Although the plant-based protein movement has been growing significantly in the last ten years, vegan and vegetarian meat and dairy alternatives have been around for much longer. Many of these alternatives are made with soybeans/protein. Soy has been a staple in the American diet since the 1960s and has been a staple of the Asian diet for hundreds of years. It is only until recently that it has come under fire.
Soy protein is isolated from soybeans. Soybeans are harvested and ground up to create a flour. Fat and carbohydrates are removed from the flour to concentrate the protein. Soy protein isolates are concentrated up to 90% protein and soy protein concentrates are concentrated up to 80% protein. The remaining 10% or 20% of the material (respectively) is a combination of carbohydrates, fats, vitamins, minerals, and other plant compounds.
Unlike other vegan proteins, soy protein is considered a complete protein. This means that it contains all the building blocks of protein (i.e., amino acids) in amounts that the body needs to function properly. (Most vegan proteins are deficient in at least one amino acid.) However, unlike other vegan proteins, soy does contain an allergen and is typically genetically modified. Most soybeans are genetically modified to be able to tolerate glyphosate (i.e., Roundup), a pesticide used to kill weeds common in soy fields. Despite thorough cleaning of the soybeans, small amounts of this pesticide often remain on the soybean, making its way into the food and beverage products. It is important to note that organic soybeans/protein are not genetically modified and will never be sprayed with glyphosate or any type of pesticide.
Soy protein is most known for its heart health claims. It has been well studied to lower bad (LDL) cholesterol and raise good (HDL) cholesterol. In fact, in 1999 the FDA authorized a health claim on soy protein touting its extensive research on heart health. Additional research has shown that it lowers blood pressure and the risk of type-2 diabetes. And studies have also shown that in Asian populations (where large amounts of soy is consumed), the risk of cancer, particularly breast cancer, is reduced.
Much of the negative press around soy has to do with its isoflavone content. Many fruits and vegetables contain isoflavones, but soybeans contain some of the highest amounts. Isoflavones are considered phytoestrogens; which means that they have properties similar to human estrogen. When ingested, these compounds can bind to estrogen receptors and (weakly) mimic some of the effects of human estrogen. However, the research behind the impact of isoflavones in the human body is mixed. For example, a recent meta-analysis (a review of multiple studies), states that the isoflavones in soy do not increase estrogen levels in men. On the other hand, multiple studies have shown that soy helps minimize post-menopausal symptoms in women (postmenopausal women have symptoms because they have less estrogen than premenopausal women). One thing that the research can agree on: it all depends!
Soy’s high isoflavones also impact the way that iodine is absorbed. Iodine is an important mineral that regulates hormone production in the thyroid. Studies have shown that for iodine-deficient people and for people taking thyroid medication, consuming soy prohibits the absorption of iodine and the production of thyroid hormones. Studies have shown that the risk of developing hypothyroidism (i.e., the thyroid does not produce enough hormones) increases when soy is consumed.
What foods and beverages do you consume that contain soy? Do you think that the positives outweigh the negatives?
Didn’t know that about soy and thyroid- thank you for sharing that!