Breast cancer is one of the most frequently occurring cancers and the leading cause of cancer death in women. The number of new postmenopausal breast cancer cases continues on an upward trend in France and other countries of the world. In 2020, over 2.2 million new cases of breast cancer were diagnosed and the numbers are projected to increase in the coming years.¹

Breast cancer is a multifactorial disease. Several modifiable risk factors have been implicated in its development such as a sedentary lifestyle, being overweight or obese, alcohol and tobacco consumption, and an unhealthy diet. Regarding diet, a Western dietary pattern characterized by higher consumption of red/processed meat, animal fats, and higher energy intake may raise the risk of breast cancer through excess weight and diet-hormone pathways.² As such, it is hypothesized that reverting to the traditional lifestyle of ancestral societies may confer benefits in the prevention of chronic diseases.

The Palaeolithic diet is based on the notion of food groups consumed during the Palaeolithic era and has gained rapid popularity in the last few years, although the literature on its scope of prevention of chronic diseases is relatively scant. The modern interpretation of the Palaeolithic diet is adapted to the current food environment and is based on higher consumption of vegetables, fruit, lean meat, fish, and nuts, and lower consumption of processed meat, dairy products, grains, and starches.³

I am a final-year PhD Candidate in Epidemiology with an interest in nutrition, chronic diseases and public health. My research focuses on understanding which factors can potentially reduce chronic disease burden. I did previous research with Dr Nasser Laouali and Dr Marie-Christine Boutron-Ruault concerning the role of dietary patterns in incident type 2 diabetes risk in the Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l'Education Nationale (E3N cohort).⁴ Could the modern-day Palaeolithic dietary pattern play a role in cancer prevention? My past experiences inspired me to tackle the role of diet in cancer epidemiology. We devised a prospective cohort study using dietary assessment data from the E3N cohort to answer this question.

We used a sample of over 65,000 postmenopausal women followed from 1993 to 2014. Their mean age was 52 years and they were cancer-free at the time of inclusion in the study. The participants self-reported their dietary intakes at inclusion and once during follow-up. A score appraising the Palaeolithic dietary pattern was developed for each participant using food groups and nutrients which are more characteristic (vegetables, fruit, fruit and vegetable diversity score, lean meat, fish, nuts, and calcium), and less characteristic (fatty/processed meat, dairy foods, sugar-sweetened beverages, baked goods, grains and starches, sodium, and alcohol) of the Palaeolithic diet. Higher scores reflected greater adherence to the Palaeolithic dietary pattern.

Over the follow-up, 3,968 participants developed breast cancer. Analyses of the risk of developing breast cancer were conducted by comparing lower and higher adherence to the Palaeolithic dietary pattern. Our findings showed that compared to women with lower adherence, those with higher adherence had a 17% lower breast cancer risk whilst controlling for other factors that may influence breast cancer risk such as physical activity, use of menopausal hormone therapy, parity, family history of breast cancer etc. We observed this pattern for all breast cancer subtypes.

In conclusion, we found that the Palaeolithic dietary pattern may have an important role in lowering postmenopausal breast cancer incidence. These findings help to improve our understanding of the mechanisms underlying the role of diets in the pathogenesis of breast cancer after menopause. These findings are also coherent with the current literature on the association of foods and nutrients with breast cancer risk. Further studies are required to better understand the role of other factors which may modify or mediate these associations.

I look forward to continuing my research using state-of-the-art analytic approaches to address the gaps in our current understanding of the mechanisms underlying cancer development such as the role of metabolites and gut microbiota in cancer risk.

This study is now published in the European Journal of Clinical Nutrition

References

1. Arnold M, Morgan E, Rumgay H, et al. Current and future burden of breast cancer: Global statistics for 2020 and 2040. Breast. Dec 2022;66:15-23. doi:10.1016/j.breast.2022.08.010.
2. Xiao Y, Xia J, Li L, et al. Associations between dietary patterns and the risk of breast cancer: a systematic review and meta-analysis of observational studies. Breast Cancer Res. 2019/01/29/ 2019;21(1):16. doi:10.1186/s13058-019-1096-1.
3. Whalen KA, McCullough M, Flanders WD, Hartman TJ, Judd S, Bostick RM. Paleolithic and Mediterranean Diet Pattern Scores and Risk of Incident, Sporadic Colorectal Adenomas. American Journal of Epidemiology. 2014/12/01/ 2014;180(11):1088-1097. doi:10.1093/aje/kwu235.
4. Shah S, MacDonald CJ, El Fatouhi D, et al. The associations of the Palaeolithic diet alone and in combination with lifestyle factors with type 2 diabetes and hypertension risks in women in the E3N prospective cohort. Eur J Nutr. Oct 2021;60(7):3935-3945. doi:10.1007/s00394-021-02565-5.