteinsproteins are are similarsimilar to the major cow to the major cow milk proteins in their general classifications of milk proteins in their general classifications of a-, a-, b-,k -caseins, b-lactoglobulin, a-lactalbumin,b-,k -caseins, b-lactoglobulin, a-lactalbumin, but but

they differ in they differ in genetic polymorphisms genetic polymorphisms and their and their frequencies in goat populations . frequencies in goat populations .

The presence of the The presence of the a-s-1-caseina-s-1-casein trait has been trait has been studied much studied much in recent years, when it was in recent years, when it was

discovered that it has discovered that it has six different typessix different types, , A, B, C, A, B, C, E, F and “null”E, F and “null” in goat milk. in goat milk.

In cow milk, a-s-1-casein is the major In cow milk, a-s-1-casein is the major a-s-caseina-s-casein..

The “The “nullnull” type or absence in some goat milk ” type or absence in some goat milk means that in different goats the major (a-s-means that in different goats the major (a-s-casein is the a-s-2-casein variant, but which casein is the a-s-2-casein variant, but which

has has different digestibility and cheese making different digestibility and cheese making propertiesproperties . .

The The differences differences in genetic types are in genetic types are due to due to amino acid substitutions amino acid substitutions in the protein in the protein

chains, which in turn are responsible for the chains, which in turn are responsible for the differences in digestibility, cheese making differences in digestibility, cheese making

properties and flavors of goat milk products . properties and flavors of goat milk products .

but the but the amino acid substitutions amino acid substitutions also enable also enable the detection of even small amounts of the detection of even small amounts of

adulteration with cow adulteration with cow milkmilk . .

In a study of In a study of k-casein digestionk-casein digestion, , 2727 differencesdifferences in amino acid sequence between in amino acid sequence between

cow and goat milk cow and goat milk casein macropeptides casein macropeptides were found .were found .

Peptides formed from Peptides formed from goat milk goat milk casein by casein by proteases tasted much proteases tasted much less bitter than less bitter than thos thos

from cow milk caseinfrom cow milk casein

Casein micellesCasein micelles, the form of casein molecule , the form of casein molecule suspended in goat milk, also suspended in goat milk, also differdiffer markedly markedly

from cow milk in from cow milk in less less complete complete sedimentationsedimentation rate, rate, greater B-casein solubilizationgreater B-casein solubilization, , smaller smaller

size of micellesize of micelle, , more calcium and phosphorusmore calcium and phosphorus, , less solvationless solvation, and , and low heat stabilitylow heat stability..

Average amino acid composition of goat and Average amino acid composition of goat and cow milk, as published in official USDA tables, cow milk, as published in official USDA tables,

shows higher levels of shows higher levels of 6 of the 10 6 of the 10 essential essential amino acids: amino acids: threoninethreonine, , isoleucineisoleucine, , lysinelysine, ,

cystinecystine, , tyrosinetyrosine, , valinevaline in in goat milk.goat milk.

In studies with In studies with ratsrats, which had , which had malabsorption malabsorption syndromessyndromes, it was found that goat milk , it was found that goat milk

improved the improved the intestinal absorption of copperintestinal absorption of copper, , which was attributed to the which was attributed to the higher contents of higher contents of

cysteine cysteine (derived from cystine) in goat milk (83 (derived from cystine) in goat milk (83 mg/100 g) than in cow milk (28 mg/100 g).mg/100 g) than in cow milk (28 mg/100 g).

Overall, the adult daily dietary nutrient Overall, the adult daily dietary nutrient recommendationsrecommendations for essential amino acids for essential amino acids

would be met equally or exceeded by a would be met equally or exceeded by a 0.5 l 0.5 l goat milk goat milk consumption compared to cow milk.consumption compared to cow milk.

4. Comparative fat composition of goat milk

A much overlooked component in goat milk is A much overlooked component in goat milk is its fat or lipid content.its fat or lipid content.

Average goat milk fat Average goat milk fat differs differs in contents of its in contents of its fatty acids fatty acids significantlysignificantly from average cow from average cow

milk fat being much milk fat being much higherhigher in in butyricbutyric (C4:0), (C4:0), caproiccaproic (C6:0), (C6:0), capryliccaprylic (C8:0), (C8:0), capriccapric (C10:0), (C10:0),

lauric lauric (C12:0), (C12:0), myristicmyristic (C14:0), (C14:0), palmiticpalmitic (C16:0), (C16:0), linoleiclinoleic (C18:2), (C18:2), but lower but lower in in stearicstearic

(C18:0), and (C18:0), and oleic acid oleic acid (C18:1) (Table 4).(C18:1) (Table 4).

CapricCapric, , capryliccaprylic acids and acids and MCTMCT have become have become established established medical treatments medical treatments for an array of for an array of

clinical disorders, including clinical disorders, including malabsorption malabsorption syndromessyndromes, chyluria, steatorrhea, , chyluria, steatorrhea,

hyperlipoproteinemia, hyperlipoproteinemia, intestinal resectionintestinal resection, , premature infant feedingpremature infant feeding, non-thriftiness of , non-thriftiness of

children, children, infant malnutritioninfant malnutrition, , epilepsyepilepsy, cystic , cystic fibrosis, coronary by-pass, and fibrosis, coronary by-pass, and gallstonesgallstones..

because of their unique because of their unique metabolicmetabolic ability to provide ability to provide direct energy direct energy instead ofinstead of being deposited in being deposited in adipose adipose

tissuestissues, and because of their actions of , and because of their actions of lowering lowering serum cholesterolserum cholesterol, inhibiting and , inhibiting and limiting limiting

cholesterol depositioncholesterol deposition..

