Orla Walsh

Soy bean prod­ucts are grow­ing more and more pop­u­lar — from milk to tofu, there is an en­tire spec­trum of foods avail­able. How­ever, there are still some con­tro­ver­sies over soy. So just how safe is it? And how much should you be eat­ing? Di­eti­tian separates t

Irish Independent - Health & Living - - FOOD MATTERS -

SOY comes from soy­bean plants, which are part of the legume fam­ily. As soy is closely re­lated to the likes of beans, peas and lentils, it too is a great source of plant pro­tein. You will find the same amount of pro­tein in 1.5 cups of cooked soy beans as you would find in 150g of meat. Un­like most other plant pro­teins, soy is con­sid­ered a com­plete pro­tein — mean­ing that it con­tains all the es­sen­tial amino acids or build­ing blocks that make up a re­ally good source of pro­tein.

Not only is it a good source of pro­tein, but it’s also jam-packed full of vi­ta­mins and min­er­als. Most no­table mi­cronu­tri­ents in­clude cal­cium and iron, mak­ing soy an ex­cel­lent choice for ve­g­ans who omit the likes of iron-con­tain­ing meats and cal­cium-con­tain­ing dairy from their diet.

Like most legumes, soy beans are also an ex­cel­lent source of fi­bre. Soy pro­vides both sol­u­ble and in­sol­u­ble fi­bre in ex­cel­lent quan­ti­ties. Sol­u­ble fi­bre is the gel-like fi­bre that helps soften the stool, while in­sol­u­ble fi­bre is the roughage that bulks it out. There­fore soy beans can act like a sweep­ing brush, clean­ing our gut and keep­ing things mov­ing!

There are two things that make soy beans unique among their legume pals — how much fat they con­tain and their isoflavone con­tent. Soy beans are about 20pc fat. Most other beans, peas and lentils are rel­a­tively fat-free. How­ever, their fat con­tent is cer­tainly not a neg­a­tive — the fat they pro­vide is healthy fat, with about 60pc be­ing polyun­sat­u­rated, and 30pc mo­noun­sat­u­rated fatty acids. Soy beans are a rich source of isoflavones, which are an­tiox­i­dants that have many health ben­e­fits. Each gram of soy pro­tein is as­so­ci­ated with ap­prox­i­mately 2.2mg to 3.3mg of isoflavones. Isoflavone con­tent can vary de­pend­ing on soil and grow­ing con­di­tions.

There are many kinds of soy foods that are made from soy beans, such as tofu, soy milk, tex­tured veg­etable pro­tein (TVP) and soy sauce. They are not cre­ated equal — their level of pro­cess­ing changes their nu­tri­ent pro­file.

Firstly, the fat con­tent of soy foods dif­fers de­pend­ing on whether the whole bean is used. For ex­am­ple, TVP is fat-free, while other soy foods such as tofu and soymilk con­tain a lit­tle more fat.

Se­condly, their isoflavones con­tent varies, de­pend­ing on how pro­cessed the food source is and how the soy pro­tein was ex­tracted from the soy bean. Tofu, soymilk, soy nuts, tem­peh, edamame, soy flour and tex­tured soy pro­tein all con­tain sig­nif­i­cant amounts of isoflavones. Very pro­cessed soy-con­tain­ing fast foods like soy burg­ers con­tain con­sid­er­ably less isoflavones than the more whole food va­ri­eties, while the likes of soy sauce con­tains none (see panel to the right).

PHOTO: MARC O’SUL­LI­VAN

Di­eti­tian Orla Walsh

gets to the core of com­mon food myths

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