Meat-heavy low-carb di­ets can shorten your life­span

The Borneo Post - Nature and health - - Front Page -

MID­DLE- aged peo­ple who get roughly half their daily calo­ries from car­bo­hy­drates live sev­eral years longer on av­er­age than those with meat-heavy low-carb di­ets, re­searchers have re­ported. The find­ings, pub­lished in The Lancet med­i­cal jour­nal, chal­lenge a trend in Europe and North Amer­ica to­ward so-called Pa­leo di­ets that shun car­bo­hy­drates in favour of an­i­mal pro­tein and fat. Pro­po­nents of these “Stone Age” di­ets ar­gue that the rapid shift 10,000 years ago – with the ad­vent of agri­cul­ture – to grains, dairy and legumes has not al­lowed the hu­man body enough time to adapt to these high-carb foods.

For the study, re­ceiv­ing less than 40 per cent of to­tal en­ergy in­take from car­bo­hy­drates qual­i­fied as a low-carb reg­i­men, though many such di­ets re­duce the share to 20 per­cent or less. At the other ex­treme, a 70 per cent or higher share of car­bo­hy­drates – such as pasta, rice, cakes, sug­ary drinks – can also re­duce longevity, but by far less, the sci­en­tists found. “Low-carb di­ets that re­place car­bo­hy­drates with pro­tein or fat are gain­ing wide­spread pop­u­lar­ity as a health and weight loss strat­egy,” said lead au­thor Sara Sei­del­mann, a re­searcher at Brigham and Women’s Hos­pi­tal in Bos­ton. “How­ever, our data sug­gests that an­i­mal-based low car­bo­hy­drate di­ets might be as­so­ci­ated with shorter over­all life­span and should be dis­cour­aged.”

Re­plac­ing meat with plant-based fats (such as av­o­ca­dos and nuts) and pro­teins (such as soy prod­ucts and lentils) re­duces the risk of mor­tal­ity, Sei­del­mann and her team found. The op­ti­mal bal­ance of food groups for longevity re­mains hotly de­bated. Many stud­ies have con­cluded that eat­ing car­bo­hy­drates in mod­er­a­tion – 45 to 55 per cent of to­tal calo­rie in­take – is best, but oth­ers re­port im­proved short-term, car­diometabolic health with high-pro­tein, high-fat di­ets. “Low car­bo­hy­drate di­etary pat­terns favour­ing an­i­malderived pro­tein and fat sources, from sources such as lamb, beef, pork, and chicken, were as­so­ci­ated with higher mor­tal­ity,” the study said.

“Those that favoured plant-de­rived pro­tein and fat in­take, from sources such as veg­eta­bles, nuts, peanut but­ter, and whole-grain breads, were as­so­ci­ated with lower mor­tal­ity,” it said, adding that this sug­gested “the source of food no­tably mod­i­fies the as­so­ci­a­tion be­tween car­bo­hy­drate in­take and mor­tal­ity.” Sei­del­mann and col­leagues poured over the med­i­cal his­to­ries of nearly 15,500 men and women who were 45-64 when they en­rolled – be­tween 1987 and 1989 – in a health sur­vey spread across four lo­ca­tions in the Unit- ed States.

Par­tic­i­pants filled out de­tailed ques­tion­naires about their di­etary habits – what foods, how much, how of­ten, etc. Over a 25-year fol­low up pe­riod, more than 6,000 of the men and women died. Peo­ple who got 50-55 per­cent of their calo­ries from car­bo­hy­drates out­lived those with very low-carb di­ets, on av­er­age, by four years, and those with high-carb di­ets by one year. A re­view of med­i­cal records for an ad­di­tional 432,000 peo­ple from ear­lier stud­ies con­firmed the re­sults, which are also in line with World Health Or­gan­i­sa­tion (WHO) rec­om­men­da­tions.

“There is noth­ing to be gained from long-term ad­her­ence to low-car­bo­hy­drate di­ets rich in fats and pro­teins from an­i­mal ori­gins,” said Ian John­son, a nu­tri­tion re­searcher at Quadram In­sti­tute Bio­science in Nor­wich, Eng­land, com­ment­ing on the re­search, in which he did not take part. But carb qual­ity, not just quan­tity, is cru­cial he added. “Most should come from plant foods rich in di­etary fi­bre and in­tact grains, rather than from sug­ary bev­er­ages or man­u­fac­tured foods high in added sugar.” Fi­bres also help main­tain a healthy gut flora, now con­sid­ered to be a ma­jor fac­tor in health and dis­ease. – Re­laxnews

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