There has been much attention paid to dietary fats and cholesterol in the last 30 years. Words not that long ago absent from the American lexicon (back when all eggs were happily fried in bacon fat) such as low fat, trans fat and “good” and “bad” cholesterol, are now the focus of some interesting and contradictory research.
Most experts would agree people need some fat and cholesterol in their diets. According to the Harvard School of Public Health, fat plays an important part of cell membranes, helping govern what gets into cells and what comes out.
“The body uses cholesterol as the starting point to make estrogen, testosterone, vitamin D, and other vital compounds. Fats are also biologically active molecules that can influence how muscles respond to insulin's 'open up for sugar' signal; different types of fats can also fire up or cool down inflammation.”
Past research from numerous sources have reported conflicting information. It typically boils down to a “quantity vs. quality” argument. Some research says it’s not the amount of fat you eat, but rather the type of fat. Others say how much dietary fat you eat matters greatly to your health.
While dietary cholesterol isn't technically a fat, it is found in food derived from animal sources: dairy products, butter, eggs, seafood, meat, poultry and lard. Intake of dietary cholesterol increases blood cholesterol levels, but not as much as saturated and trans fats do, and not to the same degree in all people, said the Harvard research.
A new study by researchers at the Kimmel Cancer Center at Thomas Jefferson University adds fuel to the fat and cholesterol debate. They discovered that elevated fat and cholesterol levels found in a typical American-style diet stimulate the growth and spread of breast cancer.
Dr. Phillippe G. Frank, a cancer biologist at Jefferson, wondered why the breast cancer incidence rate was five times higher in Western countries than in other developed countries. Frank’s interest was further piqued by previous studies that showed immigrant populations relocating from a region with a low incidence of breast cancer were experiencing increased breast cancer rates, and sought to learn if there was a link between diet and breast cancer. “These facts suggest strong environmental influence on breast cancer development,” he said.
Frank and his team used mice models of human cancer to examine the links between a fatty cholesterol diet and breast cancer. Two groups of mice were injected with human cancer cells. By feeding one group a special fat-enriched food reflective of a typical Western diet and another group normal mice chow, he was able to determine if the amount of fat consumed affected the tumors' growth and spread.
And grow they did. In the fat/cholesterol fed mice, the number of tumors nearly doubled from the control group, and the size of tumors were 50 percent larger. Frank also observed a trend towards an increased number of lung cancer metastasis in the mice fed the fatty diet.
To confirm the aggressive nature of the cancer in the animals fed a cholesterol-rich diet, the researchers examined the levels of several biomarkers of tumor progression and found a signature of a more advanced cancer stage compared to tumors that developed in the control group.
Frank explained the accelerated tumor onset and growth of breast cancer in the fat and cholesterol-diet group this way: “In a neighborhood, if you want to build more houses, you need more bricks. In tumors, cholesterol provides the bricks that are the foundation for further cancer growth, and this cholesterol comes from the blood. A drop in blood cholesterol may signify that some tumors are growing as cholesterol provides support for breast cancer growth.”
The research team also discovered the same association between cholesterol and growth of prostate cancer in mice in a study published in the December, 2010 issue of The American Journal of Pathology. The results of these two new studies indicated that “cholesterol does indeed seem to be an important factor in the regulation of tumor formation in several cancer types,” Frank said.
The breast cancer study is published in the January issue of The American Journal of Pathology.
Lynette Summerill is an award winning writer who lives in Scottsdale, Arizona. In addition to writing about cancer-related issues for EmpowHER, she pens Nonsmoking Nation, a blog following global tobacco news and events.