Ask the Nutritionist
Q: My tumor is extremely estrogen sensitive. I've been reading that there is quite a bit of estrogen in meat and dairy products, so I now avoid them. Soy is reputed to behave like estrogen, so I am avoiding soy, although there is some question about whether or not soy may actually be helpful. There is even more conflicting evidence about other plant-based estrogens (phytoestrogens). There seems to be no way to know if phytoestrogens will help or hurt. I am particularly interested in your opinion about ground flaxseed. Is this something I should avoid, or is there no way to know, or is it something I should try to eat?
Valerie, Worcester, MA, October 2015
A: A tremendous amount of controversy exists over the role of dietary plant-based or phytoestrogens in women with a history of estrogen-receptor positive breast cancer.
To first address your question on dairy and red meat, research has shown that grass fed beef has a more preferable nutrient profile than conventionally raised beef, so when possible it may be beneficial to choose organic grass-fed beef. We recommend following the American Institute for Cancer Research’s guideline of consuming no more than 11-18 ounces of red meat per week. For overall cardiovascular health, it is best to choose leaner cuts of meat to limit saturated fat intake and overall calorie intake. However, regular consumption of processed red meats like bacon, hot dogs and sausage, is not recommended as they are associated with a higher risk of colorectal cancer, heart disease and type 2 diabetes. Similarly dairy can be part of a healthful diet as it is a great source of protein, calcium and other nutrients. As with red meat, organic dairy products from grass fed cows has a more preferable nutrient profile, so choose organic dairy products when possible.
The concern with soy and cancer comes from the fact that soy contains isoflavones, which are phytoestrogens that in some ways mimic the action of estrogen. However, these phytoestrogens are many times weaker than the estrogen made in human bodies. According to the American Institute for Cancer Research and American Cancer Society, research has shown that moderate consumption of whole soy foods appears safe for both breast cancer survivors and the general public. Moderate consumption of whole soy foods, or 1-2 servings per day, does not increase cancer risk, and may actually lower the risk of cancers of the breast, prostate, and other cancers. One serving is one cup of soy milk, a half cup of cooked edamame or soy beans, or one ounce of soy nuts.
That being said, research is lacking in regard to high doses of soy in supplements like soy protein isolates. Since less is known about their effects on health, isolated soy compounds or soy supplements should be avoided if that is a concern. We suggest avoiding foods made from soy protein powder, soy protein isolate, or isolated soy protein (read the ingredient list to look for these). These forms of soy are often found in nutrition bars, soy protein powder, many high protein breads and cereals and vegetarian "meat-less" options, such as certain brands of veggie burgers or soy hot dogs.
You may choose to avoid soy altogether, however soy is a good source of protein, calcium, iron and other nutrients, so if you were already accustomed to eating soy, you may continue to do so. One does not need to begin eating soy, but can choose to do so in moderation without concern of harm.
Ground flax seed is a healthy source of Omega-3 fats and dietary fiber and, when consumed at 1-2 tablespoons per day, does not pose any risk to breast cancer survivors.
Eating a plant-based diet, engaging in daily physical activity such as walking, limiting or avoiding alcohol, getting enough sleep and incorporating stress reducing behaviors into your life are the best way to promote health as a breast cancer survivor. Furthermore, maintaining a healthy body weight is important for overall health, and is correlated with a lower risk of breast cancer recurrence. Refer to the Meal Planning Guide for more suggestions on consuming a healthful diet.