Healthful Eating Habits, Cancer, and Heart Disease

April 1, 2006

The authors of the Women’s HealthInitiative (WHI) study involving50,000 postmenopausal women concluded thata low-fat diet (goal: 20% of total calories) had no significant effect on the incidence of breast cancer, coloncancer, or heart disease. What should we be telling our patients?

"I guess I might as well live on burgers and fries, basedon what I'm hearing on the news lately." This, unfortunately,is typical of many patients' reactions to reportsof recently published results from the Women's HealthInitiative (WHI).1-3 The authors of this 8-year study involving50,000 postmenopausal women concluded thata low-fat diet (goal: 20% of total calories) had no significanteffect on the incidence of breast cancer, coloncancer, or heart disease.

Understandably, these results have left both cliniciansand patients skeptical and confused. What shouldwe be telling our patients?

Don't give up. First, stress that the WHI studyresults are not sufficient grounds for giving up on dietas a means of preventing and managing chronic diseases.There is plenty of evidence that what you eat doesmatter.

Not how much fat, but what kind. Recent evidencethat types of fat are more important than total fatin determining the risk of certain chronic diseases suggeststhat the WHI study's focus on total fat reductionwas misdirected. Study participants reduced their fat intakefrom about 38% to about 29% of calories1-3; however,this involved reductions in all types of fat. There ismounting evidence that intake of saturated fat and transfattyacids should be reduced but that consumption ofpolyunsaturated and monounsaturated fats should be increased.Both saturated and trans-fats are known to havedeleterious effects on cholesterol levels.4 In addition,monounsaturated and polyunsaturated fats have beenshown to have a protective effect.4 The Institute of Medicine now recommends a wider range of acceptable totalfat intake (20% to 35% of calories), provided that intake ofpolyunsaturated and monosaturated fats is increased andsaturated fats and trans-fatty acids decreased.5

One silver lining of the WHI results is that practitionersneed no longer feel they must coax patients toreduce total fat content to levels that are either unpalatableor unacceptable; a reasonable fat intake (20% to 35%of calories) is all that is required. However, it is essentialto stress the importance of choosing "helpful" fats instead of "harmful" fats--for example, olive oil in place ofbutter, or a handful of almonds instead of chips.

Benefits of a healthful and varied diet. The dietused in the WHI study incorporated increased amountsof fruits, vegetables, and whole grains. However, studiesof the DASH (Dietary Approaches to Stop Hypertension)diet have shown that additional dietary changes areneeded to produce maximum cardioprotective benefits.The DASH diet, which incorporates nuts, beans, and lowfatdairy products as well as plentiful amounts of vegetables,fruits, and whole grains, lowered blood pressure inhypertensive patients significantly better than did a dietrich only in fruits and vegetables.6

Strongly encourage patients to consume a wide varietyof healthful foods. Rather than counsel them aboutfoods to eliminate, discuss with them what foods theyshould add to their daily menus. These include fruits,vegetables, and whole grains as the foundation of thediet, but also nuts, beans, fish, and low-fat dairy products.User-friendly guidance on construction of a healthfulvaried diet is available at http://www.mypyramid.gov.

Above all, lose weight. It is noteworthy that 74% of participants in the WHI study were overweight orobese, and that the intervention diet did not address theissue of weight loss. There is strong evidence that losingweight lowers the risk of heart disease.7 Thus, helpyour overweight patients achieve a manageable weightloss by recommending a daily reduction of 500 kcal ormore, along with an increase in physical activity.

References:

REFERENCES:
1. Prentice RL, Caan B, Chlebowski RT, et al. Low-fat dietary pattern and risk of invasive breast cancer: The Women’s Health Randomized Controlled Dietary Modification Trial. JAMA. 2006;295:629-642.
2. Beresford SAA, Johnson KC, Ritenbaugh C, et al. Low-fat dietary pattern and risk of colorectal cancer: The Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006;295:643-654.
3. Howard BV, Van Horn L, Hsia J, et al. Low-fat dietary pattern and risk of cardiovascular disease: The Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006;295:655-666.
4. Mensink RP, Zock PL, Kester AD, Katan MB. Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr. 2003;77:1146-1155.
5. Food and Nutrition Board of the Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: National Academies Press; 2005.
6. Appel LJ, Moore TJ, Obarzanek E, et al. A clinical trial of the effects of dietary patterns on blood pressure. N Engl J Med. 1997;336:1117-1124.
7. Poirier P, Giles TD, Bray GA, et al; American Heart Association; Obesity Committee of the Council on Nutrition, Physical Activity, and Metabolism. Obesity and cardiovascular disease: pathophysiology, evaluation, and effect of weight loss. Circulation. 2006;113:898-918.