Don’t Buy the Snake Oil, Or the Butterfat!

I wrote this as a let­ter to the edi­tor of Moth­er Earth News, which is a gen­er­al­ly good pub­li­ca­tion that some­times pub­lish­es bad dietary advice:

In The Fats You Need for a Healthy Diet (August/September 2011 of Moth­er Earth News), Oscar H. Will, III, pro­vides dan­ger­ous­ly mis­lead­ing dietary advice. Sat­u­rat­ed fat does not “do a body good.” You don’t need to get any sat­u­rat­ed, monoun­sat­u­rat­ed, or trans fat­ty acids what­so­ev­er from the diet. Only two fat­ty acids are essen­tial, which means that they must come from the food. One is an omega-6 fat­ty acid called linole­ic acid. The oth­er is an omega-3 fat­ty acid called alpha-linolenic acid. How­ev­er, the dietary require­ment for these fat­ty acids is so small that you can find true cas­es of defi­cien­cy only in extreme sit­u­a­tions, such as peo­ple who were being fed noth­ing but sug­ar intra­venous­ly. For those patients, the require­ment for essen­tial fat­ty acids could be met by rub­bing a small amount of veg­etable oil on the skin. Fat defi­cien­cy is prac­ti­cal­ly nonex­is­tent because even a diet based on low-fat grains and veg­eta­bles pro­vides enough of the essen­tial fat­ty acids

The usu­al prob­lem is that the per­son is eat­ing too much fat. Excess fat of any kind pro­motes obe­si­ty, ath­er­o­scle­ro­sis, dia­betes, and oth­er chron­ic dis­eases. The omega-3 fat­ty acids tend to have a blood-thin­ning effect, which off­sets some of the effect of their con­tri­bu­tion to ath­er­o­scle­ro­sis. An excess of the polyun­sat­u­rat­ed fat­ty acids (omega-3 and omega-6) has been linked to an increased risk of can­cer, pos­si­bly because of their effect on the immune sys­tem.

Even veg­e­tar­i­ans and veg­ans often eat too much fat, and they tend to eat a dis­pro­por­tion­ate­ly large amount of omega-6 rel­a­tive to omega-3 fat­ty acids because of a large intake of nuts and oils. The obvi­ous solu­tion to this prob­lem is to restrict the over­all fat intake and add a small amount of ground flaxseed to the diet. Flaxseed is an excel­lent source of the rel­a­tive­ly scarce omega-3 fat­ty acids.

Con­ju­gat­ed linolenic acid is found almost exclu­sive­ly in foods of ani­mal ori­gin. Yet nutri­tion­al epi­demi­ol­o­gy stud­ies show that those foods pro­mote the sorts of dis­eases that the dairy indus­try is claim­ing that con­ju­gat­ed linolenic acid is sup­posed to help pre­vent.


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