Magical fruits and vegetables: Does “healthy eating” improve breast cancer outcomes?

Sadly, our culture loves to blame victims of illnesses for failing to follow virtuous diets and lifestyles, and many victims feel guilty when a health problem befalls them, believing they are at fault for failing to do something right. The blame game is mostly based on pop science. Time and again what seems intuitively correct, looks promising in the laboratory, or appears right in observational studies, doesn’t prove to be true when it’s actually tested in a well-designed clinical trial on real people.

Until now, cancer survivors have had “to rely on folklore, rumor and hearsay,” as they try desperately to do everything possible to prevent the recurrence of their cancers. This tragedy is what sparked a private philanthropist to initiate scientific research to find out the facts. The resulting ten-year clinical trial funded by the National Cancer Institute, which took place in seven cancer centers across the country and involved 3,088 breast cancer survivors, just released its findings. They should help put a stop to beliefs causing needless guilt and condemnation for countless women.

It’s long been believed that by eating “right” — usually defined as more fruits and vegetables (chocked full of antioxidants thought to have cancer-fighting properties, as seen in the laboratory), low fat and high fiber — one can stave off the recurrence of cancer. But the Women’s Healthy Eating Living (WHEL), one of the largest and most comprehensive diet prevention studies ever conducted, found these beliefs not to be true.

As we’ve often seen, the quality of research is often inversely proportional to its media attention. When a well-conducted study reaches a null finding and counters popular wisdom, the media is sure to downplay it, spin it, or try to raise doubts about its conclusions in the mind of the public. So, let’s look at a few things that you may not have heard about this study.

Study overview

Briefly, the participants were women who had had operable invasive breast cancer (through Stage IIIA) diagnosed within the past four years at ages 18-70, but had no cancer in the previous ten years. They were cancer-free at the start of the study and randomized to receive either intense dietary interventions or be in the control group. The two groups were evenly matched in age (averaging 53 years), educational levels, diversity of ethnicity/race, types of cancers and initial treatments, and their previous diets. Having cancer, most had already been motivated to eat healthy and were eating low-fat, low-calorie diets with an average of 7 servings of fruits and vegetables a day.

The controls were given the standard NCI dietary recommendations to eat at least five servings of fruits and vegetables a day, more than 20 grams of fiber and less than 30% total fat. The controls also received bimonthly newsletters for four years and attended at least one cooking class.

The women in the intervention group received four years of intensive counseling from trained counselors, nearly weekly at first and decreasing in frequency as they proved to be adhering to the diet and able to self-monitor. During the first year, they’d received an average of 18 counselor calls and monthly newsletters, and attended 4 cooking classes.Their dietary targets were to daily eat 5 servings of vegetables, 16 ounces of vegetable juice [no, I checked and the study wasn’t sponsored by V-8], 3 servings of fruits, 30 grams of fiber and only 15-20% of energy from fat.

All study participants had their dietary intakes assessed by 24-hour dietary recall interviews conducted at the beginning of the study and at 1, 4, and 6 years, as well as random samples of half of them at 6, 24 and 36 months.

All participants were also clinically assessed and seen at the beginning of the study and years 1, 2-3, 4, and 6, which included labwork and health status evaluations. Understandably, these women were highly motivated and only 2% dropped out or were lost to follow-up during the study.

The intervention group averaged 7.8 servings of vegetables a day during the first year and managed to continue eating 6 daily servings through the rest of the study, in addition to more than 3 servings of fruits. After four years, the intervention group was still eating over 65% more vegetables, 25% more fruits, 30% more fiber and 13% less fat than the control group.

Findings

There was a great deal of enthusiasm about this study and the researchers felt confident that they would see a notable improvement in the recurrence and survival rates among the women following the “super healthy” diet and lifestyle, according to the principal investigator at M.D. Anderson, Dr. Lowell Jones, Ph.D. Earlier observational studies, including an interim one of their own study population, had found the diet associated with increased survival and lower recurrence rates, he said.

But after 7.3 years of follow-up, they found “no evidence that adoption of a dietary pattern very high in vegetables, fruit, and fiber and low in fat versus a 5-a-day fruit and vegetable diet prevents breast cancer recurrence or death among women with previously treated early stage breast cancer.” Regardless of how hard the women tried to eat more produce and less fat, it made no difference.

