Soya is a protein from the bean of the soya plant. It's incorporated into many foods and drinks, such as soya milk and yoghurts, as an alternative to the protein in cow's milk.
Interestingly, the word ‘soya' is used interchangeably with ‘soy'. Although opinion is divided on whether there is a difference, all soya products come from the soya bean - so don't get confused!
Soya allergy and symptoms
Those with soya allergy develop unpleasant symptoms, such as a rash, stomach cramps, diarrhoea, vomiting and breathing difficulties when soya-containing foods and drinks are consumed. This is because the body thinks a certain protein within the soya bean is harmful; the immune system releases a substance called histamine into the bloodstream and this causes the symptoms. Not all allergic reactions involve the immune system; these are known as ‘non-allergic' and are usually of a milder nature. In contrast to other food allergies, such as peanut and seafood, the condition is rarely life-threatening.
Prevalence
In Europe, soya allergy is much less common than in Eastern Asia, where soya has been a staple part of the diet for over 5,000 years. In the UK, soya allergy is found in only about 0.5% of the population. Where it does occur, this is almost always in children, who usually outgrow it by two or three years of age. It is unusual for it to occur in adults.
Management of soya allergy
Soya and children
Some babies and young children are allergic to the protein in both cow's milk and soya. They may also be allergic to goat's and sheep's milk. None of these milks should be given to infants under six months. This is because the proteins in them are similar; this is known as cross reactivity.
In non-allergic children, cow's milk is ideally introduced at around nine months. Infants who can't tolerate cow's milk and are not breastfed should be given a cow's milk-based formula, under medical supervision. Due to some controversy over the long-term effects of soya, soya-based formulas should only be used by non-breastfed infants who are being raised as vegans.
If soya allergy has been diagnosed, rice and oat milks may be useful alternatives in older children, alongside a diet rich in calcium, but these mustn't be taken without medical advice.
Management of soya allergy can be problematic, especially upon weaning, when solids are needed to provide the energy, protein, vitamins and minerals for normal growth and development. If you suspect your child may be allergic to soya it's important you consult your GP before experimenting with alternative milk formulas and substitutes. This is for safety reasons, as well as to be sure that the replacement product(s) contain enough energy and nutrients to ensure normal growth and development.
Reading food labels
All pre-packed food containing soya, or products of soya (e.g. soya flour), are required by EU law, to state ‘Contains: soya' on the label - so check carefully when you're shopping. Some products include soya in their names, e.g. ‘Soya spread' or ‘Soya-free spread' and are therefore easy to identify, but with other foods, such as baked items, breakfast cereals, soups, sauces and processed meats, it may not be so obvious that they contain soya.
TVP (textured vegetable protein) is one ingredient to watch out for. Used as a meat substitute, it is soya flour that's been processed.
Interestingly, refined soya oil (the main ingredient in vegetable oil and soya margarine), is excluded from the legislation because the allergens (proteins which cause allergic symptoms) have been removed. This should therefore be safe to eat.
Avoiding soya, when also avoiding cow's milk, potentially limits the amount of protein and important vitamins and minerals - calcium in particular - entering the body. Soya substitutes, such as rice or oat milk, may or may not have calcium added, so it's important to look out for this information too. Cow's milk and, to a lesser extent soya milk, are key sources of calcium in growing children and sufficient amounts must be included in the diet through natural sources or food fortification (added to food). The recommended daily amounts (RDAs) for calcium in growing children are shown below. RDAs can be found in the Nutritional Information boxes on pre-packed food.
- 1-12 months - 525 mg/day
- 1-3 years - 350 mg/day
- 4-6 years - 450 mg/day
Some individuals with soya allergy will also react to foods such as peanuts, peas, lentils, chickpeas, rye and barley flour because the allergens in these foods are part of the soya bean family.
Avoiding reactions
When eating out, speak to the chef or restaurant manager to explain yours or your child's condition and ask if they can prepare a separate meal if necessary.
Amazingly, there are about 15 different proteins in soya beans! The allergenic protein might be only one of these 15, meaning that some products will cause reactions and some will not. So how do you find the culprit? Keep a food diary and note down any symptoms, or lack of symptoms, after soya foods are eaten. You may notice a pattern developing, which will help rule out certain foods as being safe, or identify those that are not.
And one final tip! Make time to prepare your meals from fresh ingredients whenever possible - most of the soya we eat is contained in processed food - so get out your apron!