Soy Protein Isolate

Last reviewed October 19, 2026

In plain words: Soy protein isolate is a soy protein food made by removing most of the oil, carbohydrate and water from soybeans, so that protein is at least 90 percent of the dry weight.

What the evidence review says

Soy protein isolate is concentrated protein from soybeans. Soy is a major food allergen. Soy contains plant compounds called isoflavones; questions have been raised about high-dose isoflavone products and soy infant formula, but adult clinical evidence does not support regarding ordinary soy foods as hormone disruptors. EFSA had too little evidence to assess some groups of women.

Two practical issues, neither of which is a petroleum-dye issue. Soy is a major food allergen. Soy isoflavones are phytoestrogens, and high-dose supplements and soy infant formula have been questioned for effects on breast, uterus, thyroid, and infant development. Adult clinical evidence does not support treating ordinary soy foods or isoflavones as endocrine disruptors; a one-year randomized trial did find small shifts in some male reproductive hormones without a clear clinical effect. EFSA had too little evidence for perimenopausal women and for women with a personal or family history of cancer.

• Source: Messina M et al., Crit Rev Food Sci Nutr, 2022 · doi:10.1080/10408398.2021.1895054
• Source: Dillingham BL et al., J Nutr, 2005 · doi:10.1093/jn/135.3.584

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This page is for general education. It is not medical advice and does not replace advice from your doctor, pediatrician, allergist or registered dietitian. Research changes; we review these pages when new evidence or rules come out. Last reviewed October 19, 2026.