Back in the early 1990s, many leading medical authorities – including the World Health Organization – touted the idea that eating lots of fruits and vegetables could significantly reduce the chances of getting cancer.
The recommendation was based on promising preliminary findings that suggested these foods contain potent anti-cancer compounds. Over the years, however, more in-depth studies have failed to clearly demonstrate that munching on a carrot stick or biting into a juicy red apple can help keep tumours at bay.
And this week brought the release a major study that suggests the cancer-fighting powers of fruits and vegetable may be modest at best.
The researchers analyzed dietary data from more that 400,000 men and women living in Europe. After almost nine years of follow-up, about 30,000 participants came down with cancer. Those who ate the most fruits and veggies had some added protection against the dreaded diagnosis – but it wasn't much.
For instance, the study found that an additional 200 grams of fruits and vegetables per day – the equivalent of two extra servings – was associated with a 4-per-cent lower incidence of cancer, according to the results published in the U.S.-based Journal of the National Cancer Institute.
Adding more uncertainty to the mix, the researchers acknowledge they can't be sure that even this relatively small reduction in risk is linked to dietary factors alone. The people who ate ample fruits and vegetables tended to have fairly healthy lifestyles – less smoking, more exercise – which may have also contributed to their lower cancer odds.
"Cancer is indeed a complex disease and it's unlikely that one single factor has a very major impact – tobacco smoking being probably the only exception," said the lead researcher Paolo Boffetta, of Mount Sinai School of Medicine in New York.
So, does this mean it's time to say bye-bye to broccoli and berries as an anti-cancer strategy? Not quite yet, Dr. Boffetta said in an e-mail. It's still possible that one or more fruits and veggies, or certain ingredients in a few select foods, may have some anti-cancer potential, he noted. The current study focused on the big picture and was not designed to determine whether one particular fruit or vegetable may be somewhat better than the rest.
Aside from cancer prevention, there are other good reasons to keep these foods on the menu, said Dr. Boffetta. In fact, the same study showed the incidence of coronary heart disease and stroke was 30-per-cent lower for those eating five or more servings per day, compared with those eating less than 1.5 servings a day.
"The recommendations to eat fruits and vegetables are fully justifiable," said Dr. Boffetta. But they may not do much to ward off cancer, if that's your chief concern.