CLARIFYING MYTHS ABOUT DAIRY

The Star Early Edition - - LIFESTYLE VERVE -

Alot of peo­ple will have al­ready made up their minds about whether hu­mans need dairy in their diet and will be think­ing that the an­swer is ob­vi­ously “yes” or ob­vi­ously “no”. So, here’s the lat­est re­search on the mat­ter.

Milk is an in­ter­est­ing food­stuff. The sugar in it is called lac­tose and lac­tose re­quires a chem­i­cal or en­zyme called lac­tase to al­low it to pass across the walls of the gut into the blood stream.

When we are ba­bies, we all pro­duce plenty of the lac­tase en­zyme which al­lows us to ab­sorb our mother’s milk. In pop­u­la­tions where milk con­sump­tion has been his­tor­i­cally low, such as Ja­pan and China, most chil­dren will have stopped pro­duc­ing lac­tase soon af­ter wean­ing and – pro­duc­ing al­most en­tire pop­u­la­tions that may be un­able to ab­sorb the lac­tose in milk – this we call “lac­tose in­tol­er­ance”.

In pop­u­la­tions where milk con­sump­tion has al­ways been high, such as in Europe, most adults con­tinue to pro­duce lac­tase for their whole lives and can di­gest milk quite hap­pily with only around 5 per­cent of the pop­u­la­tion be­ing lac­tose in­tol­er­ant.

Con­tin­u­ing to pro­duce lac­tase into adult­hood is ac­tu­ally an in­her­ited ge­netic vari­a­tion which has be­come so com­mon be­cause be­ing able to tol­er­ate milk has a se­lec­tive ad­van­tage. Milk is a use­ful source of pro­tein, en­ergy, cal­cium, phos­phate, B vi­ta­mins and io­dine, mean­ing that those with the mu­ta­tion were gen­er­ally health­ier and pro­duced more chil­dren than those who couldn’t tol­er­ate milk, and so the pres­ence of the mu­ta­tion in­creased.

The symp­toms of lac­tose in­tol­er­ance in­clude wind, bloat­ing and di­ar­rhoea so if you don’t ex­pe­ri­ence any of those af­ter drink­ing milk or eat­ing ice cream then you’re fine.

FERMENTING

efir ‘grains’ af­ter strain­ing. A. Kniesel/Wikipedia, CC BY-SA

There is good ev­i­dence that milk has been part of the hu­man diet in North­ern Europe for more than 8 000 years which is when peo­ple there first moved from be­ing no­madic to hav­ing a more struc­tured way of life. Be­cause 8 000 years ago most peo­ple didn’t tol­er­ate milk well, they quickly re­alised that if the milk was fer­mented and be­came cheese or yo­ghurt it could be bet­ter tol­er­ated. This is be­cause th­ese pro­cesses en­cour­age bac­te­ria to use up most of the car­bo­hy­drate – the lac­tose – in the milk so peo­ple who didn’t pro­duce the lac­tase en­zyme could still ben­e­fit from the nu­tri­ents in the milk. Today peo­ple with lac­tose in­tol­er­ance can drink ke­fir, a fer­mented milk drink made with a yeast starter, which some sug­gest also has pro­bi­otic ben­e­fits for the gut as well as many other health ben­e­fits.

So dairy has been piv­otal to nutri­tion and im­por­tant to the sur­vival of many pop­u­la­tions in the world and most Euro­peans and North Amer­i­cans are well adapted to di­gest it. So if you have been told that hu­mans aren’t adapted to have dairy in their diet, that isn’t cor­rect. Sim­i­larly, it isn’t true to say that dairy pro­motes in­flam­ma­tion or acid­ity.

CAL­CIUM

Nu­tri­tional sci­en­tists and di­eti­tians have of­ten as­sumed that be­cause milk is rich in cal­cium, it is there­fore good for main­tain­ing the cal­cium lev­els in our bones. How­ever, a cou­ple of re­cent big stud­ies have have brought this into ques­tion. A fur­ther sys­tem­atic re­view of the ev­i­dence con­cluded that ac­tu­ally, it doesn’t seem to mat­ter how much cal­cium you get from your diet, your risk of frac­tur­ing your bones re­mains the same.

We have seen that in cul­tures, where dairy plays a very min­i­mal part in the tra­di­tional diet such as in China and Ja­pan, the in­ci­dence of hip frac­ture – a com­mon out­come of poor bone min­eral den­sity – is 150 per­cent higher than that of white Amer­i­can or Euro­pean pop­u­la­tions.

One thing to re­mem­ber about th­ese stud­ies is that they are look­ing at cal­cium in­take in adult­hood. When we look at stud­ies of chil­dren who have an al­lergy to cow’s milk, for ex­am­ple, we see that the strength of their bones is sig­nif­i­cantly com­pro­mised by the lack of milk in their diet and that de­sen­si­ti­sa­tion through treat­ment so their diet can in­clude milk also strength­ens their bones.

In­ter­est­ingly, chil­dren with this al­lergy who are given al­ter­na­tive sources of cal­cium other than milk still find the strength of their bones com­pro­mised. This sug­gests that cal­cium-con­tain­ing al­ter­na­tives to dairy are still not good enough at pro­mot­ing bone den­sity in chil­dren.

While milk in­take is re­ally im­por­tant for the healthy de­vel­op­ment of chil­dren’s bones, con­sum­ing milk as an adult doesn’t ap­pear to de­crease your risk of frac­tures. But there are lots of other nu­tri­ents in milk and dairy foods.

Stud­ies have found that if dairy is re­placed in the diet by foods con­tain­ing the same amount of cal­cium such as green leafy veg­eta­bles or soya milk for­ti­fied with cal­cium, the diet con­tains less pro­tein, potas­sium, mag­ne­sium, phos­pho­rus, ri­boflavin, vi­ta­mins A and B12. Milk and dairy foods are also a great source of all essen­tial amino acids which are the small pro­tein mol­e­cules that build mus­cles and re­pair tis­sue dam­age. The bot­tom line is we prob­a­bly don’t need dairy in our di­ets – as adults – but milk and dairy foods pro­vide lots of essen­tial nu­tri­ents which are trick­ier to source from other foods. – The Con­ver­sa­tion

Milk is a use­ful source of pro­tein, en­ergy, cal­cium, phos­phate, B vi­ta­mins and io­dine.

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