The growing body of research on how activity – and inactivity – affects cancer risk and overall health has gotten a lot clearer this month with the release of several notable studies. It may make you want to walk around as you read.
Worldwide, one in ten cases of both breast cancer and colon cancer is due to a lack of physical activity, with inactivity as much to blame for the major non-communicable diseases as smoking or obesity, concluded an analysis published in The Lancet last week.
The analysis quantified the effects of physical inactivity on heart disease, type 2 diabetes, and breast and colon cancers. Physical inactivity was defined as not meeting the World Health Organization guidelines, which match US guidelines: Adults should get at least 150 minutes of moderate-intensity aerobic activity each week, with muscle strengthening activities at least two days a week.
“This is important science,” says Christine Friedenreich, PhD, of Alberta Health Services-Cancer Care, a leading researcher on the activity-cancer link who also spoke at last year’s AICR Annual Conference. “The Lancet team applied a lot of rigor, and these estimates are solid. And as the authors point out, these numbers likely represent the lower threshold of how many cancers could be prevented by becoming more active.”
The study determined that physical inactivity causes 6 percent of coronary heart disease; 7 percent of type 2 diabetes; 10 percent of breast cancers; and 10 percent of colon cancers. Together, inactivity caused more than 5.3 million of the 57 million deaths that occurred worldwide in 2008.
The authors concluded that if the population as a whole were only 10 percent more active, this would prevent more than 533,000 deaths every year; if the population was 25 percent more active, the world would prevent more than 1.3 million deaths each year.
It was good to see cancer included in the list of non-communicable diseases studied, notes Friedenreich, who was among a small group of scientists studying this topic. “Before, cancer was left off that list. Now cancer is accepted as one of the extremely important non-communicable diseases related to physical activity."
If inactivity links to increased risk of disease, can inactivity also affect life expectancy? Yes, finds an analysis of research published in the journal BMJ Open.
Cutting the amount of time we sit to fewer than three hours every day may add 2 years to the US life expectancy of adults. And reducing TV viewing to less than two hours every day might extend life by almost 1.4 years. Watching TV is a recognized measure of sedentary behavior.
For the study, researchers pulled data from the National Health and Nutrition Examination Survey (NHANES) for 2005/6 and 2009/10, to determine the amount of time US adults spent watching TV and sitting down on a daily basis. They then applied population studies on sitting time and deaths, taking into account age and sex.
This finding applies to the US population, not individuals, the authors caution.
“Before, cancer was left off that list. Now cancer is accepted as one of the extremely important non-communicable diseases related to physical activity."
AICR’s expert report and its updates link relatively high levels of physical activity to decreased risk of postmenopausal breast cancer. A new study published in Cancer now suggests that any intensity level of physical activity – before or after menopause – may reduce breast cancer risk. Substantial weight gain appeared to negate the benefits.
The study included approximately 3,000 women who were ages 20 to 98. About half of the women had breast cancer.
Women who exercised either during their reproductive or postmenopausal years had a reduced risk of developing breast cancer. Women who exercised 10 to 19 hours per week experienced the greatest benefit with an approximate 30 percent reduced risk, but lower amounts also were slightly protective. Risk reductions were observed at all intensity levels.
The study also found that even active women who gained a significant amount of weight – particularly after menopause – had an increased risk of developing breast cancer, indicating the importance of staying a healthy weight.
"This study provides further evidence that being physically active is associated with lower risk for breast cancer after menopause," said Patrick Bradshaw, an epidemiologist at the University of North Carolina and a Marilyn Gentry Fellow who is one of the study's authors. The majority of breast cancer is diagnosed in postmenopausal women. "What's really interesting is that the relationship was consistent when different times of physical activity were considered, during reproductive years and after menopause. This would seem to say that it's never too late to reap the benefits of being active."
Along with postmenopausal breast cancer, AICR’s expert report and its updates link physical activity to decreased risk of colorectal and endometrial cancers. The reports also find that watching too much television and being sedentary increases the risk of weight gain and obesity, which is linked to increased risk of seven types of cancer.
“The research is emerging on sedentary behavior but we already know that physical activity has quite a big impact on cancers,” said AICR Director of Research Susan Higginbotham, PhD, RD. Activity is one part of a healthy lifestyle shown to lower cancer risk. “A healthy diet, staying at a healthy weight and not smoking, those factors work together – as soon as you start combining them, cancer risk drops even further.”
Requiring restaurants to post calorie and nutritional information may lead to slightly healthier food options, but not by much, suggests a study of restaurants in one of the first counties to implement nutritional labeling. Eighteen months after the chain restaurants were required to post nutritional information, the same entrees had 41 fewer calories.
The Affordable Care Act requires chain restaurants post their menu items’ nutritional information, such as calories. One objective is to raise consumer awareness of what we are eating, which would then encourage restaurants to serve healthier foods.
The study analyzed the menus at almost 40 sit-down and fast-food chain restaurants in King County, Washington. Researchers measured the nutritional content of the same menu entrees – almost 1,800 of them – six months after the regulations went into effect and 12 months later.
