A: This is an excellent question and the answer is not entirely straightforward. The idea that soy is healthy stems mainly from the fact that certain populations, like people living in China and Japan, have lower rates of some chronic illnesses including heart disease, and breast and prostate cancers, than people in the U.S. This difference between Asians and Americans is thought to be due, in part, to differences in the typical diets in these two regions. One main distinction is the amount of soy in these diets. Therefore, the disparities between the rates of certain diseases have often been attributed to this food product.
Soy is a wonderful food, loaded with many healthful substances, including isoflavones such as genistein and daidzein. These substances are also known as plant-based estrogens or phytoestrogens. There is a substantial amount of research to show that soy foods are extremely helpful for lowering cholesterol, reducing symptoms of menopause such as hot flashes, and preventing osteoporosis.
In terms of the effects of soy on cancer, the answers are somewhat less clear. Population-based studies suggest, fairly strongly, that if people begin eating soy on a regular basis before adolescence, they may decrease their risk of developing certain types of cancer. In test tube studies in the laboratory, the phytoestrogens isolated from soy have shown both estrogen-like activity and anti-estrogen activity. Estrogen is a powerful hormone that affects the development and growth of certain cancers, including breast and prostate. Therefore, based on the research so far, soy products have the potential to both promote and to limit the growth of these hormone-related cancers.
What I believe, as do many researchers and scientists, is that there are many details that need to be studied before we can answer questions like yours definitively. Most likely, we are going to discover that there are certain instances when soy inhibits the growth of hormone-related cancers and certain instances when soy stimulates the growth of these cancers. For example, different types of breast cancer are identified by their receptors, sometimes referred to as markers. These markers are measured by your doctor at the time of surgery for a breast tumor, and provide more detailed information about the type of cancer. Based on factors such as the type of markers present on a tumor, soy may help to fight certain types of cancer, while allowing other types to grow.
A very important piece of this confusing puzzle is that there is a definite difference between soy foods and the soy isolates found in supplements. Soy in foods, such as tofu, tempeh, miso, texturized vegetable protein (TVP), and soy protein powder, are complete and whole. The phytoestrogens in these dietary forms of soy work in conjunction with all of the other substances in the food product. However, isoflavones isolated in a pill form (called ipriflavone) are synthetic and concentrated into larger quantities than would be found in a soy food. Greater levels of isoflavones also come with greater potential risks, including the possibility of stimulating or exacerbating hormone-related cancers. Asian diets are based on soy foods, not isoflavones or other soy ingredients isolated and put into a pill.
Soy is a wonderful food, loaded with many healthful substances, including isoflavones such as genistein and daidzein. These substances are also known as plant-based estrogens or phytoestrogens. There is a substantial amount of research to show that soy foods are extremely helpful for lowering cholesterol, reducing symptoms of menopause such as hot flashes, and preventing osteoporosis.
In terms of the effects of soy on cancer, the answers are somewhat less clear. Population-based studies suggest, fairly strongly, that if people begin eating soy on a regular basis before adolescence, they may decrease their risk of developing certain types of cancer. In test tube studies in the laboratory, the phytoestrogens isolated from soy have shown both estrogen-like activity and anti-estrogen activity. Estrogen is a powerful hormone that affects the development and growth of certain cancers, including breast and prostate. Therefore, based on the research so far, soy products have the potential to both promote and to limit the growth of these hormone-related cancers.
What I believe, as do many researchers and scientists, is that there are many details that need to be studied before we can answer questions like yours definitively. Most likely, we are going to discover that there are certain instances when soy inhibits the growth of hormone-related cancers and certain instances when soy stimulates the growth of these cancers. For example, different types of breast cancer are identified by their receptors, sometimes referred to as markers. These markers are measured by your doctor at the time of surgery for a breast tumor, and provide more detailed information about the type of cancer. Based on factors such as the type of markers present on a tumor, soy may help to fight certain types of cancer, while allowing other types to grow.
A very important piece of this confusing puzzle is that there is a definite difference between soy foods and the soy isolates found in supplements. Soy in foods, such as tofu, tempeh, miso, texturized vegetable protein (TVP), and soy protein powder, are complete and whole. The phytoestrogens in these dietary forms of soy work in conjunction with all of the other substances in the food product. However, isoflavones isolated in a pill form (called ipriflavone) are synthetic and concentrated into larger quantities than would be found in a soy food. Greater levels of isoflavones also come with greater potential risks, including the possibility of stimulating or exacerbating hormone-related cancers. Asian diets are based on soy foods, not isoflavones or other soy ingredients isolated and put into a pill.