A new study from the Journal of the National Cancer Institute reports that the connection between eating fruits and vegetables and having a reduced risk for cancer is smaller than one might hope. The study was carried out by Walter C. Willett and colleagues at the Harvard School of Public Health.

While the World Health Organization recommends eating fruits and veggies to prevent cancer, some studies have raised questions about the exact relationship between these foods and their ability to stave off cancer. In the current study, Willett and his team tracked over 477,000 participants and monitored their eating habits over the previous 12 months as well as their risks for developing certain kinds of cancer over the next eight years.

If people upped their fruit and veggie consumption by about 150 grams/day, about 2.6% and 2.3% of all cancers could be prevented in men and women, respectively. Just for reference, a typical apple weighs about 100 grams, and a zucchini about 85 grams.

The team found that overall, the relationship between higher fruit and vegetable consumption and having a reduced risk for cancer was only very slight. And to complicate things further, people who consumed more fruits and veggies also tended to be healthier in general: for example, these individuals tended to engage in more frequent exercise, drink less alcohol, and not smoke – all lifestyle factors that might lead to decreased cancer risk in-and-of themselves.

The cancer-preventing effects of fruits and veggies were somewhat stronger in participants who were heavy drinkers – but the cancer risk was only reduced in those forms that have already been linked to alcohol and smoking.

To put the relationship in perspective, the authors write that if people upped their fruit and veggie consumption by about 150 grams/day, about 2.6% and 2.3% of all cancers could be prevented in men and women, respectively. Just for reference, a typical apple weighs about 100 grams, and a zucchini about 85 grams.

While more research will be needed to tease apart the exact relationship between fruits, vegetables, and cancer risk, it can’t hurt to continue eating a diet rich in these foods, which, aside from cancer risk, offer a host of other health benefits to the consumer.