Ask The RD

Question: I know there is quite a bit of controversy surrounding soy products and whether they can be part of a healthy diet. But it’s hard for me to believe that edamame and tofu are considered equal to soy burgers and soy protein bars. Am I right about that?

Answer: You are correct; there are nutritional disparities among soy products, but before I get into the differences, let me address the health controversy. The debate that exists in the health community regarding soy has to do with its possible link to breast cancer. Phytoestrogens, chemicals that mimic the behavior of the hormone estrogen and are found in soy products, have been show to stimulate the growth of breast cancer cells in laboratory experiments. However, when it comes to human studies, the findings are very different, with some studies showing a correlation between soy intake and a low incidence of breast cancer.

The important point to note is that not all soy products are created equal. Most of the soy intake studies that showed a lower risk of breast cancer dealt with the pure form of soy—edamame, tofu, tempeh, etc. Today we have lots of soy options available, and while whole, fresh soybeans can be found in most markets, so can processed foods that use soy protein isolate (SPI).

SPI is a highly refined product made by removing most of the carbohydrate and fat from soy flour; the result is a product very high in protein. Like refined wheat flour, SPI has been stripped of many nutrients; specifically, components such as fiber, calcium and vitamin C have been removed from the soybean during processing. Many products like veggie burgers and soy bars contain SPI; these are processed foods. In addition, over 90% of the soybeans grown in the U.S. are genetically modified, according to the USDA.

If you enjoy your tofu and edamame, there is no need to give them up. However, you may want to watch out for SPI and opt for products made with natural protein sources like lentils, beans and nuts.