Northern Illinois University

NIU Office of Public Affairs



Judith M. Lukaszuk
Judith M. Lukaszuk

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News Release

Contact: Mark McGowan, NIU Office of Public Affairs
(815) 753-9472

October 23, 2007

Soy milk as effective as skim milk
in promoting weight loss, NIU study finds

DeKalb, Ill. — Soy milk is as effective as skim milk in promoting weight loss, according to a Northern Illinois University study published in the October issue of the Journal of the American Dietetic Association.

That’s good news for healthy-minded people with casein allergies or lactose intolerance who want the calcium and protein milk adds to a balanced diet.

Lead author Judith M. Lukaszuk, an assistant professor and the didactic program director in dietetics in the NIU School of Family, Consumer and Nutrition Sciences, said the findings also should please vegans and others striving to avoid growth hormones and pesticides found in non-organic milk.

Paul Luebbers, an assistant professor in the Department of Health, Physical Education and Recreation at Emporia State University, and Beth A. Gordon, a registered dietitian at Kindred Hospital in Sycamore, are co-authors. Luebbers is a former member of the faculty in NIU’s Department of Kinesiology and Physical Education; Gordon was an FCNS graduate student at the time of the study.

The work was funded by the Office of the President and the Division of Research and Graduate Studies at NIU. The School of Family, Consumer and Nutrition Sciences is part of the NIU College of Health and Human Sciences.

Lukaszuk conducted the research – the first study of its kind – in the summer of 2006 in response to a well-publicized encouragement to “drink three cups of milk a day (to) watch your pounds melt away.”

“I wondered, ‘Is it the milk protein, or any source of protein which is fortified with calcium?’ The only difference between skim milk and soy milk is the whey,” Lukaszuk said.

Fourteen healthy, premenopausal women between the ages of 18 and 45 who were overweight or obese participated in the eight-week study after seeing flyers posted on campus. Four other women dropped out either for scheduling problems or allergies.

Participants were randomly assigned to 24 ounces of light soy milk or an equivalent amount of skim milk. At the study’s inception, there were no statistical differences in demographics or daily intake of calcium and vitamin D between the subjects.

Everyone followed a lower-calorie diet (500 calories less than what they expended per day), avoided other sources of dairy or soy such as cheese or tofu and maintained whatever level of exercise they had before starting the study.

The soy milk definitely has a different taste than cow’s milk, Lukaszuk said, but the participants had no complaints.

Lukaszuk met weekly with the participants to provide them with complimentary skim and soy milk and to measure their fat mass, muscle mass and total body weight on a Tanita scale as well as to measure their abdominal waist circumference. Research assistants collected their three-day food records (two weekdays and one weekend day) as well as their exercise logs and counseled and encouraged individuals to continue compliance with their set calorie restriction.

Both groups also received the same level of encouragement from Lukaszuk, a registered dietitian.

Afterward, both groups lost equivalent amounts of weight and lowered total body fat percentage and abdominal circumference. In other words, one can consume 24 ounces of either skim milk or light soy milk daily to optimize the weight-loss effects of calcium.

“They all were so thrilled. One woman was pre-hypertensive when she came in to the study,” Lukaszuk said. “She lost 15 pounds and 8 inches off her waist on the soy milk.”

The two vegans have continued to drink the light soy milk, she added.

“Soy is a great source of protein for people who don’t eat meat,” she said, “and soy milk, if fortified, is a great source of calcium, vitamin D and vitamin B-12.”

Lukaszuk hopes to expand the study in the future with a larger sample of participants and continue it for a longer duration.

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