Evidence pointing to adolescence as a vulnerable period for life-long breast health stems from both animal and human observational studies. During puberty, the structure of the breast changes as a network of branching ducts develops. Cells are dividing at a quicker pace and any carcinogen that cells are exposed to puts them at greater risk of essentially making a mistake copying the DNA from parent to daughter cell.
"Some of these changes occur and are latent for several decades, waiting for a second hit, for something else to go wrong that triggers breast cancer," says Lindsay Frazier, MD, a pediatric oncologist at Dana-Farber Cancer Institute who is currently conducting an AICR-supported study related to adolescents' diets and risk of breast cancer. "It’s possible [during this time] there are ways nutrition protects the cell from acquiring a genetic mistake, or likewise it could be more vulnerable to potential carcinogens in the diet."
In studies on adolescent diet and later breast cancer, alcohol is one factor that has consistently linked to increased risk. Studies have produced conflicting findings for many other exposures, including vitamin D, milk, types of fat and vitamin E.
The challenge in replicating study findings may have a lot to do with human fallibility. The majority of studies investigating adolescent lifestyle habits ask women to recall their weight, physical activity and diet from decades earlier, a challenge to remember correctly. Unknowingly, recall bias may also play a factor. In several studies, when women diagnosed with breast cancer recalled their diet, the findings differed from women who were cancer-free. It’s possible that the cancer survivors were falsely recalling factors they thought might explain their disease.
In her research, Frazier is removing these possible measurement errors by using data from the Growing Up Today Study (GUTS), a group of approximately 9,000 girls who were ages 9-14 when the study began 13 years ago. (GUTS participants are the children of Nurses Health Study II participants.) The AICR-funded study is focusing on fiber and vitamin D; examining their link to types of benign breast disease (BBD) linked to increased risk of breast cancer.
Some of the earliest evidence suggesting a young girl’s diet may play a role in future breast cancer risk relates to soy. Researchers have long observed that Asian women, who eat soy as part of their standard diet, have a significantly lower breast cancer risk than Caucasian women. Yet when Asian women move to the West, their daughters’ risk becomes similar to that of Caucasian women.
After numerous laboratory studies and her recent review of the literature, Leena A. Hilakivi-Clarke, PhD, says the evidence shows that soy protects against breast cancer, but only when women were exposed to soy at young ages. A Professor of Oncology at Georgetown University Medical Center, Hilakivi-Clarke’s animal studies have found that soy’s genistein leads to several long-lasting changes, including activating a tumor suppressor gene and decreasing the estrogen receptor’s response to estrogen.
"There are so many different changes caused by soy and genistein; right now we don’t know which of these might be the critical ones. It’s likely multiple pathways."
Among adults, clear evidence shows that excess body fat increases the risk of post-menopausal breast cancer. Yet when it comes to body fatness of girls and adolescents, a growing body of evidence suggests the opposite.
In one of the larger studies, almost 200,000 participants who recalled their body fatness at young ages were tracked for 16 years. The study found that body fatness at young ages overall decreased later breast cancer risk; the greatest decrease in risk was observed for adolescent body fat. As body fatness increased, breast cancer risk declined. And the link was unaffected by adult weight.
Exactly how excess adolescent body fat may protect against breast cancer is not known. The next goal is to understand what is driving the association in order to focus on prevention, said Heather J. Baer, ScD, Instructor in Epidemiology at the Harvard School of Public Health and lead author of the study
"This study is part of a bigger picture, looking at cancer risk over the life course…. Now we know there are a number of factors at different stages of life that could impact breast cancer risk many years later."
Excerpted from ScienceNow.
The least physically active groups live in Kentucky and West Virginia while the most physically active live in Colorado and Wyoming, according to new estimates by the Centers for Disease Control and Prevention.
The new estimates used data collected from adults in 3,141 U.S. counties or county equivalents, such as boroughs. The analysis was based on self-reported data, and estimates were age-adjusted.
States where at least 70% of counties ranked in the highest category of physical inactivity include Alabama, Kentucky, Louisiana, Mississippi, and Tennessee. States where at least 70% of counties ranked in the lowest category of leisure-time physical inactivity include California, Colorado, Hawaii, Minnesota, and Washington.
Source: Centers for Disease Control and Prevention. County-Level Estimates for Leisure-Time Physical Inactivity.
Although studies on cancer survivors’ lifestyle behaviors has grown steadily over the past two decades, more research is needed to develop evidence-based nutrition recommendations and help survivors prevent recurrence and prevent and/or manage the many late effects of treatment, according to a commentary published in the March issue of the Journal of the American Dietetic Association.
There are now nearly 12 million cancer survivors in the United States. Cancer survivors die of non-cancer-related causes at significantly higher rates than the general population, and cancer is linked with several health disorders, including heart disease and osteoporosis.
In order to provide recommendations for breast cancer survivors based on the most current science, AICR and the World Cancer Research Fund (WCRF) is currently conducting a systematic review of the research. The study, part of AICR/WCRF's Continuous Update Project, is analyzing all published evidence on the impact of diet, physical activity and body fat in women diagnosed with breast cancer.
The review of the research will provide the most up-to-date information about how breast cancer survivors might improve their quality of life and help prevent recurrence and secondary cancers.
Current recommendations for cancer survivors by AICR emphasize achieving and maintaining a healthy weight; encouraging regular physical activity (for adults at least 30 minutes of moderate to vigorous physical activity every day); eating a diet rich in vegetables, fruits, and whole grains; and limiting red and processed meats and alcohol consumption.
One gap in research is when and how to promote positive health behavior changes among cancer survivors, note the authors of the commntary. Evidence suggests few cancer survivors are following the current diet and activity recommendations.
Source: Kim Robien, Wendy Demark-Wahnefried, Cheryl L. Rock "Evidence-Based Nutrition Guidelines for Cancer Survivors: Current Guidelines, Knowledge Gaps, and Future Research Directions" Journal of the American Dietetic Association, Vol 111, No. 3, March 2011.
The global rate of obesity has almost doubled since 1980 with the United States having the highest mean BMI of all high-income countries, finds a study published in the February issue of The Lancet. In total, the study found, more than half a billion adults worldwide are obese.
Two other papers in the same issue of The Lancet examined blood pressure and cholesterol changes between 1980 and 2008, focusing on three key cardiovascular risk factors. Excess body fat is also a risk factor for cancer. AICR’s expert report and its updates have found that excess body fat is a cause of a seven cancers, including endometrial, esophageal, and post-menopausal breast.
For the estimates, the authors gathered published and unpublished data on BMI among adults ages 20 and older in 199 countries and territories. Findings include:
Source: Finucane MM, et al. "National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9·1 million participants." Lancet. 2011 Feb 12;377(9765):557-67. Epub 2011 Feb 3.