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Following Diet Plan to Reduce Diabetes Risk Means Better Survival for Women With Early-Stage Breast Cancer

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Women diagnosed with stage I to stage III breast cancer who more closely followed a diet designed to reduce the risk of diabetes had better survival than women who didn’t follow the diet as strictly, according to a Harvard study.

The research was presented on Dec. 9, 2020, at the 2020 San Antonio Breast Cancer Symposium. Read the abstract of “Diabetes risk reduction diet and survival following breast cancer.”

Diabetes and breast cancer
About the study
What this means for you

Diabetes and breast cancer

Several studies have shown a link between being diagnosed with diabetes and a higher risk of breast cancer. Other research suggests that women who are diagnosed with breast cancer may be more likely to develop Type 2 diabetes. Still, other research suggests that being diagnosed with diabetes may be linked to worse survival after a breast cancer diagnosis.

So the researchers who did this study wanted to see if women diagnosed with breast cancer who followed a diet aimed at reducing the risk of diabetes had better survival than women who didn’t follow a diabetes risk-reduction diet.

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About the study

The study included information from 8,320 women diagnosed with stage I to stage III breast cancer who are part of the Nurses’ Health Study and the Nurses’ Health Study II.

The Nurses’ Health Study was started in 1976. More than 110,000 female nurses age 30 to 55 are being monitored for many health factors, including what they eat and the medicines they take, as well as lifestyle factors. Researchers are looking for links between health and lifestyle factors and more than 30 diseases, including breast cancer. The women fill out a detailed questionnaire every 2 years. The Nurses’ Health Study II was started in 1989 to study the same areas in a younger group of women — age 25 to 42 — and includes more than 116,000 female nurses.

Using the information from the questionnaires, the researchers assessed how closely the women followed a diabetes risk-reduction diet based on nine factors:

  • eating more cereal fiber
  • drinking more coffee
  • eating more nuts
  • eating more whole fruits
  • eating more polyunsaturated fats than saturated fats
  • eating lower glycemic index foods, meaning the foods have a slower effect on your blood sugar
  • eating less trans fat
  • drinking less sugar-sweetened beverages and fruit juice
  • eating less red meat

About half the women were followed for more than 16 years and half were followed for shorter periods of time.

During the follow-up period, 2,146 women died; 948 of these deaths were due to breast cancer.

The researchers found that women who more closely followed the diabetes risk-reduction diet were 17% less likely to die from breast cancer compared to women who didn’t follow the diet.

Women who followed the diabetes risk-reduction diet were also 33% less likely to die from any cause compared to women who didn’t follow the diet.

The results didn’t change when the researchers looked specifically at breast cancer stage or hormone-receptor status.

During the presentation, lead author Tengteng Wang, Ph.D., research fellow at Harvard T.H. Chan School of Public Health, said the researchers had tried to figure out the possible mechanism for the link.

“We looked at how [the diabetes risk-reduction diet] influenced gene expression in the breast tumor for a subgroup of our breast cancer patients, and … according to our pathway analysis, the [diabetes risk-reduction diet] is more associated with the pathway related to immune regulation and also cell proliferation, so this is, I think, an interesting finding,” Wang said.

“We felt that a greater adherence to the [diabetes risk-reduction diet] after breast cancer diagnosis was associated with better survival outcomes, which means promoting dietary changes consistent with prevention of Type 2 diabetes may be very important for breast cancer survivors,” she added.

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What this means for you

Diet is thought to be partly responsible for about 30% to 40% of all cancers, but diet alone is unlikely to be the “cause” or “cure” of cancer. Although more research needs to be done on diet and breast cancer, findings suggest that physical activity, a healthy diet (particularly one low in fat and high in vegetables and fiber), and a healthy weight can help reduce the risk of a first breast cancer or the cancer coming back (recurrence) if you’ve been diagnosed.

Right now, we do know that being overweight is a risk factor for being diagnosed with a first-time breast cancer, as well as for the breast cancer recurring if you have been diagnosed. A healthy diet can help you get to and maintain a healthy weight.

While the results of this study are promising, it’s important to keep a few things in mind:

  • The study relied on the women accurately reporting what they ate. Sometimes people don’t remember everything they ate or how much they ate, which would affect the results of the study.
  • The study didn’t look to see if the women stuck to their breast cancer treatment plans completely. Stopping a treatment, such as hormonal therapy, early would affect the study results.

If you’ve been diagnosed with early-stage breast cancer, it makes sense to make healthy diet and lifestyle choices to keep your risk of recurrence as low as it can be and your overall health the best it can be, including:

  • eating a diet low in added sugar and processed foods
  • eating a diet rich in unprocessed, nutrient-dense foods (foods that have the most vitamins, minerals, and healthy compounds)
  • exercising regularly at the highest intensity level you’re comfortable with
  • avoiding or limiting alcohol
  • not smoking

It also makes sense to stick to your treatment plan. Treatments such as chemotherapy and radiation therapy can require trips to the hospital or doctor’s office for several months. You also may need to take hormonal therapy medicines for 5 or 10 years after surgery. You get the best results when you follow your treatment plan completely and on schedule.

For tips on how to overcome common problems with following a treatment plan, visit the Breastcancer.org Staying on Track With Treatment pages.

To talk with others about maintaining a healthy diet after a breast cancer diagnosis, join the Breastcancer.org Discussion Board forum Recipe Swap for Healthy Living.

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Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser


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