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  • Writer's picturefranceswalker@thefoodinto

Are all 'Contains Soy' statements equal?



When your baby has food sensitivities, avoiding dairy and soy is often recommended because these are the most common food issues with food sensitive breast or bottle fed babies.


When avoiding soy, it is the soy protein that is causing the issues here. But soy in foods can take different forms, and can be found in the most surprising places.


Knowing about the different soy found in supermarket foods can help you make your own decision about the level of soy you avoid for your baby thorugh your breast milk.


'CONTAINS SOY'


Next time you check a food or medication to see if it contains soy, see what sort of soy a 'Contains Soy' statement is referring to. Is is soy beans? Soy oil? Soy lecithin?


What type of soy it is may impact on your decision to consume the food or drink, if you are or your breast-fed baby have a soy allergy (IgE or non IgE) or soy intolerance.


SOY PROTEIN CONTENT IN FOODS


The foods that contain significant amounts of soy protein include all the well known soy foods: soy milk, soy beans, tofu, tempeh, miso, soy sauce, edamame, soy albumin (a soy protein) and textured soy protein foods (extra high in soy protein!).


These foods or foods containing these ingredients are to be avoided, and unquestionably the 'Contains Soy' statement supports this decision.


Let's look at the soy protein content of these foods (using an Australian food database).....


FOOD OR DRINK

SOY PROTEIN CONTENT PER SERVE

SOY MILK: 1 glass

9.5 grams

TOFU: 1 cup = 170g

21 grams

SOY FLOUR = 2/3 cup = 100g

50 grams

MISO PASTE, 1 TBSP = 12g

1.5 grams

SOY SAUCE: 1 TBSP = 21g

1.5 grams

SOY OIL: 1 TBSP = 18g

0 grams

We can see some very significant food sources of soy protein, which clearly needs to be

avoided due to the significant portien content of the food/ food ingredient.


The soy in some of these foods are processed with heat, fermentation which can cause partial hydrolysis, chemical modifications and use of proteolytic enzymes which may change the structural makeup of the soy bean portein and potentially render them less allergenic.


At this point in time, the impacts of processing on the allergenicity of soybean protein have not been well studied.


Lets look at these different soy foods in more detail.


SOY FLOUR


Soy beans conatin more protein than all other legumes, hence the high amount of soy portein in soy flour.


The same can be said of soy protein concentrate and soy protein isolate.


Soy protein isolates can be treated to produced textured vegetable prtoein (think: moick chicken) and contians a high soy protein content.



Most foods such as bread contain very small amounts of soy flour, and when you read the ingredient list, it is obvious that the amount of soy flour is likely to be small.


Despite this, small amounts of soy such as soy flour are often best avoided if possible, and these small sources of soy do contain appreciable amounts of soy protein, and for most sensitive babies is often enough to cause issues.



SOY OIL


From the table above, you can see that soy oil does not contain any protein when tested (Australian database).


According to a clinical research paper in 2021 (Taylor et al.);


"Ingredients with low protein content likely pose little risk to soy-allergic individuals especially when used in small percentages in formulated food products. However, only highly refined soy oil has been clinically demonstrated as unable to provoke reactions in soy-allergic individuals (Bush et al., 1985). The allergenicity of other soy ingredients with low protein content such as soy lecithin and soy fiber remains to be demonstrated.


This means that depsite many of these low risk food ingredients likly to bewell tolerated and not provoke a soy allergy reaction when eaten diectly, only soy oil has been demonstrated as being safe.


An exception is cold pressed soy oil which is best excluded.


Cold-pressed soy bean oil has a protein profile similar to soybean flour, but is not typically used as an ingredient in foods. .


SOY LECITHIN


Soy lecithin is made from the fat components of the soy bean. The protein is mostly removed during the purification process.


Consequently, soy lecithin potentially contain trace (very small) levels of soy proteins and these have been found to include soy allergens.


Research indicates that most individuals allergic to soy can safely eat soy lecithin directly.


However, the 2021 review (Taylor et al.) concludes that other soy ingredients with low protein content such as soy lecithin, the potential impact on Ige allergic individuals (direct ingestion) needs to be properly demonstrated before it can be confidently recommended to be safe to be eaten directly by persons with a soy allergy.


UNITED STATES PERSPECTIVE: highly refined soybean oil and certain uses of soy lecithin are exempt from source labelling.


SOY FIBRE


Soy fibre may have differing amounts of protein deepening on its extraction process, and best viewed as a 'to be excluded' soy containing soy protein.


Australian perspective: soy fibre is less commonly seen in Austrlain food products, which is different to the Amercan food manufacture where soy is more commonly used. Still recommend be excluded if you come across it!


SOY DERIVED FOOD INGREDIENTS


The next level down in terms of imperceptible amounts of soy protein are food or processing components derived from soy.


Foods that are made from soy but are so far removed from soy that they are not considered to be a soy contining food are not considered to be relevant in this space.


Usually if soy (and dairy) is being fastidiously excluded from the diet for a breast-fed baby, ongoing issues (if food realted) more likely to another food sensitivity/allergen.


MAY CONTAIN SOY


Australian perspective: as this is a voluntary code, the use of this cliam gives no insight what so ever if this claim is made is to the actual risk of any soy protein cross contamination.


Refer to the 'May Contain' blog if you want to kbnow more about this.


THE SOY WRAP


This information can be used as a guide so you can make your own personal choice about which foods to exclude or not when pursuing a soy free diet for your breast fed baby with soy allergy or intolerance.


My personal interest is sharing evidence based information, with the Australian perspective - especially as this area can be fraught with lots of different information sharing and opinions.



Frances Walker

Dietitian specialising in Food intolerances in breast fed babies



UPDATED MAY 2024


REFERENCES

Steve L. Taylor, Geert F. Houben, W.Marty Blom, Joost Westerhout, Benjamin C. Remington, Rene W.R. Crevel, Simon Brooke-Taylor, Joe L. Baumert,

The population threshold for soy as an allergenic food – Why did the Reference Dose decrease in VITAL 3.0?,Trends in Food Science & Technology, Volume 112, 2021, Pages 99-108, ISSN 0924-2244,






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