More About the Research

Denke, M. Adams-Huet, B., Nguyen, A. Individual Cholesterol Variation in Response to a Margarine- or Butter- Based Diet. Journal of the American Medical Association. December 6, 2000. Vol. 284. No. 21. 2740-2747

• Published in the December 6, 2000 Journal of the American Medical Association

• The research was conducted under the direction of Margo Denke, M.D., associate professor of internal medicine and senior clinical research at the University of Texas Southwestern Medical Center at Dallas.

• This unique research study was undertaken for two purposes: 1) to evaluate the effects of an unsaturated fat (margarine) diet compared to a saturated fat (butter) diet on plasma lipoproteins among families comprised of two parents and at least two of their biological children, and 2) to test the theory that individual variability in response to a cholesterol-lowering diet has a familial basis.

• To implement this study, it was critical that biological families (mother, father and at least two of their biological children) be recruited. The study eventually involved 46 families comprised of 226 individuals: 92 adults and 134 children.

• Some of families followed a margarine-based diet for five weeks, then switched to a butter-based diet for a period of five weeks. Other families started on the butter diet first, then switched to the margarine diet.

• Blood samples were taken several times throughout the study periods.

• During both of the test periods, overall dietary composition was similar on both diets based on various factors including diet record and blood analysis.

• Consistent with the reported dietary intake and other factors, there were no changes in body weight between the two diet periods.

• The participants consumed specially formulated breads, cookies and other products made with either the regular soft margarine or butter.

• To evaluate the reproducibility of individual dietary response, two families agreed to repeat the study which lead to a confirmation of the original findings.

• For the purposes of this study, a full-fat soft margarine was used that was determined to have a representative proportion of fats as margarine products found today in the marketplace. The margarine selected contained seven percent trans fats. According to industry statistics, this is representative of the soft and reduced-fat margarine products (including sticks) on the market today. Liquid margarines have always contained no trans fats.

• The study was funded by grants provided by the United Soybean Board, the National Association of Margarine Manufacturers, and the U.S. Public Health Service.

• A disclaimer in the JAMA article notes that the two industry funders had no input regarding the design of the study, its execution, interpretation, analysis of the data, writing of the manuscript, or approval of the manuscript text prior to submission to JAMA.

Key Research Findings

• Margarine intake compared with butter intake lowered LDL (bad) cholesterol levels 11 percent or 15.7 mg/dl ("points") in adults.

• Margarine intake compared with butter intake lowered LDL (bad) cholesterol 9 percent or 11.2 mg/dl ("points") in children.

• No significant differences in HDL ("good") cholesterol were seen in adults or children, another important finding since one would want to maintain high levels of HDL cholesterol.

• Total cholesterol levels were also reduced in both adults (down by 17.6 points) and children (down by 11.3 points) when comparing the margarine diet to the butter diet.

• The findings agree with those from metabolic diet studies evaluating greater and lesser percentages of energy from margarine, confirming the longstanding advice to the public at large to choose softer margarines over butter.

• Children consuming diets high in saturated fat have higher cholesterol levels and more coronary artery plaque buildup than children on low saturated fat diets, according to lead researcher Margo Denke, M.D.

• Although differences in response to diet were observed, 80 percent of participants lowered their LDL cholesterol level on the margarine-based diet compared to the butter diet.

• In about one-fourth of the study population, the margarine-based diet even lowered total cholesterol levels as much as medication.

• Obesity also was found to play a role in dietary responsiveness. There was a direct correlation between body weight and how responsive individuals were to the dietary changes.

• Because the study involved families, the researchers also looked at why some individuals respond more positively to a cholesterol-lowering diet. They found that shared genes and environment play a role.

• Overall, this study underscores the nearly universal response to a cholesterol-lowering diet in both children and adults. Moreover, "this finding confirms the longstanding recommendation promoting a cholesterol-lowering diet for the population at large."