By Sally Squires
Tuesday, November 13, 2007
If you're feeling a little whiplash from recent nutritional news, no wonder.
First, 21 respected international scientists report that excess pounds, inactivity and overconsumption of certain foods, including red meat and alcohol, increase cancer risk. A few days later, government scientists say that being overweight does not raise the risk of dying prematurely from either heart disease or -- you guessed it -- cancer.
At first glance, the two reports seem contradictory. But dig a little deeper and there's some striking consistency that can help clear the nutritional fog.
So avoid the temptation to add calories or ease up on workouts. None of the recent findings changes "any current recommendations" for food or activity, notes Katherine Flegal, a senior research scientist at the Centers for Disease Control and Prevention and lead author of the new government study, which was published in the Journal of the American Medical Association. "You still want to eat right, get some activity and don't smoke. Nothing about our paper changes those messages. Everyone would agree."
But let's parse the details, starting with the question of harm from excess body weight. Flegal and other CDC scientists found that being just a few pounds overweight -- but not obese -- had little effect on the risk of dying from cancer. Just about 1 percent of cancer deaths were attributed to being overweight. There was also minimal risk for heart disease mortality from carrying a few extra pounds. The emphasis here is on "a few."
"We're talking about having a body mass index of 25," says Flegal, or anywhere from about five to 15 pounds above a healthy weight. "Overweight and obesity are not exactly the same."
That's the good news. Also, that carrying some extra weight seems to protect against other causes of death, such as tuberculosis, emphysema, pneumonia and Alzheimer's disease.
The bad news: Even being a few pounds overweight hiked the odds of death from Type 2 diabetes and from kidney disease, the report found. The higher the BMI, the greater the risk. And there was some added cancer risk for those who are obese -- that is, about 30 pounds or more above a healthy weight. Obesity accounted for about 4 percent of cancer deaths.
All of that fits with findings from the new report by the international scientists. They were convened by the American Institute for Cancer Research (AICR) and spent five years examining the research. They found that excess body weight, particularly obesity, was linked to an increased risk of breast, colorectal and pancreatic cancer.
Add that to the evidence that extra pounds stress joints, increase sleep apnea and cause other problems. The bottom line? Aim for a healthy weight. Or at least a healthier weight. The Diabetes Prevention Program, a large federal study of people poised to get Type 2 diabetes, found that losing just 7 percent of their body weight cut their risk of developing the condition by as much as 65 percent. And if you can't seem to lose weight, at least don't add any more pounds.
As for inactivity, the research is also very clear: Sedentary living is dangerous, whether you are lean, fat or in between. And the benefits of staying active continue to grow no matter what your age, physical condition or weight. The AICR report found "convincing" evidence that regular physical activity cuts the risk of colorectal cancer, weight gain and obesity. There's also "probable" evidence that it decreases the risk of endometrial cancer in all women and breast cancer in those past menopause.
What you put on your plate also makes a difference. The big food winners: Fruit and vegetables, so long as they are not pickled or salted.
There's "probable" data to show that eating plenty of fruit and non-starchy vegetables, from broccoli to zucchini, cuts the risk of cancer of the mouth, pharynx, larynx, esophagus and stomach, according to the AICR report. There are also probable cancer-preventive benefits for onions, garlic and other vegetables rich in allium. Fruit seems to help protect against lung and stomach cancer.
These findings fit with the 2005 U.S. Dietary Guidelines advice for most adults to eat about 2 1/2 cups of vegetables per day and two cups of fruit. The AICR report offers similar advice, saying to aim for at least 14 ounces daily.
Also, go easy on the red meat and processed meat products, from hot dogs to salami. The AICR report found convincing evidence to link these foods with a higher risk of colorectal cancer. "You see a dramatic increase in risk once you go over 18 ounces of red meat per week," notes AICR registered dietitian Sarah Wally.
The same goes for alcohol. Despite some heart benefits for men and post-menopausal women who drink moderately, there's convincing evidence that all alcoholic beverages boost breast cancer risk in women, colorectal cancer in men and cancer of the mouth, pharynx, larynx and esophagus in both. There's also "probable" evidence to suggest that beer, red wine and distilled spirits raise the risk of colorectal cancer in women and liver cancer in both sexes. The final call? No more than two drinks daily for men, one drink for women.
Another beverage, milk, seems to have some "probable" benefits in protecting against colorectal cancer, although diets high in calcium, not just milk, have some "probable" increased risk for prostate cancer -- yet another mixed message.
What does come through loud and clear: Get your nutrients first from food rather than from dietary supplements. As the AICR report notes, "Dietary supplements are not recommended for cancer prevention." So eat an orange rather than popping Vitamin C; have tomato sauce on your spaghetti rather than taking lycopene, and enjoy pumpkin, sweet potatoes and squash in place of popping vitamins with beta carotene -- a substance that in supplements has been shown to increase lung cancer risk in smokers, though it has no known adverse effects when ingested in food.