The soya bean belongs to the legume family, which includes fresh and dried peas, beans, carob, liquorice and peanut. Research has shown that a symptomatic reaction to more than one member of the legume family is rare. It is therefore in most cases not necessary to avoid all foods from this plant family. 

 

Soya is widely used in foods and is difficult to avoid. As many as 60% of manufactured foods contain soya. Soy comes from soybeans and immature soybeans are called edamame beans. Soya can be ingested as whole beans, soya flour, soya sauce or soya oil. 

 

Soya can also be used in foods as a texturiser (texturised vegetable protein), emulsifier (soya lecithin) or protein filler. Soya flour is widely used in foods including; breads, cakes, processed foods (ready meals, burgers and sausages) and baby foods. 

 

Avoidance of all these products containing soya would make the diet very restricted. However, as with many other allergies, the level of avoidance required will depend on each individual case. Some people may need to avoid all these forms of soya, whereas others may be able to tolerate, for example, soy sauce and soya lecithin. In fact, most soy sauces contain very small amounts of soy, with most of the protein in the sauce being derived from fermented wheat. 

 

Soya-derived lecithin is an emulsifier, it is a lipid (fat) which stabilizes foods which contain water and fats, which do not normally mix. This is why you have to shake many salad dressings as they contain oil and water/vinegar which do not mix. For example, lecithin stops the cocoa and cocoa butter in chocolate bars from separating. In addition, lecithin improves the texture of many foods such as chocolate and spreads, and also helps preserves some foods. Since lecithin is fat, soya lecithin contains very little soya protein, and most people with soya allergy can tolerate it.