- In Brief: Breast Cancers Rise Worldwide
- Daily Drink Increases Colorectal Risk
- Unhealthy Behaviors May Age Us 11 years
- Aerobic Crunching Belly Fat
Discovering How Fiber Fights Cancer
AICR's/WCRF's (American Institute for Cancer reserach/World Cancer Reserach Fund) Continuous Update Project upgraded dietary fiber's status from probable to convincing as preventive of colorectal cancer. AICR-funded researchers are investigating how a byproduct of fiber in plant foods – butyrate – may protect against colorectal cancer.
The theory that eating a diet high in fiber may reduce the risk of developing colorectal cancer is a longstanding one. Two possible ways fiber may offer protection from colorectal cancer are:
- By speeding the transit of waste through the colon and minimizing exposure of the cells lining the intestinal tract to potential carcinogens; and
- By the action of byproducts produced when microbes in the gut digest fiber.
One of these byproducts is a short-chain fatty acid called butyrate.
Bacterial Action Is Key
"We're in the camp that says part of the fiber effect is due to bacterial action," says Scott Bultman, PhD, a researcher at the University of North Carolina-Chapel Hill. Using germ-free mice, he controls not only what the animals eat, but also adds back specific types of bacteria into their intestines, thereby controlling their gut flora.
Not all gut bacteria breakdown fiber in the same way and many don't produce butyrate.
"We're in the camp that says part of the fiber effect is due to bacterial action..." says Scott Bultman
Dr. Bultman compared mice with butyrate-producing bacteria in their guts to mice with other probiotic strains. He found a marked difference in the amount of protection that a high-fiber diet provided against colon cancer. Mice with butyrate-producing bacteria had lower rates of cancer and fewer tumors than mice with other types of bacteria.
In future work, Dr. Bultman hopes to pin the effect directly on butyrate itself, not just to the strains of bacteria he uses.
Butyrate Seeks Cancer Cells
At The Commonwealth Medical College in Scranton, Pennsylvania, Michael Bordonaro, PhD in collaboration with Dr. Farina Lazarova, PhD, studies the molecular mistakes in the colon that lead to cancer. He is specifically looking into how butyrate from high-fiber diets might affect that process.
"Most cases of human colorectal cancer start with mutations in the Wnt pathway," he says. "Wnt" represents a group of proteins whose "pathway" (a chain of reactions) is active in cell development.
Cells of the intestinal lining undergo constant turnover. As new cells mature and move into place, the Wnt pathway is supposed to turn off. However, mutations in the Wnt pathway keep it turned on and stimulating cell growth, leading to polyps, more mutations and eventually cancer. Butyrate influences the Wnt pathway in a manner that can kill cancer cells.
Nothing about cancer is simple, of course. Some people develop colorectal cancer even on high-fiber diets. Dr. Bordonaro thinks that some intestinal cells may become resistant to butyrate's effect, so he is continuing his molecular studies in a colon cancer cell line that models this possibility.
"With any sort of treatment, cancer is always stimulated to evade it," Dr. Bordonaro says. He hopes to learn what happens at the molecular level with butyrate resistance and to find ways to reverse or prevent it. "It could be the basis of a clinical intervention in addition to a high-fiber diet," he says.
Research continues to progress on the role of butyrate in fiber's protective effect. Meanwhile, AICR advises eating a diet rich in high-fiber vegetables, fruits, whole grains and beans.
The number of cases of breast cancer around the world has more than doubled over the past three decades, with most of the growth occurring in developing countries, reports a new assessment of breast and cervical cancers published in The Lancet.
Breast cancer cases increased from 641,000 in 1980 to 1,643,000 cases in 2010. Global cervical cancer rates have also increased but at a smaller rate annually: 378,000 cases in 1980 to 454,000 in 2010.
Researchers collected different data sources from 187 countries, drawing upon cancer registries, studies, verbal autopsies and mortality data. The authors then developed a model to predict the incidence and number of deaths from each cancer in each country. The findings show that breast and cervical cancer in low-income countries are major causes of death for women of reproductive ages. Risk factors such as obesity may play a role, but divergent trends in countries of the same region suggest that other factors – such as genes interacting with risk factors – explain the pattern, the authors note.
In the United States, the incidence rate for breast cancer began to decline in the early 2000s and then stabilized.
To explore trends in breast and cervical cancer for women, visit the Institute for Health Metrics and Evaluation.
