Science Spotlight

Fats, fatty acids, and the risk of uterine fibroids

From the Harris Group, Public Health Sciences Division

The most common, non-malignant pelvic tumor for reproductive aged women are uterine fibroids. In the US, they are the leading cause of hospitalizations for gynecologic conditions and the primary reason for hysterectomies. Women who have endured fibroids can attest that the condition is associated with overwhelming pelvic pain, abnormal uterine bleeding, and adverse pregnancy outcomes which could include infertility. Unfortunately to date, the etiology of fibroids is not fully understood and only a few risk factors have been determined.

One prospective study, the Black Women’s Health Study, was the first to examine dietary fat intake and the risk of uterine fibroids. This study noted a slight increased risk in intake of specific omega-3-fatty-acids and no associations with total fat and other fat subtypes. Because diet can alter endogenous hormones and their inflammatory effects, it is important to determine if dietary factors to increase the risk of uterine fibroids. For example, trans-fat intake influences circulating levels of interleukin (IL) and other inflammatory markers. Dietary intake is reflected for months in the fatty acid composition of the erythrocyte membrane. It is only reflected for days to weeks in serum and plasma.  Therefore, analyzing these biomarkers could provide additional insight into fibroid etiology.  The Harris group, from the Division of Public Health Sciences, investigated whether intake of dietary fats and fatty acids measured in erythrocyte membranes were associated with ultrasound-confirmed or hysterectomy-confirmed uterine fibroids during an 18-year- follow-up period.  The study was published in a recent issue of Fertility and Sterility.

 

Graphical Representation of Fats, fatty acids, and the risk of uterine fibroids
Fats, fatty acids, and the risk of uterine fibroids Image from Dr. Holly Harris

A Cox proportional hazard models were used as the time scale to estimate the associate between dietary fat intake and the risk of uterine fibroids. A total of 1,536,355 person-years of follow-up contributed by 81,590 women; there were a total of 8,142 incident cases of ultrasound of hysterectomy confirmed uterine fibroids.  Logistic regression analysis was used to analyze the association between fatty acid tertiles and fibroids; also, a test for linear trend of the exposure variables was performed. In this analysis, there was a total of 553 participants – 56 fibroid cases and 497 non-cases.

Overall, total fat intake and other dietary fats were not associated with the risk of fibroids. The Harris group reported an inverse association between erythrocyte levels of total n-3 polyunsaturated fatty acids and the odds of fibroids in the 3rd vs 1st tertile (OR: 0.41, 95% CI: 0.19-0.89; ptrend=.02).  Total trans fat was associated with the likelihood of fibroids for the 3rd tertile (OR: 3.33, 95% CI: 1.50-7.38; ptrend=.002). 

In conclusion, the Harris group did not observe any association between dietary fat intake (total or specific types) and risk of uterine fibroids. However, they reported a lower risk of fibroids among women with higher n-3 polyunsaturated fatty acids erythrocyte levels. Also, participants with higher trans fatty acid erythrocyte levels showed a greater risk of having uterine fibroids. Dr. Harris added: “The inverse association we observed between n-3 polyunsaturated fatty acids and fibroids, if confirmed in future studies, could lead to dietary guidelines to reduce risk of this prevalent condition. To date, only two case-control studies and one prospective study have analyzed the association between dietary fat and fibroid risk.  The study is novel; it is the first study to examine the association between erythrocyte fatty acids and fibroid risk. Dr. Harris commented on the next step in confirming her findings: “Our next steps are to examine these associations with a larger sample size and in a more diverse group of women as fibroids disproportionately impact Black women who were underrepresented in this study.”

This research was supported by the National Institute of Child Health and Human Development, the National Cancer Institute, and the National Institutes of Health.

Fred Hutch/UW Cancer Consortium member Holly Harris contributed to this work.

Harris HR, Eliassen AH, Doody DR, Terry KL, Missmer SA. 2020. Dietary fat intake, erythrocyte fatty acids, and risk of uterine fibroids. Fertility and Sterility. 2020 Jul 14. 

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