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posted: 5/7/2014 6:01 AM

Ask the Nutritionist: Soy additives not likely to affect isoflavone levels

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Q. I see soy protein in the ingredients of so many breads, bars, cereals and other foods now. Is that likely to push me above what is considered moderate consumption of soy?

A. Moderate consumption of soy is 1 to 2 standard servings daily of whole soy foods, such as ⅓ cup tofu or 1 cup soy milk. One serving averages about 7 grams of protein and 25 milligrams of isoflavones, compounds with a chemical structure similar to estrogen.

You're right that different forms of soy protein, including isolated soy protein, are added to many foods today to improve texture or moistness or to boost protein. However, the amounts that are added are so small that the amount of isoflavones in a serving of these foods is equal to about one-tenth to one-third of a serving of a traditional soy food such as tofu, edamame, soymilk or soynuts.

Early lab research had suggested that too many isoflavones may increase breast cancer risk. Now, larger and stronger studies have demonstrated up to 3 servings a day does not link to increased breast cancer risk.

Soy is seen as a healthful part of Asian diets, where it has been a long-term dietary staple for generations. Keep in mind that whole soy foods contain many other nutrients so we can't assume that processed forms of soy protein would have the same links to health.

It is possible that if you eat large amounts of soy protein fortified bars and cereals daily, you could exceed isoflavone levels that are characteristic of healthful Asian diets. However, eating that sort of diet would have you missing out on many nutritious foods, which would be unhealthy.

Bottom line: as long as your concern is not related to some sort of soy allergy or intolerance, normal use of these foods with small amounts of soy protein added likely pose neither a concern nor added health benefits.

Q. I'm confused by the changing headlines: are low-fat diets the best way to lose weight?

A. Low-fat diets are one way to lose weight, however, cutting fat only works if it means you are eating fewer total calories.

Fat is our most concentrated source of calories, so if you cut back on the amount of fat you eat -- by adding less fat to food in cooking or at the table and choose leaner versions of some high-fat foods -- you can cut calories and lose weight. Some processed foods advertised as reduced fat may cut fat but add extra sugar, and total calories remain the same. Or if you assume that you can eat a larger portion if the food is low fat, you can end up more than making up for calories saved in a lower-fat choice.

Studies that compare groups of people often do link lower fat diets with less likelihood of being overweight. However, analysis of studies that test effectiveness of diets low or high in fat show no difference in weight loss based on fat content alone. And in one study of nearly 90,000 European adults, neither the proportion of a diet's calories coming from fat nor the type of fat made any significant difference in weight gain over four to 10 years.

Research does show that overall eating patterns high in fruits, vegetables and other plant foods are an excellent tool to lose and maintain weight. So make those foods the largest part of what you eat and choose small to moderate portions of foods high in healthful fats such as nuts or fish. It's how all your food choices and portions come together that limits calories and helps you reach and maintain a healthy weight.

• Provided by the American Institute for Cancer Research

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