Women And Heart Disease--Part 1
Chester J. Zelasko, Ph.D. | February 28, 2006

In the past few weeks, several studies of heart disease in women have hit the headlines; the results of those studies are both provocative and conflicting. In this first Newsletter on women and heart disease, I’ll discuss research from the Women’s Health Initiative on the relationship between dietary fat intake and heart disease. Part 2 will cover the other studies.

The Women’s Health Initiative (WHI) is a large multi-center research study involving almost 400,000 women that focuses on examining the major causes of death, disability, and frailty in postmenopausal women (1). As stated on their website, the overall goal of WHI is to reduce coronary heart disease, breast and colorectal cancer, and osteoporotic fractures among postmenopausal women by developing prevention strategies and identifying risk factors. One of those strategies was to compare a low-fat diet with the typical American diet in order to see what effect fat intake has on the risk of cardiovascular disease in postmenopausal women aged 50-79.

The Study
From a database of almost 400,000 women, close to 49,000 post-menopausal women who ate over 32% of their calories from fat were chosen to participate in the study (2). They were randomly assigned to a group--the control group maintained their current diet, while the experimental group tried to lower their total fat intake to 20% of total calories and to increase fruit and vegetable intake to five servings per day and grains to six servings per day. Those in the experimental group were given intensive behavioral modification and nutrition education by trained and certified nutritionists. Subjects met 18 times during the first year and then quarterly for the duration of the study, which lasted six years. Researchers kept track of cardiovascular events such as heart attacks, stroke, and death.

The Results
Subjects in the experimental group lowered their fat intake by 8.2% compared to the control group. Fruit and vegetable intake increased by about one serving per day, while grains increased by about half a serving per day. The results on cardiovascular disease were surprising: there were no reductions in the rate of heart disease in those following a lower fat diet and only minor changes in cholesterol levels and blood pressure when compared with those who maintained their regular diets.

Needless to say, the researchers were surprised at the outcome and the press had a field day. “No need to hold the fries!” was one headline I read. All the experts have seemed to weigh in on this apparent lack of results. How could these positive lifestyle changes have no effect? Careful examination of the data showed some facts that didn’t make the news.

The Problems
Not low fat: The primary problem with the study is that it didn’t achieve the goal of lowering fat intake to 20% of total calories. The data showed that fat intake was reduced from 37.8% at the start of the trial to 28.8% at Year Six. While that’s lower than where they began, it’s by no means a low-fat diet. To complicate matters, the reduction of fat was across the board. Not only did the women lower their saturated fat intake, they also lowered their intake of monounsaturated and polyunsaturated fat as well, the healthy fats that have been associated with a decrease in cardiovascular disease.

Caloric intake: Examining the total caloric intake, the number of calories was reduced from 1,790 per day at baseline to 1,432 per day by the end of six years. That should have resulted in a significant weight loss in the experimental group. In fact, there were no real changes in body weight in either group (the comparison group also decreased daily caloric intake from 1,790 to 1,546). This data makes no sense; if calories are reduced and activity level stays about the same, weight loss is inevitable.

The problem may have been the way data were collected. The researchers used a Food Frequency Questionnaire (FFQ) specifically designed for the WHI. FFQs are subject to large variations in caloric and macronutrient intake because they ask what portions were eaten over the last weeks or months; food diaries filled out at mealtime are much more accurate.

Subject losses: Finally, there was a significant loss of subjects in the study for one reason or another. In almost every study I review, significant subject losses occur and are never addressed by the researchers. When 15% of the subjects are no longer providing data to be analyzed, there can be severe effects on the results. Were the women who dropped out the ones whose health got so bad they couldn’t continue? Or those whose health improved so much they were too busy having fun to be bothered with the study? That could make a big difference in the results. In addition, over 11% of those in the experimental group stopped attending the nutrition counseling sessions--did they feel they knew the subject and didn’t need classes, or did they give up because they didn’t understand the concepts? There’s information to be derived from the dropouts because it could provide some additional answers. If nothing else, it may tell us how not to teach people to eat a lower fat diet!

Studies of this magnitude (almost half a billion dollars for all phases of this study) are designed to find answers that can influence public health education for women. Unfortunately, this part of the study provided nothing of value except to raise more questions.

What should you do?
Clinical trials have demonstrated a relationship between cardiovascular disease and a diet high in saturated fat. Your goal should be to lower saturated fat intake while increasing monounsaturated and polyunsaturated fats such as omega-3 fatty acids. Getting 30% of your calories from fat on a daily basis isn’t necessarily a bad thing as long as you get the calories from the right fats. In addition to changing your fat intake, eating more fruits and vegetables and exercising regularly can help reduce the risk of heart disease for men and women of all ages.

Bottom line: Your health is in your hands just as it always has been. Leave the confusion to the researchers to sort out. Do enough of the right things--and that includes eating less saturated fat--and you’ll stay on the path to better health.

  1. Women’s Health Initiative website: www.nhlbi.nih.gov/whi/index.html
  2. Howard, BV, et al (46 other authors). Low-Fat Dietary Pattern and Risk of Cardiovascular Disease in The Women's Health Initiative Randomized Controlled Dietary Modification Trial JAMA. 2006;295:655-666.
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