Alice Langford, Susan Dudley, PhD, and Jacqueline Britz, National Center for Health Research
What is the Women’s Health Initiative?
The Women’s Health Initiative (WHI) is a extensive study of postmenopausal women that was started in 1993. Funded by the National Institute of Health (NIH) and National Heart, Lung, and Blood Institute (NHLBI), the goal was to study more than 160,000 women in the real world – what they eat, what their health habits are, and what medications they take to find out what habits and medications are most effective to keep women healthy. The study was supposed to end in 2005 but was extended until 2020.
As part of the study, 19,541 women participated in the low-fat diet trial: one group was encouraged to continue eating as they always had, while women in the other group received training that encouraged them to modify their diets by reducing fat and increasing their consumption of fruits, vegetables, and grains.
After the first eight years, the results were surprising: Women who ate a better diet did not have better health outcomes. A lower fat diet did not reduce the chances of developing colorectal cancer or invasive breast cancer., Eating more vegetables, fruits, and grains did not reduce the chances of developing cardiovascular disease, stroke, or coronary heart disease. Even so, there were some important trends. The women in the diet modification group who had the lowest total fat intake had a lower risk of invasive breast cancer compared to women with higher total fat intake. Additionally, the women who ate less saturated fat and ate more fruits and vegetables had lower blood pressure, and cholesterol. This would be expected to lower their chances of heart attacks or stroke.
The results were more encouraging five years later. Approximately 64,000 postmenopausal women were observed for almost 13 years, and the women who had a high quality diet were 18-26% less likely to die and also were less likely to develop cancer and cardiovascular disease.
What We Learned About What We Eat
When the study was initiated, we knew less about different types of fat than we know now. In addition, the women were not urged to lower their calories, but only to change what they ate.
- Not all dietary fat is alike. We now know that saturated fats and trans-fats are dangerous but that certain fats – such as those found in walnuts or some fish oils – can be beneficial.
- The women who were trained to improve their diet were less successful than the researchers had hoped. The “low-fat” group for this study averaged 29% of calories from fat instead of the targeted 20%. The 29% of calories from fat is not much lower than the average U.S. adult who gets 33% of his or her daily calories from fat. In addition, the women didn’t make big changes in consumption of fruits, vegetables, or grains. Perhaps if they had improved their diet more, there would have been clearer health benefits.
- We now know that being overweight increases the risk of breast cancer, heart disease, arthritis, and many other diseases. The women in the WHI were not encouraged to reduce their overall calories, and that might be why there were no differences in health outcome.
- Dietary changes are easier said than done. The results are more encouraging when you compare women with different types of dietary habits, rather than comparing women who were trained to have better dietary habits but might not have complied.
So What Should I Eat?
Most women will benefit from a well-balanced diet that is low in sodium, added sugars, and saturated and trans-fats, and is high in fresh fruits, vegetables, whole grains, and unsaturated fats. A well-balanced diet includes only moderate amount of dairy products and meat protein. The USDA Dietary Guidelines for Americans suggest that women should strive to consume between 1.5 and 2 cups of fruit each day, between 2 and 2.5 cups of vegetables, and 3 cups of low fat milk products. They should eat approximately 5-6 oz. of grains each day (with a minimum of 3 oz. coming from whole grains), and between 5 and 5.5 oz. of meat/beans. “Good” fats, found in fatty types of fish (i.e. salmon, herring, sardines), plant oils like extra-virgin olive oil, avocados, seeds, and nuts, are also an essential part of a healthy diet and have been found to help prevent disease.
General guidelines for healthy eating may need to be modified for each individual. For example, people with high cholesterol may need to change their diet to specifically help reduce cholesterol. Helpful guidelines on healthy eating for women are provided by the Office on Women’s Health.
Also, calories matter. In order to lose weight, it is important to burn more calories than you consume. Diet and exercise are both important to lose weight and to maintain a healthy weight,
Remember that serving size and portion size are not the same thing. Serving size is a standardized quantity of food that we use to measure nutrients. Portion size is the amount we put on our plates. Keep in mind that one serving of cooked vegetables is usually about one-half cup (about a hand-full!) and a serving of meat is about the size of a deck of cards. This means that most people can fit in all those recommended servings of fruits and vegetables every day while still reducing their total calorie intake and losing weight. But it also means that the portions you serve yourself may be much higher in calories than the standard serving size would be.
And don’t forget that beverages have calories too! Try to limit your intake of high calorie or sugary drinks as well as alcoholic drinks. They should be consumed in moderation, or not at all. It is recommended that women limit alcohol intake to a maximum of one drink per day (i.e. 12 fl. oz. beer, 5 fl. oz. wine, or 1.5 fl. oz. 80-proof distilled spirits). More resources regarding a healthy diet for women can be found here.
All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.
 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(6):643–654. doi:10.1001/jama.295.6.643
 Prentice RL, Caan B, Chlebowski RT, et al. Low-Fat Dietary Pattern and Risk of Invasive Breast Cancer The Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006;295(6):629–642. doi:10.1001/jama.295.6.629
 Stephanie M. George, Rachel Ballard-Barbash, JoAnn E. Manson, et al.; Comparing Indices of Diet Quality With Chronic Disease Mortality Risk in Postmenopausal Women in the Women’s Health Initiative Observational Study: Evidence to Inform National Dietary Guidance, American Journal of Epidemiology, Volume 180, Issue 6, 15 September 2014, Pages 616–625, https://doi.org/10.1093/aje/kwu173
 “Design of the Women’s Health Initiative Clinical Trial and Observational Study.” Science Direct , vol. 19, no. 1, 1998, pp. 61–109., doi:10.1016/s0197-2456(97)00078-0.
 “Dietary Guidelines for Americans 2015–2020 8th Edition.” Chapter 4 – 2008 Physical Activity Guidelines, health.gov/dietaryguidelines/2015/guidelines/.
 “Office on Women’s Health.” Womenshealth.gov, 22 May 2018, www.womenshealth.gov/.