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Diet Diva
Diet Diva

Get advice on healthy eating, nutrition, and weight loss from expert dietitian Tara Gidus. 

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Is Soy Safe?

I have had several people recently ask me about whether eating foods from soy is harmful. Some have asked because they have a thyroid problem and heard that soy interferes with their synthroid, others are worried about breast cancer, and most recently I guess some negative press has been writing about men and soy. Let me try to set the record straight.

What is soy?
All soy foods come from soybeans. Soy has a high protein content as well as carbs, fiber, vitamins, minerals, and some healthy fats. Soy is an excellent source of plant-based protein because it is known as a "complete protein" meaning it contains all of the essential amino acids. Whole soy is best, meaning it has been minimally processed and you are getting the naturally occurring nutrients found in the soybean. Foods that contain whole soy are edamame, soynuts, and surprisingly a bar called SOYJOY. Tofu and soymilk are also great sources of soy.

Health Benefits/Dispelling Myths
Numerous health benefits of soy have been very well documented in literature. In addition, many myths about soy have been dismissed with research studies.

Heart health: Soy is cholesterol free, low in saturated fat, and contains healthy fats. Some evidence also shows that it helps to lower LDL, or "bad" cholesterol.
Breast cancer: A high soy intake during puberty has been shown to reduce breast cancer risk, but consuming it as an adult has not been linked to lowering risk. Some animal studies have connected soy isoflavones with breast cancer growth, but no data on humans has supported this. In fact, some studies show a favorable impact on breast cancer outcomes with soy. Check with your physician before taking a soy isoflavone supplement. The American Cancer Society suggests that up to 3 servings of soyfoods per day is safe for a breast cancer survivor.
Bone health: Soybeans and calcium-fortified soyfoods are good choices because of the soy isoflavones as well as calcium and Vitamin K which can help bone mineralization.
Menopause: Over 50 studies have examined whether soy can relieve hot flashes in menopause and the consensus is that it may for many women but it depends on hot many hot flashes you get and how much soy isflavone is taken.
Reproduction: No human data shows that consuming soy causes abnormal testosterone or estrogen levels. Several studies found no affect on sperm or semen when consuming soy isoflavones.
Thyroid: A comprehensive review of literature concluded that soy does not adversly affect thyroid function. Researchers recommended that thyroid function be reassessed if there is a large increase or decrease in soy intake, but normal day-to-day variations are unlikely to affect normal thyroid function.

Good for the Planet
Soy is environmentally friendly. The amount of fossil fuel to process soybeans is estimated to be 6-20 times less than that used to produce meat.

Bottom line
Soy foods can be part of a healthy diet for men and women. Eating 2-3 servings per day of soy foods is safe and very healthy. Soy contains important protein, amino acids, fiber, calcium, potassium, zinc, iron, and folic acid.

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About the Author


Tara Gidus is a nationally recognized expert and spokesperson on nutrition and fitness.

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