What is Soy Protein Isolate?

This ingredient is the protein source for plant-based, soy formulas.  As the name hints, it is made by separating protein from the other parts of the soybean. Like whey protein isolate it is at least 90% protein by weight, so it contains very little carbohydrate or fat.

Soy protein isolate is found in many processed foods, including  shakes, granola bars, meal alternatives, sauces, and even breakfast cereal.

Regulations and Safety

Searching for more information about this ingredient online can lead to some concerning results claiming that soy protein isolate it is not recognized by the FDA as safe (GRAS). At first blush, these allegations seem alarming, but they are based on a sorely outdated understanding about the GRAS process. The FDA has not affirmed GRAS in almost 30 years. Companies and manufacturers self-affirm with many taking the optional next step to notify the FDA of their independent GRAS conclusion.

Both the American Academy of Pediatrics and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) have stated that, while soy formulas are safe, there are few indications for their use.  A 2018 review in Frontiers in Nutrition, concluded,

“a global evaluation of the impact of modern SFs on human development seems to suggest that their use is not associated with relevant abnormalities.”

Importantly, soy formulas are not appropriate for infants with cow milk protein allergy, because 10 – 50% of those infants will also be allergic to soy. A 2020 review article from Europe recommends avoiding soy formula for infants with cow’s milk allergy who are under 6 months of age.

Dietary Considerations

Soy protein isolate is considered Pareve, however it may be processed into formula on equipment used for dairy.

While soy formulas may be plant-based, they are not vegan, because vitamin D (cholecalciferol) is typically made from lanolin, an animal product from sheep wool.