For all restaurants, the entrées had 41 fewer calories on average between the time periods; sit-down restaurants were 73 fewer and fast-service meals were 19 less calories. Sodium content dropped by 230 milligrams – a 10% decrease – in sit-down restaurants.
But over half of the entrées were still relatively high in calories, saturated fats, and sodium, compared to dietary guidelines. When comparing one entrée to one-third of the recommendations, over half had more calories, about three-quarters more saturated fats, and nine of ten exceeded sodium guidelines.
Source: Energy, Saturated Fat, and Sodium Were Lower in Entrées at Chain Restaurants at 18 Months Compared with Six Months Following the Implementation of Mandatory Menu Labeling Regulation in King County, Washington, by Barbara Bruemmer, PhD, RD; Jim Krieger, MD, MPH, Brian E. Saelens, PhD, Nadine Chan, PhD, MPH. Journal of the Academy of Nutrition and Dietetics, Volume 112/Issue 8 August 2012.
Keep a food journal, don’t skip meals, and eat at home: These are among the strategies that may help overweight women lose weight, suggests a new study published online last week in the Journal of the Academy of Nutrition and Dietetics.
The findings come from a one-year weight loss program for overweight and obese post-menopausal women. At the end of the year, the 123 women answered which of a series of eating-related behaviors they followed. The strategy that was one of the most effective for weight loss was the food journal. Women who wrote down what they ate consistently and frequently lost 4 percent more – about 6 pounds – than women who infrequently noted their foods.
Going out for meals, especially lunch, was also linked to losing less weight. Women who ate out for lunch at least weekly lost on average 5 fewer pounds than those who ate out less frequently. Women who reported skipping meals lost almost 8 fewer pounds than women who did not.
Several of these weight loss strategies are similar to those found in other studies and surveys, including the National Weight Loss Registry.
Source: McTiernan et al. Self-monitoring and Eating-related Behaviors are Associated with 12-month Weight Loss Among Postmenopausal Overweight-to-obese Women in a Dietary Weight Loss Intervention. Journal of the Academy of Nutrition and Dietetics, 2012 (in press).
For decades, researchers and health practitioners have used the Body Mass Index (BMI) as a simple metric for obesity and indicator of health risks, including increased risk of cancer. Now researchers have developed a new index to measure obesity that may provide a better correlation with death rate, independent of BMI, according to a study released last week. The new index, A Body Shape Index (ABSI), was published in open access journal PLoS ONE,
The BMI uses a person’s height and weight to calculate a number that falls into a category, such as healthy weight, overweight, or obese. The index has recognized flaws, a healthy BMI for Asians is different than that for Blacks, for example. The BMI categories may also not apply to athletes and the elderly. And over the years, research has shown that excess abdominal fat is an independent risk factor for increased cancer risk as well as other diseases.
The ABSI uses both BMI and waist circumference in its calculations.
To study the new measure, the authors analyzed data from over 14,000 US adults taken as part of the National Health and Nutrition Examination Survey. After looking at mortality data over a five-year period, they found that ABSI was a better predictor of premature death compared to BMI or waist circumference, independently. The correlation held across the range of ages, for both sexes, and for both black and white ethnicities. It did not apply to people of Mexican ethnicity.
ABSI could complement the other measures and risk factors, conclude the authors. But further longer-term studies are needed to connect ABSI to both premature mortality and quality of life.
Source: Krakauer NY, Krakauer JC. A New Body Shape Index Predicts Mortality Hazard Independently of Body Mass Index. PLoS ONE, 2012; 7(7): e39504 DOI: 10.1371/journal.pone.0039504
It’s possible these measurement errors may be obscuring the link to reduced breast cancer risk, finds a new analysis of the literature that looked at carotenoid intake assessed by both dietary recall and blood concentrations. The study was published in the online July issue of the American Journal of Clinical Nutrition.
The study was funded by the World Cancer Research Fund as part of AICR/WCRF's Continuous Update Project (CUP).
For the analysis, researchers reviewed the 24 relevant publications on breast cancer risk and six carotenoids. Some used dietary recall to estimate the carotenoid intake and others measured carotenoid blood levels. The carotenoids studied include beta-carotene, alpha carotene, lycopene and lutein.
For the dietary studies, no link was found between five of the dietary carotenoids and breast cancer risk. Estimates of high beta-carotene intake showed a slight reduced risk.
Yet the studies measuring blood concentration showed a strong link between carotenoids and reduced breast cancer risk. The reduced risk was seen for total carotenoids and the individual phytochemicals. The analysis suggests that dietary studies add blood measures when possible to better determine carotenoid intake.
It’s possible the risk reduction may be due to factors linked to higher blood concentrations of carotenoids. These people may exercise more and be less overweight, for example. Many, but not all, of the studies adjusted for these factors. More studies that take these factors into account are needed, note the authors.
Source: Aune D, et al. Dietary compared with blood concentrations of carotenoids and breast cancer risk: a systematic review and meta-analysis of prospective studies. Am J Clin Nutr. 2012 Jul 3.
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