What is soy protein isolate?
Soy protein isolate (SPI; Soy Protein Isolate) is a protein from soybeans that is isolated from all other components in soybeans. When you take soy and remove all the sugar, fiber, and other natural vitamins and minerals from it, leaving just the protein, all you're left with is protein.
Made through a process called pickling, the soybeans are soaked in acid or alcohol to remove sugar and dietary fiber. What's left is then dehydrated, ending up in a dry powder that looks like any "protein powder."
The end result is an incredibly protein-rich product that contains no cholesterol and virtually no carbohydrates or fat. Because of this, it's often used in products like soy-based infant formula, protein bars, flours, cereals, and meat and dairy alternatives to boost protein content without increasing carbs or calorie counts.
The advantages and disadvantages of soy protein isolate
There is no doubt that SPI is an ultra-high protein substance. That's why vegetarians or vegans and people with milk allergies may use products containing SPI, Richards said.
But unfortunately, when it comes to SPI, it's not simple: it's high protein so it's healthy. This is because the process by which soybeans are used to produce high-protein products is controversial.
The extraction process often leaves behind residues of chemicals and metals. So if you consume SPI, you're likely eating at least some of these residues. While the amount of metal you are exposed to from SPI is unlikely to be toxic, it is generally considered best practice to limit the amount of metal in your diet when possible, as high levels of metal can be toxic. Things like gasoline fumes, quick-drying glues, spray glue, contact with cement, arts and crafts paints, and stain removers expose us to these less salty chemicals every day.
There’s another reason some experts turn a blind eye to SPI: It contains phytates, also known as antinutrients, which reduce the body’s ability to absorb iron and zinc. It’s important to note that the extraction process removes the zinc and iron powder typically found in soy products. Is this a double whammy? certainly. But as long as you eat beans or red meat that contain zinc and iron, you don't have to worry about SPIs causing micronutrient deficiencies.
Another thing that adds to the controversy over SPIs is that they are genetically modified. This is no surprise: at least 90% of soybeans grown in the United States are genetically modified. So of course most SPIs are too.
Why is this a problem? Some say no, there is currently no scientific evidence that non-GMO foods are healthier than GMO foods. But some claim that GMOs have inflammatory effects on the body, exacerbating symptoms associated with inflammatory diseases such as arthritis, asthma and Crohn's disease.
Should I avoid soy protein isolate?
Ultimately, whether you blacklist SPIs from your diet depends on your personal needs, body, and goals.
If you suffer from inflammation or otherwise choose to stay away from GMOs, you may want to avoid SPIs. Same goes if you have a sensitive stomach. People with moody digestive systems may experience mild stomach upset from this product.
But if you're a vegetarian, both experts agree it's probably fine to continue eating SPI. Soy protein is indeed the best vegetarian alternative to whey and casein products.
You can also start eating more high-protein, vegetarian-friendly protein sources like pea protein, brown rice protein, and hemp protein. Or re-prioritize nutrient-dense whole foods, like the 35 high-protein vegan foods in this list.
