|American Cancer Society
Weighing In on Low-Carb Diets
American Cancer Society
The American Cancer Society (ACS) is a nationwide, community- based voluntary health organization. Headquartered in Atlanta, Georgia, the ACS has state divisions and more than 3,400 local offices
A pound of chicken wings with blue cheese dip now tops the so-called "healthy menu" for a national restaurant chain – one sign of the low-carbohydrate diet trend that is sweeping our overweight nation. To cancer experts, a diet that helped Americans lose weight and keep it off would be welcome. Researchers have confirmed that extra body fat leads to an estimated 90,000 cancer deaths each year.
But a low-carb diet can be a high-risk option when it comes to health. ACS nutrition expert Colleen Doyle, MS, RD, warns that low-carb dieters can fall into eating habits that may increase the risk of developing cancer later in life. In short: man cannot live on steak alone.
Visions of Steak, Bacon, and Eggs
"Eating more vegetables and fruits -- or both together -- has been linked to a lower risk of lung, oral, esophageal, stomach and colon cancer," she explained. Scientists don't know which nutrients are most protective against cancer, so ACS nutrition guidelines call for eating a wide variety of colorful vegetables and fruit. In general, the more colorful the food is, the more cancer-fighting antioxidants and phytochemicals it contains. Adults should eat at least five or more servings of fruits and vegetables each day for cancer prevention. “Actually, if people really followed the low-carb diets as they're designed, they'd likely be eating more servings of vegetables than before."
"To the extent that people limit their consumption of refined carbohydrates such as cake, cookies, and soda, that’s good," Doyle explained. But, she said, people should not limit their intake of whole grain foods, fruits, and vegetables, as some low-carb diet plans advise.
Missing Nutrients and the Problem of Saturated Fat
Nearly all grain products, fruits, and some vegetables are banned in the first few weeks of a typical low-carbohydrate diet to trigger a change in metabolism and to reduce carb cravings. Dieters are told to keep their carbohydrate intake below 20 grams a day to force the body to burn fat for energy. This can mean missing out on the important vitamins and minerals found in restricted foods like grains, fruits, milk, and yogurt – the last two being important sources of calcium. As a result, many low-carb diet plans recommend taking a multivitamin/mineral supplement with calcium.
And that raises another concern -- a concern about cancer.
"Diets high in saturated fat increase the risk of prostate and colon cancer," explained Doyle. ACS recommends people limit their intake of saturated fat." Recently, low-carb diet programs too have addressed the saturated fat issue by putting more emphasis on healthier protein sources – chicken, turkey, and fish, for example, rather than unlimited servings of red meat.
Does a Low Carb Diet Stand the Test of Time?
"At issue is whether these diets result in longer-term maintenance of that weight loss," said Doyle. "So far there's little evidence that that is the case.” One study put both a low-carb diet and a low-fat diet to the test.
Results were published in the New England Journal of Medicine (Vol. 348: No. 21, 2053-2166) and found people on the Atkins plan, the original low-carb diet, lost more weight, more quickly, than a comparison group of people on a standard low-fat diet. But a year later, the Atkins dieters were no lighter than the low-fat diet group.
So with 64% of Americans currently overweight, what are we to do? "If you want to lose weight, you've got to cut back total calories and exercise more," Doyle insisted. "The real key to long-term weight loss is watching portions and overall calorie intake. Too many people are only focusing on one aspect of the diet: avoiding carbohydrates. Counting carbs alone is not going to do it."
* Choose protein sources that are low in saturated fats: chicken, turkey, fish and legumes instead of red meats.
* Eat five or more servings of colorful vegetables and fruit each day.
* Eat at least three servings of whole grain foods each day, such as whole wheat bread, brown rice, and whole grain cereals
* Be sure half of your grain foods come from whole grain sources.
Behind the Rise in Obesity: Soda, Pizza, and 'Biggie Sized' Foods
A recent report on Americans' food intake offers clues to what dieters might do to buck the trends and lose weight instead. Over the past 30 years, the average number of calories we eat each day has surged upward -- with most of the extra calories coming from refined carbohydrates. And that’s the point, says Doyle. Eating a lower carb diet by cutting back on these types of carbs, rather than whole grains and fruits, is the way to go.
The report even points to specific foods and habits: "…factors contributing to the increase in energy intake in the United States include consumption of food away from home; increased energy consumption from salty snacks, soft drinks, and pizza; and increased portion sizes." The report by the Centers for Disease Control and Prevention breaks down calorie intake for men and women as follows:
|Average Calorie Intake per Day|
|Source: "Trends in Intake of Energy and Macronutrients – United States 1971-2000," February 6, 2004|
Couch Potato Culture
People who want to try a low-carb diet may get the best results by limiting both potatoes and long hours on the couch. Boosting physical activity should be a part of any diet or other weight control program, according to Doyle.
For cancer prevention, there's evidence that physical activity itself helps lower cancer risk – in addition to its role in helping people maintain a healthy body weight. The ACS recommends at least 30 minutes of moderate physical activity on at least 5 days a week. Doyle says the most important change in physical activity, however, is one most people can make now: to move from being sedentary to incorporating even a moderate degree of activity into their daily routines.
The Bottom Line
Eating a mostly plant-based diet with limited amounts of saturated fat, being physically active and maintaining a healthy weight are key to preventing cancer. If you’re one of the many, though, who are going the low-carb route, follow these guidelines:
* Choose protein sources that are low in saturated fat -- chicken, turkey, fish, and legumes -- instead of excessive amounts of red meats.
* Eat five or more servings of colorful vegetables and fruits each day.
* Eat at least three servings of whole-grain foods each day, such as whole-wheat bread, brown rice, and whole-grain cereals. (If you’re looking for “whole wheat bread”, the first ingredient on the bread's nutrition label should read "whole-wheat flour."). Even if you’re limiting breads, cereals, rice, pastas and the like, shoot for at least half of your grain sources to be whole grain.
Regular exercise, a nutritious diet rich in fruits and vegetables, a healthy weight…researchers have confirmed that these lifestyle factors, which each person can control, are key to lowering cancer risk.