Heart-Healthy Diet’s Mixed Results

A multi-year study involving more than 100,000 participants provides added support that eating lots of fruits and vegetables is good for the heart.

But the analysis failed to show similar benefits for reducing cancer risk, a result that prompted the Journal of the National Cancer Institute, which published the study Tuesday, to raise questions about its findings.

The report supports the American Heart Assn.’s recommendations to consume at least five servings of fruits and vegetables per day, according to the researchers, led by Dr. Walter Willett of the Harvard School of Public Health.

But for cancer, the report said, “The protective effect of fruit and vegetable intake may have been overstated.”

The research team studied 71,910 women in the Nurse’s Health Study and 37,725 men in the Health Professionals Follow-up Study. The research began in the mid-1980s, and the report followed the participants until 1998.

They found that participants who ate at least five servings of fruits and vegetables daily had a slightly decreased risk of heart disease, but there was no statistically significant difference in cancer rates.

The researchers provided several possible explanations for that result, while the journal published an editorial suggesting potential sources of error.

It may be that cancer risk is increased only in people who eat few fruits and vegetables, according to the researchers. Since most of the study participants -- nurses and other health professionals -- tended to include fruits and vegetables in their diets, no protective association would have been noticeable.

Another possibility, according to the authors, is that it takes longer for cancer to develop than heart disease, so it may take longer for a protective association from higher fruits and vegetable consumption to show up.

Also, they said, the finding did not preclude protective effects of specific vegetables.

For example, they found that eating cruciferous vegetables -- such as broccoli, cauliflower and cabbage -- was associated with lower rates of cancer in men who smoked and didn’t use multi-vitamins. They also had found a lower rate of bladder cancer in men who ate more cruciferous vegetables.

Fruits were more strongly associated with reduced heart disease than vegetables, the researchers said. Among vegetables, those most closely related to better heart health were green leafy vegetables.