Omega-3 Fatty Acids Not Linked to Cancer Prevention
They may be great for the heart, but the omega-3 fatty acids found in fish and fish oil supplements do nothing to prevent cancer, according to a study reported in the Journal of the American Medical Association (JAMA).
A new review of more than 38 studies on the subject finds no evidence that diets rich in fish fight any kind of cancer. The study was supported by the US Agency for Healthcare Research and Quality (AHRQ) and the National Institutes of Health (NIH).
Omega-3 fatty acids "definitely have health benefits, but they are not a panacea. Preventing cancer is not one of the things omega-3 fatty acids do," says lead researcher Dr. Catherine MacLean.
An earlier meta-analysis (analysis of already-completed studies), also funded by AHRQ, found that diets rich in omega-3 fatty acids did have a beneficial effect on cardiovascular health.
But evidence of any protection against cancer has been more elusive.
"There was a plausible mechanism," says Dr. MacLean, a natural scientist at Rand Health and a rheumatologist at the Greater Los Angeles VA Healthcare System.
"Omega-3s are integral to some of the inflammatory pathways that are also common to cancer, so the idea was that if you had more omega-3s maybe that would dampen this inflammatory process."
But proof for the theory was scanty.
"I think there were a lot of high hopes, but very little evidence," says AHRQ director Dr. Carolyn Clancy.
While some research - mostly animal studies - suggested omega-3s might have an anti-cancer effect, other studies found no such link.
"So the office at the NIH that deals with dietary supplements asked AHRQ to do a very rigorous review of the studies that had been done," explains Dr. Clancy.
In the study, Dr. MacLean's group analyzed data from studies conducted over the past 40 years.
The vast majority showed no effect of even high-dose omega-3 fatty acids on the incidence of a wide range of cancers, including breast, colon, lung, and prostate malignancies, the researchers found.
Colleen Doyle, R.D., director of nutrition and physical activity at the American Cancer Society (ACS), says the finding was "not surprising," since the evidence had always been slim that the nutrient might fight cancer.
But she adds that the results would not change current ACS dietary guidelines.
"We will still recommend that people include fish in their diets," Doyle notes. "It's a source of healthy fat, it's associated with a reduced risk for heart disease, and we'd rather see people eat fish with healthier fats than eat red meat with unhealthy fats."
Doyle says healthy diets can discourage cancer by keeping obesity at bay.
"Being overweight, especially, increases circulating hormones such as estrogen and insulin that we know are associated with cancer cells and tumor growth," she explains.
Dr. MacLean agrees, adding that fish-rich diets are proven to fight heart disease.
"The results of this study need to be taken in the context of the body of literature on omega-3 fatty acids," she says.
"We know that for people with cardiovascular disease, omega-3s reduce the risk of having another heart attack and they reduce the risk of arrhythmias in people who have had heart attacks," comments Dr. MacLean. "They also reduce mortality in people with cardiovascular disease."
Dr. Clancy says, "Eating fish, as opposed to a hamburger with cheese and bacon, would be a great idea, in general. And it is not going to hurt you."
Always consult your physician for more information.
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Omega-3 Fatty Acids Not Linked to Cancer Prevention
New Research Clarifies Understanding
Omega-3 and Weight Management
Obesity Prevention May Reduce Cancer Risk
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Obesity is a chronic disease affecting increasing numbers of children and adolescents as well as adults.
Obesity rates among children in the US have doubled since 1980 and have tripled for adolescents.
Fifteen percent of children aged six to 19 are considered overweight compared to over 60 percent of adults who are considered overweight or obese.
Earlier onset of type 2 diabetes, cardiovascular disease, and obesity-related depression in children and adolescents is being seen by healthcare professionals.
The longer a person is obese, the more significant obesity-related risk factors become.
Given the chronic diseases and conditions associated with obesity and the fact that obesity is difficult to treat, prevention is extremely important.
A primary reason that prevention of obesity is so vital in children is because the likelihood of childhood obesity persisting into adulthood is thought to increase from about 20 percent at four years of age to 80 percent by adolescence.
Many of the strategies that produce successful weight loss and maintenance help prevent obesity.
Improving eating habits and increasing physical activity play a vital role in preventing obesity.
Recommendations for adults include:
Eat five to nine servings of fruits and vegetables daily. A vegetable serving is one cup of raw vegetables or one-half cup of cooked vegetables or vegetable juice.
A fruit serving is one piece of small to medium fresh fruit, one-half cup of canned or fresh fruit or fruit juice, or one-fourth cup of dried fruit.
Choose whole grain foods such as brown rice and whole wheat bread. Avoid highly processed foods made with refined white sugar, flour, and saturated fat.
Weigh and measure food in order to be able to gain an understanding of portion sizes. For example, a 3-ounce serving of meat is the size of a deck of cards. Avoid supersized menu items.
Balance the food “checkbook.” Taking in more calories than are expended for energy will result in weight gain. Regularly monitor weight.
Avoid foods that are high in “energy density,” or that have a lot of calories in a small amount of food. For example, a large cheeseburger with a large order of fries may have almost 1,000 calories and 30 or more grams of fat.
By ordering a grilled chicken sandwich or a plain hamburger and a small salad with low-fat dressing, you can avoid hundreds of calories and eliminate much of the fat intake.
For dessert, have fruit or a piece of angel food cake rather than the “death by chocolate” special or three pieces of home-made pie.
Remember that much may be achieved with proper choices in serving sizes.
Accumulate at least 30 minutes or more of moderate-intensity activity on most, or preferably all, days of the week. Examples of moderate intensity exercise are walking a 15-minute mile, or weeding and hoeing a garden.
Look for opportunities during the day to perform even ten or 15 minutes of some type of activity, such as walking around the block or up and down a few flights of stairs.
Always consult your physician for more information.
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