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Soy, Obesity: What Actually Increases Breast Cancer Risk?

By Margaret Martin, RD, MS, LDN, CDCES October 22, 2014Pearls of Wisdom Blog

Recently, many magazine and internet articles have cropped up discussing the link between soy, obesity, and breast cancer risk. What actually increases breast cancer risk, and what can you do about it?

Soy and Breast Cancer Risk

Soy is one of the most misunderstood foods when it comes to breast cancer. Old studies still pop up from time to time that may confuse breast cancer survivors. Before cutting soy out completely, make sure you have all the facts from a reliable source.

The American Institute of Cancer Research (AICR) is one of the foremost authorities on nutrition and cancer. Here is what AICR has to say about soy:

  • Soy in moderate amounts does not increase breast cancer risk (or risk of any type of cancer).
  • Eating soy during childhood or teenage years may actual help lower risk of breast cancer according to some research.
  • Eating soy does not trigger increased estrogen levels in women.
  • Survivors of breast cancer who eat moderate amounts of soy do not have an increased risk of recurrence or death.
  • A moderate amount of soy is about 100 grams of soy daily or one to two servings of soy. Examples of soy include: soy beans, soy milk, soy butter, edamame, and tofu.
  • Soy supplements are not included in the moderate amount described. The best source of soy and other nutrients is food, not dietary supplements.
  • Soy can be part of a healthy, plant-based menu that helps reduce cancer risk. Soy offers many benefits: protein for muscles, calcium for strong bones and teeth, iron for healthy blood cells, and fiber, magnesium, and potassium for fighting oxidation and inflammation.
  • You can add soy in many tasty ways. Snack on crunchy soy chips. Try soy milk in place of regular milk. Steam edamame for a quick side dish. Go low-fat with tofu in a pasta casserole.

Obesity and Cancer Risk

Obesity, or being very overweight, does increase cancer risk. According to the American Society of Clinical Oncology, in 2007, more than 84,000 new cancer cases were due to obesity. AICR estimates that being at a healthy weight could prevent about 120,000 cancer diagnoses a year. Here are some facts about obesity and cancer risk:

  • How do we measure or determine obesity? Body Mass Index (BMI) is one tool to evaluate body size and the risk of some diseases. When a person’s BMI is 25-29.9, he or she is considered overweight. When a person’s BMI is 30 or greater, the person is considered obese.
  • Waist measurement of greater than 35 inches for women and 40 inches for men is another sign of increased risk of disease, including cancer. The World Health Organization (WHO) recommends a waist measurement of less than 31.5 inches for women and less than 37 inches for men to help reduce cancer risk.
  • Fat tissue is different from lean or muscle tissue. A person with a BMI greater than 29 tends to have much more fat tissue than lean tissue. Fat tissue can lead to:

o Increased levels of estrogen which may influence estrogen-sensitive breast cancers.

o Higher levels of certain tumor growth regulators.

o More chronic inflammation which has been linked to increased cancer risk.

What You Can Do?

  • Move every day for at least 30 minutes. Include activities that you enjoy, like walking, dancing, swimming, video exercise, or whatever is fun for you!
  • Choose more fruits and vegetables. Try to eat 5 to 8 servings of fruits and vegetables a day. If fresh is available, go for it. If frozen and canned are within your resources, that’s great as well. Get you fruits and veggies any way you can.
  • Try to keep your BMI in the healthy range, 18.5-24.9. Achieve a healthy weight by controlling your portions. Try using smaller plates, bowls, and cups. Eat slowly and take smaller bites.
Margaret Martin, RD, MS, LDN, CDCES

Author Margaret Martin, RD, MS, LDN, CDCES

Nutrition Educator Margaret Martin is a Licensed Dietitian and Nutritionist in the State of Tennessee as well as a Certified Diabetes Educator. Margaret graduated from the University of Alabama with a Bachelor of Science in Dietetics and received her Master’s Degree in Nutrition Science & Public Health from the University of Tennessee. With more than 10 years of experience in Clinical Nutrition, Margaret has also worked in the insurance industry with WellPoint Inc. and Blue Cross Blue Shield providing telephonic nutrition consultations, service assistance, and web-based nutrition education. In her free time Margaret volunteers with the American Lung Association’s annual “Lung Force Walk" in Middle Tennessee. She belongs to the Oncology Nutrition & Diabetes Care and Education Dietetic Practice Groups of the Academy of Nutrition and Dietetics.

More posts by Margaret Martin, RD, MS, LDN, CDCES

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