Why raw milk is dan­ger­ous

NZ Lifestyle Block - - Feature Warning: Raw Milk -

Raw milk is un­treated milk that typ­i­cally comes from cows, goats, or sheep. This means it has not been heat treated to kill the harm­ful bac­te­ria (pathogens), and noth­ing has been added or re­moved.

Pas­teuri­sa­tion is the process that elim­i­nates al­most all harm­ful bac­te­ria through a spe­cific heat treat­ment. Pas­teuri­sa­tion is achieved by heat­ing milk to 72°C for 15 sec­onds. Con­sumers at home can achieve the same re­sult by heat­ing milk to 70°C and hold­ing it at that tem­per­a­ture for 1 minute.

Is un­pas­teurised milk safe to drink?

No mat­ter how care­fully an­i­mals are milked, there is al­ways a risk of harm­ful bac­te­ria be­ing present. Con­sum­ing raw milk can cause se­vere ill­ness due to the pos­si­ble pres­ence of harm­ful bac­te­ria. Preg­nant women, young chil­dren (par­tic­u­larly ba­bies), the el­derly, and peo­ple with weak­ened im­mune sys­tems are at great­est risk of get­ting sick and the con­se­quences for them can be more se­vere.

How does milk get con­tam­i­nated?

Harm­ful bac­te­ria can pass di­rectly into milk from var­i­ous sources, but fae­cal con­tam­i­na­tion is the main cause of pathogens in raw milk. Fae­cal con­tam­i­na­tion can come from: • poor hy­gienic prac­tices, such as teats that haven’t been cleaned and sani­tised, or milk har­vesters with dirty hands; • milk­ing equip­ment that is poorly de­signed or not prop­erly cleaned and sani­tised; • the farm dairy en­vi­ron­ment dur­ing milk­ing; • Ud­der in­fec­tions can also re­sult in pathogens in raw milk - an­i­mals can look healthy even when in­fected, so farm­ers may not re­alise there is a risk; • Poor cool­ing, stor­age, and han­dling will al­low the pathogens present to grow.

Even if care is taken in pro­duc­ing raw milk, there is still the risk that it con­tains harm­ful bac­te­ria (pathogens). This is be­cause there is no process used to de­stroy the harm­ful bac­te­ria.

How can I tell if raw milk is con­tam­i­nated?

There is no way of telling by taste, sight, or smell that raw milk con­tains harm­ful bac­te­ria. How­ever, any milk that ap­pears to have gone off or looks ab­nor­mal should be avoided as this in­di­cates that it has not been cooled, stored or han­dled cor­rectly and the pathogens present in the milk, whether good or bad, have had an op­por­tu­nity to grow. An out­break is recorded when two or more peo­ple have be­come sick and the ill­ness is linked to a com­mon source.

Glob­ally, out­breaks of ill­ness caused by raw milk con­sump­tion oc­cur regularly. Recorded out­breaks in­clude cases of se­vere ill­nesses, which can be lifethreat­en­ing. Ac­cord­ing to the US Cen­ter for Dis­ease Con­trol and Preven­tion, raw milk is re­spon­si­ble for nearly three times more hos­pi­tal­i­sa­tions than any other food­borne source.

The num­ber of out­breaks of food­borne ill­ness in NZ where raw milk con­sump­tion is a recorded risk fac­tor have been con­sis­tently higher since 2009. In 2013, raw milk was recorded as a risk fac­tor in eight out­breaks af­fect­ing 33 peo­ple.

All out­breaks that recorded peo­ple’s age in­cluded chil­dren younger than five years old. In ad­di­tion, raw milk was a risk fac­tor for two chil­dren younger than five years old who were hos­pi­talised with se­ri­ous re­nal prob­lems.

An on-go­ing MPI sur­vey has spo­rad­i­cally iden­ti­fied the pres­ence of harm­ful bac­te­ria such as Shiga toxin–pro­duc­ing E. coli, campy­lobac­ter and sal­mo­nella in raw milk. No mat­ter how care­fully the an­i­mals are milked, there is al­ways a pos­si­bil­ity of harm­ful bac­te­ria be­ing present in raw milk. This is be­cause pathogens regularly oc­cur in an­i­mal guts and are ever-present on farms. Pas­teuri­sa­tion is one of the few proven meth­ods to kill harm­ful bac­te­ria in milk. There is lit­tle ev­i­dence that ‘good’ bac­te­ria or other com­po­nents in raw milk kill the ‘bad’ bac­te­ria to pre­vent ill­ness.

The cur­rent sci­en­tific ev­i­dence shows that the nu­tri­tional value of raw milk is not sub­stan­tially dif­fer­ent to that of pas­teurised milk.

There is no rea­son to be­lieve that raw milk would ben­e­fit lac­tose-in­tol­er­ant peo­ple. All milk con­tains lac­tose. Heat treat­ment can con­vert lac­tose into a more sol­u­ble and easily ab­sorbed form, but this hap­pens at tem­per­a­tures much higher than those re­quired for pas­teuri­sa­tion.

There is no con­clu­sive ev­i­dence to show that raw milk helps pro­tect against se­ri­ous dis­ease. There are a few stud­ies that sug­gest that drink­ing raw milk at an early age, along with other fac­tors, may help re­duce the risk of de­vel­op­ing asthma, hay fever, or eczema, but the science is not con­clu­sive be­cause of a lack of data, and the ab­sence of any bi­o­log­i­cal rea­son for why raw milk could help pro­tect against these con­di­tions.

What is known is that raw milk may con­tain harm­ful bac­te­ria that can lead to se­ri­ous con­se­quences, such as re­nal fail­ure and paral­y­sis. This is why it’s rec­om­mended that young chil­dren and other peo­ple with low­ered im­mu­nity should not drink it. Keep­ing raw milk un­der re­frig­er­a­tion (4°C or less) re­duces the risk of any harm­ful bac­te­ria in the milk grow­ing to lev­els which make peo­ple sick when they drink it. Peo­ple should dis­card raw milk if it has been left out of the fridge and has reached room tem­per­a­ture.

Sci­en­tific ev­i­dence shows that the best way to min­imise the risk of get­ting ill from drink­ing raw milk is to heat it, for ex­am­ple to 70°C for one minute. This will kill off the bad bugs but still leave be­hind healthy milk.

To view MPI’S literature re­view:

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