Field Notes

Cancer Prevention Guidelines May Lower Risk
of Obesity-Linked Cancers

Low alcohol consumption and a plant-based diet, both healthful habits aligning with current cancer prevention guidelines, are associated with reducing the risk of obesity-related cancers, a New York University study shows. The findings appear in the journal Cancer Causes & Control.

“Our research aims to clarify associations between diet and physical activity in relation to cancer to encourage at-risk individuals to make lifestyle modifications that may reduce their risk of certain cancers,” says lead study author Nour Makarem, a nutrition doctoral student at NYU Steinhardt.

One-third of cancers are estimated to be related to excess body fat, and are therefore considered preventable through lifestyle changes. Obesity-related cancers include cancers of the gastrointestinal tract, reproductive organs, urinary tract, blood, bone, spleen, and thyroid.
In 1997, the World Cancer Research Fund and the American Institute for Cancer Research released cancer prevention guidelines advising on weight management, diet, and physical activity. These guidelines, updated in 2007, provide an integrated approach for establishing healthful habits that reduce cancer incidence.

In their study, Makarem and her colleagues sought to evaluate whether healthful behaviors aligning with the diet and physical activity cancer prevention guidelines are in fact associated with reduced risk of obesity-related cancers and the most common site-specific cancers (breast, prostate, and colorectal cancers).

The researchers analyzed medical and dietary data for 2,983 men and women who were part of the Framingham Heart Study, a 60-year population study tracking factors related to cardiovascular disease as well as cancer. Focusing on data from 1991 through 2008, they identified 480 obesity-related cancers among the participants.

To calculate the relationship between the cancer prevention recommendations and cancer incidence, the researchers created a seven-point score based on the recommendations for body fat, physical activity, foods that promote weight gain, plant foods, animal foods, alcohol consumption, and food preparation and processing.

After adjusting for other factors that could contribute to cancer risk, including age, smoking, and preexisting conditions, the researchers found that the overall score, as a proxy for overall concordance to the guidelines, wasn’t associated with obesity-related cancer risk. However, when score components were evaluated separately, two different measures emerged as strong predictors of cancer risk.

In the current study, adherence to alcohol recommendations—limiting alcoholic drinks to two for men and one for women per day—was protective against obesity-related cancers combined and against breast, prostate, and colorectal cancers. In addition, among participants who consume starchy vegetables, eating sufficient nonstarchy plant foods (fruits, vegetables, and legumes) was associated with a lower risk of colorectal cancer.

“Based on the study’s results, dietary advice on preventing cancer should emphasize the importance of eating a plant-based diet and restricting alcohol consumption,” says senior study author Niyati Parekh, associate professor of nutrition and public health at NYU Steinhardt.

Source: New York University


Vitamin B May Counter Negative Effect of Pesticide on Fertility

Women who have adequate levels of B vitamins in their bodies are more likely to get and stay pregnant even when they also have high levels of a common pesticide known to have detrimental reproductive effects, according to new research from Johns Hopkins Bloomberg School of Public Health.

The findings, published in the December issue of the American Journal of Clinical Nutrition, suggest that B vitamins may have a protective effect that counteracts the levels of DDT in their bodies. DDT, a known endocrine disruptor, is still used to kill mosquitoes in many countries where malaria remains a serious public health concern. The United States banned the pesticide in 1972; China, where the study was conducted, followed suit in 1984. DDT, however, can remain in the body and environment for decades.

“Our previous work has shown that high levels of DDT in the body can increase the risk of early miscarriage,” says study leader Xiaobin Wang, MD, ScD, MPH, the Zanvyl Krieger professor and director of the Center on the Early Life Origins of Disease at the Johns Hopkins Bloomberg School of Public Health. “This study tells us that improved nutrition may modify the toxic effects of DDT, by better preparing the body to cope with environmental toxins and stressors. We’ve shown that women with high levels of DDT who also had high levels of B vitamins had a better chance of getting and staying pregnant than those who were deficient in those vitamins.”

The findings suggest that looking at toxins and nutrition in isolation doesn’t paint a full picture of how these different factors intersect. She says studies like this may provide a model for how future research groups can examine the relationship between other toxins and nutrients.
For the study, conducted between 1996 and 1998, Wang and her colleagues recruited and followed a group of female Chinese textile workers who were trying to get pregnant. Every day for up to one year, researchers tested the urine of the women in the study, detecting their levels of hCG, the hormone that signals conception. This approach allowed researchers to determine whether a woman was pregnant much earlier than she might normally find out, in the days or even weeks before she realized she’d missed a menstrual period. It also enabled the researchers to determine whether women had an early pregnancy loss (miscarried before six weeks of pregnancy). DDT and DDE (a major degraded product of DDT) and B vitamin levels were measured in the women before conception.

A 2003 study by Wang and colleagues showed that one-third of all conceptions end before women even know they’re pregnant. “This is a very vulnerable period,” Wang says.
Among the 291 women ultimately included in the study, there were 385 conceptions, 31% of which were lost before six weeks. Women with high DDT levels and sufficient levels of vitamin B had a 42% greater chance of early miscarriage than women with lower DDT levels. But in those with high DDT levels and vitamin B deficiencies, women were twice as likely to suffer a miscarriage before six weeks of gestation. The researchers looked at three types of B vitamins (B6, B12 and folic acid), and determined that the risk to a pregnancy was higher with B12 and folic acid deficiencies and with deficiencies in more than one type of B vitamin.

The researchers also found that women with high DDT and low B vitamin levels took nearly twice as long to conceive in the first place.

The standard of care in many nations is to give an iron-folate supplement to women once they seek prenatal health care, which typically occurs between eight and 12 weeks of gestation, if at all. But that supplement rarely is taken before conception, meaning it likely comes too late to prevent early pregnancy loss. And unlike in the United States, where many foods are fortified with folic acid, this isn’t the norm around the world.

Difficulty conceiving is prevalent in both developed and developing countries. In the United States, the percentage of married women between the ages of 15 and 44 who had difficulty achieving and maintaining pregnancy increased from 8% in 1982 to 11.8% in 2002, an increase that can’t be completely explained by the age of the women.

Better nutrition—including fortifying foods with B vitamins—in countries where DDT is still in wide use could improve pregnancy outcomes, Wang says. She says there also may be implications in the United States, particularly among women who immigrate from countries where DDT is still common and among low-income women whose diets may not include foods high in B vitamins, such as leafy green vegetables and beans. Even women from the United States may have DDT in their systems; it may come from imported foods or even from local food grown in soil still contaminated with DDT.

“Health care providers need to make sure women get adequate micronutrients including B vitamins in their diets not only during pregnancy but also before they even conceive,” she says. “Otherwise, we may miss that critical window.”

— Source: Johns Hopkins Bloomberg School of Public Health