Source: Mohammad H Forouzanfar, Kyle J Foreman, Allyne M Delossantos, Rafael Lozano, Alan D Lopez, Christopher J L Murray, Mohsen Naghavi. "Breast and cervical cancer in 187 countries between 1980 and 2010: a systematic analysis." The Lancet, Early Online Publication, 15 September 2011.
A new analysis of the literature has confirmed the conclusions from previous studies – and AICR's continuous update report – that drinking alcohol increases the risk of colorectal cancer, with this latest review finding that risk increases for those consuming more than one alcoholic drink daily. The analysis was published last week in the Annals of Oncology.
Drawing from 61 population studies from around the world, the researchers concluded that drinking two to three alcoholic drinks every day increases the risk of colorectal cancer 21 percent when compared to those who drink only occasionally or not at all. The more alcohol consumed regularly, the higher the risk. Four or more drinks per day (50 or more grams of alcohol) increased colorectal cancer risk by 52 percent.
The link was stronger for men than for women. And no results were given on types of alcoholic drinks.
AICR's expert report and its updates have found alcohol consumption is also linked to increased risk of cancers of the mouth, pharynx, larynx, esophagus liver, and breast.
Source: Fedirko V, Tramacere I, Bagnardi V, Rota M, Scotti L, Islami F, et al. Alcohol drinking and colorectal cancer risk: an overall and doseresponse meta-analysis of published studies. Annals of Oncology 22: 1958, 2011.
Eating well, being active, not drinking much and not smoking at all are all ways people can live longer, according to a new study published in American Journal of Public Health. The more healthy behaviors people engaged in the more likely they were to live longer; people who engaged in all four healthy behaviors were 63 percent less likely to die during the study period compared to those who practiced none of the behaviors.
Research has already suggested that healthy lifestyle behaviors improve longevity, but this study is one of the largest of its kind. The study by researchers at the Centers for Disease Control and Prevention used data from almost 17,000 adult participants in a national survey. Participants were recruited from 1988 to 1994 and followed through 2006.
People who engaged in all four healthy behaviors were 66 percent less likely to die early from cancer, 65 percent less likely to die early from cardiovascular disease, and 57 percent less likely to die early from other causes compared to people who did not engage in any of the healthy behaviors. Each behavior by itself also reduced the risk of dying during the course of the study.
The researchers calculated that practicing all the high-risk behaviors (such as smoking and eating poorly) represented 11 added years of aging for death from any cause, compared with those who practiced none of those behaviors. The high-risk behaviors equated to over 14 years of aging for dying from cancer.
Source: Ford ES, Zhao G, Tsai J, Li C. "Low Risk Lifestyle Behaviors and All-Cause Mortality: Findings from the National Health and Nutrition Examination Survey III Mortality Study." Am J Public Health. 2011 Aug 18. [Epub ahead of print].
Overweight people looking to lose belly fat may want to choose aerobics, suggests a new study. The study, published in the American Journal of Physiology, compared the benefits of aerobics to resistance exercise on abdominal fat and other indicators of health.
Abdominal fat, also known as visceral fat, is located deep within the abdomen and is an independent risk factor for cancers of the breast, colorectum, and pancreas.
In the study, Duke University researchers randomly divided 196 overweight and sedentary adults into one of three exercise groups: resistance training, aerobics, or a combination of aerobics and resistance. The aerobic group performed exercises equivalent to 12 miles of jogging per week. The resistance group performed three sets of 8 to 12 repetitions three times per week. All programs were supervised and monitored.
After eight months, the aerobic group had significantly reduced visceral fat and liver fat. Blood tests also revealed that aerobic exercisers showed more improvement than resistance exercisers at improving fasting insulin resistance, and reducing liver enzymes and fasting triglyceride levels. All are risk factors for diabetes and heart disease. For the outcomes in the study, there was no statistical difference when aerobics and weight lifting were combined compared to aerobics alone.
Resistance training reliably improves strength and increases lean body mass, conclude the authors, but aerobics burns more calories and it may be the calorie difference that leads to these effects.
Source: C. A. Slentz, L. A. Bateman, L. H. Willis, A. T. Shields, C. J. Tanner, L. W. Piner, V. H. Hawk, M. J. Muehlbauer, G. P. Samsa, R. C. Nelson, K. M. Huffman, C. Bales, J. A. Houmard, W. E. Kraus. "The Effects of Aerobic versus Resistance Training on Visceral and Liver Fat Stores, Liver Enzymes and HOMA from STRRIDE AT/RT: A Randomized Trial. "AJP: Endocrinology and Metabolism, 2011.
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