August 2011

Longitudinal Association between Animal and Vegetable Protein Intake and Obesity among Men in the United States: The Chicago Western Electric Study. Deborah Bujnowski, PhD, MPH, RD; Pengcheng Xun, MD, Phd; Martha L. Daviglus, MD, PhD; Linda Van Horn, PhD, RD; Ka He, MD, ScD; Jermiah Stamler, MD

The purpose of this study was to determine the long-term association of protein intake and obesity. Specifically separating animal protein from plant. Participants included 1,730 white men ages 40-55 who were employed at Chicago Western Electric Company in 1858. Age, education, occupation, religion, and anthropometric measures were collected at baseline and at each annual visit. To be included, participants must have attended at least four of the seven annual examinations after the initial.

Dietary information was taken twice at baseline, and compared to decrease error. Information was also received at the one year follow-up visit through interviews and questionnaires, completed according to Burke’s comprehensive dietary history method. Questionnaires were mailed home to the men’s wives to receive information on cooking practices; information was also obtained from the workplace cafeteria and local restaurants and bakeries that participants often ate at.

All dietary data was then coded by nutritionists and daily intake of energy, protein, fat, carbohydrates, alcohol, iron, calcium, phosphorus, thiamin, riboflavin, niacin, polyunsaturated fat, and vitamins A, C, and D were calculated. Data was not collected on supplement use and values for certain nutrients were not obtained (fiber, sodium and potassium).

The association between protein and weight was measured using the data from the initial two diet assessments and the BMI at every annual check up. Adjustments were made for age, education, smoking, alcohol intake, energy, carbohydrate, and saturated fat intake, and history of diabetes or other chronic disease.

Participants who were overweight (BMI >25) or obese (BMI >30) at baseline were in the higher quartile for animal protein consumption. Those that reported heavy alcohol consumption were in the lowest quartile for animal protein consumption. Research saw a trend in low energy consumption over quartiles of animal protein intake that was not observed in plant protein intake. Saturated fat and total fat intake were higher in those who consumed more animal protein. There was no association between plant protein intake and each quartile, however there was a significant association with plant protein and decrease in obesity when comparing the lowest to the highest quartile. In comparing total, animal, and plant protein with BMI; total and animal protein were positively associated with BMI whereas there was an inverse relationship between plant protein and BMI.

This study looked at long-term affects of protein and BMI where many short-term clinical trials have found no association between protein intake and BMI. Other factors that were different between this study and short clinical trials were; using Burke’s diet history instead of 24 hour recall, looking at types of protein not just total protein, and data was obtained in nature not clinical setting.

Deborah Bujnowski, PhD, MPH, RD; Pengcheng Xun, MD, Phd; Martha L. Daviglus, MD, PhD; Linda Van Horn, PhD, RD; Ka He, MD, ScD; Jermiah Stamler, MD. Longitudinal Association between Animal and Vegetable Protein Intake and Obesity among Men in the United States: The Chicago Western Electric Study. Journal of the American Dietetic Association-August 2011 (Vol 111, Issue 8, Pages 1150-1155.e1, doi:10.1016/j.jada.2011.05.002