Lard (rendered pork fat) is undergoing a resurgence in American cooking, as various celebrity chefs have highlighted its usefulness in frying and baking. Other commentators are attempting to debunk lard's reputation as an unhealthy, high saturated fat ingredient. However, while there may be room for debate regarding lard's influence on cardiovascular health, available studies indicate that lard is a risk factor for breast cancer. Epidemiological studies in regions and during times when lard was a more common cooking ingredient have reported relatively strong associations between lard consumption and breast cancer risk. For example, Chinese, Brazilian and Tanzanian studies have reported links between use of lard and breast cancer. Now a new study has reported that a high-fat lard-based diet resulted in higher cancer incidence and produced larger mammary tumors than a low-fat diet in a mouse model of triple negative (ER-/PR-/HER2-) breast cancer.

Latest research finds lard diet increases tumor number and size

The study referenced above was designed to investigate the impact of a high-fat lard-based diet compared to a low-fat diet on the development of mammary tumors in a mouse model of triple negative breast cancer. To conduct the study, the authors weaned 16 C3(1)SV40TAg mice at age three to four weeks and then assigned them to one of two dietary groups. The high-fat diet group were fed 5.3 kcal/g, including 60% of calories from lard, whereas the low-fat group received 3.7 kcal/g, including 17.2% of calories from vegetable oil. The mice were administered specialized MRIs of their mammary glands at 12 weeks, after which the animals were sacrificed. The mammary glands were then removed and formalin fixed for additional MRI studies.

Based on the live mouse MRIs, the lard-fed mice were found to have an average of 3.88 tumors whereas the low-fat group had an average of 1.25 tumors. The average tumor volume was also higher in the lard-fed group (0.53 mm3) than the low-fat group (0.20 mm3). Analysis of the remaining MRIs as well as histology images showed that the lard-fed mouse mammary glands had higher breast density, irregular and enlarged ducts, dilated blood vessels, increased fat tissue, and greater tumor invasion. The authors conclude that the high-fat lard-based diet resulted in higher cancer incidence and larger mammary tumors. The authors also comment that, unlike other imaging techniques for assessing environmental effects on mammary cancer growth, MRI facilitates multiple accurate measurements and reliable detection of small tumors as well as assessment of the three-dimensional distribution of tumors over time.

Please see our article on triple negative diet for more information.