Goat milk exceeds cow milk Goat milk exceeds cow milk in monounsaturated in monounsaturated ((MUFAMUFA), polyunsaturated fatty acids (), polyunsaturated fatty acids (PUFAPUFA), and ), and medium chain triglycerides (medium chain triglycerides (MCTMCT), which all are ), which all are

known to be known to be beneficialbeneficial for human for human healthhealth, , especially for especially for cardiovascularcardiovascular conditions (Table 4). conditions (Table 4).

This biomedical superiority has This biomedical superiority has notnot been been promoted much in promoted much in marketingmarketing goat milk, goat goat milk, goat

yoghurt and goat cheeses, but has great yoghurt and goat cheeses, but has great potential in justifying the uniqueness of goat milk potential in justifying the uniqueness of goat milk in in human nutrition human nutrition and and medicinemedicine for treating the for treating the various gastro-intestinal disorders and diseases, various gastro-intestinal disorders and diseases,

besides its value in alleviating cow milk besides its value in alleviating cow milk allergiesallergies..

Fatty acid composition of goat milk fat also can Fatty acid composition of goat milk fat also can be be changedchanged towards even more of the towards even more of the beneficialbeneficial

fatty acids fatty acids by different regimes of feed by different regimes of feed supplementation supplementation to goats including changes of to goats including changes of

forage: concentrate ratiosforage: concentrate ratios..

Goats fed a Goats fed a high level of pasture high level of pasture forage had forage had higher milk fat contents of higher milk fat contents of C4:0, C6:0, C18:0, C4:0, C6:0, C18:0,

C18:l, C18:3, C20:0, C18:l, C18:3, C20:0, isoiso-, ante--, ante-isoiso-,-, and odd fatty and odd fatty acids, but acids, but lower values of C10:0, C12:0, C14:0, lower values of C10:0, C12:0, C14:0, C16:0, and C18:2C16:0, and C18:2, than those fed the low levels , than those fed the low levels

of forage. of forage.

However, However, high levels of alfalfa high levels of alfalfa forage also forage also produced the produced the lowestlowest contents of the less contents of the less

desirable desirable transtrans-C18:1-C18:1 fatty acids. fatty acids.

The conclusion was that The conclusion was that decreasing the decreasing the fiber fiber content and content and increasing the grain increasing the grain part part

in the goat daily ration would in the goat daily ration would lead to lead to higher higher contents of the undesirable contents of the undesirable transtrans--

C18:1C18:1 fatty acid in milk. fatty acid in milk.

Recently more “beneficial fat”, Recently more “beneficial fat”, conjugated conjugated linoleic acidlinoleic acid (CLA), has been identified as a (CLA), has been identified as a

potent potent anticarcinogenanticarcinogen and is primarily and is primarily provided to the human diet by dairy products.provided to the human diet by dairy products.

But it has But it has not been studied not been studied much in goat milk much in goat milk yet.yet.

Branched-chain fatty acids Branched-chain fatty acids have been studied have been studied in goat milk recently, because they lend in goat milk recently, because they lend

characteristic flavorscharacteristic flavors to dairy foods. to dairy foods.

Monomethyl-branchedMonomethyl-branched substitutions on substitutions on C4 C4 and C6 and C6 fatty acids are present only in goat fatty acids are present only in goat

milk and milk and not in cow milk. not in cow milk.

A comparatively A comparatively high number of minor high number of minor branched-chain fatty acidsbranched-chain fatty acids is found in goat is found in goat

milk and the content of milk and the content of transtrans-C18:l -C18:l fatty acids fatty acids is significantly is significantly lower lower in goat milk under in goat milk under

average feeding regimes than in cow milk, average feeding regimes than in cow milk,

also a benefit for also a benefit for coronary heart coronary heart disease risks.disease risks.

5. Other unique components in goat milk

There are a number of unique There are a number of unique physiological physiological and anatomical differencesand anatomical differences between goats between goats

and cows which translate into differences in and cows which translate into differences in composition of goat milk and its products.composition of goat milk and its products.

This was already recognized by the Goat This was already recognized by the Goat Milk Task Force of the National Conference Milk Task Force of the National Conference on Interstate Milk Shipments (NCIMS, USA).on Interstate Milk Shipments (NCIMS, USA).

lead to important decisions by this governing lead to important decisions by this governing body of the US dairy industry towards setting body of the US dairy industry towards setting

separate standards for goat milk from cow separate standards for goat milk from cow milkmilk for for butter fat content minimumbutter fat content minimum, solids-, solids-

not-fat content, somatic cell count maximum, not-fat content, somatic cell count maximum, method for only nucleated cells in milk, lower method for only nucleated cells in milk, lower freezing point level, different natural inhibitor freezing point level, different natural inhibitor

test, test, different milk pasteurization testdifferent milk pasteurization test, , validity of validity of brucellosis ring testbrucellosis ring test, , detection of detection of

cow milk in goat milkcow milk in goat milk, all of which had to , all of which had to insure fair market quality control regulations insure fair market quality control regulations

and practices for goat milk producers.and practices for goat milk producers.

Further comparative differences between Further comparative differences between goat and cow milk in contents of goat and cow milk in contents of

enzymesenzymes, , mineralsminerals, , vitaminsvitamins, , miscellaneous constituents and physical miscellaneous constituents and physical properties have been reviewed in detail.properties have been reviewed in detail.

Reference

G.F.W. Haenlein . Goat milk in human nutrition. Small G.F.W. Haenlein . Goat milk in human nutrition. Small Ruminant Research 51 (2004) 155–163.Ruminant Research 51 (2004) 155–163.