During the study, 16.9-16.7 percent had a recurrence of their breast cancers and 10.1-10.3 percent of the women died, with no statistical difference between the groups.

More fruits and vegetables were not only no better, but “we observed little evidence of recurrence benefit in the quartile of the intervention group that was consuming less than 5 daily servings of vegetables and fruit at baseline.” In fact, those eating the fewest servings of fruits (≤ 1 3/4 servings/day) had identical risks of dying as those eating the most fruits (> 4.4 servings/day). Similarly, the women eating the fewest servings of vegetables (≤ 2 1/2 servings/day) had slightly lower risks than those eating the most (> 4.8 servings a day).

Nor was there any indication in their findings that the percentage of fat in the diet would make a difference, as they saw no dose-related effect on breast cancer events or all-cause mortality. Those eating 28.7-33.4% fat, for instance, had identical risks of dying as those eating the least fat (≤ 23.8 %).

Some have claimed that perhaps if the women had eaten less, they might have lost weight and seen more favorable results. But what hasn’t been reported is that the (disease-free) women were already eating less and at the start of the trial were eating an average of about 680 kilocalories/day less than recommended for their age, activity and body size. The U.S. Dietary Guidelines recommends using the USDA/ARS calorie calculator developed by the National Academy of Sciences to calculate how many calories we need for our weight, gender, age and activity level for good nutrition. Despite its flaws and tendency to underestimate calorie needs, it still shows these women were already restricting their calories at the beginning of the study. And after the study began and throughout the six years, the intervention group had cut out another 181 kcal/day from their diet and the control group cut back an additional 158 kcal/day. Yet, just as the research has shown happens when people restrict their eating and undereat, metabolism slows; and during the study years, the women gained weight, an average of one pound.

It’s also important to note that there was no evidence to support beliefs that being thinner, eating less or being more physically active improved outcomes. In fact, there were no tenable differences in risks at all. But if we want to nitpick, the least active women (≤ 210 MET-min/week) had 20% lower risk for all-cause mortality than any of the women exercising more (even up to >1,290 MET-min/week). The women eating the least (≤ 1,430 kcal/day) had slightly higher risks than those eating more (1,680 kcal/day). And the women with the highest BMIs ≥ 30 had the lowest risks — 20% lower risks for cancer recurrence even than women of “normal” BMIs <25.

There was another belief refuted in this meticulously-done study, yet has not received mention. During the first year of the study, the researchers looked at the psychological factors typically associated with cancer outcomes. The mind-body connection is big in pop psychology. We’ve all heard the belief that a positive attitude, sunny outlook and psychological support can help cancer patients live longer. This belief has persisted since 1989 when first proposed by psychiatrists at Stanford University School of Medicine who’d looked at women with metastatic cancer. But the WEHL researchers “found no between-group differences for depression, social support, or quality of life during year one, when the intervention was most intense.”

This concurs with research just published in the May issue of Psychological Bulletin led by Dr. James C. Coyne at Abramson Cancer Center of the University of Pennsylvania, Philadelphia, PA. These researchers did a comprehensive investigation of all available evidence on the popular belief that psychotherapy can help cancer survival. They found: “No randomized clinical trial designed with survival as a primary endpoint and in which psychotherapy was not confounded with medical care has yielded a positive effect.” Further research on the effects of psychotherapy on survival after a diagnosis of cancer “are not justified by the strength of the available evidence.”

Of course, we want to support friends and loved ones facing cancer... because we care for them and want to help make this difficult time easier. But there is no credible support for pointing blame at cancer patients that feeling blue could mean a worse outcome or cause their cancer to reoccur. Just as there is no sound evidence to point blame at them that their natural body weight or failing to eat “right” could mean a worse outcome or cause their cancer's recurrence. This isn’t a time to chastise or blame. Sometimes things can just happen through no known fault of anyone’s.

This is a time for cancer patients and survivors to enjoy the things they most love about life. They deserve this time to live life to the fullest, not in fear and guilt.

© 2007 Sandy Szwarc