A team of US scientists have claimed that following a low-fat diet could reduce the risk of death from breast cancer. The scientists were based at the City of Hope National Medical Center in Duarte, California among others. The study was published in JAMA Oncology in May 2018, a peer-reviewed journal and the abstract and summaries can be read for free online. It has been estimated that 1 in 8 US women could develop the disease in their lifetime.
The study was based on a randomised controlled trial which took place in the 1990s. It assigned postmenopausal women to a low-fat diet. The aim of the original trial was to see if the low-fat diet reduced the risk of breast cancer. The current study aimed to examine whether women who had developed the disease lived longer if they followed the low-fat diet. The study was randomly designed which balanced confounding factors between the two groups of women, one group following a low-fat diet and the others following a more normal diet.
The groups of women were matched to take account of underlying cancer risk factors, undergoing mammography screenings every 2 years. If the women were on hormone replacement therapy (HRT), then they were offered screenings more often. This study was based on a follow-up after the original study which took place between 1993 and 1998. The group which were placed on the low fat diet were encouraged to reduce their fat intake to 20% of their daily food. They could also eat more fruit, vegetables and grains. Nutritionists guided the diets, by leading group sessions and an individual session. The participants were each given a fat intake goal and were asked to complete food frequency questionnaires throughout the study.
Those women who developed breast cancer during the study were able to continue with the low-fat diet with the nutritionist. The nutritionists helped the women with their diets for around 8 years. Fat intake goals were set and food frequency questionnaires taken during the study. 1764 women developed the disease during the study. They were followed up for around 11 years to examine the effects the diet had on the disease.
The study showed that those women who were already on a low-fat diet who developed breast cancer, were less likely to die by 22% when compared to those who were not on the diet. 82% of participants on the low-fat diet, survived 10 years compared to 78% in the group who followed their usual diet. 516 women died during the study, from those who were on the low-fat diet. Most of the deaths were from breast cancer although 91 were from cardiovascular disease. The researchers felt that their study showed that women following a low-fat diet could reduce their risk of dying from breast cancer, although not necessarily their risk of developing the disease.
The study was unusual in the high number of participants who took part, the length of time the study ran for and the follow-up. The study confirmed that a diet high in saturated fats is a risk factor for breast cancer. The low-fat diet enabled more women who developed the disease to survive for longer. The diet included more fruit and vegetables and wholegrains, but the study did not prove that these had a direct effect on breast cancer survival as opposed to reducing the consumption of saturated fat. Women who follow a low-fat diet are less likely to be overweight or obese - both of which are known to raise the risk of developing breast cancer.
Breast cancer kills - women a year, and some of the factors which affect risk are beyond control: such as hereditary genes or hormones, however women can control their lifestyle and this in turn could reduce the risk.
In order to reduce their risk of developing breast cancer, it is important to stay at a healthy weight, take regular exercise, avoid smoking, follow a diet which is low in salt, sugar, and saturated fats and high in fibre, fruit and vegetables and following the guidelines on alcohol.
Chlebowski R.T., et al. Association of Low-Fat Dietary Pattern With Breast Cancer Overall Survival A Secondary Analysis of the Women's Health Initiative Randomized Clinical Trial, JAMA Oncology, May 2018